I'm stumped.

With my new coolant return plumbing (got rid of sharp 90 deg fitting) I
relocated my temp sensors.

Return from left rad used to sit on (black) 45 deg fitting and return
from right rad on a 90 deg brass fitting.

Now I have the right sensor under a silicone hose contacting the 3/4"
alum tubing out of the radiator.

The left sensor contacting the 3/4" tubing going into the return (was
planning on moving it to left rad output tubing).

The right probe now reads significantly lower (60F) than a non-contact
thermometer pointed at rad and also when pointed at silicone hose.

All sensors read the same when cooled down overnight.

I realize I could clamp the right probe to the silicone hose, but felt
that the hose would act as an insulator.

Probes are LM35 or equivalent ICs. I had tested them in boiling water
and ice baths and they were accurate within 1 to 2 deg F.

I feel I'm missing something. An alum tube is a good heat conductor,
right?  Does its color matter when sensor is directly touching it (with
heat sink compound to ensure better contact)?

I'd rather not go the route of inserting 3/4" copper tuning (with well
for sensor) into the return hoses, but perhaps the only way to get
accurate measurements?

Finn





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