An issue with my recently purchased '05 MCS is my a/c which has a mind of it's own. Within a couple of days from purchasing it - the summer temps here in Mississippi were high as was the humidity - I noticed the a/c was not cooling at all.

So, I took it back to the dealer to get it fixed. His mechanic gave it a look over, replaced the dryer, and said all was good. Well, it wasn't. When I pick it up, the air seemed to be as hot as ever. Since the mechanic had the car parked outside, he asked me to drive it home, monitor it, and bring it back in the morning.

Here's where things got me scratching my head. The next morning I was heading back to the shop, but for some reason the a/c worked like a champ. Thinking the issue was corrected, I told the mechanic I'd drive it for a week an monitor the performance.

This is what I've noticed over the last few days. Whenever temps and humidity are not oppressive (under 95°/90%), the a/c works fine. But afternoon temps/humidity here exceed the oppressive levels which is when the a/c decides not to work. The compressor will on kick on in spurts for just a few seconds, whereas in the mornings it stays on much longer.

So, why is it the a/c works in cooler temps, but doesn't in hotter temps? Could it be a relay issue? My dealer/mechanic are eager to correct the problem, but I'd like to go in with some suggestions so they can avoid chasing rabbits down the wrong holes.

I look forward to seeing your replies,

Mark

 

Mark,

My guess would be the clutch is sticking in the higher temps and humidity. Just my guess though... I would probably recommend that they replace the compressor and clutch.

 

Thanks, daflake. I'll pass that thought along to them

 

could be too much freon. There is a high pressure safety switch and when it's hotter the pressure will be higher.

 

That's and interesting take on it, rckrzy1. Would that cause the compressor to sporadically kick on and off in short bursts?

 

I would also check your serpentine belt. When I first got my pulley on they used too long of a belt. Would work fine in cool temps. But once it got hot and I started to rev it up the belt would slip and no more AC.

Does it work better when parked?

 

Comp on, high pressure switch turns back off due to high pressure and the cycle continues

 

Ding. Ding. Ding. We have a winner!

Thanks for the tip, rckrzy1. I had my mechanic take a look at it and it turns out the dealers mechanic over a half pound too much freon in it. My guy flushed the system and got the freon back to manufacturer's specs. Now, although not as icy as it was before at sub 90 temps, it now cools at all temps.

Thanks again for the advice, everyone!

Mark

 

I had a secondary MOS as a A/C tech when I was in the Marines, glad to know I can still use my skills . The system on a MINI is like only 1.2 pounds so easy to over charge.

Glad you got it sorted out.