Air conditioning

ford
f150

#1

My F-150 ac shuts down when air temp reaches above 80 degrees. The freon has been checked, the compressor clutch cycling switch & high pressure switch have been replaced with no effect.


#2

When this happens, are you still getting air blowing from the vents? How was the freon level checked? Low pressure switch?


#3

Do the electric radiator fan(s) run when the A/C is on?


#4

Air is still blowing from the vents but hot air. The freon level was checked by a ac mechanic. Note: the compressor can be visually seen stop rotating . The fan runs off the water pump. There is no electric radiator fan


#5

What really needs to be known are the high and low side pressures, both at idle and at elevated RPMs.
If everything is fine with the pressures, etc. then maybe there’s a blend door problem and that is the cause of the hot dash air rather than an A/C problem.

With the engine and A/C running for a while pop the hood and check the accumulator lines around the firewall. If the larger line is cold, sweating, etc, and there’s a condensation drip underneath the vehicle then this could be a sign the problem may be related to the blend door.


#6

I’m assuming that when you say that the compressor stops turning you mean it de-clutches. The belt and the pulley are still going around normally, correct? Does the clutch re-engage after a minute or so and then de-clutch again, or once the clutch has dropped out it stays that way until the engine has cooled off completely?
As ok4450 has asked, is the larger line sweating?


#7

To answer neburex’s Q, the clutch drops out & it stays that way until the engine has cooled off completely.


#8

This means the problem is electrical in nature.

When it fails measure the voltage on the line to the clutch. Usually it’s one thin wire.
If there’s voltage there the problem’s in the clutch: coil opens when hot.
You can confirm this with an ohmmeter.

If there’s no voltage then the next question is where does that line get its power from.
Simple switch or relay? Or a Body Control Module? Engine computer?

There may be some bad temp sensor telling the system to shut off the AC.


#9

What year truck? Any EATC? (electronic air temp control)


#10

Its a Ford F-150 2000 year 4.6L v8. I do not know if it has a EATC.