I have 1998 F150 4.2L. The A/C runs perfect at all times while I'm actually driving. If I put in park and sit idle for a few minutes (eating on lunch break, stuff like that) it feels as if the idle gets a lot lower and the cold air will turn hot for 20-40 seconds or so. After that it will go back to normal idle and the air will turn cold again. It will do this off and on the entire time I'm parked. It only does this when I'm sitting still in park though. Like I said, the A/C is perfectly fine and doesn't do this while I'm driving around. It won't do it while I'm stopped at stop lights or anything like that either.

I don't know a whole lot about engines so I won't be able to check a lot of things you guys might mention. I think I've read enough about the MAF and IAC to be able to find those if you think that is the problem. Thanks for any help.

 

1. Have your charge checked with a set of real guages.

2. Check the radiator fan clutch for proper operation.

3. Check the compressor clutch for slipping (bad air gap).

Steve

 

Thanks, I will look into that. Anyone else got any ideas?

 

This problem is usually related to a fan problem. Like previously stated, stick some guages on it and watch the pressures while it is sitting at idle.

 

I will check the fan. Also, I realized that it never does it in the morning when it is much cooler outside, even though I sit idle in park for at least 15 minutes. It always happens when its hot outside and the sun is really beating down.