GEN 1 Charging issue

[Murderouswolf]

Hello all. I am new to this site but not CUCV's. Bought a blazer to replace my last one which was stolen. It had been converted to 12v single alternator, 2 battery system. The guy had actually done it correctly but I wanted it in stock config. Changed everything back and found that one alternator was dead. I had it rebuilt and now the GEN 1 light comes on and stays on after starting. It only dims slightly after revving the engine. I removed the dash and cleaned all of the contacts and saw no difference. Heater fuse is good. Voltmeter is showing barely below the green. Both alternators are good. What gives? Thanks for your input. Relays and bulbs are good. Is there some kind of external voltage regulator somewhere? It seems like the driver's side is just not getting excited even though everything else appears to be functioning properly. Both batteries are brand new 6TL's. Filled them with acid myself and tested them both. 12.7v.

Toby

 

[m38inmaine]

No external voltage regulators, verify gen 1 is hooked up correctly. Sounds like gen 1 internal regulator may be bad. Try swapping generators and see if the light staying on problem follows the suspect gen.

 

[Murderouswolf]

Already tried that with no change. Forgot to mention it.

 

[Warthog]

Welcome to SteelSoldiers.

Make sure you visit the Cucv Wiki - Steel Soldiers::Military Vehicles Supersite (CUCV Wiki) that is at the top of the page on the CUCV Forum.
All of the CUCV Technical Manuals are listed and many other helpful bits of information.

Make sure you download the repair manuals. You can get then for free. A couple of our members have posted them on their websites.

Also the wiring diagrams are in the appendix of the -20 and -34 manuals.
JATONKAM35s HOME ON THE WEB

Also checkout the http://www.steelsoldiers.com/cucv/20600-faq-thread-cucvs.html stickey. It is where we try to post helpful tips and tricks.

Almost every question you will have has been asked and answered many times. The advanced search will become your best friend. Please don't hesitate to ask something that you can't find.

Read the TM 9-2320-289-10 Operators Manual to find out how a stock system should work. It is simular to the Operators Manual for Civilian vehicles. It tells you where all the lighs, switches, etc are located and what they do.

Three of the most important tools you can buy are:

Voltmeter and know how to use it - ~$10 and up
12v Battery Charger - ~$50 for a decent one
Battery Load Tester - ~$30 for an okay one at Harbor Freight


Now to your question.

When you reattached the alternator, which one was it? Was it an "isolated ground" (military) unit?

If it was the drivers side, did you reinstall the ground wire from the case to the engine? You will also need to check the larger RED feed wire from the alternator to the 12v terminal block on the firewall near the master cylinder. Some timess the fusable link will break.

Also double check the 2pin plug at the alternator. The contacts will get dirty and not make good contact.

Here is a wiring diagram for the alternators.






Warthog

 

[Murderouswolf]

Yes it is an isolated ground military alternator and yes I have the case ground going to the stud on the intake manifold. I have not checked the fuseable link yet so I will do that when I go home for lunch. Will update later. Thanks

 

[Warthog]

If you have a voltmeter, you can check the output voltage at the 12v positive of the alternator. Use the frame as a ground.

You should see the battery voltage at the positive terminal with the truck off and ~14.5v with the truck running.

If you do see the battery voltage with the truck off, the fusible link should be good.

But beware that if the link is partially bad, you can see voltage when it is sitting and no voltage when under load. (not enough good wires to handle the load)

 

[Murderouswolf]

There is voltage with the truck off and the same voltage with the truck running. Tried bypassing the fuseable link with no change in voltage. On the 2 wire plug going to the alternator I have 6.xx volts when it is running.

 

[m38inmaine]

If the voltage is the same as "off" then it is not charging.

 

[Warthog]

You can test the alternator on the truck. Just go to the parts store and purchase a new pigtail and some wire.

Make a jumper to excite the alternator and attach it to the 12v side of the system. Attach both leads to one wire and then the 12v source.

Start the truck and check your voltage.

This bypasses all the truck wiring and tells you if the alternator is working.

Excuse my crude drawing

 

[Murderouswolf]

If the voltage is the same as "off" then it is not charging.

Exactly. What I'm trying to figure out is, why?

 

[Murderouswolf]

Resolved the problem. Guy that rebuilt the driver's side alternator didn't get it right. Not sure yet what he did wrong but I replaced it with another alternator I had that was working when I took it off. I had the other one rebuilt at Roger's Automotive in Greeley CO. Stay away from them. Going there after work to try and get a refund. They told me that they tested it after the rebuild and it was working great. My own fault for not testing it sooner. Thanks for the help guys. Wish me luck.

 

[mistaken1]

Be polite but firm. Good luck.

 

[Murderouswolf]

Got all the money credited back and bought a new alternator instead.