Part 1. I have nothing but my own observations on this...so please correct me if I am wrong. Mid 60s through mid 80s GM factory oil pressure sending units for "idiot lights" are "always" kinda flat as opposed to the factory oil pressure sending units for gauges which are "always" kinda bulb-shaped.

Part 2. Can you tell the difference between water temp sending units for "idiot lights" and gauges by visual inspection alone? I found some strays recently.

Thanks in advance.

C.J.

 

That reminds me... if anyone doesn't have that special oldsmobile shaped socket. A store a few miles down the road had a couple and had no idea what they were for. If anyone needs one let me know and I'll pick em up if they are still there.

 

The water temp sending unit for the idiot light has a regular prong set in bacalite plastic at the top. The sending unit for the gauge has a round connection which the plug slides onto sideways. If your still not sure you can test them out. The sending unit for the idiot light should have a very high resistance at normal temperatures because the switch is open. You can heat up the sensor on an electric stove (be very careful) and watch as the resistance suddenly drops to zero when the switch closes. The sending unit for the gauge will only change in resistance slowly as it is heated up and will never have a sudden change because it is a variable resistor rather than a switch. I hope that helps, if you have any questions let me know.

 

That was my experience until I bought a 72 parts car with factory Rally Pak. The Water Temp sender has the spade termnal. Forgot about throwing it in a pan of hot water (DUH!)

C.J.