The Stovebolt Site Forums The Shop Area The Electrical Bay 41 gmc vs. 41 chevy wiring harness

I am rewiring an "original" 228 gmc and I have bought a poor man's harness from American Classic. After eight hours of study it is good with three exceptions:
1 it has no ground wire from the voltage regulator mounting screw to the generator
2 It does not have a "cross over" wirw from the headlight switch to the amp gage,from the lead of the headlight switch to the voltage regulator {bat}.
3 no wiring from the thermosat to thermosat gage.
All of the above creates no major issue but when I really looked at the thermosat gage I noticed that both posts on that gage have a metal bracket which covers them upon which it tells you that one post goes to eng. and one to ign. The same for the fuel gage. The question is are these brackets on the back of the gagues due to the difference in polarity of gmc vs chevy? Are these brackets on gmc gagues only or has anyone seen them on chevy? Long winded Hope you understand the question. As a side question I have a one an half inch by one quarter inch tin tag wired to the engine block, near the bell housinf with the number 7 stamped on it, is this an inspection tag/

I can help with one question. The Chevy used a capillary tube type gauge so that's why there's no wire for it.

I, too, would assume the different polarity is why the gauges are marked.

the tag sounds like a rebuilder's tag to me.

did you already remove the old harness? if not carefully trace it out before you tear it out and then install the new wiring the same way. i rewire a 40 gmc and a 40 chevy. for the temp gauge they both have the cap. tube. after i traced out my old harness on my gmc and tore ot out back to the battery i noticed that a previous owner converted it to neg ground. for other reason i left it the way it was. i took two prints as i ripped out the old wiring i highlighted what i had ripped out. when all the wiring is removed the whole print should be highlighted. when installing the new wiring doing the same thing. when the print is all high lighted there shouldnt be any loose terminals left over. when you lay out the harness in its correct orientation mark both ends of a circuit with tape as to where it comes from and where it goes. this made it simpe for me. both harnesses i did came from carter. yours should be the same except from american classic. it was only wired from the factory one way and any new harness should reflect that. the 39 - 46 harness are the same with some optional wires for park lights and turn signals.

Thanks for the reply. The thermosat response makes perfect sense. On the "inspection tag" I too thought it might be a rebuild tag but I had it rebuilt and it had not been before. Also the metal appears to be the same size and quality as that of the cab floor tag and the pickup bed tag. Both of which are riveted on the truck Thanks again for both replies.