1966-67 HCS resistance of temp sending unit

Hi all,

Anybody know (or would be willing to measure), the resistance, in ohms, of the temp sending unit for a '66 - 289?

With the connection to the gauge removed, mine measures 195 ohm's from the negative side of the battery to the top connection point of the sender, and also 195 ohm's from the bottom of the sender itself to the connection point at the top.

In other words, I am checking the sender two ways. - (1) the complete circuit from the top of the sender back to the negative side of the battery (which tells me the engine is grounded properly) and (2) the sender itself. In both checks, the resistance I get is 195 ohms.

Wondering if that is a correct resistance value - is my sensor good? I looked in the shop manual, and can't see any reference to what the resistance should be.

The measurement's are done at about 70 degree's.

THANKS, Dave

Did you remove the sending unit when you tested it top-to-bottom, or did you test it with it attached to the engine?

Sounds like a job for......... RVRTRASH!!!! Steve is the sparky on our site!!

Rob

Mosesatm said:

Did you remove the sending unit when you tested it top-to-bottom, or did you test it with it attached to the engine?

Click to expand...

The temp sender is still screwed into the intake manifold. The #2 part of the test that I did, was with one test lead at the very top of the unit and the other test lead at the bottom of the unit at the exposed threads where it screws into the manifold. The temp in the garage is around 70 degrees.

Thanks, Dave

I measured the resistance of the temp sender in my 289. Cold engine, 180 ohms (base-to- stud) at 80 degrees OAT.

Neil

franklinair said:

I measured the resistance of the temp sender in my 289. Cold engine, 180 ohms (base-to- stud) at 80 degrees OAT.

Neil

Click to expand...

THANKS Neil.

That is a few ohms less than the one I have. Does the resistance decrease as the temp goes up?

Shoot, I'll go get some ice cream with the car & see what the resistance is when I get home.

THANKS, Dave

Dad,
Once again you are to the rescue!!!

Your Son Rob!

Dave;
The temp sensor resistance decreases as temperature increases.
The instrument voltage regulator (IVR) supplies a constant 6VDC to the temp gage. When the engine temp is 'cold' the sensor resistance is 175 ohms+/-. As the engine water temp increases the sensor resistance decreases causing the temp gage pointer to deflect towards H.
The temp sensors are not a high tech, super calibrated unit. A lot of people (me included) let the engine warm up (with the radiator cap removed). When the thermostat opens (180 degrees) you'll then see the coolant circulating in the radiator. Put a thermometer in the coolant and see what the coolant temperature is. Then look at the temp gage in the car and you'll have a reference point for engine temp and pointer location.

Neil

franklinair said:

Dave;
The temp sensor resistance decreases as temperature increases.
The instrument voltage regulator (IVR) supplies a constant 6VDC to the temp gage. When the engine temp is 'cold' the sensor resistance is 175 ohms+/-. As the engine water temp increases the sensor resistance decreases causing the temp gage pointer to deflect towards H.
The temp sensors are not a high tech, super calibrated unit. A lot of people (me included) let the engine warm up (with the radiator cap removed). When the thermostat opens (180 degrees) you'll then see the coolant circulating in the radiator. Put a thermometer in the coolant and see what the coolant temperature is. Then look at the temp gage in the car and you'll have a reference point for engine temp and pointer location.

Neil

Click to expand...

GREAT idea - I'll check it that way.

Thanks, Dave

franklinair said:

Dave;
The temp sensor resistance decreases as temperature increases.
The instrument voltage regulator (IVR) supplies a constant 6VDC to the temp gage. When the engine temp is 'cold' the sensor resistance is 175 ohms+/-. As the engine water temp increases the sensor resistance decreases causing the temp gage pointer to deflect towards H.
The temp sensors are not a high tech, super calibrated unit. A lot of people (me included) let the engine warm up (with the radiator cap removed). When the thermostat opens (180 degrees) you'll then see the coolant circulating in the radiator. Put a thermometer in the coolant and see what the coolant temperature is. Then look at the temp gage in the car and you'll have a reference point for engine temp and pointer location.

Neil

Click to expand...

Dad,
I worked in a radiator shop from 1971 to 1973. Did re-cores of heaters and radiators, and remove and replacements. Way too much under the dash stuff!!

You are right on as always. Back in the day we had a radiator cap with a thermometer to check thermostat opening temps. To ensure proper opening at the proper temp.

Below is a link to a cap you can install and monitor the temp. You can share it amongst your "herd" of cars if you have more than one. Take it off for car shows or if you are like me, who cares and leave it on.

Rob

http://www.summitracing.com/parts/mrg-2470s/overview/

I use them on all my cars.

Neil

You guys are incredible! THANKS for the information and help. I will definitely
get one of those.
Dave

Here's the thermometer radiator cap I use:

Neil