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Amedee, Saturn Technician
Category: Saturn
Satisfied Customers: 24150
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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Our 1995 SOHC Saturn SL Sedan 216,000 miles has started

Customer Question

Our 1995 SOHC Saturn SL Sedan 216,000 miles has started running on the warm side. Instead of the temperature gauge needle being centered, it has started creeping toward the 3/4 mark - and the engine cooloing electric fan does NOT turn on to bring it back down. It has proper antifreeze level. I hooked a 12v source to the fan - it works. Using the Actron scanner, the PCM also turns on the fan during the diagnostic routine. Codes are only 3 12s - nothing wrong there, or with the CTS. Temperature gauge works, so I don't think the sending unit is bad. 30 amp Fuse looks good. Have tried a different relay - no change. So to make the temperature go down, I turn the heater on high. Radiator is maybe 4 years old. Help!
Submitted: 4 months ago.
Category: Saturn
Expert:  Amedee replied 4 months ago.

Hello and welcome! My name is ***** ***** I can assist you with your question. Are you sure the coolant is full and there are no air pockets in the cooling system? If so, it can and will cause this tempature fluctuation you are talking about.

Expert:  Amedee replied 4 months ago.

This can and will prevent the cooling fan from coming on as well.

Expert:  Amedee replied 4 months ago.

However, if the coolant is full and there are no air pockets present, then yes, we have an electrical issue that needs to be diagnosed. Keep in mind, the engine coolant temp sensor for the guage may be different from the one the computer uses to control the cooling fan. These engine coolant temp sensors go bad all of the time.

Expert:  Amedee replied 4 months ago.

Just a heads up, the coolant fan does not come on until about 225 degrees. If coolant boils before this, check for a pressure cap not holding pressure. Here is the cooling fan inoperative test.

Expert:  Amedee replied 4 months ago.

Check the 30 amp cooling fan maxifuse (labeled COOL FAN) in the underhood junction block.

If the fuse is OK, disconnect the cooling fan motor connector and connect a DVOM from terminal B wire (BLK/RED on 1991-94 models or LIGHT BLUE on 1995-98 models) to ground.

Disengage the A/C compressor clutch connector in order to prevent the air conditioning system from overpressurizing and releasing refrigerant from the pressure valve.

Start the engine and turn the air conditioning ON:

If there is voltage at the B wire, check for open at terminal A (BLK) wire to ground which would prevent circuit completion and keep an otherwise good motor from operating. If there is no open and voltage is present, the motor must be faulty. Repair the open wire or replace the faulty motor, as applicable.

If there is no voltage at the B wire, turn the engine OFFand with the DVOM still connected to terminal B, unplug the PCM connector. Install a jumper wire between the following PCM connector terminal and ground:

1991-94 models-PCM terminal J2A03 (DRK GRN/WHT)

1995 models-PCM terminal J2A03 (DRK GRN)

1996-98 models-PCM terminal J1C01 (DRK GRN)

If there is no voltage at the connector, the fan relay is faulty. If there is voltage, the PCM is bad.

The fan motor may also be checked by jumping 12 volts to the 2 wires (A = negative, B = positive). The motor should run while voltage is applied.

Expert:  Amedee replied 4 months ago.

Here is a wiring diagram of this circuit to help you diagnose this problem.

Expert:  Amedee replied 4 months ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "Excellent Service" for assisting you today.

Please let me know if you have any further questions.