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Discussion Starter #1
This is a weird one, and I will try to explain this to the best of my ability. It will be a little lengthy I am sure. When it is below 80°, this problem is hardly noticeable. My air conditioner is cycling off before it starts to get cold enough when the temp is above 80° outside. It starts to feel great, then it cycles off, gets warmer, then cycles back on. It seems to be performing well otherwise. Last year this problem was worse. I had a certified mechanic flush, replace the schrader valves, vacuum down, confirm it held vacuum, then charge according to the car's capacity. He said it looked great on the gauges, and when he was done, it worked better, but would still cycle before it got cold enough.

Playing around in the engine bay around last September, I discovered that the wires to the high pressure transducer/switch had fallen out and weren't connected all the way. I removed the plug and fixed the pins, then crimped the wires back in. I had a considerable improvement in performance. But the problem hasn't gone away at high outside temperatures.

What could cause this problem? I wonder if I had put the transducer wires back into the plug correctly or not, if it's a computer or evaporator probe issue, I am not sure. But it seems my AC system has a lot of potential and it's being held back. On a side note, my AC compressor clutch makes a clinking noise when it disengages sometimes, just in case that is relevant. Thanks for your replies in advance!
 

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I had a certified mechanic flush, replace the schrader valves, vacuum down, confirm it held vacuum, then charge according to the car's capacity. He said it looked great on the gauges, and when he was done, it worked better, but would still cycle before it got cold enough
When service personnel say things are good or look great but do not specify any quantitative values, I would be suspicious. What is the suction pressure and discharge pressure when the compressor cycles off? If the suction pressure is around 50 psi then the evaporator is not reaching design temperature which is 32 deg F.

If the system over pressures and the high pressure transducer switch is signaling excessive system pressure to the PCM (powertrain control module) then the PCM disengages the compressor until the discharge pressure reaches a safe level before allowing the compressor clutch to re-engage.

Now if you can verify that the suction and discharge pressures are within the operating design range for outside temperature, then its possible that the evaporator temperature probe is malfunctioning and giving a false signal to the PCM and causing the compressor clutch to disengage prematurely.

The resistance of the probe is proportional to the probe temperature. At 50 deg F it should be around 9950 ohms and at 100 deg F is should be about 2912 ohms. At 32 deg F the resistance would be about 12472 ohms. If the probe is giving excessively high resistance values above its design range, this will fool the PCM and cause it to disengage the compressor clutch.
 

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Discussion Starter #3
Looks like it's time to get me some gauges. I have some for r-12 but not 134a. Use to have an old Honda...

I guess I would be wise to remove the evaporator probe and present it to one of the temperatures and check resistance. How difficult is it to remove the probe? Does it require removal of the dash? I guess if not, I would wait till the AC cycles off and see what the resistance value was.

When I bought the car, coincidentally, it DID have an overcharge. Code 33, AC volts too high, and I decided to take it in. It was a $100 dollar service. You could be right, I never saw the gauges. But I brought it in after the service complaining, and my mechanic's AC tech came out saying he couldn't find a problem. He is a personal kind of mechanic, and I knew him back when he was running his shop out of his house as a one-man-band. Now that he owns his own separate shop, I would hope he isn't corrupt yet. Maybe his AC tech is though.

What should be the high side pressure? If I get some 134a gauges, I will be hooking up both sides. Thanks for your prompt reply!
 

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Even honest mechanics sometimes ignore “the rules” and rely on “experience.” Sometimes they can get away with it, but the best carb tuneup I ever had was from a mechanic who actually, only time I've ever seen this done, hooked up the exhaust gas analyzer and did everything by the book.

Paid twice as much but it solved a lot of drivability problems, some permanently (he adjusted the float level as well as mixture).

A/C is an area of mystery to many mechanics, in my experience.
 

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Discussion Starter #5
Yeah. It literally seems to be like rocket science, and odd problems all the time. And lots of money in equipment to diagnose. It would be nice to have the computer tell me its conditions for disabling the clutch too.
 

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I had a similar problem on my 96 minivan and in my case, it ended up being the insulation around the evaporator core had rotted away leaving gaps for air to flow around, but not through the evaporator. That caused premature cycling because the evaporator probe sensed a very cold evaporator because not much heat was being drawn off of it with the majority of the fan air going around the outside.

As in your case, the pressures were nearly perfect in the system and it worked fine in cooler weather but would not perform when outside temps got in the 90's. The self diagnostics and cooldown test (a feature included in my minivan) always passed, but that system uses the evaporator probe for the cooldown diagnostics.

Finally, I pulled the probe out of the evaporator half way to reduce cycling and soon found that the evaporator quickly iced over, blocking all the air flow through it. By thinking about what could be going on, it occurred to me that air must be bypassing the evaporator. Fortunately on the mini-van the evaporator probe grommet is large enough so that when it is removed, you can fit your hand inside the HVAC box and stuff foam strips around the sides of the evaporator. I used 1-1/4"square foam strips from Home Depot that compress nicely to about 1/2"and worked perfectly. Now my AC blows ice cold, even at outside temps of near 100 degress outside.

I don't know if this could be your issue, but I thought you might want to hear my situation since your problem sounds like the symptoms that I had.
 

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Discussion Starter #7
That information is PRICELESS. What is your '96 minivan? My neighbor had a '97 Chrysler Minivan, and it was the same vintage as my car. Same grille, hood design, the same brake lights and headlights, and stock stereo. I am sure there are more similarities, but I do not know any off the too of my head. Possibility that we have the same "air-box"? I will attempt to find my AC evaporator probe and see if my hand will fit inside. Do what you did and investigate. I have wanted to remove the whole dashboard and remove the air box, since I have a minor water leak, the car smells like wet dog when it rains. But I didn't wanna evacuate, vacuum down, recharge, etc.
 

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95chryslercirrus said:
That information is PRICELESS. What is your '96 minivan? My neighbor had a '97 Chrysler Minivan, and it was the same vintage as my car. Same grille, hood design, the same brake lights and headlights, and stock stereo. I am sure there are more similarities, but I do not know any off the too of my head. Possibility that we have the same "air-box"? I will attempt to find my AC evaporator probe and see if my hand will fit inside. Do what you did and investigate. I have wanted to remove the whole dashboard and remove the air box, since I have a minor water leak, the car smells like wet dog when it rains. But I didn't wanna evacuate, vacuum down, recharge, etc.
Good luck and I hope it works out for you. My mini is a 96 G Voyager and the evaporator probe was accessable by removing the glove compartment door. Of course on your car, the design could be a bit different. Let us know what you find out.
 

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Discussion Starter #9
Well that was sort of a bust. I could barely put 2 fingers into the hole provided for the evaporator probe. I could barely see inside there, but the evaporator appeared to be covered in dust, lint, and black mold. I was not able to pull the probe out, and I am sure the whole car needs taken apart to access it. I tried to feel around the evaporator with the best of my ability, but I could not get to the edges to feel for a seal strip present. I am reluctant to take apart the whole car, but I do not have a choice it looks like. At least then I could rule out the climate control as causing the issue.
 

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If you can sample a piece of that 'black mold' and it feels oily, it may be refrigerant oil from an evaporator core leak mixed with dust.
Many refrigerant PAG oils had a green UV dye added, so if the surrounding core has a green tint to it and it smells musty, it may need an evaporator. Especially if your pressure readings are low.
There is no really effective way to wash or treat an evaporator inside the HVAC housing anyway. Many fungicide treatments are basically just an aerosol foaming fragrance.
Evaporator replacement for refrigerant leaks was common back then. The LH and ZJ's had an extended 7/70 Valeo evaporator replacement warranty because of it.
 

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Discussion Starter #11
That would make much sense. My car is halfway torn apart and it is going to be downpouring outside for the next 3 days, otherwise I would tell you. I would guess that my evaporator is original, but there really is no way of telling unless I see signs of someone tearing into the dash. Found some screws loose, would account for the annoying rattling... I have to tear it apart anyway to get to the evaporator all the way. And if it isn't oily substance, then I will just clean it. I do have fluorescent die in my PAG. It should be reactive to UV black light. If it lights up like a highlighter, we'll know if it's broken alright.
 

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Discussion Starter #12
I thought I would update everyone on this topic.

Me and my brother bought a can of 134a with his car, and it conveniently included a gauge for the low side. Today, being curious, I hooked it up to my car. I did an experiment on my car and poured water on the condenser, which made the AC colder as expected. It was 80° outside when I did the check. My low side pressures were 20-25 PSI. Looking at 134a temperature to pressure charts, it should be around 40-50 PSI.

Anyone have experience with this on the cloud cars? Does it sound like I am low on refrigerant? I added the last of the refrigerant I had, and it bumped the PSI up about 5. The condenser got hoter than before as I added refrigerant and the fans kicked up to the 2nd highest speed. Made me think it was becoming more efficient and transferring heat better. I don't want to accidentally add too much and trip code 33, so I am checking my basics. Thanks guys!
 

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Code 33:

Code 33

A/C relay open or shorted

This has NOTHING to do with the pressure in your system, you can't cause this by over or underfilling.

You really need a high side pressure gauge as well as low. And pressure is proportional to ambient temperature, so you can't just state that the high pressure should be ___ psi. It will be higher as the outside temperature climbs. Generally it should range from 200 to 300 psi over a range of ambient temperatures between 70 and 90. And 50 psi is a little high.
 

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Discussion Starter #14
http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c152800898a3

Figure 5 shows code 33 as AC volts too high, too low, or as you said, clutch relay circuit. When I took it into the mechanic last year for AC re-work, he said he pulled code 33 out for AC pressure sensor volts too high. If this does not apply to my vehicle though, I will not worry about it.

I agree about the high side pressure gagues, but my manifold set is for R12 and I do not have money to buy adapters to make the gauges fit 134a couplings. I did however, list that the ambient temperature was 80 degrees outside with 20-25 PSI on the low side. According to charts found on the web and on my 134a can, with an ambient temperature of 80, low side pressure should be between 40-50 PSI.

I am not trying to start an argument here, I am willing to be proved wrong on whatever it takes to get my car fixed using the friendly people here at Allpar. If I got ripped off by my AC mechanic and code 33 does not apply to my Cirrus, then I will not go back to him again. He did say he found extra and wasn't able to put back in what he took out, according to the cars refrigerant capacity label, but that doesn't mean he didn't lie and kept extra for himself. I was never charged for refrigerant, but never reimbersed me for the "extra" they kept.
 

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Code 33 can be set if the A/C clutch relay is removed anytime the ign. is on. This may have been set unintentionally during a diagnosis where the relay might have been temporarily removed for jumping or voltage checks?
Is it blowing cold inside and the condenser getting warm outside? The fans are coming on, so some pressure differential exists and that is good.
Too high a pressure in the system might have happened if air was already present in the system and a complete reclaim and evacuation wasn't done before charging. Too high a concentration of air is bad. It must be pure refrigerant.
It may not have originally been too much refrigerant in the system for the reason that the tech had to take some out, although you don't want to arbitrarily add refrigerant unless you can prove that it is low first and only then monitor how much you are adding.
 

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Discussion Starter #16
ImperialCrown said:
Code 33 can be set if the A/C clutch relay is removed anytime the ign. is on. This may have been set unintentionally during a diagnosis where the relay might have been temporarily removed for jumping or voltage checks?
Is it blowing cold inside and the condenser getting warm outside? The fans are coming on, so some pressure differential exists and that is good.
Too high a pressure in the system might have happened if air was already present in the system and a complete reclaim and evacuation wasn't done before charging. Too high a concentration of air is bad. It must be pure refrigerant.
It may not have originally been too much refrigerant in the system for the reason that the tech had to take some out, although you don't want to arbitrarily add refrigerant unless you can prove that it is low first and only then monitor how much you are adding.
Very possible. It was present when I got the car. After I had the AC worked on, he cleared the code. It has not come back, but summer is just starting.

Yes it is blowing cold inside, but to a point. Condenser was getting hot enough to steam the water off of it (I took the front grilles off and cleaned the condenser). I also continued to run water over the condenser for about 10 minutes, and was getting the AC to cycle on and off because of the increased performance, then it was REALLY cold inside, and that is when I was reading 20-25 PSI on the low side. Both fans come on, and the hotter the condenser gets, the faster the computer makes them spin. I have only heard them kick into full speed about once or twice. Usually they spin on low or medium speeds. I am considering adding a small fan in front of the condenser to push the air better.

I took it in because on a 100 degree day with the AC on it was coming out the vents at 80 degrees traveling on the freeway at 70MPH. That is way too hot. I had him change the schrader valve seals and the receiver/drier, flush the system, then vacuum down and verify it held, then refill. I can confirm both were changed, because the seals quit leaking UV dye and a different receiver/drier unit was installed.

It was cheaper to take it to him to have him do it, than buy my own recovery tank, vacuum pump, refrigerant+ester or PAG oil, and gauges for 134a. If I cannot pinpoint my issues, I may need go and do it myself and properly diagnose this. I have read reviews, and this car, along with many other Chrysler products have had amazing air conditioners. Grandpa has a Grand Caravan and it's AC will freeze you out on a summer desert day!

I have a way to monitor the low side of the AC system, I need to figure out some adapters for the R12 gauges I have to monitor high too. How would I be able to prove that it is low? Thanks!
 

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Many of the deluxe R-134a refill kits at the auto parts stores have a small low pressure gauge and adapter hose for refilling that come with the can.
I have used these to make a simple low-side checker. No psi #'s on the gauge, just indicator colors and that will give an idea of what you have.
Did you replace the evaporator?
 

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Discussion Starter #18
This is the gauge that I am using to look at my low side pressures. It came with the can.

http://www.amazon.com/gp/product/B004BSNNY2?ie=UTF8

No I did not. It did appear to be mold on the evaporator coil, no signs of leakage anywhere that I can see.

How can you modify the AC hoses and still be able to use them? It looks like the r12 ends are crimped on well. I would be able to use the hoses and get some 134a hose fittings and put them on if I could figure out how to make them stay on the ends.
 

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Don't try to use R12 gauges on R134a systems. You can cross-contaminate the mineral oil into the R134a system. Just use R134a gauges.
 
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