Very strange gen 2 problem

[dstang97]

When the truck is cold both my gen 2 light works and also my volt meter. After the truck warms up. Both of them stop working. Alternator is good And wiring is good. I’m thinking it has to do with the relays by the starter or the gen 2 diode behind the cluster. Anyone else have this problem?

 

[dstang97]

Ain’t nobody no nuffin?

 

[antennaclimber]

Check fuse #12, it is common to the GEN 2 light and the voltmeter relay.

 

[dstang97]

Check fuse #12, it is common to the GEN 2 light and the voltmeter relay.

Fuse is good. Just switch it out or is there a way to test?

 

[antennaclimber]

I would clean the contacts and change the fuse out to a new fuse.
If it is still happening, while in the failure mode, check the voltage at the fuse to ensure that portion of the circuit is functioning.

 

[dstang97]

Update. i changed the 2 relays next to the starter relay and also the gen 2 diode. Nothing changed. I have my rear battery on a charger for now. I have no idea what’s going on. I may swap generators again and see if the problem goes to the other side. Idk I have replaced the whole system.

 

[dstang97]

I would clean the contacts and change the fuse out to a new fuse.
If it is still happening, while in the failure mode, check the voltage at the fuse to ensure that portion of the circuit is functioning.

so I cleaned the whole gauge cluster, verified everything worked. Started the truck up. Everything was working perfect. After 5 minutes I loose, volt gauge, light bulb on start up, low coolant light. After I loose everything I tested voltage at the fuse panel and getting 28v. I’m starting to think it may be a ignition switch. It’s the only thing I have not replaced. Btw. I have good batteries and alternators.

 

[Warthog]

Have you ever split and cleaned the wiring block on the firewall? I have seen strange issues because of dirty contacts in this connection. Whatever GM used as a lubricant at the factory turns into a black tar. May not fix your issue but worth looking at.

 

[dstang97]

Have you ever split and cleaned the wiring block on the firewall? I have seen strange issues because of dirty contacts in this connection. Whatever GM used as a lubricant at the factory turns into a black tar. May not fix your issue but worth looking at.

hey man, I took apart the bulk head connector and everything looked great. I’m stumped on this problem. I have fixed lots of these trucks and know these things pretty well.

 

[Keith_J]

Alternators get warm so it might be a voltage regulator intermittent issue.

 

[dstang97]

Alternators get warm so it might be a voltage regulator intermittent issue.

I switched 2 rebuilt ones and they all are doing the same. Even had them tested.

 

[dstang97]

Update I switched out the gauge cluster. Then put in a 4th alternator. Still no change. Still getting 24v to the fuse panel. At this point the only thing that has not been changed is the interior harness. After 5 minutes I’m still loosing voltage guage, 2gen light and low coolant light. Then after a few hours after it cools down everything works as should. Gonna switch out the harness and report back.

 

[frank8003]

HEAT
You already described the problem statement
Heat from somewhere is causing it
Wrapping anti-heat stuff around and about pickups and wires is inexpensive.

 

[dstang97]

HEAT
You already described the problem statement
Heat from somewhere is causing it
Wrapping anti-heat stuff around and about pickups and wires is inexpensive.

There is not much heat at 3 minutes of starting.

 

[frank8003]

There is not much heat at 3 minutes of starting.

OK, something in the wiring that sees excessive heat to itself in the first 3 minutes.

 

[chevymike]

I might be wrong but I didn't think the fuse block should be seeing 24v. My understanding is everything there is 12v.

 

[dstang97]

OK, something in the wiring that sees excessive heat to itself in the first 3 minutes.

I might be wrong but I didn't think the fuse block should be seeing 24v. My understanding is everything there is 12v.

the fuse at the bottom is 24v

 

[Keith_J]

The 2 relays by the starter relay are for the blackout light system. You have to take the dash cover to see the alternator relay. Trace the voltmeter wires to find it.
Since this relay is energized on run to enable the right side alternator, it gets warm. It doesn't draw much through the contacts, I bet it gets warm and opens. Oxidation and humidity conspire to make silver contacts less than reliable.

 

[dstang97]

UPDATE: Ok guys I figured it out and I’m pretty embarrassed but oh well. The first thing you should do is test your fuses. And I did.

I failed to see one was missing completely and did not realize it until I really stuck my head underneath. It caught my eye as I was plugging in my gp card. The fuses go from the top 1,3,4,3. Right away I realized I was missing a fuse. Thanks everyone for trying to help.