Air Conditioning Issue
 

I have a 2002 Diamante LS with 93K miles. The aircon has been great requiring no attention until now. I live in phoenix with that dry heat. When the ambient temperature is above about 90 degrees F the Aircon fails to cool. When below 90 F the Aircon blows nice cool air.

When the ambient temp is above 90F; I do note that the electric cooling fans in the engine compartment come on when the Aircon is turned on but both the High pressure and Low pressure Freon lines are hot to warm respectively. The site glass shows no signs of bubbles.

When the temp is below 90 F the Freon lines act more normally with the High pressure and Low pressure Freon lines are hot to cool respectively.

Is it a correct assumption that I only need a recharge ? or do I have a switch that may be bad given this condition only exists during hotter outside temps.

I would have expected that if a recharge was required that I wouldn't get cooling regardless of ambient outside temp.... and the site glass would show bubbles.....

Is there anything I can do to validate what I really need for a repair before I take it to the dealer?

Thanks for any tips or suggestions.

When it is not cooling, does the AC compressor clutch activate and the compressor is actually turning?

This morning, I checked and the clutch does activate and so the compressor is turning... I am suspecting at warmer temps (above 90)... the low pressure switch is not switching to activate the Compressor... So I may try one of those quick DIY recharge kits from autozone....

the point being... I'll need to verify that (clutch operation) this evening after my commute home when the temp is above 90....

Just adding refrigerant without knowing if the refrigerant level is low is not a good idea. You need to diagnose the problem as called for in the factory service manual.

If you don't have the Diamante factory service manual, I recommend downloading the ISO file from http://www.lisho.net/files/magnaworkshop.iso and burning it to a CD, then using the CD to install the manual. Once installed, go to the TJ/KJ section and read all about the Diamante AC system in Group 55. You should be able to diagnose your problem with the manual. It even tells you how to check for an AC trouble code using a voltmeter.

Thanks for the link. I will do that. Amazingly enough, Aircon blew cold all the way home from work today in 95+F temps. So my best guess at this point is either the low pressure switch or low freon right on the edge of acceptable pressure levels.

Very curious symptoms.

Hi,

Please do not worry about that. It is a pity that i have not much time to give you some tips but I think you should consult on Webpages or search tips on the net. There are a variety of useful information for you. Hope your matter can be solved soon.

sounds like a bad expansion valve

Well, I had a technician check the low side and high side pressures and they were fine, the compressor was cycling just fine, and the fans were also cycling good as well.

Seems you may be correct in that the expansion valve may be bad. This is clearly an intermittent issue.

Doesn't look good. I suppose that is located under the dash near the condenser?

If all the pressures were fine and you weren't getting cooling, then perhaps the expansion valve is at fault. Did you verify compressor rotation and correct pressures when there was no cooling?

If you were getting normal cooling when the pressures were tested, you haven't verified what is happening when there is no cooling. In that case, there is something intermittent that is shutting down the compressor or affecting cooling function. I wouldn't rule out an intermittent high or low pressure switch. Also, if the serpentine belt is loose and the compressor slips a bit, the computer will shut down the compressor. There also could be a problem with the AC control unit that is shutting down cooling.

In any event, the expansion valve is part of the evaporator assembly (evaporator and casing) under the dash and not available separately. The condenser is in front of the radiator. You better hope that the problem is not the expansion valve. A new evaporator assembly retails for $1000 at the dealer ($756 at parts.com).