Charging and Starting Electrical Issues

[Refalgren]

Hello there. Having a few issues with my M1008 CUCV. Recently had my GEN 2 fail on me in both power generation bearing life. When it went out it took my batteries with it.

I've replaced both batteries, the GEN 2 Alternator, the Glow Plug Solenoid/Relay, and the Doghead Starter Solenoid/Relay.

Unfortunately, i'm still getting issues with the system. The glow plugs do not seem to be activating, but they all seem to be in good condition. Each still lights the test lamp when grounded. Also, there seems to be an intermittent overcharging issue. The overcharging is more pronounced when the engine is operated at a higher speed, and less so at lower speed.

The voltage readings are as follows:

BATTERIES
Front - 12.89v
Rear - 12.88v

GEN 1
Red Exciter Key Off/Plug Out - 12.89v
Brown Exciter Key Off/Plug Out - .02v
Red Exciter Key On/Plug Out - 12.7v
Brown Exciter Key On/Plug Out - 12.6v

GEN 2
Red Exciter Key Off/Plug Out - 25.7v
Brown Exciter Key Off/Plug Out - .07v
Red Exciter Key On/Plug Out - 25.7v
Brown Exciter Key On/Plug Out - 25.3v

GLOW PLUG SOLENOID/RELAY
Top Key Off - 12.88v
Upper Key Off - 0v
Lower Key Off - 0v
Bottom Key Off - 0v
Top Key On - 12.7v
Upper Key On - 12.3v
Lower Key On - 12.5v
Bottom Key On - .007v

DOGHEAD STARTER SOLENOID/RELAY
Red Key Off - 25.7v
Purple Key Off - 0v
Purple/White Key Off - 0v
Black Key Off - 0v
Red Key On - 25.6v
Purple Key On - -.001v
Purple/White Key On - .005v
Black Key On - .005v

Any insight in to where I should start looking?

 

[MarcusOReallyus]

GLOW PLUG SOLENOID/RELAY
Top Key Off - 12.88v
Upper Key Off - 0v
Lower Key Off - 0v
Bottom Key Off - 0v
Top Key On - 12.7v
Upper Key On - 12.3v
Lower Key On - 12.5v
Bottom Key On - .007v

Please clarify what you mean by Key On. Is this in the RUN position, or the START position?

Also, let's make sure what you mean by "top" and "bottom", etc. Here's my guess:

TOP = Large red wire (12v supply).
UPPER = Blue wire (goes inside the cab to the GP controller card)
LOWER = Small red wire (12v goes inside the cab to the ignition switch/fusebox)
BOTTOM Yellow wire (feed to glow plugs)

Did I get that right? If so, and if these readings are during the GP cycle, it seems your GP controller card is not providing the ground your relay needs to operate. You can test this by grounding the UPPER terminal. Might want to disconnect the blue wire first. When this is grounded, and 12v is at the LOWER terminal, you should hear the relay CLUNK and the GPs should get 12v.

If this is NOT during the GP cycle, then this is normal operation. The GP card is not grounding the blue card, so you should see 12v at both the blue and the small red wire. The top large red wire should ALWAYS have 12v (since you have done the resister bypass and have a 12v only system), and the bottom yellow should be pretty much ground.

 

[Refalgren]

- The "Key On" means its turned to the point where the glow plugs would cycle, but not turn the starter over

- Yes, that's what I meant by top, upper, lower, and bottom.

- Now that you mention it, i'm not hearing a click/clunk from the relay when I cycle the GPs. Does that affect the overcharging issue? Also, does that mean the entire card needs to be replaced, or is it something specific on the card that needs repairing?

- The resisters are the two large tubes behind the metal plate correct? If so, then yes they have been bypassed. The previous owner did that, so I'm not sure what the exact changes were regarding the modification.

 

[tequilaiam]

You shouldn't see anything on the exciters with the ignition off. Shouldn't see 24V across the pigtails on Gen 2 pigtails either. Gen 2 pigtails should be +12V between the two or +24 and +12 compared to the chasis.

Speaking of chasis, is your Gen 2 connected to vehicle ground? It shouldn't be. Gen 2 (passenger side alt) is an isolated ground. If you bought something at autozone, it likely isn't and you have two alternators in parallel both putting out +12V trying to charge two batteries in series at +24V.
But if you did that, I'd expect you'd know because of sparks/smoke/fire. But perhaps a fuseible link did it's job.


I'd worry about making sure the charging circuit is correct before the GPs and GP controller or you're going to be fighting uphill.

Start by unhooking batteries and testing continuity between the gen 2 neg. port and chasis then gen 2 neg port and +12V harness block /front battery + connector. You should see an open-circuit for the first test and zero/low resistance for the second.

My hunch is that your gen 2 is not an isolated ground unit and you will fail that first test.

 

[MarcusOReallyus]

I think you posted this to the wrong thread. I'm thinking maybe you meant to post to this thread about alternators....

 

[MarcusOReallyus]

- The "Key On" means its turned to the point where the glow plugs would cycle, but not turn the starter over

- Yes, that's what I meant by top, upper, lower, and bottom.

Okay, gotcha.

- Now that you mention it, i'm not hearing a click/clunk from the relay when I cycle the GPs. Does that affect the overcharging issue?

I don't think so.

Also, does that mean the entire card needs to be replaced, or is it something specific on the card that needs repairing?

Unless you know your way around circuit board repair, don't try to repair the card. A member here, antennaclimber, makes new cards for sale. Check out his sticky on the GP theory. You should probably start there so you have a better understanding of the system. He's done a really good job. While you're at it, check out the other useful threads. There's a good one on alternators there for you, too.

As for repairing or replacing, I don't think we're there yet. Lets find out if the GP relay is functional. If you have a good 12 supply at the small red/black wire (LOWER, in your description), the next step is to ground the blue wire (UPPER). That should engage the relay and put 12v to the plugs.

If that works, then we need to find out why the GP card is not providing ground when it should.

But back to a question that didn't get answered: Are your "key ON" readings taken during the GP cycle, or are they taken later, after the GPs should have turned off?

- The resisters are the two large tubes behind the metal plate correct? If so, then yes they have been bypassed. The previous owner did that, so I'm not sure what the exact changes were regarding the modification.

Yes, that's to drop the 24v to 12v for the GPs. Since you are already 12v, your setup is correct. You don't need those resistors. Many folks get bypass them anyway, even if they are still running 24v. So, you're good to go there.

 

[Refalgren]

That seems to be it then.

-Tested continuity between the GEN 2 neg. port and multiple chassis ground points. All show continuity instead of an open loop.

 

[cpf240]

The OP mentioned replacing the GP relay/solenoid... do we know if it is the correct type, IE isolated ground? If not, it is my understanding that a non-isolated ground GP solenoid can cause issues with GEN1.

 

[firefox]

Not sure, but I think there are kits to convert the grounded gens to isolated ground.

 

[MarcusOReallyus]

The OP mentioned replacing the GP relay/solenoid... do we know if it is the correct type, IE isolated ground? If not, it is my understanding that a non-isolated ground GP solenoid can cause issues with GEN1.

Good catch!

 

[Refalgren]

-GP relay is a new ST85 from NAPA with an isolated base.

- since the GP relay is not automatically engaging, im assuming the "key on" reading is NOT during the GP cycle.

- Removing the upper blue wire from the GP relay and then manually grounding that post DOES cycle the GPs

- As I stated in the prior response, it does not appear that the GEN 2 has an isolated neg. post. I'll be bringing the altenator to F&B Electric in Columbus, GA tomorrow morning to have it retested.

 

[MarcusOReallyus]

Okay, once you get the alternator squared away, it's time to troubleshoot the relay issue. Might be the GP card, might be a bad connection or bad ground.

 

[Refalgren]

-Charging problem fixed. Ended up being a second bad regulator on GEN 2. So I had F&B Electric replace both the GEN 1 and GEN 2 regulators with heavier duty voltage regulators that have a slightly lower set point (14v compared to 14.7v) so there wouldn't be any compatibility issues as if I had just changed out one regulator.

-engine is still hot so I cannot test the GP system yet. Will do that tomorrow.

 

[Refalgren]

Sorry for the long update delay.

- Glow Plugs are now working. Root cause was a bad card. Replaced the bad card with the updated version produced by Antennaclimber.

- Get highly irritated that I keep blowing the internal regulator in my GEN 2. This is the third one. Blew this one before I installed the new card, so I am not sure if the old card could have caused the regulator to fail.

Any ideas on what could cause the regulators to fail?