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I recently bought a 2008 f150 4x4 when I bought it the ac did not work now I'm trying to get the ac going the compressors not engaging so I checked all the fuses and relays I put my gauges on it and it's got freon in it I jumped the low pressure switch and still nothing so I checked the power at the compressor and no power I then checked the relay and diodes under the hood and the diode had no power so here's where I'm at with it I got power at the low pressure switch but no power at the compressor even with the switch jumped and all fuses and relays are good any help would be greatly appreciated
Last edited by Collinmsummerlin@gma; 06-12-2017 at 10:30 AM.
Reason: Typo in subject
You realize the diode is just to absorb the kick from the coil
When ac releases a reverse polarity kick results and the diode absorbs it as a short . That's to protect your other electrical items and cushion the blow to your ac shutoff elements . Big coils are bad about that such as your clutch coil . .
My ac relay was intermittent in engine compartment box . Its a small relay that most supply houses have .It's on the small side for what it does ,definitely try that first as it's cheap .
The relay has the grd side controlled by the PCM in the engine compartment it processes the ac controls thru it so it's more complicated than the old systems .Your temp control in the dash is another thing to the pcm .They do go bad .
This is an 05 drawing , but you can see that there is 3 fuses just in this part . There are some in the dash temp control circuit , which people screw up tying in other stuff-- radios etc . Time to get your multimeter out and see where you are losing the voltage .If you have it across the ac clutch relay coil including grd side then thats your problem .
I recently bought a 2008 f150 4x4 when I bought it the ac did not work now I'm trying to get the ac going the compressors not engaging so I checked all the fuses and relays I put my gauges on it and it's got freon in it I jumped the low pressure switch and still nothing so I checked the power at the compressor and no power I then checked the relay and diodes under the hood and the diode had no power so here's where I'm at with it I got power at the low pressure switch but no power at the compressor even with the switch jumped and all fuses and relays are good any help would be greatly appreciated
What about the switch itself on the dash.. did you read 12vdc on it ? And the clutch is what engages .. not the compressor.. did you read power to the clutch ?
06-12-2017, 10:18 AM
2008 f150 no power to ac compresser
