heat gauge sending unit on 318 poly or rad issue?

[MyStarCCar]

Two questions here-is the heat gauge sending unit different on a 318 poly vs a 1988 LA 318?

I put a 1988 LA 318 in a '63 Plymouth and the gauge shows it runs slightly hot on the highway but drops off at idle--there are no clear signs the car is running hot (no excessive heat and no loss of antifreeze) and it never gets into the critically hot area. Could the newer sending unit to the old heat gauge on the '63 be a factor in this?

The only other thing that may be a factor is that I used the newer '88 Fifth Avenue radiator in the '63--it's a bit longer and little lower so a small part of the radiator is blocked at both ends by the configuration of the '63 Plymouth rad housing.

Any thoughts on this?

 

[threewood]

They are different, but in what respect I don't know. Sender for a poly is Standard TS52 whereas the sender for an 88 5th Ave is Standard TS149.

I guess if you wanted to see if the resistance is different you could buy the TS52 and compare ohms at certain temperature levels.

Is your wiring all good and tight? Any drop from the gauge to the sender?

 

[MyStarCCar]

thanks-I'll check that for sure