Temperature Sending Unit

[Dozer1010]

Hi all,

We have a 1972 Chevy with the 350 small block in it and we are struggling with the temp sending unit. It is reading beyond hot even when the vehicle is turned off/cold. We replaced the sending unit with a brand new one today and it made no difference. It is reading hot when the key is off or on accessory or the vehicle is running.
What could be going wrong?

[jocko]

Is it the original 350 or a later model? Did you buy the sender for a 72 Chev? If you have a newer 350 (or newer heads, anyway), the stock sender won't fit. A Wells TU5 is the correct one for a 72 350 with the original heads still on it. If you have all original stuff, then I'd check for a bad ground. I know a bad ground will cause it to peg one way or the other (sorry don't remember which way though).

Reason I asked about the heads (newer or older) - if you're buying a sending unit that fits newer heads because that's what you have - then resistance isn't correctly matched for that original 72 gauge.

Let us know what you've got and folks can pitch in to help. If all original and you have the correct sender, then it's either the gauge or the wiring.

Just caught that it's hot before you even turn the key? Hmm. Gotta be a wiring (or ground) or gauge issue.

Welcome to the board!

[leftybass209]

Originally Posted by jocko

Is it the original 350 or a later model? Did you buy the sender for a 72 Chev? If you have a newer 350 (or newer heads, anyway), the stock sender won't fit. A Wells TU5 is the correct one for a 72 350 with the original heads still on it. If you have all original stuff, then I'd check for a bad ground. I know a bad ground will cause it to peg one way or the other (sorry don't remember which way though).

Reason I asked about the heads (newer or older) - if you're buying a sending unit that fits newer heads because that's what you have - then resistance isn't correctly matched for that original 72 gauge.

Let us know what you've got and folks can pitch in to help. If all original and you have the correct sender, then it's either the gauge or the wiring.

Just caught that it's hot before you even turn the key? Hmm. Gotta be a wiring (or ground) or gauge issue.

Welcome to the board!

I agree with this. The sending unit is unique to the temperature gauge. The temp gauge could also be bad, but you should stick with identifying the sender first.

[Dozer1010]

Gonna go see what we can do. Think it might be a head problem like you suggested.

Thank you! we Will let you know what we find