Ohmeter. You can check the resistance between the wire term post and ground with still in vehicle. You should see it change as temp heats up. 73 ohms would be cold and resistance will drop as it heats up. Grounding the senders wire will peg the gauge to check that portion of the circuit. My source is restoring these old vehicles for the last ten years. Mainly 66-77 year range. Electrical gauges are mostly the same, just different faces and type of sender. Ford used one standard, Chev another etc. All the Ford gauges can be checked by grounding the sender wire, just not for too long, as they have an IVR, instrument voltage regulator, supplying voltage to them. The idiot light senders just supply voltage to the light when the senders value reaches a certain point, a switch for all entensive purposes.
Last edited by gfw1985; 11-06-2010 at 04:16 PM.
Reason: Add info
Thanks again. I did test in the manner indicated. I was not able to come up with 73 in fact the cold readings were more like 0.46. However I checked just after the engine started warming and got 62. Further along it got lower and finially came in at 10.3 at 179 degrees (in tank). Now if I only knew where the needle is supposed to point I'll have it made.