Mtman6698

Before I spend thousands at a dealer, I thought I'd try you guys' vast knowledge. Electrical problems are always expensive and elusive and usually cost the most 'cause they are so hard to pinpoint but here goes.
Got a '96 3500 dually. 150k miles. Had a bunch of stuff done to it(see sig). No problems 'till now. Got in it yeasterday to drive home. Drove it over next to my buddy's truck, maybe 100 yds. no problems. Had the a/c on...everything worked fine. Was loading some stuff from his truck to mine. Decided to save fuel and rolled down the window, turned off the a/c and shut it down.
Got finished, got in and started it. Saw the ABS light did not go off, nor did the emerg. brake, or air bag lights. Ran fine. Turned off the key. Started it again. Same problem. Hummmm, I said and started off. Went to roll up the window, no go. Switch dead. OK, I just go with the window open... then noticed I wasn't getting a/c. Turned off the fan switch and wala...the emerg brake light and air bag light go out. The abs light is still on and the windows still don't work. Turned the a/c fan switch back on and the emerg brake and air bag lights come back on.
Stopped and took inventory: Radio works, as does the elect seat. The wipers work, cigar lighter works as does the lights. Horn works, interior/exterior lights and even the cruise control and elect door locks work. The key buzzer thingy works and all the lights come on, that normally come on, when ya turn on the key.
I got home and left it. Today I went back out and had the same broblems. So took all the fuses out and checked 'em. All are OK. Checked the engine fuses(under the lid by the battery)... all OK. I have had no burnt wire smells and no other problems. I am usually not too bad at chasing down stuff but this one has got me baffled. Any Ideas????
Thanks in advance...
Wayne

59FORD

First I would disconnect the battery then run around the truck 3 times
in a counter-clockwise direction.

Reconnect the battery and see what happens.


Hey! it's a thought


I'm still working on the pulsing alternator.

John Faughn

sounds like a bad ignition switch to me , need to get a wiring diagram and see if the wires that should have pwr. key on, have power when the key is off, if some of the circuts have power key off that should'nt then unplug switch and check your lights again if there still on then its some thing els ,but if the lights go off then its most likly the swt.

Mtman6698

Hey 59FORD, I know you thought you would be a smart a$$ and inject some humor into this mess, but by golly, it was something I had not checked. I figured if it still started, I had juice. Checked the batts and they are low, meaning the alt probably kissed me goodby. Can't find my Haynes now. Anybody know how to check the output of the alt with an ohm meter? And, would a bad ign switch(thanks John) cause the alt to quit charging the batts? I am pretty much in over my head on this. I don't want to just run out and buy a bunch of un-needed parts, just the ones to fix it!
Thx...
Wayne

camelracer

You could check the alternator output voltage with your meter. Should be about 14v if its working. Check it with everything off and the engine warm (heaters off). Most parts stores will check it for free.

handymantim

I'd pull the batteries and have a parts store give them a load test. If one of them is bad get two new ones while you're at it.

Once you get the batteries sorted out then check the output of the alternator by putting the volt meter leads on the battery terminals....like already said should be about 14 volts.

My bet is you have a bad battery and/or dirty terminals.

Mtman6698

I've got the bats on a charger now and going to let it run all night. Hopefully, it will right itself and I can get the window closed. I am in Florida right now and it is not the place to have your windows down. Then I will get a new alt. I had one bad batt a week ago and replaced it and charged it all up. Now they are low again so I suspect the alt. Sure don't want to spend the 300 bucks but it lasted nearly 10 years, so no complaints. Still have not figured out how low batts are causing only partial outages. Think John Faughn has narrowed it some to the switch. I have no idea how to swap that out. Guess I'd be a poor car thief. I'll get after it again tommarrow.
Thanks again all....
Wayne

handymantim

When a battery shorts out internally it does weird things. Things like you are experiencing.

You could also have a ground problem which will also do weird things.

I would not replace that alternator until pulling the old battery out and giving it a load test. Make sure your terminals are clean. If the battery wires are corroded consider replacing them. They can corrode inside the terminals and fail where you can't see.

When/if you pull your alternator, have a parts store (or two) bench test it before buying a new one.

59FORD

Mtman6698

You thought I was I know. I have found that them high dollar
batteries will sneak a vacation when you least expect it.

BTW, doesn't the pcm control the alt on a 96 ???



I keep having these thoughts, BUT I don't hear voices ......... yet.

RAM2940

If your alt. checks out on a bench test, it could be your voltage regulator which i believe is in the PCM. If this is the case you can install a seperate regulator by following the directions in the tech facts section. If it does turn out to be the voltage reg. a replacement pcm is around 400 to 500 dollars.

John Faughn

If you get the truck started then drive to the checker auto parts place you mentioned and ask them to load test both the Alt.& batteries , most of those places do that for free, never replace just one batt. in a battery bank becouse the way they work is its like a chain , the batt. bank is as good as the weakest one, if its been that short a time scince you put in the one then it will not cause a problum , when you get a 2nd battery make sure its the same mk. & md, . Next is when there is low voltage it causes all kind of problums with electrical , espeacally relays and computors, but if the prob. is rectifide soon enough then it usally will not cause a problum.

apwatson50

Parts stores like checkers, at least the one I worked at, have a hand held battery and alternator checker. Although I am not sure how it would work on a system with two batteries. It does work on single battery systems just hook it up to the batter, checks the battery, start the truck, checks the starter, then it checks the alternator with no loads, then turn head lights on checks with the loads on. It can sometimes tell whats wrong in the alternator, like the diodes, etc.

SoTexRattler

Hey fellas, doesnt the PCM have to sense that the engine is running via the crankshaft sensor on 2nd Gens? If it doesn't see rotation, it won't enable the voltage regulator ckt. At least that is what I have learned from reading DTR...
I believe if the Tachometer shows to be working, the PCM is indeed seeing engine rotation, and SHOULD enable the alternator regulator to function.. But a simple misalignment or failure of the RPM sensor over the harmonic balancer notches can cause a bunch of things to act weird on these trucks!
Make sure you check that out before $pending lot$ of buck$ on a replacement PCM...

Good luck!

My "esperience" with alternators is most die simply because the brushes are worn down to mere nubbin's, or you were a good samaritan and helped someone jumpstart their electrically screwed up vehicle. (will I ever learn?)

Keith

Sidewinder

You might want to check for a recall on the ignition switch and the headlight switch. I got them both done on my '95 last year - free. Might be the problem.

Mtman6698

Well, back from work. Got 2 new 800 ccw batts. As I suspected, no change. As I had the batts disconnected and put new ones in, the system had a chance to "reset", if it does such a thing. I put the charger on it for a while and then tried all the things again. Window inop, abs, emerg brake, air bag lights on, no heater-a/c fan. Now then, I might have a short thru???? Here goes: The abs light stays on all the time but the air bag will go on/off with movement of the fan sw and the emerg brake light goes dim. Those two lights will also go on and off with changing the gear lever. Drive or reverse they do like moving the fan sw. As a side note, when I turn on the a/c, the compressor kicks on...just no fan. I still can't find my book. If any of you have one that covers my truck, does it show where any of these wires meet; the windows, the abs, the fan, the emerg brake and the air bag? Is it in the ign sw?
Got the weekend to work on it now. Only have to dodge the hurricane that is comming to my house. No biggie... they seem to show up on a regular basis nowadays...lol.
Thanks for your help and suggestions.
Wayne