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Discussion Starter · #1 ·
The resistance (ohms) reading on a new "black" plastic housing coolant temp thermostat was 900 on test compared with a new "blue" unit at 1380 and a 90K unit at 1400.

This is my second bad experience with the black plastic unit made by Delphi. The blue housing seems more reliable.

What hapened - 400 miles on rebuilt engine and the AC turns off last night along with the engine temp guage dropping to zero.

New installed sensor immediatly worked sending the temp guage up correcting the problem.

I've read other threads about changing the stat to solve this problem. It seems to me a bad stat will not zero out the temp guage.

Checking ohms was relatively easy by placing the two probes below the coolant hose first - then moving them inward to find the 2 contacts.
 

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Yes a bad stat will zero out the temp guage. the ECU will do that as a way to say look at me there's something wrong...

If the car does not achieve running temp in the correct amount of time or does not stay at the correct level over a certain period the ecu is programmed to do that..

Have you ever changed out the stat? That may be your problem.. but of course the sensor could be bad but sounds funny you keep getting bad ones no?
 

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Discussion Starter · #3 ·
Sould have clarified that this is the 2d black sensor in my experience J - only the first with this car. The ohms differential was of significance showing a faulty sensor.

My purpose was to alert other to only buy the blue sensor and to check sensor ohms before changing.

Good to know about the temp guage alert function if a stat goes bad.
 
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