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Discussion Starter · #1 ·
Noticed this weekend that neither of my cooling fans are running when the AC is on. As I remember, only one runs when the AC is turned on and then the second fan comes on with temperature from low to high (along with the first fan going from low to high on temperature of the engine)? Correct?
 

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A quick review of the repair manual did not provide any information on when the cooling fans start running, so can't confirm your information.

A possible place to start the diagnosis, if you are not familiar with the fan wiring is to check the fuses and relays for condition. Your owner's manual will have a diagram for the under hood fuse panel. Check the fuses and the three relays for condition. The relays are the same so you can swap them around.
 

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rhmvette said:
Noticed this weekend that neither of my cooling fans are running when the AC is on. As I remember, only one runs when the AC is turned on and then the second fan comes on with temperature from low to high (along with the first fan going from low to high on temperature of the engine)? Correct?
I found some info. The Fans come on when the high side of the A/C is above 225psi so below that it may not come on. There needs to be enough refrigerant in the system for that to happen.

The engine temp turns the low fan at 221f and the high speed at 245f.

Three fuses, the emissions2, cooling fan 1 & 2. Both fans are wired separately.

There's 3 relays, left right and speed.

Check your fuses and maybe you can test the power and ground at the motors. I'm seeing some A/C pressure sensors and connectors causing the fans to not come on or stay on.

Keep in mind these are PCM controlled so having a scanner with live data and even bidirectional controls can help.

I found a description that may help:




The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.

During low speed operation, the ECM supplies the ground path for the low speed fan 1 relay through the fan 1 relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the Fan 1 fuse through the cooling fan motor supply voltage circuit to the left engine cooling fan. The ground path for the left cooling fan is through the S/P fan 2 relay and the right engine cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the ECM continues to supply battery positive voltage for the right cooling fan by grounding the coil of the fan 1 relay. The ECM also grounds the high speed fan 3 relay and the S/P fan 2 relay through the fan 3 relay control circuit. This energizes the S/P fan 2 relay coil, closes the relay contacts, and provides a direct ground path for the left engine cooling fan. At the same time the fan 3 relay coil is energized closing the relay contacts and providing battery positive voltage from the Fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
 

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Discussion Starter · #4 ·
Great info, thanks for finding this. Fuses good. I have a leak in the condenser on the bottom of both sides and I have a replacement coming this week to install this weekend. I suspect that since I've been limping along adding refrigerant that the pressure isn't where it should be. Gotta get it changed soon...wife is on to me!

Thanks again! :cheers:
 

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I found some info. The Fans come on when the high side of the A/C is above 225psi so below that it may not come on. There needs to be enough refrigerant in the system for that to happen.

The engine temp turns the low fan at 221f and the high speed at 245f.

Three fuses, the emissions2, cooling fan 1 & 2. Both fans are wired separately.

There's 3 relays, left right and speed.

Check your fuses and maybe you can test the power and ground at the motors. I'm seeing some A/C pressure sensors and connectors causing the fans to not come on or stay on.

Keep in mind these are PCM controlled so having a scanner with live data and even bidirectional controls can help.

I found a description that may help:




The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.

During low speed operation, the ECM supplies the ground path for the low speed fan 1 relay through the fan 1 relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the Fan 1 fuse through the cooling fan motor supply voltage circuit to the left engine cooling fan. The ground path for the left cooling fan is through the S/P fan 2 relay and the right engine cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the ECM continues to supply battery positive voltage for the right cooling fan by grounding the coil of the fan 1 relay. The ECM also grounds the high speed fan 3 relay and the S/P fan 2 relay through the fan 3 relay control circuit. This energizes the S/P fan 2 relay coil, closes the relay contacts, and provides a direct ground path for the left engine cooling fan. At the same time the fan 3 relay coil is energized closing the relay contacts and providing battery positive voltage from the Fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
Hello,
My Enclave 2014 is starting the high speed on the fans at around 230 psi, however when the cooling fans go to high speed the pressure of the HVAC refrigerant drops after about 10 seconds and the fans go to slow speed. Seems like its cycling like that every 3 minutes or so. Any ideas of why the pressure drops ?
 
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