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I have an '86 W100. I replaced the coolant temp sensor because the temp gauge was not working. Now it works, but only when the key is in the start position. It also has a searching idle, sometimes high, sometimes low, and backfires frequently when cold. All of this makes me think that the temp sensor circuit is not being completed. Why it works when I am starting the vehicle I can't understand. Im hoping that by solving the temp sensor issue the idle issue will fall into place. But maybe my problem is in the ignition switch? Any ideas? Im from a younger generation and carbureted vehicles are new to me (as evidenced by my spelling). Any and all replies welcome.

 

[brad12kx]

That sure sounds like a wiring issue of some sort. I don't have a manual on the 86 Ram, so can't look at the wiring to offer any suggestions. Purchasing a Chilton book or similar with the wiring diagram might be a good starting point.