battery problem

[jsd563]

having trouble with my front battery ..... here's whats up... this truck has the driver side alt replaced with the caddy one for over a year with no problems , about 1 1-2 months ago the truck was dead so i charged both batteries and noticed the front battery didn't pass a load test so i replaced it and no problems since today ... truck was dead again so i tested both batteries and once again the front battery had 12v but wouldn't pass the load test ... last week i noticed the gen 2 light com on and off a few times and the batt gauge was charging high like on the green/red border but has been in the normal green range since .... i did notice that there is a brown wire not connected and it looks like it should go to the driver side alt. where does it go? i don't see any spot on the alt for it

 

[richingalveston]

post a pic of the wire and someone here can tell you what it does and where it goes. sounds like your alt is putting out to much voltage causing your battery to cook. probably need to rebuild the alt. I need to rebuild my rear alt at this time. It is putting out almost 16volts.

if your truck will start, start the truck make sure the glow plug cycle is finished and then measure your voltage at the battery post, if you are over 15 volts this may be your problem.

 

[jsd563]

ok ill do that now .... ill take a pic but ive had problems in the past posting pics... the wire def goes to the alt someplace it has a rubber boot like an alt wire

 

[jsd563]

after i start it should i disconnect the rear batt to check if the front batt is charging?

 

[jsd563]

ok back batt charging at 15v and the front at 13v

 

[Warthog]

Disconecting batteries while the alternators are running is a bad idea. The electronic parts of the alternator don't like that.

Sounds like your voltage regulator is not fuctioning correctly. A rebuild may be inorder. Remove the alternator and have a parts house test it.

Have you ever looked at the wiring diagrams in the Tech manuals. Looking for any pictures of the alternator wiring (there are more than one) shows a single brown wire connected to the tach port. (diagram E-11 in the TM 9-2320-289-34). This is ONLY used for the STE/ICE diagnostic unit.

Working on and diagnosing these old trucks is like being a detective. The answer won't be right in front of you. You have to do some investigation of what is wrong and how to fix it.

Or just post here on SS and someone will do it for you.

 

[jsd563]

i didnt disconnect the batts while running .... which alt should i take off n test? or both?

 

[Warthog]

Let's see. You are cooking your front battery. I would start with the alternator that charges that one.

Hmmmm let me answer your question before you ask it. That would be the drivers side Cadillac alternator.

 

[Warthog]

i didnt disconnect the batts while running ....

"after i start it should i disconnect the rear batt to check if the front batt is charging? "

Sure sounds like you where going to.

 

[jsd563]

hahaha... nope i ask first cause i know its a different system and dont wanna fry anything or get yelled at for stupidity lol

 

[Recovry4x4]

The shift key might be the problem.

 

[jsd563]

ok found the problem while checking all the alt wires ... the driver side alt where the red wire goes, the stud that the wire goes on came out with the wire it looks a little burnt no idea why this happened but it looks like a trip to get a new alt

 

[jsd563]

Any clue why this would happen? before I fry another battery and alt.... Oh BTW I fixed the shift key problem HAHAHA!

 

[swbradley1]

The shift key might be the problem.

That's hilarious.

Unfortunately it is lost.

 

[doghead]

Is the plastic burned or the broken stud end?

If it's the plastic, heat From electrical load.
If it's the stud burned, arced after it broke.

Hard to say anything for sure, other than you need to fix the stud or replace the alt.

 

[cpf240]

Back to part of the original question, my guess would be that the disconnected wire is probably for the tach output for the STE/ICE test port under the dash. The caddy alt probably doesn't have a connection for it.

 

[jsd563]

Both, the plastic and the stud it did arc on the body of the alt but no idea why it burned the plastic in the first place to let the stud hit the alt body ... New alt on the way

 

[patracy]

Any clue why this would happen? before I fry another battery and alt.... Oh BTW I fixed the shift key problem HAHAHA!

Not so much.

Any clue why this would happen? Before I fry another battery and alt.... Oh BTW I fixed the shift key problem HAHAHA!

Might try to fix these keys while you're at it as well. . ,

Any clue why this would happen? Before I fry another battery and alt. Oh, BTW, I fixed the shift key problem HAHAHA!

 

[ARYankee]

Just to add on what Warthog said earlier in Post # 6. Not only do the TMs help but read the stickies at the top of the CUCV forum because there is a great amount of info and troubleshooting tips in there. That is usually the first place that I go if I can't figure it out from the TMs.

As far as your arcing burnt plastic issue. Vibration is usually a huge problem that causes a lot of electrical issues. Connections become loose then that creates arcing, which creates heat, then a failure occurs. A good habit to get into is to check your connections during your PMCS and check them really good during a PM such as oil change. Also using a little dielectric doesn't hurt on some connections.