Engine fan kicking in too often when using A/C when ouside temp is above 75 F.

W900 Guy · Jun 27, 2016

purpleprime said: ↑

Is the condenser dirty and not allowing proper air flow , normal driving down the road should provide enough air flow that the fan shouldn't need to kick on , stop and go driving the fan is going to run alot anyway ,

Added also check that the fins aren't all smashed in they actually make a fin comb to straighten the fins on a condenser just not sure where to get one
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I can see light through the condenser. I put a light between the fan and rad and see the light up front when the hood is closed. I have run a wire brush through the condenser like a hair brush to free it from dirt.

W900 Guy · Jun 27, 2016

NorthernMechanic said: ↑

I'm gonna say you need to have the condensor cleaned out (cleaned as in so air can flow through, not on the inside where the refrigerant flows). A/C runs on pressures. The harder the system has to work, the higher the pressure (higher pressure = higher condensor temperatures). Once the pressure gets too high, the fan kicks in to help pull heat out of the condensor (lowers the pressure).
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Yup starting to think the same. Thanks!

Smellfunny · Jun 28, 2016

If the high side pressure gets around 320 the fan is going to kick on for whatever time is preset in the ECM (usually 3 mins) but some turn off when the pressure gets to the lower pressure around 150 or so. If the high side pressure is staying high or getting high quickly then the fan is going to stay on. You need to see what high side is doing. If the high side is climbing fast or coming down slowly after fan comes on then you have a blockage somewhere or the condenser needs cleaning or replaced.

Hammer166 · Jun 28, 2016

upallnite said: ↑

Have qualified a/c tech evacuate the system, flush the system to make sure there no restriction in the condensor, lines or the evaporator. Change the drier and expansion blocks, vacuum the system for at least an hour, then charge to the proper amount. The problem is in the drier, the dessicant has done its job and needs to be replaced. good luck and be safe!
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Yep, I'd bet on the dryer, too. Although usually when one goes bad, the pressure spikes enough to keep the fan on all the time.

As far as where the ambient temp is coming from, check in the intake tract somewhere upstream of the turbo. That reading is part of the engine management system, not the chassis.

W900 Guy · Jul 11, 2016

Thanks everyone for your advice. I will definitely replace the dryer and have condenser recleaned.

TFord · Sep 26, 2022

So did you ever get the fan to act normally? What was the fix?

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