Both gen lights not working

[devilbw0y]

Okay, I have searched and searched. All I have found are instances where one or the other light was not working, or both out and a no charge issue.

On my m1009 both gen 1 and 2 lights never come on when key is turned, and once running I have 29 volts so that tells me both alts are working. I have checked the bulbs and they are both good.

Anyone else have this issue? Since both alts appear to be working should I just ignore the lack of idiot lights? Was worried because I read they were required for the charging circuit to work properly.

 

[idM1028]

Hmm. . . Are your exciter wire plugs hooked up at the alts? If you bypass them (I.E. if you make a jumper wire/plug to hook your GEN1 up to the front battery) the lights won't come on. How did you check the bulbs? Did you actually apply power to them and check them? At a minimum you can check your GEN2 bulb by pulling out the relay (its under the dash around the diagnostic plug/radio slot) and using a jumper wire. Another thing you can try is pulling out your instrument panel and checking to make sure you've got voltage there and a good ground. Also try checking your fuses. The GEN1 bulb should be fused off of the heater fuse and the GEN2 bulb uses the 24V fuse.

 

[Barrman]

What about the 6 legged ground wire at the top of the parking brake bracket? That ground has a part in just about everything electrical under the dash.

The filament in the ALT lights has to conduct electricity for the exciter wires to work. That doesn't always mean the lights will glow.

 

[devilbw0y]

Thanks for the help!

All wires are pugged into both alts, and it all looks stock. I see no jumpers to the battery. I checked the bulbs by pulling the instrument panel, taking out the bulbs, and using meter to check for resistance.

Also I took the 6 legged ground off, roughed up both sides with sand paper and cleaned with contact cleaner. My wait light and water in fuel light were working so didnt really expect the ground to be the issue. Have not checked the fuses yet (), but heater works so fuse for gen 1 light should be good.

Im going to clean everything really good and re-assemble and hope for best. Any other things to check while instrument cluster is out let me know.

 

[idM1028]

When you pull the instrument panel off it looks a little like a circuit board on the other side. Theres also a plug and a connector for the instrument panel on the back. Trace the wiring on the back side from the bulb sockets back to the plug and check the wires there for voltage/continuity. I've also seen folks who had the wiring on the back side of the instrument panel burn up, so lets hope thats not the case.

 

[devilbw0y]

When you pull the instrument panel off it looks a little like a circuit board on the other side. Theres also a plug and a connector for the instrument panel on the back. Trace the wiring on the back side from the bulb sockets back to the plug and check the wires there for voltage/continuity. I've also seen folks who had the wiring on the back side of the instrument panel burn up, so lets hope thats not the case.

I traced them as you said and have 10.6 volts for gen 1 at the plug, and nothing at gen 2...

Looks like a good cleaning may solve gen 1 light not working, but not sure what to do about gen 2. 24 volt fuse checks good.

The filament in the ALT lights has to conduct electricity for the exciter wires to work.

This is odd, because with my instrument panel still off and engine running, I still have 29 volts.

Also something else I always thought was odd, my voltage gauge in dash always stays right on the yellow/green line. Never halfway in green like everyone elses I see. Like its barely charging, but 29 volts I would think is close to overcharging. Didnt know if it meant anything just wanted to throw it out there.

 

[mistaken1]

If you have not downloaded these color wiring diagrams yet they may help:
http://www.steelsoldiers.com/cucv/75505-cucv-wiring-diagram-color-except-m1010.html


You have all the manuals?
http://www.steelsoldiers.com/cucv/67999-download-cucv-tms-here-where-download-cucv-tms.html

 

[Warthog]

What type of alternators do you have? Are they stock or are they one wire self exciting?

What type of truck is it? Is the wiring all stock?

 

[devilbw0y]

What type of alternators do you have? Are they stock or are they one wire self exciting?

What type of truck is it? Is the wiring all stock?

Truck is a M1009.

All wiring is stock.

Both alternators are stock.

 

[rfischba1]

Check the fuse and bulbs first thing then check the procedures listed in the TM, great referance to allow step by step checks.
My problem was #2 light stayed on even with a new alt.
I still drive it just keep a charge on #2 battery from time to time.