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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6667
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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I have a 2007 Ford F150 with a 4.6l V8. The AC blows cold on

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I have a 2007 Ford F150 with a 4.6l V8. The AC blows cold on starting, but a few minutes later it gets hot. Then it gets cold. Then hot. Intermittent. It does not appear to vary with acceleration, just random. I checked the AC pressure. High side at idle was about 250psi and low side was about 35-40psi, ambient temo about 90. It was cool while I was checking it, then there was a click, pressure dropped to 120/20 or so, and it was hot. So it appears compressor is turning on and off intermittently.

The problem is either the high side cut out switch, low side pressure switch or the AC compressor relay in the Auxiliary relay box on the drivers inner fender well. See below to locate the relay.

Swap the relay out and retest the AC system. These smaller relays are known for failing.

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