Just wondering what my problem could be when i turn my AC on through the vents it works fine when idling or coasting but soon as i step on the throttle it stops blowing out the vents and starts blowing out the defrost vents any info would be nice and its a 1999 4.6 thanks in advance.

 

I had the same problem a year ago I thought It was the climate control so I took it out and found nothing. while replacing plugs I found a broken vacuum line on the firewall between the battery and the pcv valve. easy repair. works great now. But you will have to take the plastic loom loose to find it. Its worth the effort. Hope this helps.

 

thanks for the help i will look into doing that.

 

You guys are so lucky try DX'ing AC issues on a circa 1967 Cadillac. The Climate control systems on these cars where great as long as they where working but they are entirely operated by vacuum, Vacuum motors, vacuum switches, vacuum distribution blocks, and about 543 and a half miles of vacuum lines. And then there is the infamous Master Vacuum Switch, it always stopped working when it was 20 below zero and you desperately need heat to keep from freezing to death, if it didn't kick in nothing worked. Trying to figure out what was wrong was a complete nightmare.