Battery draw

[72Chey]

So I have an electrical gremlin that lives inside of my 72 K20. Not sure where or why. For a while I was just disconnecting the negative cable as a quick fix. I work 6 days a week and live as a care taker for my uncle who is dying of cancer. I got tired of popping the hood over and over (the hood latch doesn't pop, have to pry it with a screwdriver) so I installed a battery kill switch and thought that would solve it until I had time to really dive in and investigate. Everything was going good. Started up fine everyday. I had 3 days off to take my uncle to San Francisco for some doctors appointments and the truck was parked the whole time with the kill switch in the off position. When it was time to leave it was dead. Just our luck. I posted some pics of the install. Maybe I did it wrong? I know I really need to find the real problem but I need a bandaid for now. Thanks fellas!

[ratty69]

In the second pic, it looks like you've got a small black wire ( 10 gauge? ) that comes from the negative terminal, and goes through a yellow but connector. If that's connected to anything, you've bypassed your kill switch.

Before you go deeper, load test your battery. Once a battery has been run flat, it never comes back 100%. The more you do it, the weaker it gets. Quickly.

Then, verify your kill switch is actually open. I work will lots of equipment with kill switches, and have seen a couple fail in the closed position ( handle shows off/open but contacts inside stuck closed ).

[B. W.]

Ratty is correct, check to insure the switch is indeed open when off. If you're running the kill switch through the negative side & the battery is still discharging with the switch off then the battery case is dirty (allowing a path to ground) or you have a bad battery. Did it discharge when you were disconnecting the cables?
The real solution is to locate the key off drain. Unlike newer vehicles, these trucks don't have a lot of components that will cause key off drains. I would check anything aftermarket that is wired in first, second I would check the alternator/regulator. You really need an amperage meter to check for drains but a test light will work in a pinch.. I'm sure there are some youtube videos out there that do a better job explaining than I can.

[72Chey]

I think the battery has been dead and jumped so much it won't hold a charge anymore. Did a roll start the other night (thank God for 4 speeds) and it runs and drives fine with the lights nice and bright. The 10 gauge wire coming off the negative post isn't connected to anything and I don't have any accessories. I don't even have heat ac radio or a cig lighter. I found a test light in the barn and the switch seems to check out. I'll look into some YouTube vids

[72Chey]

Oh also I put a new altenator in last month too because it was overcharging the last battery. It actually got so warm the tie down caved in the sides. The current battery is from my uncles '51 willy's that is in the barn. Says it's from O'Reilly June 2015 so not to old

[B. W.]

First, confirm you have a good battery. Most parts houses will load test it for you.

You replaced the alternator, is it an internal regulator alternator or external regulator? (is there a regulator on the driver's side radiator support?)
If it is external, you need to replace the regulator, it controls over/undercharging of the alternator.

If you still think you have a key-off drain then here goes: With everything turned off, disconnect the negative cable. Clamp the lead for the test light on the battery terminal, touch the light to the cable. (or vice versa) The test light should NOT light up. If there is a drain the light will be on. It may be very dim (small drain) if it is is bright it has a large drain. Remove fuses from the fuse block one at a time & watch the light. When it goes out, the drain is on the circuit you just pulled. If you pull all the fuses & the light is still lit, start disconnecting anything that has power straight from the battery. I'd start with the alternator. Same thing, the light will go out when you disconnect the drain.

[MagmaJct]

Looking at your pics, it seems to me your kill switch only prevents the starter from receiving power. Unless you think your starter is the source of your parasitic load, that's not going to work.

It looks like you have a yellow wire going from the battery positive to the junction block on the fender.

But I agree with what others have suggested. Perhaps your battery has an internal resistance that is causing it to self drain. A load test would likely rule that out.

[72Chey]

I'm taking the battery in for a load test tomorrow. I put a new regulator in this morning (external) but it has This connected to it (see pic) was bolted on the regulatorbut not plugged into anything. I did a role start yesterday and it ran fine except I have no low beams now lol I'm so confused

[MagmaJct]

Originally Posted by 72Chey

I'm taking the battery in for a load test tomorrow. I put a new regulator in this morning (external) but it has This connected to it (see pic) was bolted on the regulatorbut not plugged into anything. I did a role start yesterday and it ran fine except I have no low beams now lol I'm so confused

You can buy a decent load tester at Harbor Freight.

That device you're holding looks like a condenser. Considering the original voltage regulators were mechanical devices (with contacts) a condenser was likely used to extend the lifespan of those contacts.

I should double check my truck. I think I have the original regulator, and I'm not sure it has a condenser.

['68OrangeSunshine]

Originally Posted by 72Chey

I'm taking the battery in for a load test tomorrow. I put a new regulator in this morning (external) but it has This connected to it (see pic) was bolted on the regulatorbut not plugged into anything. I did a role start yesterday and it ran fine except I have no low beams now lol I'm so confused

That condensor in the picture is for noise suppression for the Radio, CB, Cassette Deck, etc. The Ignition Capacitor [boosted spark] was inside the distributor cap, bolted to the breaker plate with the points.

[MagmaJct]

Originally Posted by '68OrangeSunshine

That condensor in the picture is for noise suppression for the Radio, CB, Cassette Deck, etc. The Ignition Capacitor [boosted spark] was inside the distributor cap, bolted to the breaker plate with the points.

Thanks for the clarification! Much appreciated.

[dmjlambert]

A couple of thoughts:

As MagmaJct mentions, the way you have that cut-off switch wired, it just prevents the starter motor from getting power. But that doesn't mean you have to wire it that way. You could go ahead and run the large wire directly to the starter as from the factory, and then run the smaller wire (yellow wire on your truck) through that cut-off switch.

I recommend make sure you have a 16 GA fusible link wire connected to the battery and then connect to the rest of the electrical system from the fusible link. Fusible link is a special type of wire that will burn up before the biggest unfused wire in your electrical system (12 GA) and therefore protect the system, so it is sort of like a fuse. It has a special non-flamable insulation.

I recommend not using repair terminals, the type with a clamp that goes on the battery terminal, and another clamp to connect the wires. Get a fresh wire with the battery post connector built-in.

So, if you want to use that cut-off switch, get a fresh positive battery cable from O'Reilly and connect the fat cable between the battery and starter. I bought the 4 ft 4 GA one for the positive side and the 30 in 2 GA one for the negative side. Connect the small wire leading from it to 6 to 9 inches of 16 GA fusible link. Connect to the other side of the fusible link to enough 12 GA wire to go to the cut-off and back to the junction block on the fender.

My thoughts do not address your key-off drain, but tips about that stuff are covered by others such as B. W.'s answer. The cut-off switch is probably a good addition to your truck.