3rd Gen / L98 Engine Tech 1982 - 1992 Engine Related

Cooling Fan will not come on Need Help!

Old 04-05-2005, 10:19 PM
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Cooling Fan will not come on Need Help!

I have a 1992 RS Camaro and My Fan works but will only turn on when you run the a/c. Which rite now my a/c compressor is out so my a/c is not working. But other wise if your sitting at with the car on like in bad traffic the car fan will never come on. It will just keep rising. Since it comes one with the a/c I'm pretty sure my fan switch is working. So we replaced the temp. sensor and it still does nothing. So there only one more thing does anyone know if the factory temperature guage would have to be used? Because mine quite working so I just got a aftermarket one and it seems like I have been having fan problem since. I just did not notice till now because it just now getting hot weather around here. If anyone would have a good solution that would get my fan to come on again!
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Old 04-06-2005, 10:03 AM
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Re: Cooling Fan will not come on Need Help!

It is the fan switch, or the wiring to it. It's located on the passenger side cylinder head, in between the #6 and #8 spark plugs. You'll probably have to jack up the car to get to it. To test the wiring, just remove the electrical connector from the fan switch, turn the car on, and ground that wire. If the fan comes on, than the wiring is good, if the fan does not come on, than there is a problem in the wiring.
So there only one more thing does anyone know if the factory temperature guage would have to be used?
The temp. gauge in the dash uses the coolant temp. sending unit that is located in the driver's side cylinder head in between the #1 and #3 spark plugs. The factory temp. gauge does not have to be hooked up at all. Just for clarification, the ECM uses the coolant temp. sensor on the intake manifold next to the thermostat housing.
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Old 04-06-2005, 10:21 PM
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Re: Cooling Fan will not come on Need Help!

maybe you should just hook the fan up to a toggle switch that way you can turn it on when you want so the cool will run cooler sooner
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Old 04-06-2005, 10:58 PM
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Cool Re: Cooling Fan will not come on Need Help!

You might want to and go ahead and replace your cooling fan switch with a aftermarket one like from Hypertech for about $42.95 and use a 160 Degree thermostat that Hypertech also makes for your camaro and it's about $14.69 and there made for hot weather so they will help you a lot. The cooling fan switch is located in a hard to reach location on the passenger side of the engine just below the heat shield connected to the block make sure you drained the block of all coolant, because when you finally remove the sensor, you could end up getting wet in radiator coolant!

Last edited by Nitro; 04-08-2005 at 12:09 AM.
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Old 04-07-2005, 03:34 AM
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Re: Cooling Fan will not come on Need Help!

Originally Posted by 92_RSCamaro
... Since it comes one with the a/c I'm pretty sure my fan switch is working. So we replaced the temp. sensor and it still does nothing. So there only one more thing does anyone know if the factory temperature guage would have to be used?... If anyone would have a good solution that would get my fan to come on again!
No, the A/C fan pressure switch bypasses the (coolant) fan switch, and the ECM which, uses the coolant temperature sensor on the intake (CTS.)
If you disconnect the coolant fan switch and ground the wire the fan should work, if not you have faulty wiring.

Is the car actually over heating, or are you just concerned because of the temp gauge?

My electrical diagrams do not show a hi-temp fan switch for a single fan system so it doesn't show at what temperature the coolant fan switch closes, but many have argued that they do have the switch on their single fan systems, which is good, and it's probably set the same as a 2-fan system.
I have a primary coolant fan with it's own relay controlled by the ECM, and a heavy-duty coolant fan controlled by the heavy-duty coolant fan relay switch which has been refered to on this thread as fan, or cooling fan switch. the diagram shows the heavy-duty fan relay switch closes at 223C (238F.)
One way to test the Primary fan is to jumper the diagnostics ALDL terminals A & B forcing the ECM to ground the primary fan relay.
Since your A/C isn't working you can disconnect the A/C fan pressure switch and wire a toggle switch to it until you find the problem in the circuit.

There are 7 things to consider: (the first 4 are ruled because you said that the fan worked when the A/C was working.)
Item 5; either the coolant temperature isn't reaching 238F, or faulty wiring to the relay.
Item 6; ECM fan driver may be bad. unforunately the ECM will need replacing.
Using an adjustable temp switch (for winter/summer) would save you the trouble of buying a new ECM, but you'll lose the control the ECM has for different conditions.
  1. Power
  2. Fan Fuse
  3. Fan Motor
  4. Fan Relay
  5. Coolant Fan Switch (on head) grounds the fan relay when temperature exceeds 238F.
  6. ECM grounds the fan relay at programmed temperatures.
    There are four Fan settings in the ECM constants Table to turn the fan off and on.
  7. Faulty wiring
GM programs a high operating temperature for lower emissions.
Of the 9 binary files from ftp.diy-efi.org/pub/gmecm/bin_lib/1227165/6E folder 6 had the following settings: (I don't know if they're unmodified files)
  1. Turns Fan ON (A/C ON) 108C (226.4F) to keep the fan on when the A/C pressure is below 233psi.
  2. Turns Fan OFF (A/C OFF) 107C (224.6F)
  3. Turns Fan OFF (A/C ON) 105C (221F)
  4. Turns Fan ON (A/C OFF) 108C (226.4F)
3 files had:
Turns Fan OFF (A/C OFF) 105C (221F)

Please post your findings to help others save time and money.
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Old 04-07-2005, 09:33 PM
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Re: Cooling Fan will not come on Need Help!

Originally Posted by Nitro
You might want to and go ahead and replace your cooling fan switch with a aftermarket one like from Hypertech for about $42.95 and use a 160 Degree thermostat that Hypertech also makes for your camaro and it's about $11.95 and there made for hot weather so they will help you a lot. The cooling fan switch is located in a hard to reach location on the passenger side of the engine just below the heat shield connected to the block make sure you drained the block of all coolant, because when you finally remove the sensor, you could end up getting wet in radiator coolant!

Ben91RS found a cooling switch that turns on at 200* and off at 185* and costs about $20 shipped. i think a 160* thermo is too cold if you live anywhere where a heater is needed. a 180* thermo and that cooling fan switch seem like the perfect combo IMO.
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Old 04-08-2005, 12:08 AM
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Re: Cooling Fan will not come on Need Help!

Originally Posted by 92RS305#2
Ben91RS found a cooling switch that turns on at 200* and off at 185* and costs about $20 shipped. i think a 160* thermo is too cold if you live anywhere where a heater is needed. a 180* thermo and that cooling fan switch seem like the perfect combo IMO.
Your right about that but I use a 160 Degree themostat because I live in TX and it gets real hot usually about at 100 Degrees everyday in the summer and our winter is nothing compared to people that live up north. And Hypertech also sells a 180 Degree Thermostat for $7.39
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Old 04-09-2005, 01:53 AM
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Re: Cooling Fan will not come on Need Help!

texas i guess is okay, but if your gonna buy a cooling fan switch, buy the one from this site:

http://www.madvet.com/shop?frame=1.138.944

part# 609-106

it'll save you a couple bucks and will put you in the temp range that you want.
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Old 07-18-2017, 08:55 PM
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Re: Cooling Fan will not come on Need Help!

Originally Posted by raul.garcia View Post
No, the A/C fan pressure switch bypasses the (coolant) fan switch, and the ECM which, uses the coolant temperature sensor on the intake (CTS.)
If you disconnect the coolant fan switch and ground the wire the fan should work, if not you have faulty wiring.

Is the car actually over heating, or are you just concerned because of the temp gauge?

My electrical diagrams do not show a hi-temp fan switch for a single fan system so it doesn't show at what temperature the coolant fan switch closes, but many have argued that they do have the switch on their single fan systems, which is good, and it's probably set the same as a 2-fan system.
I have a primary coolant fan with it's own relay controlled by the ECM, and a heavy-duty coolant fan controlled by the heavy-duty coolant fan relay switch which has been refered to on this thread as fan, or cooling fan switch. the diagram shows the heavy-duty fan relay switch closes at 223C (238F.)
One way to test the Primary fan is to jumper the diagnostics ALDL terminals A & B forcing the ECM to ground the primary fan relay.
Since your A/C isn't working you can disconnect the A/C fan pressure switch and wire a toggle switch to it until you find the problem in the circuit.

There are 7 things to consider: (the first 4 are ruled because you said that the fan worked when the A/C was working.)
Item 5; either the coolant temperature isn't reaching 238F, or faulty wiring to the relay.
Item 6; ECM fan driver may be bad. unforunately the ECM will need replacing.
Using an adjustable temp switch (for winter/summer) would save you the trouble of buying a new ECM, but you'll lose the control the ECM has for different conditions.
  1. Power
  2. Fan Fuse
  3. Fan Motor
  4. Fan Relay
  5. Coolant Fan Switch (on head) grounds the fan relay when temperature exceeds 238F.
  6. ECM grounds the fan relay at programmed temperatures.
    There are four Fan settings in the ECM constants Table to turn the fan off and on.
  7. Faulty wiring
GM programs a high operating temperature for lower emissions.
Of the 9 binary files from ftp.diy-efi.org/pub/gmecm/bin_lib/1227165/6E folder 6 had the following settings: (I don't know if they're unmodified files)
  1. Turns Fan ON (A/C ON) 108C (226.4F) to keep the fan on when the A/C pressure is below 233psi.
  2. Turns Fan OFF (A/C OFF) 107C (224.6F)
  3. Turns Fan OFF (A/C ON) 105C (221F)
  4. Turns Fan ON (A/C OFF) 108C (226.4F)
3 files had:
Turns Fan OFF (A/C OFF) 105C (221F)

Please post your findings to help others save time and money.
I know this is old but thank you! We are trying to fix my sons soon to be first car and this is kicking our A**!
rushtk is offline  
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