lovin1stgens

My truck needed a jump today, it showed all signs of the battery just being run down. So I had a kind apartment neighbor give me a jump start. It started very rough but did fire. After getting it going, I realized I had absolutely no electricity. No lights, signals, radio, horn, nothing. A random side not is my odometer isn't running (which is odd because I thought the entire system was entirely mechanical).

I'm wondering if anyone has had this sort of a problem. I can go through and chase down all the wires and look for ground shortages or burnt wires, throw a new battery in it, or a new alternator. Those were my ideas to solve the problem. All of those are either extremely time consuming or expensive.

I have never really understood exactly what the fuseable links were connected to or what relied on them. Could this be my issue?

Any help is greatly appreciated.

oliver foster

If the PCM is dead it will not charge.
Other things that stop working when the PCM is bad, is the cruise control and wait to start features.

I am thinking a bad PCM would have caused the battery to drain the last time you drove it.
Now this morning the battery is dead and the alt in not charging because the PCM is the Voltage regulator in a '93

oliver foster

Also the '93 speedo is not mechanical, its electrical.

Rick 12v CTD

Could be an issue like above but it could be the alternator as well.

My truck did the same thing when the alternator went out.

oliver foster

Very good point...

lovin1stgens

to add to my confusion, the lights, signals, radio, and horn would not work, but my windshield wipers would work SLOWLY as would my windows. My "Brake" light was working at first, I guess I never checked it towards the end of this discovery process.

Im assuming that a bad alternator would cause the electronic speedometer to not work, but then why would the windshield wipers and side windows still work (slowly) ????

If it is an alternator, where is a trusted place to have this tested? Ive always been partial to O'Riely's out of the auto parts stores as they seem to be a little more...competent.

lovin1stgens

Also, would a PCM out of a 91 work on a 93? I believe I yanked one of those out of a parts truck. That being said I have no clue in what type of condition it is in. The parts truck was a 91 2 wheel drive manual everything getrag. Mines a 93 4x4 nv4500 conversion LE power everything (cruise hasn't worked for about a year...still need to fix that)

simplysmn

Your 91 PCM if it's from a 91.5 truck will Not Work . the early truck's had external reg on charging system and no CPS on the crank .so no signal for over drive .

lovin1stgens

Ok, at least I know it won't work. Thanks for the heads up.

I went out and fiddled with it a little more. The alternator looks fine. The connectors haven't arced and welded themselves together like I have heard of happening before. I understand that doesn't mean that it's not junk. I'm probably going to pull it and have it tested tomorrow.

I would turn the key to the grid heater cycle stage and the dash lights would come on, as would the headlights. That's when it started making some odd sounds. It started popping like the grid heaters were turning on and off. Once that stopped for the most part I heard a ticking noise. I do have an electronic 2nd gen fuel pump, so it may have been that sounding different than ever before due to less power bein thrown at it.

It's always one thing then another on this pig, but what can ya expect from 21 year old components? I'm trying to tell myself that I'm "restoring it one piece at a time" haha

Brian.B

would the ignition switch wires cause this ,,mine melted under the ignition switch a little my switch was getting really hot and caused me to loose power to different things.

bannerd

Anything that is electrical in these trucks are not mechanical. They require some sort of alternate resource. It shouldn't stop the truck from running by any means though. The engine is truly mechanical at heart and needs only diesel to run.

With that said, the alternator supplies power but it's not a steady power because it's based off the engine RPMS. All you would really need is a strong battery to tell you if the PCM is gone. A brand new battery should have enough juice to supply power to the truck to start it and run all the accessories for a short while. The alternators job is to keep that battery charged. With that said it could be those two things. The battery is just shot and even though the alternator is giving power to it.. it's not holding the charge. OR it could be the other way around.. the battery is good but the alternator is bad and now putting power down to the cell.

If those two things check out to be working fine then look at the fuses, check them for breaks inside the plastic or black blown out crud. Also check the in-line fuses by the grid heaters, sometimes these rot and cause all sorts of issues. An electrical tester would be a easy way to figure all this out Craftsmen makes one that also does continuity which makes quick work of fuses.

j_martin

Like he says^^^

All your symptoms are those of low voltage, ie dead battery. The battery dies when it's not being kept up by the charging system.

If you have about 6 volts or more to the fuel shut off valve on the IP, the engine will run. That's low enough so nothing else will work right.

Usually there's no external burn marks or melting indicating a failure in the alternator. The most common fault is simply worn out brushes so the field doesn't get current. The whole charging system has to be systematically checked out to find the actual fault. Just throwing parts at it can be expensive and usually isn't that productive, unless you have found a way to reliably win the lottery.

Rick 12v CTD

^^ what he said.

You can check to see if the alternator is making power when the truck is running if you have a volt meter

Check the easy stuff first (battery and alternator) and then move on from there.

Low voltage can create some interesting issues, and so can a bad ground.