55.2-59 Battery draining

[leegreen]

The setup Mr48chev posted will work. My understanding of connecting the voltage sense wire direct to the alternator output as shown in his picture is that it can lead to undercharging the battery. The alternator always senses it's output so it sets the output power to achieve the correct voltage right at the alternator, not the voltage at the battery or elsewhere in the system.

if you have big, thick, short wires between alternator and battery it should not matter as there is little voltage drop, but if you have a longer length, thinner or corroded wire and there is voltage drop between alt and battery the alternator wont maintain battery at correct voltage.

this wire I circled:

[Phungki]

Originally Posted by mr48chev

The diode is a one way check valve for electricity that lets power go though that diode in the exciter wire to the alternator to tell it to charge but blocks electricity from feeding back from the alternator to the ignition. This is to prevent the feedback from keeping power to the ignition when you turn the key off.

Normally people either use the idiot light for the alternator or that diode to prevent the feedback. That is the fix for "I just put and alternator on my truck and drove it and it charged great but now the engine won't shut off when I turn the key off.

There should be no power though that wire with the key off. None=0

There should be no power at the pin for the exciter wire on the alternator with the key off.

This is how many of us who aren't putting in a complete wiring kit install an internal regulator Delco alternator


The white band on the diode shows which way the power flow goes.

There are two sets of diodes inside the alternator. The diode trio and the diode bridge. One or the other of those is what usually goes bad. They can be tested by taking the alternator apart but most parts houses don't keep them in stock. 25 years ago I was told by the counterman in a NAPA store that I was the only person in the area still rebuilding his own alternators. It isn't that common for an individual to do that anymore even though for someone with training and experience the degree of difficulty isn't that hard.

These diodes are again one way check valves for electricity

The tri diode


And or the diode bridge or Rectifier.


Those two from Summit cost almost as much as a lifetime guareentee alternator from O'Reilly's" That is why folks normally don't rebuild an alternator at home unless it is an "original" to the car or truck unit with the correct numbers that it left the factory and you are doing a 100 point restoration. Or you are cheap like me and hunt down the discount price parts and rebuild your own.

I really don't want you to take it apart because then I will have to write out a lengthy set of instructions and have to go take one apart to add photos to those instructions. I can do it and may do it as a separate tech thread some day.

The 10 gauge wire in your picture goes to a junction box or ammeter? Mine goes directly to the positive side of the battery. Is that wrong?

No worries, tearing apart the alternator is above my pay grade as a mechanic.

I did pay attention to the orientation of the diode when I put it in. Pretty sure its correct.

[dsraven]

Agreed LG. It's why I posted that link previously that explained that problem of not sensing true system voltage. It would get him running without a problem in that from the harness, for testing.

[Rickysnickers]

Originally Posted by dsraven

sorry, i misread that the post was from rickysnickers and not phungki. Lol. Please disregard my post 48.

lol!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Phungki]

Originally Posted by leegreen

I should have explained more: pull the main battery positive cable off to confirm the multimer does go to zero: I want to confirm the MM does go to zero and that there is no other power source, a capacitor for instance we are chasing.

If the Ign switch is faulty with internal short between multiple wires you may need to disconnect all the wires at once.

I disconnected the battery completely. MM goes to zero.

I reconnected the positive side of the battery (MM reads -13.56) and disconnected the 3 wires for the alt, MM reads a -0.07.

leaving the alt disconnected I then disconnect all the ignition wires. Still reads -0.07.

So I move to the fuse box. Leaving ignition disconnected completely and I Pulled each fuse and relays one at a time. Still reads -0.07.

I tried to get a reading with the MM on the exciter wire and the other 2 wires and it would read between 0.01 and 0.00. Im sure a test light would be better for that. Just got back from a grad party and haven’t made it to town yet.

[Phungki]

Originally Posted by dsraven

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

I do not have that fuse/breaker hooked up yet. It did come with my kit tho and will get put on when I know I’m done routing wires and relocating the battery.

[Phungki]

Originally Posted by leegreen

here is the manual for that harness
https://www.painlessperformance.com/Manuals/20105.pdf

and the battery/charge section
Attachment 2275667

So the red wire to alt will always be hot, but when the alternator is not running connecting it should not result in a current draw so test your alternator

The white wire should not be hot when the switch is off. Put MM or test light between white wire and ground.
1) unplug everything on the ign switch, if it is still hot pull the midi fuse between battery and fuse block, it should go dead. If it does not maybe there is a short between two positive wires between fuse box and battery.

2)If the voltage goes to zero with midi fuse pulled put it back, lets look at fuse panel:
Attachment 2275669
The hazard flasher, horn relay and all the fuses in lower diagram (constant power) should be pulled one by one until the voltage goes away or you have them all pulled.
If you still have voltage on white wire start pulling everything else on the fuse panel until it is empty.
If you still have voltage with empty fuse panel there is a short in the panel or the main wiring harness. and maybe it is time to call painless

Hope this helps

My alternator hook up isn’t like the one in the diagram. Originally I was just trying to start the engine after the rebuild and installation and get it to the muffler shop which did happen.

The 2 small wires (exciter and power) come directly from the fuse box into the plug in alternator.

The heavier gauge red wire goes from alternator output directly to the battery.

Thats it.

[Phungki]

Im guessing this is the “midi fuse”? Looks like the wire (heavier gauge) that goes between the fuse box and battery and the wire that goes to the alternator runs thru it.

[leegreen]

that looks like a junction.

The Midi fuse is described on pg62 of the PDF I linked. Looks like they supplied a fuse with a bolt on each end, so when I said 'pull' it in the earlier post, just unbolt one side. Trying to narrow down the search area.

[mr48chev]

Now we have the issue of not knowing exactly which kit was installed in your truck.

That Car PFD that Leegreen poststed may or may not have a lot of the same pieces that a truck harness has and if it is a generic from the parts house shelf "universal" harness it may not have features a vehicle specific kit has and searching shows that there is no 55 second series specific kit but several that "will fit" That has been my big gripe with Painless and wiring trucks, you end up with a universal harness that you have to make work.


The Midi fuse has absolutely nothing to do with charging, If it is letting power go through it to the fuse block and switch it is working perfectly. It's only real function is to blow an cut off power if there is a short or draw that exceeds it's amp rating. Otherwise it is just part of the wire and absolutely has no affect on on charging or anything else and cannot have any effect.
Depending on the age of the harness (when it was made and sold) it may have a circuit breaker, Midi fuse, fusable link or if the installer didn't put one or the other in nothing. Still if you get power to the inside of the truck it is working end of story.
I HAVE TO SAY IT AGAIN AND READ THIS GOOD, PLEASE DO NOT POST NONSENSE THAT HAS ABSOLUTELY NOTHING TO DO WITH HIS ACTUAL PROBLEM JUST TO SOUND LIKE YOU KNOW SOMETHING AND THIS IS AN EXAMPLE OF THAT. This is an on going problem that we have when people throw out things that have nothing to do with the person's problem.



Now, when the key is off there should be no power at the exciter wire. That could keep the alternator energized an quite possibly cause the draw. Other than that I suspect that the alternator has been carried to where it can be tested by now.

[leegreen]

The PDF I posted is to the same painless part number as phunki said he was using.

This is a recap of where I think we are at:
1) white wire always shows 13 volt current , even with ignition switch disconnected and everything in fuse box pulled. It now has a diode which did not change that.
2) there is .7 volt current when ignition is disconnected, fuse box is empty and only the main battery cable is connected to alternator

1 is probably why the battery goes dead overnight 2 would drain the battery eventually but slower

[mr48chev]

That should mean a blown diode in the alternator.

The diode added to what painless calls wire 914 is insurance that power isn't feeding back from the alternator to the ignition switch. I don't know if they wire it through the ignition circuit side or the accessory circuit side though. Accessory side wouldn't feed back to the ignition circuit and keep the truck running when the key was off. I'm going to have to dig out my text books on alternator testing and study up a bit on that one.

Lets still stay on track with the actual issue an not go off base with things that cannot be part of that issue.

Issue: the battery drains when it is hooked up in the truck.

Normal reasons why a battery drains"
Bad battery
Bad alternator
some accessory (usually electronic) staying on and drawing power. Head unit, amp or another device.
A light staying on such as a glove box light, dome light or the brake lights coming on because the pedal dropped just enough to trigger the switch. I once worked on a car on a car lot that had a dead battery every morning. tested this,tested that and got under the dash to check something and looked up and the map light next to the dome light was on. Had a couple that the glove box light switch stayed on all the time. My mom's F250 I still need to adjust the brake light switch some because it sometimes doesn't shut off. That is off base but each is simple stuff that caused a problem at one time.

My understanding is that there are not a whole lot of extra things on that truck that might be a cause. That is good because that eliminates those from the list.

[my56chevytruck]

Originally Posted by unclebrad

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

great suggestion, thanx

[mr48chev]

A battery cut off is good for minor parasitic drains but shouldn't be the cure for the kind of drain that Phungki has. That has to be fixed. If something is causing a drain on the battery in a two or three week time period then the cut off switch would be good. Trouble is that in a lot of rigs that is the memory in the sound system or the clock in your radio or your high dollar clock that took three years to find. Do you really want to reset your clock or reprogram you radio after you have the battery disconnected for a length of time?

[Phungki]

I couldn’t get out there much last week but I was able to yesterday and so far today. Though Id give an update.
Took the alternator in, checked out good but they offered to switch it out since it’s warranted I did that.

I bought a new MM since mine was a hand me down from my late granddad and was showing a -14 plus volt draw on a 12v system. New one reads -12.7 volt draw. Not good of course but at least more accurate. Also picked up a test light.

Still has the -12v draw with everything hooked up BUT the ignition. I haven’t hooked that back since I started diagnosing the issue.

So we eliminated the ignition and alternator (i think, right?). The battery is a brand new optima red top battery. Should be ok. Reads 12.70 when I hook the MM up to it. I’ve looked at the back of the fuse box to see if it had anything looking odd. Looks like good clean work. No wire strands crossing terminals or anything odd. Doesn’t mean that the right wires are being put where they belong though I guess.

Question:is it odd that the parasitic draw is exactly the same as what the battery reads? 12.70/-12.70

Again, nothing is hooked up or even in the truck. No lights or radio. If it wasn’t required to start it than its not in it. Once this issue is resolved, I’ll start putting doors and fenders on. Right now they would just be in the way.

Thank you to those who have offered suggestions. I’m afraid Im failing Mr48’s class at the moment.

[leegreen]

the voltage you read will always be same as battery voltage unless there is resistance in the circuit. A current leak that would drain your battery overnight I would expect to read full battery voltage.

With the new MM do you still have the fractional volt draw you saw before?

With the ignition switch totally disconnected you should only have power at one wire for ignition switch, at the main wire to alternator , maybe red wire on alternator and at starter main terminal.

Take your test light and go on a hunt for anything else that is live

[mr48chev]

I'm thinking that you are showing battery voltage and not a draw.

From the items that you said you had or didn't have on the truck you just don't have a lot of places for electricity to trickle off to.

One thing that I didn't think of and we may be missing. Pull the plug off the alternator and with the switch off and the key out check for voltage at the end of the exciter wire in the plug. You should not have voltage there unless the key is on in the run position.
That would energize the alternator and you should not have power there when the key is off. That would mean that the exciter wire is wired wrong and is going to a hot all the time pin rather than being switched on when the ignition is on. If you are following behind somone else, they may have changed it because the engine wasn't shutting off because of feedback to the ignition.

If there is no power at that pin on the plug with the key off and power when the key is on it is working correctly.

If there is power at the exciter pin in the alternator with the plug unpluged you have a blown diode or bad regulator as that should not have power at it.

In other news, I am amazed at the number of wiring issues on hot rods, custom cars or vintage pickups start out with "I've got a Painless wiring harness" . I'm thinking that the people wiring them up are not following the instructions to the letter or the "universal" aspect of the kits add a lot of confusion. There are a lot of either, or and iffs in their instruction sheets.

[dsraven]

thats kinda what I was saying back a few posts about unplug the alternator and check to see what is what. if the alt is completely disconnected and there is still a draw then something else has been gremlinized.

[mr48chev]

Originally Posted by dsraven

thats kinda what I was saying back a few posts about unplug the alternator and check to see what is what. if the alt is completely disconnected and there is still a draw then something else has been gremlinized.

That is a method of no cost testing that works.

The big problem is that the truck is in a spot away from home base far enough away that it takes a bit of effort to run over there. That and like a lot of folks his time for the truck is a bit limited. That cuts down on what he can do at one time and he probably doesn't have internet access or even a computer there or good enough internet to use the app on his phone. Meaning, Try something, check something and go home and post it and start over.

[dsraven]

I suggest to take some tools, go do some tests and write down exactly what you did and how, what was connected and what was turned on etc. take pics if you can. then if it still does what its been doing and you run outta time you can write a detailed post about those tests and results.

[Phungki]

Originally Posted by mr48chev

That is a method of no cost testing that works.

The big problem is that the truck is in a spot away from home base far enough away that it takes a bit of effort to run over there. That and like a lot of folks his time for the truck is a bit limited. That cuts down on what he can do at one time and he probably doesn't have internet access or even a computer there or good enough internet to use the app on his phone. Meaning, Try something, check something and go home and post it and start over.

my truck is here in my garage, I can’t use that as an excuse.. We have taken guardianship of our 4 yr old grandson earlier this year. That has pushed the truck further down the line. I wouldn’t have attempted this when my kids were little. I had no money or free time. A couple more years and he can help 😁. Right now it has the opposite result. I tried lol.

I have tried posting things I’ve tried and the results. It has to be something so simple its stupid. Im just too stupid to know it’s simple 😁. Dont know what I don’t know. Kinda like taking a mechanic and telling him to build a house. Totally by different mind frame and set of skills.

Something that seems redundant to me is this and I’ll attach a picture

Red wire running between battery and fuse box intersects with a wire that runs between the alternator and the fuse box. They both run to the same side of the fuse box that is always hot : headlights, horn, dome light.

[Phungki]

Originally Posted by dsraven

I suggest to take some tools, go do some tests and write down exactly what you did and how, what was connected and what was turned on etc. take pics if you can. then if it still does what its been doing and you run outta time you can write a detailed post about those tests and results.

I will do this. I’ll put it all back together and start over.

[Phungki]

Originally Posted by dsraven

thats kinda what I was saying back a few posts about unplug the alternator and check to see what is what. if the alt is completely disconnected and there is still a draw then something else has been gremlinized.

Yeah I’ve done this already and I’m pretty sure I posted that. I only get a .07 parasitic draw then which led me to getting the alt tested. It tested fine but changed it anyway. Its under warranty

[leegreen]

Which terminal on alternator does that siamesed wire go to?

[dsraven]

It is pretty common to find siamese wires like that. It is to feed enough amperage without the larger gauge wire that system may normally need. Smaller gauge wires bend easier in the harness.
If you have a test light, the grandkids are in bed or otherwise supervised, and you have time, and feel like looking at your truck, unplug the white wire at the alt, with key off, and see if there is voltage there on the wire end and also on the terminal it plugs into on the alt. There should be none. If it all tests good plug it back in and do the same for the red wire. It should show voltage on the wire but not the alt side
The third wire should be larger gauge and go to the battery and have a bolt on terminal at the alt. A fuse slightly larger than the alt output should be in that line.

Those 4 year old boys wanna follow grandpa everywhere. It's awesome.