1990 M921A2 Tractor, lights and ignition start problem

[ET48]

Hi guys, new to the site. Just bought my first military 6x6.

Problem:
Truck will jump start just fine at the starter. (will not start using the start switch on dash, no dash power)
After running, rev the engine up a bit and the dash powers up gauges and parking brake light comes on (as supposed to, just late).

No matter how charged the batterys are, I can't seem to get the lights, or blackout lights to work.

Do I have a dead battery, or perhaps a wiring issue?

I checked everything behind the dash, traced wires. The protective control box (black pcb next to the washer bottle) clicks when the master disconnect switch is turned on and off.

I just don't get anything when I turn the ignition on.

Any thoughts?

Thanks,

 

[fuzzytoaster]

Sounds like a bad PCB (black box) for the starting issue. I've had 2 bad boxes that click but don't power anything up, broke them down and one was vibrated to death and the other was corroded. Try a manual bypass with two jumper wires on the PCB plug (cant find thread for the how-to). If it starts with the bypass it's the box, if not then test your main power switch in the dash to see if it's going bad. The no-go on the lights is likely a different issue entirely but one thing at a time.

P.S. Make sure the gear select is firmly seated in neutral.

 

[MtnSnow]

Could be a bad ignition switch. Have you tested it with a DVM (Digital Volt Meter) to verify that power is present to the switch and if power is leaving the switch when moved to the other positions?

 

[MtnSnow]

This post will show you how to bypass the PCB
http://www.steelsoldiers.com/showth...-Control-Box&p=1557388&viewfull=1#post1557388
Also I would suggest reading the whole thread as there is a lot of useful info in there.

 

[ET48]

Ok thanks ill investigate the pcb more. Does anyone have a wiring schematic? I would like to find where the lights get power

 

[73m819]

Ok thanks ill investigate the pcb more. Does anyone have a wiring schematic? I would like to find where the lights get power

In the back of the -20

 

[ET48]

I opened and replaced the bottom solenoid in the black box, that fixed the starting issue.

Current issue at hand: still no lights
No stop, turn, brake or headlights.

Started cleaning grounds, no luck

 

[fuzzytoaster]

I opened and replaced the bottom solenoid in the black box, that fixed the starting issue.

Current issue at hand: still no lights
No stop, turn, brake or headlights.

Started cleaning grounds, no luck

Could be a bad 3 way switch, blinker box, and/or turn switch. I'd start in that order.

 

[ET48]

Is there anyway to fix the 3 way switch boxes? Ive got power going in to it

 

[ET48]

Opened up the three way switch box, everything looked brandnew! Replaced in 2004 by the yellow stamping. Turns out i had a flakey power wire, fixed that and life is good!