SirDemos369

Hello Everyone,

I just purchased a 1990 Pickup 22re DLX MT. It started, and ran without issues for the first couple of days. I drove it on a handful of short trips, and had no issues whatsoever. During this particular day last week I drove the truck two times in the morning, and then when I went to start it in the afternoon, absolutely no power anywhere. No gauges, no horn, no hazard lights, no responses to anything. There was probably a 4 hour stretch where it was parked in the driveway between the last trip and the power loss, nothing else happened to it that I am aware of.

I assumed that the battery had died, and I pulled up my other car next to it to give it a jump. While the cars were connected I measured the voltage of the battery with my voltmeter, it read 12.8v, and eventually climbed up into the 13.xV range. I jumped in the truck, turned the key...nothing. Again no power at all inside of the cab. I pushed the truck into the garage and left it for a couple days. When I got back to it I measured the voltage of the battery, 12.5v. I took the battery to O'reilly's and they tested the battery, they said everything was good. I checked the fuses in the engine bay visually, nothing seemed blown. Checked the fuses by the drivers door, visually everything looked fine.
I checked the fuse link cable between the battery and the fuses, nothing looked frayed or melted. I checked the 4 grounding points in the engine bay, all seemed to be in order. I disconnected them, cleaned the contact point, and replaced them.

From here I tried to trace the power through the truck, and this is where I am getting lost. I think I have found a problem, but I haven't found the source of the issue:
Battery across the terminals 12.6V
From the battery to the 80A fuse, I read 12.6V (negative terminal on battery to fuse link on the bottom of 80A fuse).
Negative battery terminal to top of 30A and 40A fuses, reads 12.6V.
Ignition key turned to On, Negative battery terminal to top of smaller fuses, reads roughly 12.5V on all of them. Under the hood and in the cab.
Positive battery terminal to 4 major grounding points: 3.8V (This is very low, and I cannot determine the cause. All of the grounds read exactly 3.8V).
Positive terminal to starter cable, 12.6V.
Disconnected the cable leading to the starter, measured grounding points again, Positive terminal to ground: 1.6V. (I cant explain this one. I thought maybe that the starter had shorted and grounded itself, I was hoping disconnecting it would return the ground voltages to normal).

This is where things get weird: Yesterday, I bought a new battery, as I ran out of things to stick my multimeter into. I connected it to the terminals, and everything worked great. Power restored in the cab, radio turned on, voltages to the grounds read 12.6V, everything is as it should be. I let it sit for about 10 minutes to see what happens, and then I go to start it up. When I turn the ignition from "ON" to "Start" everything goes dark. No power in the cab, no click from the starter, nothing. It was instantly dead again. I get out, measure the voltages, 3.8V on the grounds again. I have not had power restored in the cab since, with either battery, and the grounds are consistently reading 3.8V, while the batteries are reading 12.5V and 12.6V respectively.

My next idea is to remove the starter and take it in to be tested.
Has anyone seen this before? Is there something I am overlooking in my measurements or findings? Am I taking the measurements incorrectly?

Things to note:
The truck does have an aftermarket stereo and speakers. But, they were installed a few years ago, and I was given all of the receipts that shows that. I am not ruling those out as the issue, but it does seem odd that it would all the sudden be an issue right after I buy the truck.

Thanks in advance for the help!

JoeS

Did you do parasitic drain measurement on the battery? Disconnect the neg cable, connect a multi meter to the neg post and cable to measure the milliamp draw. It's always good to know if there is a draw or not.

SirDemos369

I wasn’t sure how to test that before. Okay, negative battery terminal disconnected, alligator clamp voltmeter negative cable onto the disconnected cable, positive multimeter cable in contact with the negative battery terminal.
I assumed we want DC, but I took both. Readings are: 0.002A DC, or 2mA, and 0.009A AC, or 9mA.


when I disconnect the cables and cross the multimeter cables with themselves, I read 0.2mA DC.
let me know if I didn’t hook up the wires correctly.
Thank you!
Edited: changed V to A labeling in description.

2ToyGuy

Just so you know, automotive systems are entirely DC, unless you find an inverter in there someplace. Especially directly from the battery. By definition, batteries are DC. In other words, you can ignore any AC readings you might get. They're false indications.

Having said all that, sometimes the current coming off the alternator, if the converter electronics in it are getting old, can have a slight variation to it. Makes the alternator output simulate AC slightly. It's really just DC with a slight voltage variation to it, not an actual AC voltage.

Does that help any?
Pat☺

JoeS

The hook-up appears correct. The positive cable is connected? The cable clamp looks painted so did you get clean metal contact with the alligator clip? My 86 22RE normal drain is 9 to 10 mA. I only have the ECU and dash clock draining. The 2 mA seems low and not sure why your meter reads 2 mA when touching leads. Mine reads 0 mA. I admit my electrical knowledge is very basic. Enough to do checks, but I struggle to find fixes. Seen replies here by people way more knowledge about electrical issues. Hope someone else can help.

SirDemos369

Thanks Pat, that does help. All of my previous measurements have been DC. With my voltmeter I could choose between AC and DC for the Amp measurement, and I hadn’t thought about it before that. I just flipped it to DC voltage, and went on without a thought before.

I am not thrilled about the painted cables, but they are bare on the inside where the connection is made to the battery. I used the normal probe ends to take the measurements originally, I swapped the alligator clip on there to free up my hand to take a picture. I got the same readings each time, so I think it was a good connection. The positive cable was connected to the battery at the time of measurement. Also the ignition switch was off. I just redid the measurement with the ignition switch on and got the same thing.

I am at a loss at the moment, I can’t figure out why I am not receiving power to the cab. I appreciate the help though! At the very least it gives me more things to test!

JoeS

If it really is just 2 mA it's definitely not a drain on the battery as the cause. Next!

SirDemos369

I was concerned about a parasitic ground, but didn’t know how to test it. I think that test eliminated that as an option.

the 3.8v when measuring between the positive battery terminal, and any of my ground points really jumps out at me. I know it should not me 3.8v, as far as I know it should read the same voltage as the battery. I’m not sure what would cause it to be such a low voltage.

My next thought is to remove the starter, and have it tested. I am wondering if it failed and grounded itself. The nut on the top of the starter assembly is seized at the moment, I am waiting for some anti-seize to creep through it, and then I’ll try to get it off again.

Any ideas what could be causing such a low reading at the grounding points?

scope103

The starter didn't ground itself; that would be a fiery mess and your battery would be smoking.

You are correct, the battery positive to any ground should be within tenths of a volt of battery voltage (especially when you only have 2 ma flowing). So work systematically. Attach the positive lead of the voltmeter to the positive battery terminal with the alligator clip. Then check voltage at the negative post of the battery, then at bolt in the negative battery connection, then at the other end of the main battery ground lead where it attaches to the sheet metal. Then where it attaches to the engine block. You'll start at battery voltage (around 12.6v, depending on temperature), and at some point your measured voltage will drop from battery voltage to something lower (your 3.6v). That's the location of your (first) bad ground.

2ToyGuy

Yesh, if you look at a lot of my posts, you'll see that bad grounds are a "thing" I have. There should be a ground in the sheet metal, one for the engine block, one for the head(s), and two inside the cab, behind each kick panel. It doesn't take much to make a ground no longer any good. Some corrosion, oil intrusion, paint under the bolt, and so forth. The ground points must all be clean, with bright, shiney metal under them, as well as the end of the wire. The terminal, which should be clamped good and tight, not loose. A good, steel wire brush can be your best friend in these cases.

Something to check is that quite often, the wires from the battery are corroded like mad. INSIDE the insulation, where it's not visible. The acid mist that regular, liquid filled, lead/acid batteries put out when they're charging, gets down inside the insulation and corrodes the wire, making them break. Ohming the wires end-to-end will telll the tale. Flexing while ohming is important to prevent a false indication of a good wire. A wire should be pretty much a dead short end-to-end. Anything much higher than zero ohms means the wire is bad, and should be replaced. I make my own cables, if needed. I make them bigger than the original, with a good, heavy terminal o both ends, and heat shrink on where the terminal clamps to the wire. The melt-wall heat shrink. It seals the connection like a dream, and prevents the intrusion of the battery's acid mist. Just need to clean the terminal once every couple of years.

SirDemos369

Alright Everyone, I am ashamed, but excited to say that I found the cause of the issue.
As everyone has mentioned, the cable coming off of the negative battery terminal was corroded, and I overlooked it in all my measurements. I bypassed it every time, and measured the negative cable connection at the battery, and then straight up to the ground on the side of the engine bay. The cable connection had some rust and dust buildup on it; quick wire brush cleaning and everything was right back to normal.
I supposed I should've just poured a can of coke on it a week ago, like my Dad told me to.

Either way, everything is running well again, and I took it for a lap around the town with no issues.
I appreciate the help everyone! If nothing else, I learned a lot about the truck over the last week or so.

Thank you!