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jasson67 08-07-2011 09:33 PM

Air Conditioner Problem
I hope someone can shed a little light for me.
2003 Grand Cherokee Larado
original a/c system, evaporator replace when vehicle was a year old
nothing has been touched since vehicle has 40K miles

A/C worked fine till the beginning of summer. It blows cold when the vehicle is first started and driven, but if you turn it off and and restart, it won't cool very well. From start vent temp is a consistent 40. On restart it won't go below 60.

I live in the desert and had to drive to LA a few weeks ago and the a/c started out ice cold and then slowly lost it's cool. It's been doing that pretty consistent now...starting out blowing cold and then losing it's cool.

I connected a set of gauges this morning and here are the readings:
93 with 11% humidity
static pressure was about 100 low side 350 high side (I think..forgot to write them down)
after the Jeep had warmed up the readings were 33 low side and 240 high.
The high side did fluctuate a little with higher engine RPM's up to 250 and the low at one point went to 35. When the vehicle was at idle the readings held steady at 33/240. Clutch cycled as normal at higher RPM's.

The recycle door works fine. When you turn the temp to hot it blows hot and when turned back to cold it blows cool. It's a Laredo so I don't think the issue with the blend doors is a problem like on the Limited's.

I think it just needs a shot of r134a, but just wanted to pick someone else's expertise before adding. Maybe it's a start to a much bigger problem. Desert heat is killer so a properly working a/c is a must. And help is greatly appreciated.

Before I forget, thanks to all who post here. It has helped many times getting me out of a jam with my Jeep. I have learned a lot and hope someday to have a trip or trick that I can post to help others!

Thanks again.

JeepMe 08-08-2011 09:21 AM

Re: Air Conditioner Problem
Your reading while running are pretty normal.

To me it sounds like your starting out with good cold air because the R-134 is starting out cool. As you drive and run the A/C, the R-134 picks up more and more heat. It should be rejecting the heat to atmosphere through the condenser. Have you looked at your condenser? Are the fins all bent? Sounds to me like it's not doing it's job properly.

The second thing I would think is that it's simply time for a complete system recharge. I believe that it's very possible for R-134 to loose it's heat exchanging capabilities. My familly has had lots of old vehicles. When the A/C "works" it will blow semi cold air. We've taken a few vehicles in and got new R-134 and there's a HUGE difference when they come back.

jasson67 08-08-2011 10:54 AM

Re: Air Conditioner Problem
Thanks JEEPME.

Pressures seemed pretty good to me too. Condenser is clean and looks fine.

Sunday afternoon I had to drive cross desert and the outside temp was 109 with 11% humidity. Driving over the vent temp was a solid 40 which was great. The Jeep sat for an hour and the drive back it would only pull down to 48. Outside temps didn't change.

I am going to keep gauges with me so when it acts up I can throw them on and get the readings.

Something just isn't right for it to cool sometimes and not others.

Thanks for your input.

bacernate 08-12-2011 09:03 PM

Re: Air Conditioner Problem
Suck it dry and pull the orfice tube and see if there is any debris in it. If the compressor is starting to die it can partially clog the orfice tube.

2005JGC 08-13-2011 12:47 AM

Re: Air Conditioner Problem
I have seen compressor clutches go in this mannor... when its so hot like this and you turn it on it will engage and continue running the whole trip never having to cycle, yet when you shut if off and try to turn it back on it wont engage. a quick bump on the face of the compressor clutch and it will engage indicating that is the failure.

That said 60 degrees out the vent still indicates some heat being pulled out of the air and not a completely inop system.

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