bad terminal contact to earth in particular causes most electrical problems. remove them all one at a time clean well and reinstall with a smear of automotive bulb grease aka dielectric grease to seal them from moisture vasaline can also be used for this just a light smear don't need much. any push on spade terminals squeeze gently with pliers to tighten them. it could also be a bad ignition switch easily replaced and a universal unit will work as long as it has a glow position. check the glow plugs with a continuity test or simply replace them all.

if nothing works it could be a bad wire to the starter solenoid or the solenoid could be bad. a bad wire can look fine but be broken or corroded internally i have seen that happen it took an auto sparky to find it.

Hi guys. Thank you again for all the tips and wisdom. The good news is that Hanna is back in business! After much sleuthing and terminal cleaning, etc., I discovered the issue--the hot wire running from the solenoid to the start switch was broken and shorting out in the metal tube that transported the wiring harness from the front of the engine compartment to the rear, with holes for various leads to come out. To make life more interesting, the metal tube made contact with the temperature indicator capillary tube, melting it. And of course I did not know what damage had been to the wiring harness within the metal tube. It was packed solid with 53 years worth of crud, so there was nothing to do but cut all the wires, remove the tube, and rebuild the wiring harness. So that is what I did. Fortunately, the leads coming off of the pin connector were in good shape. So I was able to splice equivalent gauge wiring to the pin connector and effectively rebuild the harness. (All my splices are soldered and then sealed with heat shrink wrap.)

So all is now working with the electrical system. She started fine, though I am not convinced that all the glow plugs are glowing. But that's for another day.

Thanks again to all!!!

Oh yeah...I was able to replace the temperature sensor as well--though I ended up paying Caterpillar one arm and part of a leg for it...

Hello,
Your 12F grader was built in Canada and is a 67 year. Numbers run 00423--00507. catskinner

catskinner wrote:

Hello,
Your 12F grader was built in Canada and is a 67 year. Numbers run 00423--00507. catskinner

Thanks, Catskinner. Much appreciated.