I have a 2003 Ultra Luxury and I started experiencing some problems with the AC, sometimes it blows really cold and sometimes it doesn't, I have confirmed there isn't any leaks via a vaccum test, and the compressor kicks on when the AC is turned on, which leads to my next guess which would be the expansion valve, has any one of you guys changed an expansion valve before? Is it located under the dash on the passenger side? Any tips/tricks? I do have some mechanical background.

 

Ironically, I just got of the phone with the dealer where I just bought my 2005 ML. The AC was sporadically working last week, so I took it in on Friday to have them figure it out. They tell me the compressor is failing, so they will replace it and purge the system all covered under warranty.

It looks like the expansion valve is on the drivers side, next to the center stack

 

Under the dash on the driver's side? Kind of above the gas pedal?

 

2005 and still under warranty???

Niiiiice. Mine is a 2004 and just started to experience the same intermittent issue.

 

Here's a diagram of the A/C...

 

The dealer gave me a 30 day warranty with the car. I did opt for the 3 years of protection as well, but that cost me 1750 bucks, and it has a 100 dollar deductible.

So, since I'm still (barely) inside the 30 day window, they're picking up the tab on the compressor.

 

This was the image I was trying to post as well, but I'm at work, and I couldn't do it on the Delta computer...

I do have full access to Alldata, however...

 

With the Ultra Luxury models, there is a rear AC unit. The high-pressure line going to the rear is known to corrode and leak after 10-13 years. Most non-dealership places would not be aware of this rear AC configuration.

Someone on these forums DIY fixed it himself. I had the dealership repair mine.

Have you performed the basic AC refrigerant diagnostics using the sight glass, to ensure your refrigerant isn't underfilled or overfilled? Also, to check for leaks, you need to do the UV dye test, and don't forget to check all the way back to the rear AC unit.

 

I've had the same issue for years with my 2002 UL. A/C would take ten minutes to start blowing cold air. Replaced compressor about five years ago and fixed it. Recently started again, takes ten mins to blow cold air from a cold start. Symptoms were prevalent last Summer and Fall, went away for a couple of the cooler months here in Miami, then started again last month. Seems to be exacerbated by hotter, humid weather.