No electric; Ignition Switch?

[Somemedic]

Went to start the truck yesterday and in the middle of cranking it cut out like I flipped the ignition switch off. Now, the truck has no electrical power at all, like a fuse is blown. Batteries are tight, no obvious pops, burning smell, magic smoke, or wires hanging loose.

At the same time I was cranking I was also using the manifold heater. Did I burn out the ignition switch??

 

[ida34]

There is a large relay that is activated by the power switch. It is next to the starter on the passenger's side. There is a wire behind the engine at the firewall. On my truck it rubbed on the engine lifting bracket. When it rubbed the insulation off it grounded and this cut it in half. The GI just twisted the wires together and taped it. It rubbed through again one day while I was driving. I spliced in a new section of wire and put some conduit around it. Check this first. I think the wire is labeled 10 or possibly 11. The switch takes power from the large relay (starter relay) and provides power to the rest of the truck including the starter switch.

 

[ida34]

Also, check the troubleshooting section of the -20 and -30 manual available in the resources section. This is where I stole the diagram.

 

[Stretch44875]

I've also had half the master switch fail. 4 wires, and it connects 2 pairs. One pair of wires wasn't being connected by the switch.

 

[cranetruck]

This should help with the troubleshooting...

 

[ida34]

I meant to post the one with the starter button. I must have grabbed the wrong one. Thanks for taking up the slack Bjorn.

 

[Somemedic]

I didn't realize the ign switch went to a relay. I noticed there appears to be a wire that has pulled out of a crimped connector near the starter. Doesn't appear to have burned but I will check it after work tomorrow on saturday. Thanks for the diagram fellas.

 

[Somemedic]

Ida and Bjorn... thank you.

How timely I caught Bjorns article in MilVehs Magazine! A good read for those of you who havent caught it yet.

After a closer inspection it appears the relay wires were spliced intoto add something which was cut away at some point. Anyway one of the spliced wires, with the copper being partially exposed and the crimp nut being a different metal had corroded and become brittle til it finally succombed to vibration. It was in 2 pieces. I spliced into the wiring and attached a new loop terminal onto the relay lead but still have some sort of issue where the new terminal may not be making good contact. If the wire is in a certain position in the crimped loop terminal, the relay engages. I'll fix it tomorrow after work since I'd prefer a working deuce when the snow hits the chicagoland area... you folks stay warm.

 

[Boatcarpenter]

Somemedic,
When using crimped terminals, I most always "tin" the wire first ( solder all the strands together), then crimp the connector on, then solder the wire in the terminal also. Makes a better connection and lessens the chance that the strands of wire will break due to vibration.
Try it, you'll like it.
BC