Gen 1 Light Issue

[Haoleb]

So I have read all of the threads about the Gen lights I can find.. Several times. I have looked at the schematic up and down. I am just not sure where to go from here.

So for some back story when I bought the truck most of the lights in the dash did not work. The Gen 2 light worked and that was about it. I took the dash apart. Cleaned all the terminals on the circuit board. Cleaned light sockets. Replaced all bulbs. Tested each light with a power supply all worked fine. Now that I have also gone through and replaced the oil pressure sender and high coolant temp sender all of my lights work.. Except the Gen 1 light.

I have 12v on the red wire all the time on the two pin connector for the alternator. And I have 12v on the brown wire when the ignition is on. I replaced the alternator with a rebuilt delco Wilson alternator (another story) but it has never worked with either the new or old alternator. I also replaced the two pin connector on the alternator with a new one. In addition I took apart and cleaned the electrical plug going into the firewall on both sides. I also ran another 10AWG ground wire from the drivers side alternator to a good ground just to make sure it was grounded well.

The blower motor works fine. I just can't get the GEN 1 light to come on no matter what I have tried... The alternator does work. Puts out 14.7VDC if I remember correctly.

Any suggestions?

 

[cpf240]

...I also ran another 10AWG ground wire from the passenger alternator to a good ground just to make sure it was grounded well.

Has this been converted to 12v? Otherwise, the passenger-side alt, GEN 2, is NOT supposed to be grounded at all. It gets its ground reference from the output of GEN 1.

As for the GEN 1 light, is the correct bulb installed? They are different between GEN 1 and GEN 2. Your voltages at the 2-pin plug sound correct, and as you say it is charging, it must be getting the correct voltage for excitement.

 

[Haoleb]

It has not been converted to 12v. Gen 2 has a floating ground connected to the battery directly I meant to say the drivers side alternator.

I put 168 bulbs in all of the idiot lights and 194's in the dash backlighting.

 

[cucvrus]

Check all the wires under the buss bar and make sure the alternators are plugged in correctly at the voltage regulator. I suspect you have a problem in the printed circuit board on the back of the cluster. I have good luck working on clusters while they are still in the dash and then reassemble them in place. I can do them both ways but lately being they are so fragile from age I take them apart while sitting in the drivers seat. very seldom do my own need any work. If you do the cleaning and repairs correctly the first time they seem to last for many years.

 

[Haoleb]

I finally had a chance today to dig into the Gen 1 light issue again. Traced the alternator wires and they were all good. So then I started taking voltage measurements off that two pin plug again. Previously I had noticed I would get a stray voltage that would drop with my meter hooked up on the brown wire. Typically I see something like that with a capacitor in the circuit somewhere which I thought was odd but kept looking elsewhere... So today I decide to pull out the gen 1 light just to see if I had voltage on the brown wire still. And I did!... So next I pull the heater fuse and check again. Still I have 12v when the ignition is on. Now im sure I either have some type of short somewhere or someone messed with something. I took the main wiring bulkhead connector apart and continuity check the brown wire to the pin in the plug.. Nothing... hmm.. So then I just touch the lead to any of the terminals in there and low and behold I have continuity on a yellow wire.

Same yellow wire that has a piggyback splice on it to another yellow wire going into the main loom on the drivers side. Pull the loom apart and sure enough someone spliced the brown wire into this yellow wire that is tied to ignition. The original brown wire was right there capped off. Tested good back to the main connector block so I spliced the brown wires back together.. Tested the voltage again. Ok no voltage when the key is off and 12v when it is on and no stray voltage anymore. Turn the key and we have GEN 1 illumination!

I'm guessing there was previously an issue with the light and it was not charging leading to someone rigging it up the way they did. Probably the same hack who wired the manual GP switch wrong. Either way it is working perfect now and thankfully they did not touch anything else as far as I can tell. Very happy to have another issue checked off the list and have all of my lights fully functional again!

 

[cpf240]

Awesome find! Who knows what they were thinking, but now it is back to the way it was designed. Great job!

 

[Tinstar]

Nicely done!
Patience, persistence and a multimeter work wonders.

 

[Haoleb]

The resources here on this forum are also an immense help both the membership base and the TM's available for download. Thanks guys.