RED-C5

I have a 69 350 and initially the temp gauge was maybe 120 fully hot. I grounded the gauge wire and it swung way past 250 almost pointing down. When I left it open (off the unit) it went under 100. A shop replaced the sending unit and said a "sender for a fan" had been installed. Now the gauge shows 230 to almost 250. Can this be corrected with a resistor? Or what would be the correct sender and source? Thanks for any help!

kansas123

If you have an infrared temp indicator, after the car is warmed up, point it to the upper radiator hose at the engine where the thermostat is, see what that reads.

drwet

As far as I know, fan senders are on/off devices and such a sender would not work with a gauge. Correct senders are readily available but are notoriously inaccurate. Get the right sender, and then install the adjustable resistor from Willcox. Use another gauge that you trust to calibrate the gauge in your car by adjusting the resistor.

RED-C5

Do you have a p/n for it? I have no idea on the one that was put in or where it came from. Willcox is not working either.

zwede

I recently got a sender from ZIP and it is correct. I have EFI with its own sender and the EFI reading matches the gauge. PN M-3518 $28.99.

drwet

Rock Auto lists senders from several manufacturers. Should also be available from any of the Corvette Suppliers. Not sure what is up with Willcox. Hopefully they will be back in business soon.

RED-C5

Got the infrared temp indicator, and pointing it at thermoset housing getting ~190. gauge reads >250 idling. Looks I need to increase resistance going to the gauge??

zwede

You need the proper sender.

drwet

I can’t really answer that. I got the adjustable resistor kit from Willcox. The instructions were very clear and it worked perfectly, but IIRC the kit replaces the factory resistor so I don’t know if I was increasing or decreasing the resistance from the factory value. Hopefully Willcox will be back on line soon and you can order the kit. I also think you should start with the correct sender.