CUCV GEN2 wiring Gremlin on 1986 M1008..assistance needed!

[glimmertwin01]

Hey Guys especially you electrical gurus. Here is a new one for you! to start off YES, I have read the sticky, yes i have read and studied the TM and trouble shooting... which under 5.1 basically says trace all circuits.
History... Bought the truck and GEN2 light meter did not work. Removed and had Pass side Gen2 alternator rebuilt... still no light...

BACKGROUND
other issues that were fixed... the truck had a fragged flex plate due to a loose Un braced starter Had starter shaft replaced, and replaced flex plate.... all components installed properly...

A previous Genius (owner) had Cobbed in a push button starter. with single strand 12 ga. romex from the 24 v buss into dash to button and back out directly to starter solenoid. the wire was ugly....
diagnosed that the under dash relay was not passing 24v. only about 12. on the purple trigger wire for the solenoid. My solution was similar to the doghead bypass. My version is... 24 V solenoid on firewall next to 24v buss and fuel filter assembly. 24v lead to one terminal, 12 Ga. lead from other to starter solenoid. purple wire to trigger, other leg to ground buss. result the trucks starts with key as it should.

All of this is mentioned as background "Just in case"

also replaced both relays in Gen 2 circuit.

(all other "idiot" lights (except Gen 2 lamp) in IP work and function)

this is where it gets good....

Here is the symptoms..... even after the above... No Gen 2 light... no Voltmeter. unplugged the plug on Gen 2 red wire +/- 24v key off, Brown/white wire key on less than 3v. the same low voltage is present throughout the entire circuit.
Removed instrument panel light and circuits... good
Removed and tested Gen2 Diode... good.

continuity tests... (good meaning passed continuity tests)
1) Gen2 plug on harness to firewall pass thru (junction block) Engine side... good

2) corresponding pin on female side of junction block pass thru to plug above the 10amp fuse as shown labeled as V/MTR (as shown on schematic) Good

3) fuse panel (in number 2 above) TO CORRESPONDING terminal on harness to Inst. panel plug...good

4) no broken damaged or cut wires found....


I just tried back feeding 24V GEN2 interior circuit with a lead directly from the 24V buss to the fuse panel V/MTR plug.... still no GEN2 LIGHT or Voltage at voltmeter ( voltmeter was replaced with a good 30v DC meter. )

should I try and locate a known working replacement interior wiring harness?? that is about where I am at....

HELP!!!!!!!!!!!

 

[Warthog]

Are you broke down on the side of the road and your life is in danger?

If not, please do not use "HELP" in your thread titles. That is a BIG pet peave on this website.

 

[Warthog]

I see that you have had this truck since Aug 2012. Is this a new issue or has it always been this way?

 

[Warthog]

Have you checked the very bottom fuse? It is 24v and should be hot at all times. It feeds the GEN2 circuit and the voltmeter.

Check for voltage at both sides of the fuse holder

Also did you split the wiring harness firewall plug? Did you clean the black goo off the connectors?

 

[glimmertwin01]

the GEN 2 light issue has been present since I owned it...yes I have thanks... Im at my wits end... the fuse has continuity... ill change my title if i can and remove the "help" from it...

 

[glimmertwin01]

ahh i see it was changed... thanks..

 

[glimmertwin01]

OK first dumb question.... should i remove the fuse and test both contacts in the fuse panel?

 

[Warthog]

You can leave the fuse in. Most fuses of this style have an exposed metal tab that will allow for voltage testing. Check both sides. If we do not have 24v then we need to find out why.

 

[glimmertwin01]

tested fuse out left fuse contact in fuse panel... no volts. right contact... +/- 1.3 v..(same as the rest of circuit)

 

[dependable]

You might want to try cleaning contacts on dash cluster, check bulbs before you replace harness. If harness has been hacked up, replacing it is not too hard. Hillbillywizard might have one.

Bulb holder in lower center of picture is gen 2 light, there is a 24 in black ink to left of it. Those are the gen 2 contacts.

 

[glimmertwin01]

as a note the terminals on the pass thru were all good clen with a nice coating of factory dielectric grease...
i restore the old square bodies.. ive worked on many electrical issues...this dual system has me scratchin my head

 

[glimmertwin01]

as I stated in the initial post..... I have checked the circuit board on the IP all is good to go... all connections are clean etc.. bulb works when circuit is energized on bench from the points where the connector goes..

 

[glimmertwin01]

it sounds stupid but ill split the connector and clean the factory grease off the corresponding pins....
it is 5 balmy degrees in the sun up here in upstate NY in the "POLAR VORTEX" miserable..

 

[dependable]

Missed it where you said bulb circuit works. Also you and Warthog posted about 5 posts as I slowly ambled though mine. Good luck.

 

[Warthog]

You are not feeding 24v from the 24 Postive Terminal Board too the fuse. Without it you will never get the GEN2 to work. That is probably why the PO hotwired the starter.

Here is your task.

Split the firewall plug and check for 24v at this terminal



See how gooey the contacts are? I don't know what GM used but over the years it turned to a black tar and causes alot of electrical issues. I use some Electrical Contact Cleaner and an old toothbrush to remove a lot of it.

If you do not have 24v at that contact then your fusible link is shot. It is the slightly larger red link. The others are orange. The diagram shows it to be a 16ga fusible link.

 

[glimmertwin01]

contacts cleaned.... no change... ill split it again and test that pin... its too cold to stay out very long... BRB

 

[glimmertwin01]

that terminal yields 12.3 v... but then it broke off.. tested the "stub" left inside still 12.3v

 

[Warthog]

You need to check the fusible link. In a stock system that terminal is wired directly to the 24v terminal buss.

Sounds like you will need to wait until it warms up in order to fix the broken "stub"

 

[cpf240]

um... I've seen no mention of the GEN2 relay... has it been checked?

 

[Warthog]

He isn't getting 24v to the firewall plug so nothing to the relay. He replaced the GEN2 and voltmeter relays in his first post.