Alternator trouble

[Davidg]

This is an 85 model cucv 1008 truck. It is currently being used in the fire service.

Here is the story. Still 24 volt system. Volt meter shows voltage of the front battery. It will continue to go down until we finally have to charge the front battery. We sent alt. 1 off to be rebuilt. After reinstalling, still had same trouble. Then sent alt. 2 in for a rebuild. After reinstalling alt. 2 we still have the same trouble. I would also like to add that this trouble started after we got the truck back from having head gaskets replaced. Don't really think that has anything to do with it, but wanted to add it. Gen. 2 light comes on with the key in the on position. I don't think Gen. 1 ever has. Both bulbs are good and contacts look ok. Both batteries checked good at the parts store.

Not running - front battery voltage is 12.10 Rear battery is 12.95

Running - front battery 11.98 Rear battery is 14.37

Running - Alt. 1 shows 11.94 volts and alt. 2 shows 26.3

All the wires on alt. 1 appear to be doing what they are supposed to. Wire 1 shows front battery voltage all the time. Wire 2 shows voltage when the key is turned on. Big red wire show front battery voltage. Ground wire shows to be grounded. There is one other wire that snaps on the back of alt 1. Haven't figured out what it does yet.

Where do we go from here?

Thanks,

Davidg

 

[Ken_86gt]

If you havn't yet, you need to download the TMs for the vehicle from the resources section. The TM 9-2320-289-20 and -30 have electrical diagrams and troubleshooting instructions. If you look in the appendix F-9 you will see the charging circuits.

If you don't see the GEN 1 light on when the key is turned to on, then that alternator will not charge. Sometimes it is simple as a bad bulb in the dash or a bad connection somewhere.

 

[glcaines]

I would immediately suspect that whoever did the head gasket repair reconnected some wires incorrectly. Too much of a coincidence that the problem started when the vehicle was returned to service. As Ken mentioned above, download the TM and trace all wire for proper connection.

 

[1stSarge]

Agree with everything said so far. If the bulb is good, then a bad/dirty connection is suspect. This could be at the firewall connector, the fuse block, or in the instrument cluster connector or bulb socket. Also, look for things like this;

 

[camogriz]

It sounds like a bad or not re-connected ground strap or wire after the head gasket replacement. There are several that reside on top of and the sides of the motor and might explain the erratic electrical problems.

 

[Warthog]

Welcome to Steel Soldiers.

Visit the CUCV Wiki page and download the Tech Manuals that are listed

Cucv Wiki - Steel Soldiers::Military Vehicles Supersite

From your description your GEN1 is not working. With the key on and engine not running, both idiot lights must be working for the alternators to work. They are part of the excitor circuit.

When testing the alterernator wiring on a stock system you should have the following

GEN1
large red wire - battery voltage from the front battery via the 12v terminal block
small red wire on 2plug - battery voltage from the 12v terminal block at all times
small brown wire on 2plug - battery voltage when key is in run position
large black wire - ground from engine block to alt case ****** This is probably your problem ****** **** THIS WAS HIS PROBLEM ****
small black wire w/white stripe - ground for STE/ICE diagnostic system
small brown push on wire - tach for STE/ICE diagnostic

GEN2
large red wire - 24v from both batteries via the 24v Positive terminal block
small red wire on 2plug - 24v from both batteries via the 24v Positive terminal blockat all times
small brown wire on 2plug - 24v via the GEN2 relay when key is in run position
large red wire w/white stripe - 12v feed from 12v terminal block
small orange wire - ground for STE/ICE diagnostic system
small black wire w/capacitor - removed on most trucks

The CUCVs run most of the truck off of GEN1 which is on the drivers side and the front battery. The starting system, glowplugs and the diagnostic system run on both batteries and GEN2 which is the passenger alternator and feeds the back battery.

Check and clean the 2plug connector on the alternator and replace it if necassary. Also check the black ground wire on GEN1.

Right click on thumbnail and choose "Open Link in New Window"

 

[Screamin' Metal]

Just let me say this....I can take these puppies apart and put them back together with my eyes closed....

1.Check for bad fusable links.
2.Clean all your ground wires and electrical connectors everywhere on the alt., on your 12 v. tap on firewall.
3. Download the TMs and study them thoroughly....they area very valuable part of your troubleshooting procedure...
4. Charge your batteries up. On a CUCV, between 12.75 and 12.5 is what your batteries ought to stay, the minute one hits 12, you got a problen somewhere....either the elect. system on the truck OR the battery.

 

[Monty]

It sounds like theres a problem with the front alt. Start the truck and check the posts on the back of the alt, you should have 13-14vdc when running on each altenator.

If not the one that is low has an issue, I ran through the same problem with my 1009 when I got it. I changed out the one altenator and it still wasn't correct, tested it and I had the same readings seems I recived a bad alternator. I replaced it with the other one I purchased and the gen lights went off when the switch was turned like it supose to and everything was right as rain.

It sounds like someone hooked up the wiring wrong.

 

[MuleMac01]

ok can i ask a question? If a grounding wire on the driver side alternator breaks can power be drained out of the batterys to a point where the truck wont start?

 

[CUCV85]

nice post

Welcome to Steel Soldiers.

Visit the CUCV Wiki page and download the Tech Manuals that are listed

Cucv Wiki - Steel Soldiers::Military Vehicles Supersite

From your description your GEN1 is not working. With the key on and engine not running, both idiot lights must be working for the alternators to work. They are part of the excitor circuit.

When testing the alterernator wiring on a stock system you should have the following

GEN1
large red wire - battery voltage from the front battery via the 12v terminal block
small red wire on 2plug - battery voltage from the 12v terminal block at all times
small brown wire on 2plug - battery voltage when key is in run position
large black wire - ground from engine block to alt case ****** This is probably your problem ******
small black wire w/white stripe - ground for STE/ICE diagnostic system
small brown push on wire - tach for STE/ICE diagnostic

GEN2
large red wire - 24v from both batteries via the 24v Positive terminal block
small red wire on 2plug - 24v from both batteries via the 24v Positive terminal blockat all times
small brown wire on 2plug - 24v via the GEN2 relay when key is in run position
large red wire w/white stripe - 12v feed from 12v terminal block
small orange wire - ground for STE/ICE diagnostic system
small black wire w/capacitor - removed on most trucks

The CUCVs run most of the truck off of GEN1 which is on the drivers side and the front battery. The starting system, glowplugs and the diagnostic system run on both batteries and GEN2 which is the passenger alternator and feeds the back battery.

Check and clean the 2plug connector on the alternator and replace it if necassary. Also check the black ground wire on GEN1.

Right click on thumbnail and choose "Open Link in New Window"

Your the man, great post

 

[Warthog]

ok can i ask a question? If a grounding wire on the driver side alternator breaks can power be drained out of the batterys to a point where the truck wont start?

On a stock system, yes.

A stock alternator uses the ground post and black ground wire, and not the case to complete the circuit.

If the drivers side ground wire is missing, broken, corroded or defective in any way, then the circuit can not be completed and the batteries will not charge.

The truck will run until the front battery is drained and can not supply the required 12v to the Injector Pump fuel solenoid.

Good question.......

 

[Davidg]

We found the problem!

Somebody on another shift found the problem. Haven't got to talk to them about it yet, but I think the ground wire from gen. 1 had a break in it. They found the wire to be getting hot. Wire replaced and now it is charging like it never has in the past. Gen 1 light now comes on along with gen 2 light when the key is in the on position.

Thanks for all the help!

 

[Warthog]

Somebody on another shift found the problem. Haven't got to talk to them about it yet, but I think the ground wire from gen. 1 had a break in it. They found the wire to be getting hot. Wire replaced and now it is charging like it never has in the past. Gen 1 light now comes on along with gen 2 light when the key is in the on position.

Thanks for all the help!

Good job!!!

If you haven't done it already, make sure you visit the CUCV Helpful Threads sticky and also download all the Technical Manuals. They are a life saver and they have all the wiring diagrams to boot.

http://www.steelsoldiers.com/showthread.php?123199-CUCV-Helpful-Threads

And check out the CUCV sticky. Alot of good info and some junk also .

http://www.steelsoldiers.com/cucv/20600-faq-thread-cucvs.html