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Cooling fan not turning on

Tiny
LEON MANLEY
  • MEMBER
  • 1998 SATURN SC2
  • 1.9L
  • 4 CYL
  • 2WD
  • MANUAL
  • 230,000 MILES
I drove my car a couple of blocks to meet a fellow and left the car running for about 30 minutes. The car started to overheat.
I turned on the A/C, which should make the cooling fan come on, but it didn't.
I removed the fan and tested it. The fan is good. I removed the temperature control switch and replaced with a new one. Still no fan, even with the A/C turned on.
I unplugged the temperature control switch and the fan would run, but my temperature gauge wouldn't work. When I plugged the temperature switch in again, the fan would cut off.
I either have a fan running with the A/C on, with no temperature indication, or temperature indication with no fan.
I was under the assumption that the A/C switched on was a straight shot to running the fan.

Thanks
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Tuesday, December 29th, 2020 AT 6:44 AM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

The fact the fan works when you removed the connector for the coolant sensor tells me all the wiring and relay are good. You either have a bad sensor, which I would replace, or the coolant is not hot enough from the thermostat partially open.

https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works

I attached the wiring diagram for you to view the system.

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

Roy

REMOVAL

1. Turn ignition Off.

NOTE: Engine coolant must be drained below level of engine coolant temperature sensor before removal.

2. Disconnect electrical connector from engine coolant temperature sensor.

NOTE: The connector must be removed by squeezing the sides. Apply pressure to sides of connector gently with pliers. Do not pull on wires.

3. Remove engine coolant temperature sensor using a deep well socket.

INSTALLATION

NOTE: Tap out sensor mounting hole in engine to remove any thread sealant residue. Clean any thread sealant from sensor threads and coat sensor with correct thread sealant if installing the same sensor.

1. Apply thread sealant Saturn P/N 21485277 (Loctite 242 Threadlocker or equivalent) to sensor threads.

2. Install engine coolant temperature sensor.
Torque: 8 NM (71 in. lbs)

3. Connect electrical connector to the engine coolant temperature sensor. Push in until a click is heard and pull back to confirm a positive engagement.

Thermostat

. Drain coolant from the radiator (1) and engine drain plug (2) located at the right front of engine.
2. Disconnect lower radiator hose at thermostat housing. Use Snap-on Tool HCP10 or 20 (or equivalent).

imageOpen In New TabZoom/Print

3. Remove two bolts in water inlet housing.
4. Remove water inlet housing and thermostat assembly.
5. Remove O-ring.

IMPORTANT: The O-ring gasket must be replaced whenever the thermostat housing is removed.

IMPORTANT: The thermostat element should not be removed if the assembly requires testing.

imageOpen In New TabZoom/Print

6. Remove the thermostat element using the service tool provided with the replacement element.

NOTICE: The thermostat will not function correctly once it is contacted by oil. If oil is found in the cooling system, it must be flushed and the thermostat's cartridge replaced.

7. Inspect the thermostat components for damage, seat deterioration, etc..
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Tuesday, December 29th, 2020 AT 7:44 AM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
New temperature sensor installed.
Temperature gauge works.
Fan will not run with temp sensor connected.
Fan will run with temp sensor disconnected and A/C on regardless of engine temperature.

Does the temperature sensor and the A/C fan start share the same fan relay?

In my past experience, the A/C on would override the temperature sensor and make the fan operate regardless of the temperature.

I don't think there is a thermostat problem.
When I disconnect the temperature sensor and turn on the A/C the fan runs and the temperature will drop within normal operating range quickly, when the A/C is off and the temperature sensor is connected, the temperature rises excessively high with no response from the fan.

Thanks
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Wednesday, December 30th, 2020 AT 2:51 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, can you check the voltage at the temperature sensor and verify 5 volts to the sensor? It would be the yellow wire at the connector.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

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Wednesday, December 30th, 2020 AT 3:27 AM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
It'll be a few hours. I'm in Georgia and it's still dark and cold outside.

Thanks
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Wednesday, December 30th, 2020 AT 3:55 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You are welcome.

Keep me updated.

Roy
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Wednesday, December 30th, 2020 AT 3:57 AM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
I have 5 volts on the yellow wire.

The Freon was low in the A/C, I charged it up.
Evidently the fan on signal comes from the A/C compressor starting.

Temp sending unit plugged in- Vehicle running, A/C on, fan runs, temperature gauge works.

Turn off A/C, fan stops, unplug temp sensor, fan runs, temperature gauge doesn't work.

Service engine code 117 (low voltage to temperature sensor) was cleared.

I really do not like electrical problems. 10 hours to find and 10 minutes to fix.

This isn't a daily driver so I'm not walking.

Thanks
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Wednesday, December 30th, 2020 AT 6:36 PM
Tiny
ASEMASTER6371
  • MECHANIC
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I would not dismiss the thermostat as I suggested.

I would change it and see if it works.

Roy
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Wednesday, December 30th, 2020 AT 7:05 PM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
That thermostat is a pain. I changed it a couple of years ago.

Why would the fan come on when the sensor is unplugged but turn off when the sensor is plugged in.

I'm going to plug in the sensor that I removed to the sensor wire and apply some heat.
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Wednesday, December 30th, 2020 AT 7:32 PM
Tiny
ASEMASTER6371
  • MECHANIC
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It is supposed to come on when it is disconnected. When it is disconnected, it sends a high temperature signal to the ECM and turns on the fans.

Roy
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Wednesday, December 30th, 2020 AT 7:39 PM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
That's interesting.

I guess I could have received a faulty sensor when I bought the replacement last week.

If the new sensor checks out I'll change the thermostat but it could be a while.

I had the rack and pinion for 3 or 4 months before I finally changed it.

I'll let you know what I find.

Thanks again.
Happy New Year.
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Thursday, December 31st, 2020 AT 2:42 AM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Thursday, December 31st, 2020 AT 3:35 AM
Tiny
LEON MANLEY
  • MEMBER
  • 14 POSTS
I plugged up the old sensor and applied some heat. Once the temperature gauge reached the halfway mark the fan started. I did this 2 or 3 times and the fan reacted appropriately with the temperature gauge.
I plugged the wire to the new sensor, cleared the low voltage code, and let the car idle. When the temperature reached half way the fan started. I'm not sure what the problem was, but it seems to be working for now.
Thanks again for all your help.
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Thursday, January 14th, 2021 AT 7:17 AM

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