AC Issues - 2007 Chrysler Pacifica

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I have a 2007 Chrysler Pacifica that I'm having AC issues with. I bought the car last year and pointed out to the dealer that the AC wasn't working. He added some refrigerant & dye so I could see if the compressor would kick on and that the system itself was working, hopefully indicating that it's a leak and not anything major. The compressor did kick on right away and it blew cold air for a week or two.

I took it to a trusted independent mechanic a couple weeks ago to have them determine what is wrong, and they replaced the condenser which had a substantial leak. I assume they topped up the refrigerant, he told me they added dye, ran it for 45 minutes or so to test for any other leaks, everything looked good so they sent me on my way.

Yesterday was the first good hot day I could really put it to the test, and it's blowing out what I would consider "cool" air (definitely cooler than ambient temp), but far from cold. In 80+ degree temps it fails miserably at keeping the interior a comfortable temperature.

I checked the compressor with the vehicle running and it is cycling on and off repeatedly. About 5-10 seconds on, 5-10 seconds off, does this constantly. I have a DIY gauge for the low pressure side, so I plugged that in to see if perhaps it was low on refrigerant, and the gauge reads right where it should. The "filled/green" part of the gauge spans 25-45 PSI, and I'm getting approx 40 PSI when the compressor is running. When the compressor kicks off, the gauge goes higher to about 55 PSI which is in the yellow/warning area of the gauge. When the compressor kicks back on, it goes back to 40 PSI. Don't know enough about AC to discern whether the gauge going up and down with the compressor cycling is appropriate behavior.. But I do know that the compressor should not cycle on and off like this.

Anyone have any idea what might cause this? Would like to at least have a sense of what might be wrong before I bring it back to the mechanic and drain my wallet further. Any help or insight would be appreciated!
 
Originally Posted by Chris142
No idea without a high side reading.


Yes, you NEED proper gauges to troubleshoot, you can get some cheap but effective real gauges from Harbor Freight. Come back with readings.

I will guess and say that either it is over charged with R-134a OR the shop added too much oil! Something that is often missed in diagnosis.
Lots of incompetent shops out there, the rare one is competent!
 
I will pick up a set of good gauges. Do I do the same on the high side--- i.e turn air on max, plug in gauge and take reading? Or is there a more elaborate procedure? Learning here, be easy on me! I can repair pretty much anything on a vehicle but AC I haven't done much with.
 
That constant cycling of the compressor is common behavior, if not normal as well, for the Mopars I've owned recently. If it's an indication of something wrong, I've got the same problem to deal with on mine.

Going just off your post's info, and in the absence of more info from the folks that touched it, I would say the system has too much refrigerant in it. That can manifest itself in different ways, but one way a slightly overfilled system (as opposed to grossly overfilled) will behave is to blow cold air most of the time, but then only blow cool or even warm air when you really need it most.

I had this situation on my last Challenger. It was fine until temps outside got above 80 and vehicle forward movement was little or none, like in stop and go traffic. At those times, it would just blow outside air inside the car, so no cooling at all really.

The system turned out to be overfilled with Freon, and removing the excess amount fixed the behavior it was exhibiting previously in the adverse conditions. The high side pressure rating was the final data point that verified my suspicions, but I obtained it via the relevant PID in the WOT datalogs I was generating with my DS tuner. You wont have that luxury it sounds like, so you'll need the gauges.

As for the proper procedure to use when obtaining that high side pressure on the gauges, I do not have it, sorry. Hopefully someone can provide it here. (It May be as simple as hook up gauges, turn on a/c, read red guage's psi; but it may be more involved too, best to wait for others to chime in).

Good luck with it,
Nuke
 
Originally Posted by Chris142
Were the cooling fan (s) running?


Yes, the cooling fans are running at high speed as one would expect when the AC is on. They keep running even as the compressor cycles on and off.
 
Originally Posted by Chris142
No idea without a high side reading.



True here ^^^^^^^

Based upon what has been presented... Like others have thought... It is overcharged.
 
Bought the gauge kit from Harbor Freight. Previous LP reading I took was at idle. I'll read high and low @ 1500-2000rpm and report back.
 
Here's a video of the gauge readings after the AC had been running for 10 minutes or so. When I first kicked the AC on, the compressor ran steady for about 1-2 minutes, with low pressure around 40 and high around 300-350. After running a bit it began the compressor cycling which became quicker the longer the AC ran. The cycling will continue in perpetuity, the high pressure peaks, compressor kicks off, high pressure drops while low pressure rises, compressor kicks back on and repeat.

RPM was being held between 1500-2000rpm, with my wife in the driver's seat it's not all that steady, but I'm certain it didn't go above 2000 rpm or so.

video here

Hard to read the gauge increments after I compressed the video, the high pressure reads in 50PSI graduations, low pressure first black indication is 0, then 10 PSI increments. If this is a classic symptom of overcharging, how do I remove some of the refrigerant?
 
Wow. It goes straight up to the high pressure cutoff at 450. That should not happen in normal operation. If the condenser fans were running the whole time, it's seriously overcharged with refrigerant and / or oil.

The only way to be sure of a correct charge of refrigerant is to remove it all (down to vacuum) then charge the specified amount by weight. Excess oil is harder to get out.
 
Originally Posted by mk378
Wow. It goes straight up to the high pressure cutoff at 450. That should not happen in normal operation. If the condenser fans were running the whole time, it's seriously overcharged with refrigerant and / or oil.

The only way to be sure of a correct charge of refrigerant is to remove it all (down to vacuum) then charge the specified amount by weight. Excess oil is harder to get out.


Is there anything else that can cause this? i.e bad dryer, accumulator, expansion valve or such? Perhaps blockage in the system? Or is this a surefire overcharge situation?
 
You have to know the charge is correct before any other diagnosis can be made.

Generally if there is a blockage, no refrigerant can get to the low side and the pressure there goes down to near or below zero. Unless the blockage is in the condenser (and the high side port is before the condenser), the high side will stay reasonable or even low. No refrigerant flowing means that it all condenses in the condenser and receiver and then sits there.
 
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I agree. Needs a complete evac and refill.

What I see makes me think overcharged due to restriction.

What do I mean? A restriction will cause a high side pressure to be high, and low side pressure to below or negative. Someone notices low pressure on the side and thinks, " Needs more!".

By the time low side pressure makes any sense, high side pressure is just off the charts.

Last time I saw a vehicle do that, it was due to ridiculous over-oiling eliminating condenser efficiency. Condenser was so jammed with (Stop Leak?) oil that the condenser continued to discharge after removal. Sounded like Jiffy Pop.

Start with a proper charge to bring it back to Stage Zero, and then see what's going on.
 
The receiver / drier is integral to the condenser on this vehicle, so that's not a question mark since the condenser has been replaced.

I'll take it to have the refrigerant captured, then I'll vacuum /evac the system for 30 mins and fill by weight. Does this sound like the right thing to do at this point? What do I do about oil, is it necessary to add any extra?

I have no idea what the mechanic did when he replaced the condenser, sounds as though he either overfilled it or did not put it under a vacuum before filling it. All he said was that he ran it for 30-45 minutes to check for leaks after filling. Wouldn't putting it under a vacuum / properly evacuate the system negate the need for a leak check while running?

This particular mechanic is in an area of town where his customers probably favor cost over getting things done right. They've been good on other repairs, but I don't think I'll use them for AC going forward. I knew within 15 minutes of driving it that something was not right, no idea how they missed it if they had it running for 30 minutes.
 
this also could have nothing to do with the freon charge. the low side reading alone means little but does give some indication of not being zero or crazy high. The running then cycling is also a good sign. This could also be a blend door issue, which would not be uncommon for a Chrysler of that era, or really any 10+ year old vehicle with servo-controlled dampers. It could also be offset by higher humidity levels - try running it recirc after the first 3 minutes to see if removing the humidity load improves.
 
I decided to pull some refrigerant to see if anything improved, wanted to test the overfill theory. I'll have a vacuum pump tomorrow and will evacuate & recharge the system with the correct amount (hood label says 1.5 lbs) regardless. Valvoline down the street will do the refrigerant recovery for $20 which I thought was a good deal. Here's what I discovered. Hooked the gauges up and cracked the manifold open on the low side with the car off to vent some refrigerant. I let it come out for 2-3 seconds, it was fairly high pressure and came out as a liquid mist (oil or dye perhaps?), then I closed the valve.

Started car and the pressures are now pretty rock solid. The low will stay between about 38-40 and the high settles in at 250. Once in a while it would begin to move toward 300, but the cooling fans went to high speed and it dropped back down to 250. I left it running for about 15 minutes and the compressor never cycled and the pressures stayed consistent.

The gauge readings changed a bit when I changed the climate control setting to recirc, but I can't remember which direction they moved (up or down). Ambient temp during the test was mid 70's, about 80% humidity. Air coming out of the vents feels like it could be a bit colder, a thermometer read about 55 degrees.

Does the above sound like normal behavior for the AC system? Can someone please let me know what to do about oil when I evacuate & recharge the AC system. Specifically, will some come out and do I need to add any? Thanks all for the help, this is a great resource and you folks really know your stuff about AC!
 
Oil doesn't come out when a recovery machine or vacuum pump is used. Of course some oil will come out if you open the high side with the compressor running, but it is less than you'd think. It is not legal, safe, or in any way recommended to vent out refrigerant. There's no way to tell how much comes out.
 
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