Ok this is the problem I am having. I have a 02 F-150 5.4. When I am sitting in park my A/C blows nice and cold with no problem. When I put the truck in drive I can go until it warms up with no problem. Once it reaches the normal operating temp, my A/C gets warm and the clutch clicks on and off. I can put it in neutral or park and it stops but as soon as I put it in drive and step on the brake, it begins clicking on and off about every 2 seconds. I tried adding some 134-A and this did not solve the problem. It would not take any from the can. The reason that I initially noticed it was because it caused my check engine light to come on. Any help would be greatly appreciated.

 

I don't think the compressor cycling caused your check engine light to come on. What code did you get?

Also, when the compressor starts cycling, what speed do you have the fan set on? If you've got it on MAX A/C, with the fan on the first or second speed position, the system may be freezing up - the compressor will cycle to prevent this from happening.

If not, then the system may be slightly low; just 'cause it won't suck the stuff in from the can, does not mean that it's fully charged. The only way to be certain that it's fully charged is to recover the refrigerant that's in there with a charging station.

 

Take it in like I just did, even if they are just going to top it up, they will and have to do a inspection to eliminate other problems as well. Yours sounds like mine, that was just less than a pound down and now, problem solved.

 

That CEL code is likely a very important piece of data that is currently missing from this discussion.

The compressor clutch is directly controlled by the PCM via the WOT relay.

I'd therefore conclude that the PCM is cycling the compressor clutch based on a faulty input sensor.

Check refrigerant pressures with a guage set before attempting to charge. Overcharging is just as bad as undercharging.

Steve