Is this how the Aztek Cooling Fans Work?
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Author Topic: Is this how the Aztek Cooling Fans Work?  (Read 3260 times)
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dashingDaryl
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« on: October 04, 2006, 07:17:22 PM »

I found this on the internet, and thought it would be awesome to know if it applies to the Aztek. Does it?
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Cooling Fan Control
The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood junction block. The ground path is provided at G103.

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

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan s/p relay through the high speed cooling fan relay control circuit. This energizes the cooling fan s/p relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool 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.

The PCM commands Low Speed Fans on under the following conditions:

Engine coolant temperature exceeds approximately 106C (223F).
A/C refrigerant pressure exceeds 1310 kPa (190 psi).
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140C (284F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.
The PCM commands High Speed Fans on under the following conditions:

Engine coolant temperature reaches 110C (230F).
A/C refrigerant pressure exceeds 1655 kPa (240 psi).
When certain DTCs set.
Engine Coolant Indicators
Engine Coolant Temperature
The IPC illuminates the engine coolant temperature indicator when the body control module (BCM) determines that the coolant temperature is greater than 123C (253F). The BCM receives a class 2 message from the PCM indicating the coolant temperature. The BCM sends a message to the IPC via the class 2 requesting illumination.

Low Engine Coolant Level
The IPC illuminates the low engine coolant level indicator when the body control module (BCM) detects a low voltage level on the signal circuit, indicating a low coolant level condition, for greater than 10 seconds and the ignition is ON. The BCM sends a message to the IPC via the class 2 requesting illumination.
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Karl
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« Reply #1 on: October 05, 2006, 08:25:42 AM »

That's verbatim from the service manual.
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Another North Carolina Aztek, Red Maple
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« Reply #2 on: October 18, 2017, 05:28:35 PM »

I realize that this is an old post, but I just cannot believe the fans are designed to come on at 223F ?! Isn't that too late and the gauge is already creeping into the red zone? Shouldn't our engines be kept from going anywhere above 200F???
« Last Edit: October 18, 2017, 05:29:23 PM by none » Logged

2003 Aztek 2WD
BlueGT
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« Reply #3 on: October 18, 2017, 07:11:14 PM »

I do agree about them coming on a little late, mine goes up to 3/4 of the gauge before they come on and it's unnerving.

The engine nor the trans are happy above 200F but not sure what to do about it.

In my L98 powered GMC truck, I wired the fan to be on constantly. Not sure I could do that in the 'tek without disrupting the PCM.
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2001 Steel Blue Metallic GT 1 of 1956 FWD blue GTs.
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