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Intermittent Hot Air - but not on NPR

We have a 2004 Chrysler Town and Country Limited, approximately 160K. Recently, the air conditioning started working intermittently - or not working intermittently, depending on how one looks at it. When the van is first started, it will blow cold air. More than once, switching to the recirculate setting has affected the function. But at other times, it will just stop blowing cooled air and blow swampy, warm air.

Sometimes, after a “rest” it will work again for a while. The Freon was found to be low and charged and dye placed in the system. It seemed OK for a few days. Now, back to intermittent cooling. I suppose the Freon could be low again? What else might affect the function of the air conditioning in this say?

Did the shop that put the dye in check for leaks? They put the dye in to make finding the leaks easy. You didn’t say if you have been back to the shop yet.

The dye was added to track any leaks. Freon can only be low if it leaks out…thus the dye to determine if and where the leak is occurring.

I understand both of those concepts. I understand that low freon level would diminish the ability of the AC unit to cool and may freeze up the condenser. What I don’t know is if it had leaked back out, would this intermittent cooling issue be an expected consequence. The air is plenty cool - except when it isn’t. Thanks for the guidance.

Yes, the dye was placed in the system to check for the leak which caused the freon level to be low. I believe it takes an infrared light to reveal the presence of the dye at the site of the leak. I have not been back to the shop yet; the mechanic seemed to thin the charge would last the summer. So, I don’t really know if it has leaked off. I’m wondering if low freon might cause this symptom. When it is working, the air is plenty cool. But then there are times that it is warm and swampy feeling

You have a large leak and the symptoms your AC has reflect that. BTW, the shop will use an ultraviolet light to see the dye. They will fix the leak(s) when you go back.

That’s helpful; I guess it is time to make another appointment

You could buy an ultraviolet flashlight for around $10 and look for the yellow’ish leaks.

Not a bad idea. Thanks

The shop might show @TandCx2 the leaks when he goes in for the leak check. I wouldn’t try to repair the AC system myself since I don’t have the tools, and I imagine the OP doesn’t either. Why spend the ten bucks if all you see is a little glow but can’t do anything about it?

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If the system had a large leak the refrigerant would have leaked out the first day and the A/C would not work again without a repair.

The most common cause of intermittent A/C on Chrysler minivan is a sticking expansion valve. When it starts blowing warm, open the hood and see if the compressor clutch is cycling or if it is not engaging at all.

The A/C pressure transducer or the evaporator thermistor could be failing, there are other things that can cause intermittent operation. If you could take the vehicle to your A/C technician when it is blowing warm he should be able to diagnose this in a short amount of time.

Thank you. I’ll pay attention to the function of the clutch when it is blowing warm.

The condenser freezing guess is a good one too. Modern AC is very sensitive to the amount of refrigerant. Too much or too little can both cause problems such as this. Too much is worse than too little. I think what I’d be inclined to do if I had this problem is find an AC specialist shop that will totally evacuate the system, then pump the exact amount (weight) spec’d in the factory service manual of refrigerant back in. If that fixes it, but the problem returns, they can evacuate the system again and weigh how much comes out. If it is less than they put in before, you know you have a leak.

You can also use an ultraviolet flashlight to detect Dog Urine, Pet Stains and Bed Bugs… I mean…just in case…:grin:

Why not just put pressure gauges on? Keep evacuating the system seems to be an expensive test.

Pressure gauges are better than nothing, but aren’t an accurate measurement of how much refrigerant is contained in the system.

If OP wants to find out whether he is losing refrigerant, the best way to do it is to put a pressure gauge on it. Test it for 3, 4 days in a row or even more and compare measurements. Evacuating the system and weighing it is silly and costly.

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Evacuating and weighing might not always be necessary, but here’s what one AC pro says is the proper way to charge a modern AC system. Opinions vary of course. Even so their 4 part tutorial on AC systems is pretty informative I think. OP might want to give it a look-see.

"Charge kits with only a low side gauge should NEVER be used. Severe damage can be caused by adding refrigerant to a system without knowing the high-side relationship. This is critical on modern, variable-displacement compressors.

Even with both gauges, seeing the correct charge level on these units is impossible. Extracting the system and adding the proper weight of refrigerant is the only way they can be charged.

Paying a professional to test and charge these systems, is far less expensive than to destroy a compressor and evaporator core from an overcharge."

I noticed at Harbor Freight the other day, the shelf that stocks the AC manifolds and gauges also has vacuum pumps designed to evacuate AC systems.