The Stovebolt Site Forums The Shop Area Engine Shop Water Temp testing

I have a 1962 235 new rebuild with a new water temp sending unit (2 wire) Engine runs, green light for cold lights up, but does not go out when engine warms up. Wonder if it would show "hot" if necessary. How can I test it?

Just replaced the “Idiot Light” sender that I broke removing it from the ‘62 235 to put it in the 350 I’m putting in the ‘62. Bought it thru Amazon. None of the FLAPS around here had it in stock. I’m sure there is a way to test the sender but someone else will have to tell you how.

I’ll take a stab at this without knowing the 62. You must have two idiot temp lights in your dash. One is green for cold, the other red for (too) hot. The sensor most likely has two bimetallic switches. One is normally closed (green), the other normally open. My crude test procedure would be to pull sensor, turn on switch, see green light, hold cigarette lighter under it to warm it up till hot (don’t overdo it). If green light doesn’t go off then sensor is incorrect or bad.
The above is assuming that your wire is correct and functional.

Have you used an IR temp gauge to see how warm engine is AND compare that to the HOT temp. You might not be getting hot enough to turn the switch on if it is hot (overheating light).

Just my 2 pennies,

Chris

Take the sender out and drop it into a pan of boiling water and see what happens.You may have to run a ground jumper wire from sender body to the engine block.

There are two "switches" inside sender. One for hot and one for cold. When starting, I believe red hot should come on as a bulb test, then go off. Green on to about 100 deg and red comes on about 200 deg. No lights in between 100 and 200.

I believe a hot wire goes to the bulb(s), out each bulb to the sender (two wires on sender). The sender grounds the wires for hot and for cold and lights the appropriate bulb. So take off wires from sender, ground each wire to see if red and green bulbs light up with ign on. You must have good working bulbs and wiring to continue testing. Be sure thread sealing tape is not keeping sender from grounding thru threads. Report results.

If the green light is lit then I believe that grounding is not an issue. Grounding each wire with switch on is a good test of whole system minus the sender.