Wiring problem to the master switch (M35a2)

[yakovfoley]

Hello all, this is my first post, sorry if the placement or format is wrong. I recently bought a 72’ deuce and a half multi fuel. Hasn’t run in a decade, and seems as if nothing works. That being said wrenching on it has been a blast, and I’ve already learned so much. Now the fun stuff.

I have no power to the master switch. 2 brand new charged batteries 990cca. New terminals. Cranks over just fine by jumping the starter posts. No gage cluster (one on the way) Using a multi meter there was no power to any of the 4 wires into the master switch. However using a jumper wire from the positive on the battery, on 2 terminals on the switch, the starter would engage (w/ the starter button pushed). Now the weird part. In the process of pulling on the dash to try to get it off the switch randomly started working. Would turn on and off, send power to the starter, and low air buzzer. Worked for a whole 5 min then stopped working. Haven’t been able to get it going again. (6 days ago)

Before I bite the bullet on a new front wiring harness is there anything else I can do? (New master switch, rearrange the wires on the master switch, new light switch, a circuit breaker, fuse, install the gage cluster first, etc.)

I’ve been looking through the TM and wiring diagram and haven’t been able to figure it out.

Thank you all,
Yakov
Leadville, CO

 

[Jeepsinker]

With the dash out, inspect the harness carefully. Pay particular attention to wires near connectors and in places where the harness is bent, folded, or rubs on anything. You probably have the #10 wire broken inside the insulation somewhere, or the insulation is missing near a connector and there's a lot of corrosion inside the wire.

 

[Barrman]

Follow the positive wire from the battery tray. It should go to the starter motor. The number 10 wire mentioned above should come from the starter motor or a connection on the engine hidden by the air filter. Verify voltage along the way and keep following through the firewall until you have no voltage. Go back a connection and find your problem.

 

[yakovfoley]

Follow the positive wire from the battery tray. It should go to the starter motor. The number 10 wire mentioned above should come from the starter motor or a connection on the engine hidden by the air filter. Verify voltage along the way and keep following through the firewall until you have no voltage. Go back a connection and find your problem.

I think I might of found my problem. I saw a video and on the magnetic starter relay on the bottom hot side, there was 2 wires. 1 to the main starter relay and 1 that supply’s power under the dash. I only have the wire going to the main starter relay. (Pic below) My question is where under the dash would I run a hot wire to power the gauges and switches? Could it be this wire (pic below) with the number 19, 207,87,106,and 38. Thank you.

 

[Barrman]

The first picture shows evidence of an electrical arc. Did you do that?

The dash wiring picture shows you have several wires cut. I hate to write this because I have done this job twice. But, a new front wiring harness swap might be where you are headed. I see 5 cut wires and you mentioned another wire missing under the hood. If you are comfortable with wiring and reading schematics. Then buying a few dozen male and female Packard fittings, downloading the wiring diagrams, good crimpers for these connectors and going to it will work.

I did the fix option on my M715. But, the wires were all good and pliable. My M35A2 the wire insulation would fall off if I touched a wire. A new harness seemed a good idea. Only you can make that decision.

 

[Jeepsinker]

You need to find the number 10 wire under the hood. It has to be there somewhere in the vicinity of the starter and relay, or at the very least there will be a cut off nub of wire close to where the harness tape ends if someone cut it off to use on something else. It's a 14 gauge wire that feeds everything in the cab. If there are any loose wires or ends in that area that aren't labeled, that's probably it. There are no ground wires in that area, so don't be afraid to hook any loose wire there to power and try it. Once you get power to the cab, figuring out the rest is easy. I actually made a video about this years ago. Watch it at the link below.