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post #1 of 7 (permalink) Old 08-25-2013, 09:26 AM Thread Starter
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Cooling Fan Not Working with AC On.

Hi, A very informative forum here. A lot of great information!
I would like some assistance with a problem I am having that I could not find anything similar on the forum. 2008 Cobalt with 2.2 was hit in the front end, Replaced Rad/ Cond. and Fan Assy.
I have yet heard the fan turning on. I thought by turning on the AC the fan would start. I can here the compressor turn on, but no fan. I checked the wiring of the fan in case the wires wire broke, but they checked out ok. I jumped the pin 87 of the coolingfan1 relay to pin 30 and the fan worked.
I replaced the relays (Coolingfan1 and 2) with the rear fogger relay to verify they operated. (Which they did)
I cannot find what the ECM voltage should be coming into the relay. Coolingfan2 has 2.95V using the ground lug on the engine as reference when the relay is out of the socket. It does not change when I turn on the AC. However with the replay in position that same pin is the same voltage as pin85 and 30. Pin 87 0 volts.
Do you think those to points could be bad coming out of the ECM? (Everything else is working)
Any help on this would be appreciated.
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post #2 of 7 (permalink) Old 08-25-2013, 09:51 AM
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post #3 of 7 (permalink) Old 08-27-2013, 05:27 PM Thread Starter
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Cooling Fan Not Working with AC On

Thanks for the diagram! WIth a meter it looks like most everything checks out.
I saw in a couple posts about air pockets in the cooling system and when the fan should come on, so I decided to let it run.
THe fan actually came on at 214 F. So I am some what relieved. I swapped the relays and turned on the AC, but the fan did not come on.
THe check engine light is not on, so there are no codes per autozone.
Any ideas?
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post #4 of 7 (permalink) Old 08-27-2013, 05:34 PM
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WoW, fan one should come on when A/C is switched on. Unless pressure readings from sensors is way out of wack.

Are you getting cold air?

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post #5 of 7 (permalink) Old 08-28-2013, 05:09 AM Thread Starter
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No I am not. I left that information out till now.
Do you think if the freon level is wrong the fan will not come on?
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post #6 of 7 (permalink) Old 08-28-2013, 07:55 AM
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Correct, fan comes on to cool refrigerant but if there is no refrigerant no need to come on. The sensor doesn't get the right parameters to start the fan.

The ECM commands Low Speed Fans ON under the following conditions:

• Engine coolant temperature (ECT) exceeds approximately 106C (223F).

• A/C refrigerant pressure exceeds 1 310 kPa (190 psi).

• After the vehicle is shut off, the ECT 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 ECM commands High Speed Fans ON under the following conditions:

• ECT reaches 110C (230F).

• A/C refrigerant pressure exceeds 1 655 kPa (240 psi).

• When certain DTCs set

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.

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Last edited by Coby7; 08-28-2013 at 07:58 AM.
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post #7 of 7 (permalink) Old 08-28-2013, 12:12 PM Thread Starter
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Thanks for the info. I will get theAC guy to check it out.
Steve
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