Skip the auto shop - Our mechanics make house calls

Q: AC system

asked by on

On this 1998 Ford F150 the engine has been rebuilt so the miles that it says on here are the frame miles. On the truck there was a weird sound as if something was rattling, so I looked in the engine compartment and the AC clutch was bad. I replaced the AC clutch and when I turned the truck on and turned the AC on, the clutch continually moves. But once I turn off the air-conditioner (with the truck still running) the AC clutch disengages. I hooked an AC manifold gage to the high side and low side. The low side said 40 and the high side said 30. The truck blows cold but the gage reading does not make sense to me unless it's the expansion valve. Should I just evacuate the system and put new freon in? The truck does not have r24 the truck has r134. Ultimately, what should I do?

My car has 386 miles.
My car has an automatic transmission.

A: If the low side said 40 and the compressor ...

If the low side said 40 and the compressor was running, then the high side should be above 175 or more. I think your gauge is not working correctly. Try an check the pressures with the engine off and cool them. The pressure should be about 10 to 15 above your ambient temperature if the system is full. This means it is 90 degrees outside, then you will read around 100 to 115 psi on the gauge with the engine off. When you start the truck, the low pressure should go down as the inside cools down. It should cycle around 24 psi. If you want to have a mechanic take a look at this in person, a certified technician from YourMechanic can come to your home or office to diagnose your AC system.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: How do I enable the autolamp control?

The Autolamp Control on your truck can make turning on your headlights easier. The Autolamp Control turns your headlights on automatically when it senses darkness. To enable Auto Lamp Control. Turn the Headlamp Control knob to the fourth spot....

Q: Power window broken

If your passenger window works from the drivers window switch only, then the window lock switch on the drivers door needs to be checked to see if it locks and unlocks to the other doors. If it works properly for...

Q: I was driving home and came to a stop light and it just stalled and refuse to start.

From what you've described, there may be a piece of carbon lodged in the EGR valve. This can cause a stall and hard start conditions. This accounts for the vehicle having fuel pressure and spark still. Try to see if...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...