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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 47956
Experience:  16 years experience
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I have a 2007 Ford F150 4.6l V8. The AC would sometimes blow

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I have a 2007 Ford F150 4.6l V8. The AC would sometimes blow cold, but sometimes not. Pressures were fine when I tested. So I replaced the relay. BUT, either the fitting on my gauge or the valve core in the charging port was bad, and when the relay didn't work, I checked and now there is no pressure!So I replaced both valve cores (high and low side) and tried to charge, but I could not get the compressor to kick on to take in freon. And it leaked all around the low side port, so I guess my gauge fitting is leaking (never heard of that). But I have another gauge. But the compressor did not ever kick on. Could it be something like a low or high pressure switch? If so, how do I replace it, is it screwed in?

Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.

The compressor will not kick in till there is the presence of freon pressure in the system. You can do that by pulling the system into a vacuum with a pump or AC machine. Then you charge with a can or AC machine to get the pressure up so the compressor will then run and you can then adjust the freon level to get the pressure right. If you would like to know how to manually get the compressor running I can help with that too.

Prior to completing the mandatory rating at the top of your screen. Let me know if I have not yet provided you with ~5 STAR EXCELLENT~service. Reply and let me know in more detail what you need to be pleased with my help.

Thanks Chris

Customer: replied 9 months ago.
Sorry, I forgot to mention that I did pull vacuum with a vacuum pump, then immediately tried to charge with a can of freon. It still didn't start. That's why i wondered if it was the low or high pressure switch maybe?

The PCM needs to see the clutch cycling switch closed. Power flow in and out of this switch. It also monitors the pressure transducer signal. When those are good the PCM will ground the clutch relay and energize it. Below are the steps for diagnosing the ACP sensor.

Customer: replied 9 months ago.
When I follow the decision tree, DS1 says, if no DTC (there are no DTCs), go to DS17. The decision there says "does the voltage change within 5 seconds of clutch engagement". The whole problem is the clutch does NOT engage. So we go to DS18. It asks "Does the pressure change more than 30psi within 5 seconds of clutch engagement. Again, the clutch will not engage. It didn't engage at first, before my bad low pressure valve core leaked out all the freon. And it still does not engage, but this is not new with the loss of freon, it didn't engage when I had a full charge of freon (again, the low pressure port valve core was bad and I have now replaced it.So, how do I get the clutch to engage? That seems to be the whole problem.

Did you verify the cycling switch was closed from my comments on testing it?

Customer: replied 9 months ago.
You didn't mention how to do it. You just said power flows in and out of the switch, and then sent me the flowcharts that I mentioned above.

Sorry, engine running, AC commanded on, cycling switch plugged up, confirm both of those wires are power.

Hello again Chris here,

  • Sorry you were not pleased with my help.
  • What would you like to do regarding your question now.
  • This post is coming up on the 7 day mark where it times out. When a post times out, that means it's no longer on my active list (you reply and I may never know it.)

Thanks Chris

Customer: replied 9 months ago.
Your help is fine. I've just had to deal with a couple of higher profile issues the last couple of weeks. I just haven't had a chance to look at the truck again so I left this open.


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