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Kevin Bourcier
Kevin Bourcier, Technician
Category: Pontiac
Satisfied Customers: 385
Experience:  35 Years experience , Electrical , Air Conditioning , Diagnostics , Computers , Fuel Injection
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95 pontiac grand prix: liter..Engine temp gauge on dash..cooling fans

Resolved Question:

I have a 95 pontiac grand prix with 3.1 liter. Engine temp gauge on dash does not work and the electric cooling fans also will not come on up to boil over point. Any ideas? Assuming faulty sensor, but how do you tell? I've also checked all fuses I can find, and have power to fan relays.
Submitted: 7 years ago.
Category: Pontiac
Expert:  Kevin Bourcier replied 7 years ago.
Hello . With the engine temperature gauge sender unit wire unplugged and the key " ON " using a jumper wire connect the sender wire to ground . You should see the temperature gauge go to " full scale " ( hot ) . If that is the case simply replace the sender . The engine fans are normally controlled by the ECM and the signal is given by a 2 wire " ECT sensor " which is different from the " temperature gauge " sender . The engine coolant temperature sensor wires are black and yellow . You may also want to check the under hood fuses labeled Maxi fuse - # XXXXX & 3 , ENG EMIS ( 15 amp ) , ECM BAT ( 20 amp ) .
Customer: replied 7 years ago.
Ok, I need some clarification. There is a two wire (black and yellow) sensor at the base of the thermostat housing. When this is unplugged the cooling fans run. When this wire is plugged back in the fans shut off. Is this the black and yellow wire that I should ground to test the gauge? Which wire should be grounded or both? There is a single green wire sensor that appears to be installed in the head on the drivers end of the engine toward the firewall.
Expert:  Kevin Bourcier replied 7 years ago.
Okay . The 2 wire sensor is for the cooling fans . The fact that the fans turn on confirms that the ecm and the fan circuits are working properly . If you are having a problem with overheating due to the fans not coming on then you should replace that sensor . The temperature gauge is operated by the single green wire sender on the cylinder head . ground the green wire to see if the temperature gauge will go to full scale ( hot ) . Do NOT ground either wire on the 2 wire connector !!
Customer: replied 7 years ago.

Thanks Kevin! I grounded the green wire and the dash gauge did go to full hot and the red "temp" light came on as well. Guess I need to replace both sensors.

Expert:  Kevin Bourcier replied 7 years ago.
Yes that would be the solution .
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