AC works only after 3 mins

[joecrow]

Hi all,
I have an AC problem I hope someone can help me figure out. The AC works fine, but only after the engine has been running for about 3 mins. It takes that long for the compressor to kick in. During the first 3 mins, the vents blow ambient temp air. After the compressor kicks in, the vents blow cold air. The AC system works great after that, except for having to wait. However if I stop the engine, sometimes it works immediately and other times I have to wait another 3 mins. There are times I arrive at my destination (sweating) by the time cold air starts blowing. I attached a gauge set to the system and noticed that the low side starts at @20 and slooowly climbs to @35 and then the compressor kicks in. I tried jumpering the plug on the low pressure switch, but it did not make the compressor kick in. Anyway, I have had this problem for a few months, but the "HOT Texas heat" is forcing me to fix it. And by "HOT Texas heat", I mean my wife. :woot: Any suggestion would be appreciated. Thanks.

[Destroyer000]

i would try changing the low pressure switch i just replaced the one on my moms stang past 4 years the a/c didnt work... well i got a switch today that was 20 bucks an it works awesome now..

[joecrow]

Thanks for the reply. If you short the plug, does it make the compressor kick in? Mine doesn't. Just wondering.

[mhughes165]

sounds like the pressure in the system is slightly low, so it takes longer for it to build pressure.....

[MAKG]

sounds like the pressure in the system is slightly low, so it takes longer for it to build pressure.....


How does it build pressure with the compressor unclutched?

I suspect the low-pressure switch as well; it's not closing until underhood temps warm it up (or perhaps vibration). It's easy to check with an ohmmeter; the switch should be closed with the engine off and stone cold.

[mhughes165]

How does it build pressure with the compressor unclutched?

I suspect the low-pressure switch as well; it's not closing until underhood temps warm it up (or perhaps vibration). It's easy to check with an ohmmeter; the switch should be closed with the engine off and stone cold.

what happens when gasses get hot......it could just be to the point where the pressure is low enough that engine heat bumps the pressure to the proper point, ive seen it happen....however un likely, i was just giving another suggestion to check aside from the obvious low pressure switch

[joecrow]

OK I'll check my pressures again and throw in a new low pressure switch. Thanks for the responses guys. I really appreciate it.