Battery draining
 

So my battery completely drains overnight. I only have the ignition, starter, distributor and alternator hooked up. Just what is necessary to turn the key and start it. Its a new painless wiring system. The key is taken out so its not accidentally left on acc. Im new to this vehicle restoration stuff. Some days its a lot of fun and some days I think I’m spending money just to be frustrated.
I don’t understand why a battery drains overnight with so little hooked up.
Im using a new optima redtop if that matters

Re: Battery draining
 

Disconnect the battery, does it still drain? Then the battery is shorted inside.

If battery is good, then you have a sizable power draw to drain it overnight.
Disconnect battery negative, put a test light or multimeter between battery and ground, Can you see current? Disconnect other circuits (or pull fuses) one at a time until the test light goes out.

The starter, alternator and power to ignition switch, are likely culprits, but there are also some points that always have power regardless of ignition switch, depending how much you have wired or is prewired in the kit harness:
brake lights
4 way flashers
horn
headlights
dome light
maybe other things. You may not have these wired, but the circuits will be live in the fuse block, whatever wires are connected to it and probably inside your steering column if you have a newer column and have the column plugged in.

Re: Battery draining
 

I ended up putting in a simple battery cutoff.

Top Post Battery Disconnect Switch, Qiilu Power Battery Disconnect Switch Negative Terminal

https://www.amazon.com/dp/B0B1TP732B...roduct_details

https://67-72chevytrucks.com/vboard/...1&d=1687017136

Re: Battery draining
 

Thank you for the response. I have taken out the battery. It was sitting on a trickle charger for a few hours before I removed it. Does the alternator usually get warm when its charging? Never noticed it before but it was pretty warm. It’s garage kept and not warm inside the garage

Re: Battery draining
 

check the alternator rectifier. if one of the diodes goes bad it will drain the battery

Re: Battery draining
 

A blown diode will cause the battery to drain.

First, take you volt meter and put the positive lead on the positive post and touch around the top of the battery with the negative lead to see if you have any drain across the top in dirt/moisture. If the battery top is dirty this can happen. I've seen one that drained in a little over two hours as it had over a 9 volt drain across the top of the battery.

Re: Battery draining
 

Warm alternator: Sounds like either a bad alternator or possibly a wiring error and you are providing voltage to the field coil when ignition is off

Re: Battery draining
 

It takes about five or ten minutes to unbolt the alternator and pack it down to a parts house with an alternator tester. Test, don't start assuming.

Disconnecting the battery overnight is testing,

Checking across the top of the battery with the volt meter is testing.

Having the alternator tested on a test machine is testing.

Walking out a couple of hours after you put it away to see if maybe for some reason the pedal has dropped and the brake lights have come on is testing/checking.

Re: Battery draining
 

does your radio lose its memory when you turn the key off?


I have done a bunch of trucks and probably thousands of radios, and I can say with certainty that some aftermarket harnesses and ALL GM harnesses (aftermarket are usually based on GM) have a common wiring anomaly in the radio harness where the CONSTANT 12v is orange or red and the IGN wire is yellow, which is exactly backwards of the EC standards aftermarket radio wiring harness where the constant 12v is yellow and the IGN is red.

so you can see what happens, people hook yellow to yellow and red to red. which lets the radio work fine except the presets go away every time the key is cycled. it also drains the battery because the radio is "on" but not on when the key is off.

i cant say with certainty that this is your problem (you may not even have a radio installed) but knowing this anomaly maybe you have something else installed that requires a constant and an ign both, or something that requires either that can possibly be wired as 12v constant that should be IGN.

Re: Battery draining
 

How does removing the battery change anything? Not at all. Just disconnect the wires/cables.
If the alt gets warm when the engine isn't running it's a problem.
You can disconnect the firewall connector while measuring battery current for a quick check.

Re: Battery draining
 

Yes it is normal for an alternator to get warm when the engine is running and it is charging,

Remember TEST DO NOT THROW MONEY AT IT. Going out and buying parts to replaceparts that you aren't sure about is not testing.

If you aren't sure about how to do something the right way you can PM me with a question any time, That goes for everyone else too. I do not give BS answers that will mix someone up. I don't believe in that .

Re: Battery draining
 

my first check would be to see if the alternator is wired correctly. if that checks out correctly with both a visual wiring trace and also a voltage test to check if the wiring is working as it is supposed to with key on and key off. sometimes new doesn't mean correct. if it still has a draw with the key off then the second check would be to remove the alternator and have it tested. the alternator shouldn't be getting warm with the key off, like LG says in post 7.
phungki, post 4, are you asking if the alternator should get warm with the engine running and alternator charging like usual, or are you asking if the alternator should get warm with the engine off and a battery charger connected? if the latter then the answer is no. alternator should not get warm with key off and a battery charger connected. that is why I suggested to check the wiring for a possible crossed wire or a fuse panel error from the factory and also do mechanical tests for what the wiring is actually doing at the alternator plug with key on and key off-alternator plug disconnected while testing for powered circuits and while key on and then with key off.
you could pull the alt for testing but if the wiring to the alt is incorrect for some reason then the alt will test fine. testing it would be for peace of mind so not a bad thing for time spent
have you checked for powered circuits at the fuse panel when key is off? sometimes things get done wrong from factory or maybe a circuit got inadvertently overloaded and melted some circuits together where you haven't seen them yet. pinch points and places where the wiring passes through something like firewall would be a good place to look

Re: Battery draining
 

I removed the battery because leegreen said it could have a short. Never ran into that before and it came off the shelf fully charged but its an easy test. It stayed fully charged. Battery test complete.

I disconnected the alternator. The battery still died overnight. So its not the alternator. Alternator checks out.

There isn’t a radio or any lights hooked up (or even in the truck) so its not that stuff.

I appreciate the suggestions

Re: Battery draining
 

I would suggest to use a volt gauge inline with the battery cable and the battery. Disconnect one thing at a time with key off while checking the volt gauge for a drop. Check the state solenoid as well. What have you got for ignition system, fuel system etc. Are there relays? Sometimes a relay welds its contacts closed and keeps the current flowing even though there is no signal to the relay from the ignition.

Re: Battery draining
 

I was asking about the alternator getting warm with the engine off and just a charger on it. I did remove the wire that goes from the alternator to the battery. Battery still drained overnight.

I have not checked the fuse panel yet. I will trace the wires and see if anything is shorted. I use rubber grommets when passing thru the firewall. Could be something going on with the 50 other wires I don’t have hooked up yet. I did cap all the ends so they couldn’t short out.

Thank you

Re: Battery draining
 

Sounds like enough of a power loss that if you disconnect the ground wire from battery and wire a test light (or headlight etc) between battery and the disconnected battery ground cable it should light up when the key is off.

For a very small current leak you might need to use a LED or a multimeter, but this sounds like it is bigger than that.

then start unplugging things, wiggling wires until you find something that makes the light go out.

Re: Battery draining
 

If the alternator is getting warm with the key off then it is getting power from somewhere. Totally disconnect it then check which wire has power with the key off.

Re: Battery draining
 

curious, without going through your build thread, what engine do you have and how is the starter/alternator/ignition switch wired up? a couple of pics would be great just so we can see what kind of vintage/era of equipment you have. do you have an old fashioned key switch on the dash with screw on connections or a column mounted ignition switch with a plug in down the column? what sort of starter solenoid do you have, is there a relay anywhere in that system? are you running an electric fuel pump and if so is there a relay in that system? is there an ecm or are you running a carb? is there a spark at the terminal when you disconnect the battery after running it? if you have ANY relays connected check them for proper operation with a test light. possibly one is not turning off due to welded internal contacts even though the wiring to the relay is correct.
here is how I would start
run the engine for a minute then shut it off like normal. does it shut down immediately or try to run on?
go to alternator and do power checks at each connection to see if any are still hot. obviously the battery feed wire will be. carefully disconnect the battery feed wire and put the test light inline with that wire and the alternator terminal it came off. does the test light come on, even dimly? if it does that would indicate a power draw from inside the alternator.
go to battery and disconnect one terminal watching for that spark, which would indicate a power draw somewhere. next install the test light or a volt meter between the battery terminal and the cable. does it light up with the key off? if so there is a draw.
go to the ignition switch and disconnect the main power feed wire. is there a change to the test light at the battery? (assuming it was lit due to a draw in the system) if so then reconnect that wire to the switch and disconnect another wire, one at a time, until the test light goes out. that will be the circuit that is still powering something. now you can see which circuit is still being powered and if it is a switch problem or a circuit problem.

Re: Battery draining
 

Alternators always have power to the Batt post on the alternator.

One wire alternators have a built in excitor that is usually triggered when you rev the engine when you start it. Those were originally designed for farm equipment with diesel engines or magnitos that don't have battery ignition systems.

The exciterwire in a normal three wire alternator usually connects to the ignition side of the igniton switch and has either a diode or idiot light in the line to keep the alternator from feeding back to the ignition and keeping the truck running after the key is shut off. We have answered a few of those (I put an alternator on and now it won't shut off) questions over the years that we both have been on here.

Phunkie is just like about half of the 700 beginner high school auto shop students I taught over 13 years. A lot of want to but limited skills because he most likely wasn't around anyone who was able to teach him a lot. It's up to us to give solid and simple step by step instruction on how to test things like this out and so far in this thread we have done that.

I preach "test rather than replace" a lot because over the past 60 years I have seen too many guys waste too much money on things that they changed but didn't need changing as their test method.

Charge the battery and let it sit disconnected and check it to see if it is holding voltage = that is testing. No cost unless you have to pay somone to charge the battery.

Checking the top of the battery with your volt meter (multimeter) to see if you have a drain across the top of it in the dirt and moisture if the top is dirty. Again testing. Plus an easy fix, Clean the battery.

Taking the alternator off and taking it to a parts house or auto electric shop to be tested. Good test Put it back on, test bad either fix it or replace it.

Thinking back, Did you add anything to the truck that ran on electricity between the time it worked good and the time the battery started draining?
Anythign like parts for the sound system, backup camera, or other accessories?

Re: Battery draining
 

Dsraven and Mr48 chev, thx for the ideas. I’ll get back on here with pictures.

Mr48chev not far off. I don’t recall there being auto shop in the schools I went to and there definitely wasn’t anyone showing me anything growing up. I fumbled thru changing minor stuff, alternators, mufflers, brakes and other simple things. Always did my own stereo stuff but nothing crazy electrical. If I can see it done then I can mimic easy enough.

It does have a carb and an Hei distributor, Mechanic fuel pump. No electric fans no stereos no lights of any kind. Literally only what I need to turn the key and start it.

Thx ya’ll I get some pictures

Re: Battery draining
 

seems like you have something feeding your alternator juice with the key off. do you have an alternator with one large cable that feeds the battery and then a smaller rectangular plug on the side? like this set up shows?
https://smithcoelectric.com/blogs/te...wiring-diagram

Re: Battery draining
 

Well we try to help you learn the best we can one step at a time. This bunch is one of the better ones as we don't have those clowns who think it is funny to give bad information just to be the jokester like some groups have.

The real good thing about nothing fancy on the truck is that there isn't much to go wrong and figuring it out gets a lot easier.

Re: Battery draining
 

I'm having a similar issue with an Optima Red top. I fully charge it , yet it dies when trying to start the truck. It checked out as being good at the parts store but that obviously cannot be right. I can start it by boosting it off, but otherwise, it's dead.

Re: Battery draining
 

Sometimes the parts store has a dinky little digital battery condition tester. Yup, all good.
The best way to actually test a battery is to fully charge it, let it sit for a bit with no charger attached so it can off gas the flammable gasses, then load test it at room temp with a tester capable of applying a load of half the cold cranking amp rating of the battery. For 15 seconds. During this time the battery should not get below 9.6v. If it does its toast.

Re: Battery draining
 

Another reason for that, mobileortho, is a voltage drop between battery and starter. Check/clean all your connections. A poor starter solenoid internal connection can also cause havoc. Load test battery, do the connections and cable checks, then do a starter draw test. This basically checks what the starter is drawing while cranking the engine. Engine needs to be set up so it wont attempt to start and skew the load test. No fuel, no ignition.

Re: Battery draining
 

I really don't want to get too distracted or off base in this thread.

Testing the battery you really do have to have it fully charged and then use test equipment that Dsracven mentioned in post 24 that actually puts the proper load on the battery for the correct amount of time and shows the results.

I don't know brand or model but the local Les Schwab tire store (big chain in the Pacific Northwest ) has but it is one of the best and most complete testers I have seen. You need equipment like that to test it right and it will test the charging system along with the battery.

Back to Phungki's truck, from reading what it has and doesn't have there isn't much there to cause a parasitic drain. None of the usual stuff that drains a battery after a period of time if you don't have a battery tender on it. The anti theft system in my BMW draws a tiny bit of power all the time even if you don't have the alarm turned on. It's not a bother if you drive it on a regular basis but drains the battery if it sits for a month.
Things like an alarm system, clock in the radio, an amp that isn't shut off by the ignition switch. light in the glove box that doesn't go off when you close the door, trunk light that doesn't go off when you close the trunk.

I had a student who owned a nice 64 Chevy lowrider that he had a lot of work and money in and left at home when he went to work beause the parking lot where he worked was famous for door dings by careless people. Every morning the battery was dead and he would have to jump it to start it to get to school. we tested battery, alternator and everything else and no issues. We even had the sun scope hooked to it to check the alternator on the scope. After a couple of weeks of battling it he was fussing about it to his mom and she goes "oh, your brother and his friends have been listiening to your car sterio while you are at work at nights." Little bro found out real quick that that was not to happen again and no problem from then on out. Billy's dirty battery in his mid 60's Chevy truck was the other one. That was the first time I had seen that and I have seen it several times since.

Re: Battery draining
 

So I was able to get back out there tonight. I have a -13.08 parasitic draw.

Started with the alternator. Disconnected the main wire, alternator to battery. nothing changed. Reconnected wire.

I disconnected the white (exciter) and the red (battery) wires and the draw went to -4.36. left them disconnected and disconnected the main wire again and the draw went to -0.07.

If I connect either the white or red wire again by itself the draw goes back to -13 again.

I do not have a diode on the white exciter wire. possibly the issue? from what I've read its supposed to allow the vehicle to be shut off, right? Something about stopping the current from traveling back. It does shut off normally.

ya'll have been great btw. I spend half my time frustrated and the other half happier than i pig in ....well you know. Is this normal?

Re: Battery draining
 

sounds like you figured it out. it's what I personally thought it was gonna be after you said there was basically nothing else connected except stuff to make it run. otherwise I figured a stuck relay that won't turn off. again, a pic would be great just so we can see the style of alternator you are workng with. do you have another spare one you could lay next to the other one and simply do the wiring on it without mounting it? use a jumper wire to ground the housing. would be worth doing just to see if it is your wiring or the alternator that is giving you an issue.
this link explains it pretty well. basically the one connector in the rectangular push in plug (the one closest to the battery cable connection charge wire) is not really needed unless you want a "no charge indicator" light on the dash.kinda a good idea I think but thats just me. this works by feeding keyed battery power to the light on the dash. the other side of that light connection that usually would go to ground actually goes to that terminal on the alsternator and uses that connection as a ground when the alternator isn't charging. that makes the bulb light up according to the amount of ground the alternator is giving. this may be dim or maybe even pulsating when the engine is first started and hasn't been revved up yet to get the alternator to charge. when the alternator has been revved up some it will start charging and feed power down the ine that is connected to the charge indicator bulb. this effectively gives the bulb power on both sides of the bulb filament so it will go out because it just lost it's ground circuit. the other terminal on the plug in connection, the one that goes to the ignition switch and is powered with the key on, is the one that will "excite" the alternator and make it charge. a lot of guys wire that directly to the battery charge connection on the alternator. some of these alternators have a third terminal in the plug whicch is for running a tachometer. not too many of those out there so you don't likely need to worry about that.
https://smithcoelectric.com/blogs/te...wiring-diagram
and here is another link that explains it further in depth than what I could muster up from memory. haha
https://vintageautogarage.com/p10si-...ug-with-diode/

Re: Battery draining
 

The numbers you give are volts right?

The exciter wire drawing power when the key was off is clearly a problem.
But the fact that you still had a current leak of 4 volts when the alternator was fully disconnected says to me the alternator is either not the problem or not the only problem. Getting only 4 volts indicates a high resistance somewhere.

I'm wondering about your ignition switch, is it new or used? OEM style in dash or attached to the steering column? How many connectors on it? If you unplug it does the rest of the current leak stop?

There is a possibility the new wire harness has issues, but it sounds like you were careful with it and assuming a factory flaw on a name brand kit maybe a stretch

Re: Battery draining
 

Yes, and that was why I asked sorta the same questions. What alternator and what sort of ignition switch scenario.
Again, a pic says a thousand words.
Disconnect the alternator completely and look for any other draws with key off. Actually, with alt disconnected try what LG says and also disconnect your ignition switch plug in or, if dash mounted old fashioned key switch, pull the power wire off that and see if your draw goes away.
Are you running any relays? Have you checked them to ensure they turn off with key off? Do you have a fuse panel and if so have you checked the fuses to see if they are all non powered with the ignition off?

Re: Battery draining
 

It still draws 4v when the plugs containing the 2 small wires is removed but the wire going between the alternator and battery is still connected.

It is a new ignition switch, oem style in the dash from LMC. I will look further into the ignition switch next

Re: Battery draining
 

I don’t think I have any relays. There is a fuse panel. Its a painless wiring kit. Oem style ignition from LMC.
I don’t know how to check to see if the fuses are powered down with the key off. I’ll need to look into that. I believe there is a wire that goes between the battery and the fuse box directly. Wouldn’t that mean there would be some power to the fuse box all the time? A small amount at least

Re: Battery draining
 

>draws 4v when the plugs containing the 2 small wires is removed but the wire going between the alternator and battery is still connected.

This sounds like alternator problem. does it go to zero when all the wires are disconnected from alternator?
Yes -> leave alternator fully disconnected and use some other piece of wire to bridge from battery to the main terminal on alternator, if you still get 4v I think the problem causing the low voltage leak is inside alternator, if the problem goes away there is a short in that main cable to ground.
No -> there is another leak somewhere with high resistance, unplug more stuff until you see the voltage go to zero - start with ignition switch

The larger leak when either red or white wire is connected:
the white exciter wire problem is either the ignition switch or you do need to add a diode to stop back feed of power from alternator to ignition. Does wiring kit instructions say anything about diodes? White wire basically turns the alternator on with ingition.

The red wire, where does the other end go to? Red wire should be live only when ignition is on, its purpose is to let the alternator see the voltage of the system from somewhere away from the battery to adjust for any voltage drop due to the loads. Usually goes to somewhere near fuse box. without it, the alternator may overcharge, if it connects too close to the battery and there is voltage drop in the system some parts of the truck may be getting too few volts.

Fuse box will always have some power: horn lights and brakes at least will always have power. other fuses will only be hot when the ignition is on.

a test light like this is my goto for finding out what has voltage and what does not. get them anywhere for a few bucks
Attachment 2275420

Also very handy is a few wires with jumper connectors on each ends so you can hook stuff up temporarily to see if it works. I made up a pair of truck length jumper wires from some old speaker wire, it has been very useful for testing on several car and boat projects we have going on.

ps: I edited the yes/no paragraph a couple hours after the original post as what I wrote earlier did not look right after a cup of coffee.

Re: Battery draining
 

LG is on the same diagnosing thought process as me on this. It's why I said to totally disconnect the alternator and see if the problem goes away. New alternators can be faulty too, maybe a bad part or maybe dropped somewhere along the supply chain. Who knows.
A test light is a must have and are only a few bucks. Some have an audible alarm as well as a light. Try to get one that has a decent clamp on the end so it grips well and will stay put. Test wires, or jumper wires can be made up cheap as well or you can buy a cheap set too. Try to find some with good alligator clips on the ends with color coded flexible insulators over the clips as sometimes you need to test a circuit that is right next to another circuit or ground. Also try for flexible wire as regular car wire can be kinda stiff sometimes and will pull the clip off.
If you need to check power from a connector with small connectors and the test light light is kinda big to fit I use a small pin with a little circle bent into one end and then flattened to form a T. You can get them cheap from an office supply or a craft store or online. They are called t pins. Used for cork boards, fabric etc.

Re: Battery draining
 

t pins
https://www.thefibrenook.com/products/t-pins
alternator charge plug
https://www.wiringdepot.com/store/c/...s-Sockets.aspx
circuit tester
https://www.harborfreight.com/612v-c...ead-63603.html
test leads
https://www.harborfreight.com/18-inc...ads-66717.html
https://www.harborfreight.com/36-inc...ads-66712.html
clips only to make your own leads
https://www.harborfreight.com/28-pie...set-67589.html
not saying any of these items are any good, just some pics to show what to look for.
to test the fuse panel for what circuits are hot with key off simply connect the test light clip to a good ground, test it on a circuit that is hot so you know the ground is good, then touch the pointed tip to the fuse and see if it lights up the tester. without knowing what type of fuses you have I would assume you have the newer style push in plastic fuses, like an ATO or ATC fuse. these have 2 little tabs that protrude a little through the plastic on the outboard side of the fuse, you can see them when the fuse is installed. these are extensions of the blades that actually plug into the circuit. you can touch these with your tester to see if the fuse is powered or not. if you have power on one side but not the other then the fuse is getting power but it is also blown, thats why it's only powered on one side. this makes it easy to test for power without pulling the fuse out for each circuit. if you have the old fashioned glass fuses simply touch the one end of the barrel of the fuse where the metal part is. its good to test both ends of any fuse just to ensure it isn't blown.
do you have a fuse or breaker on the power wire that feeds the fuse panel? something close to the battery maybe? otherwise that run of wire is vulnerable to a short. sometimes one of these fuses will look like this link, called a mega fuse
https://www.summitracing.com/parts/a...BoC6AUQAvD_BwE

Re: Battery draining
 

When all 3 wires on the alternator are removed I have a .07v draw. I do need one of those lights for sure.

Re: Battery draining
 

Yes I get a parasitic draw of .07 when all 3 wires are removed.

I need to dig into the ignition switch again when I get back out there.
I found the diode in my wiring kit, pretty sure I need to put that in. Might not solve the problem but I’m going to do that before taking the alternator back and having it tested.

Yes I’ve bought brand new/refurbished parts before and had them not work or cause a fuse to blow. Jeep TJ wiper motor comes to mind. Tried twice then just bought a used one on ebay.

I actually already have “T” pins. As soon as I can wrap my head around how you want me to use them I’ll dig them out 😁

Thank you all for the help

Re: Battery draining
 

I put in the diode. Nothing changed. I looked over the ignition switch. Everything seems to where it’s supposed to be. I pulled every wire one at a time. I would get little movements on the multimeter but was still a 13v draw. Pulled all the fuse one at a time. Same results as the ignition switch. I guess now I’ll take the alternator in and have it checked. I’ll grab a test light while I’m there

Re: Battery draining
 

Confirm you can make it go to zero - pull the main battery + connection ?

With the ignition switch unplugged you still got full voltage on the 2 alternator wires?

Your fuse panel probably has a relay for horn and flasher for hazard - they will always have power, did you try pulling them?

what painless kit # is it?

Re: Battery draining
 

the T pins work for pushing into a connector on the back side where the wire comes out so you can get a reading on voltage etc as the friction between the pin, the connector housing and the terminal inside the housing is enough to keep the pin in place and also give a reading thats pretty accurate. this is without poking a hole through the wire insulation on the wire so no mechanical damage is done. some guys do that poking thing all the time with the sharp end off the test light and think nothing of it. it drives me crazy because somebody like me, who works in a shop (used to), would have to find the spot in that circuit that is causing the resistance problem and then fix the spot by cutting the bad corroded spot out and repairing it. if you do that poky thing because you have no choice ensure you seal the hole you poked with some liquid electrical tape or something more than regular electrical tape. if you do use regular electrical tape use the bright red stuff so that spot sticks out like a sore thumb and the repair guy after you can easily find it.
end of rant.
T pins work good for that. I also have used a strand of wire pulled from a spare length and wrapped around the terminal in question when the connector is unplugged. then plug the connection together and that short strand of wire sticks out enough to connect a tester or aligator clip to.
another thing i will mention is that while the digital multimeter is great but for doing tests to find parasitic draws sometimes an analog multimeter is easier to use because the digital readout ones are always hunting for the number. the analog ones simply move the needle a little or a lot and o can give sort of an average number that is close enough for testing like this until you get right down to the short hairs. what I have also done in the past is use an incandescent trailer light with an alligator clip on each of the pigtail wires . the kind of light that is a sealed beam. disconnect the negative battery post and install the trailer light in the circuit between the cable and the battery terminal. you can do the same thing with your test light but you gotta hold it there or clamp it to the battery post somehow. a large draw will light the bulb brightly, less draw will light it dimly. you are looking for no light at all. simply do one change at a time and look at the bulb from where you are working. it is easy to see if the bulb is lit brightly, dimly or not lit. when not lit it may be because there isn't enough draw to light the bulb. that is when you start using the analog multimeter. it can also be set up so you can see it from where you are working if you have a large enough gauge. some surplus stores have panel meters which are larger and possibly cheap too. I have also done that trick using a buzzer from a car instead of the trailer light. for those times when you are looking for a draw in a spot where it is awkward to see the light or meter or whatever. if the buzzer is buzzing then there is still a draw enough to make the buzzer operate.