This spring I purchased a 2002 Mini Cooper Base model (R50 to be specific). The weather warmed up and I tried to use the AC but only warm air came out.
- The compressor does engage when the AC is turned on.
- So I bought a can of R143 and fill valve (A/C Pro brand)
- When I sent to fill the pressure was acting different than anything I have seen. The needle would go into the red (high pressure). The needle would go down when the compressor was running. Not sure about what was going on I didn't add any refrigerant.

Figuring I needed more information I bought the dual gauge manifold from Harbor Freight. Here's what I got...
Ambient temperature was 75 degrees. Humidity about 45%
- When I plug the hoses in after the car had been sitting for a while the pressure reads about 80lbs on each dial.
- When I start the car and let idle with the A/C on dials climb as follows: The High side climbs up to about 250 and the low side about 48. At 250 the fan kicks in and the pressure drops to about 175H and 40L before starting to climb again. The fan turns off at about 200. Then the process repeats- the pressure slowly builds until the high side hits 250 and then the fan kicks on and the pressure drops.
- When fast idling at 2000 rpm the high side hits 270 before the fan kicks in and the pressure drops. The low side drops to 30 during this time. The low pressure goes up and down some as the pressure builds. The pressure on the low side seems to go down as the engine is rev'd up.

Is it possible to attach a video? I took a video of this.

Any help on this? Thanks!

 

Start with finding an AC repair facility that can actually tell you how much refrigerant is in the system. The little gauge on the can is useless, pressure is different from weight and the refrigerant requirement is rated in weight. Spec is .91 +/- .02 lbs.

The readings you're getting are fairly normal, and the fan is kicking in and doing exactly what it is supposed to. If the shop verifies that the correct level of refrigerant is in the system then you need to start looking at the HVAC controls and blend door operations.

But you cannot properly measure the level of refrigerant without an AC machine.

 

Thanks for your input. I'm not sure if its over charged. Based on the cold, engine off pressure of both high and low side of 80psi I'm not sure if the problem is overcharge.

Any idea what would cause the other behaviors I describe if its NOT an over charge?

I live in a small community and don't know of a shop that I would trust to work on A/C. The nearest mini dealer is an hour and a half drive away. Not that I trust them to be reasonably priced.

 

Any shop with an ac machine can vacume out the r134a and oil, then refill both a know quantity....
Like it was said, it's really the only way...seen places that do it for $79-139 on signs.
One thought...
The cans that are sold with guages also have oil....the directions say to shake them continually to inject gas and oil, or steady to do oil only (usually takes but side up) you gas only upsidedown....
Many folks THINK they are adding gas, and add extra oil....result is the ac system is ok in moderate temps, but fails to have capicity to do much in hot temps.
My 2005 could fog the windows of my car if I left a shaded garage in a few minutes....took longer if it was parked outside....but at about 100,000 miles and 10 years, there was no noticeable change in temps.
The MINI has a TINY capicity....so it is easy to overfill.
Good luck.

 

Does everyone agree that putting the a/c system under vacuum to remove R134a - and moisture if the system has been opened - also removes the pag oil?

 

No, normal evac of a car AC system removes very little oil. It's a type of oil that doesn't evaporate easily. Just measured this on a mini for kicks that had the refrigerant properly recovered. Got about two ounces of oil out of the compressor and another two ounces out of the lines and evaporator. (Didn't measure condenser/drier assembly).

Anyway, OP readings sound a little high but not crazy. Would probably be more reasonable with a strong fan blowing on the condenser.

I would check the mixing door inside the car isn't stuck to making heat. What is the air temp coming out of the duct after the car sits overnight? (give it maybe 15 seconds for the AC to start, and before the coolant warms up) and compare that to the temperature after the engine and coolant warms up

 

P.s. Way too many people use the quick fix cans of refrigerant with leak stop goo. Mostly hear horror stories. If the history of the car is unknown, you have to suspect it was treated with that stuff to hide a problem. Makes future repairs unpredictable. The local BMW dealer tests for it (yes, there is a test kit) and will insist on replacing everything ... Compressor, condenser, expansion valve, evaporator.... Not a cheap joke! Haven't heard if MINI dealers are doing the same now.

 

To resurrect my old thread. Back on this as the weather has warmed up here in the great white north...

The AC has not healed itself over the winter...

I hooked up the gauges to check the pressure and see that there is only about 10psi on the low side and 0 on the high with the car off.

So obviously there is at least one leak somewhere. We did see stuff leaking out of one of the coolant line connections down near the bottom of the condenser.

So my plan of action is to get a o-ring kit and change out o-rings. Then I'll hook it up to a vacuum pump to see if the system is sealed. Then I figure I need to add some refrigerant to pick up where I left off last year. Does this make sense or do I need to do something else? I know I should probably take it to a shop but we'd like to try to fix it at ourselves.

At what point do I need to replace the drying container?

Thanks for any advice.

Something to add - We did replace the radiator fan last fall after we noticed it wasn't working correctly. No low speed fan if I remember correctly. Not sure if this plays into issues with the AC system we were seeing. I'm guessing no as the AC turned the fan on high speed as expected.

 

You asked for advice, so here goes -

its a little weird the high and low pressures don't equalize with everything off. May be an indication of a plugged orifice or a side effect of leak stop.

Get the remaining refrigerant properly recovered, change out the drier and o-rings and let the vacuum pump run. Give it a day if you can to get air and water out. If it holds vacuum, refill by weight. Pretty easy DIY.

if it won't hold vacuum, you are probably better off having a shop with a leak tester check it out.

 

The below thread has a video that explains the car AC system.

Also pretty sure that if you read the instructions on the can it says to measure the charge while the compressor is running.

https://www.northamericanmotoring.co...d-working.html

 

If your low speed fan was not working then the high side went to overpressure from high heat and the system purged the freon out. You may not have a leak but if it was my car, I might want to put a new dryer on.