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The blower for the air conditioning continues to run at a moderate speed even after the engine has been turned off. Also while running, the fan seems not to change speed even when run on automatic.
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Both radiator cooling fans are running all the time ? Key off ? The cooling fan opperation
HOW they work
Cooling Fan Control
The engine cooling fan system consists of 2 cooling fans and 3 relays. The relays are powered by the battery positive voltage circuit and controlled by a switched ground from the powertrain control module (PCM).
During low speed operation, the PCM supplies the ground path for the low speed cooling fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan low relay coil, closes the relay contacts, and supplies battery positive voltage from the COOL FAN LO fuse through the cooling fan motor supply voltage circuit to the cooling fan. During high speed operation the PCM supplies the ground path for the cooling fan low 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 high relay and the s/p cooling fan relay through the high speed fan relay control circuit.
The PCM commands the fan on under the following conditions:
• Engine coolant temperature exceeds approximately 98°C (208°F) Low Fan Speed
• Engine coolant temperature exceeds approximately 102°C (216°F) High Fan Speed
• A/C refrigerant pressure exceeds 361 kPa (52 psi) Low Fan Speed
• A/C refrigerant pressure exceeds 2100 kPa (300 psi) High Fan Speed
• When the engine coolant temperature exceeds 112°C (234°F) at key off, the fan high speed will run for up to 300 seconds. If within that time frame 102°C (216°F) is reached then fan speed will change from high to low speed. If within that time frame 99°C (210°F) is reached then fan speed will change from low to off.
The PCM commands the fan off under the following conditions:
• A/C is requested and engine speed exceeds 6,240 RPM
• Engine coolant temperature exceeds approximately 99°C (210°F) turns the cooling fans from low to off.
sounds like one of the relays are stuck closed .
Cooling Fan Always On
Step
Action
Yes
No
Schematic Reference: Engine Cooling Schematics , HVAC Schematics in HVAC Systems - Manual
Connector End View Reference: Cooling System Connector End Views
DEFINITION: One or both engine cooling fan motors run continuously in high or low speed.
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, command the Fans Low Speed ON and OFF.
Are one or both cooling fans ON?
Go to Step 3
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
3
Are both cooling fans running continuously?
Go to Step 4
Go to Step 6
4
Are both cooling fans running continuously in high speed?
Go to Step 5
Go to Step 7
5
Test the low reference circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 18
Go to Step 14
6
Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.
Remove the cool fan S/P relay.
Did the right cooling fan turn OFF?
Go to Step 10
Go to Step 8
7
Remove the cool fan LOW relay.
Did the cooling fans turn OFF?
It's not the resistor. That just lowers the voltage going to the motor. Once you have turned the ignition off. There shouldn't be voltage getting to the resistor.
I'm making some assumptions, here.. I've been told I make too many assumptions... but, I'm assuming that you're talking about the engine cooling fan.. If I'm correct in this assumption, my guess is that you've not taken the vehicle to a good, reputable mechanic or repair shop. There are several reasons that an engine fan would not turn off, and each reason would have to come from a qualified mechanic. For example, there is a sending unit for the air conditioning system that might cause continuous running... or a sending unit in the air conditioning system that could cause the same thing. To complicate that issue, quite likely your air conditioning system purposely kicks on the engine fan any time you run your defroster. Also, your inside heater should function correctly, regardless of the engine fan running continuously. If I'm wrong on that score, then your engine has a thermostat problem "to boot"... which, by itself, could cause poor heating of the inside of the vehicle. NOW, backing up a little, if you so happen to be talking about the fan INSIDE the vehicle that is part of your heating OR air conditioning, we have a little different matter on our hands... First, some vehicles legitimately have a fan running on slow speed at ALL times.. for continuous air circulation purposes (sometimes, you can't actually hear this). Also, I might add that THIS fan running all the time should not be a problem for the heater to work properly.
The problem is the blower motor speed control resistor, it is located near the blower motor in the housing. I exchanged mine and it works like a charm now.
Ralph, Most common cause of this is the blower fan (proper name for the fan you refer to) continuing to run is a shorted out Electronic Climate Control Module. This solid state device replaces the older style fan speed resistor block (at about 4 times the price) This unit is found on the top of the HVAC box under the hood. (HVAC means heating, ventilation and air conditioning) The HVAC box is found on the passenger side of the firewall. Look behind the A/C's accumulator. It will have an electrical wiring plug on top of it. It will be fastened to the HVAC box with a few 7mm hex head screws. Very easy to change. FYI, do yourself a favor and replace the blower fan motor at the same time. The Electronic Climate Control Module usually fails because the motor is drawing to many amps of current. This is because it's bushings are worn out or the brushes are worn out. This is very common on Cadillacs and Buicks. Charlie PS Not sure why car won't start. Either you drained the battery or blew a fuse which controls starting the engine. Need more info regarding the "no start" condition.
Per your description, I believe you may have a blower fan relay that is stuck closed. Remove the relay from the under-hood fuse center and see if the fan stops. If it does stop, put the relay in slowly and see if you here the relay "click" and the fan come back on. Let me know. Regards,
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