No Cold on 2000 BMW 323 AC - Help!

My 323 has been in & out of the shop four times in the past month for the A/C. First to evacuate & recharge freon (still blew hot air). Second to replace condenser, AC drier, valve (still blew hot air: condenser was “defective”). Third to replace condenser AGAIN (still hot air) then to replace heater control valve. Now it no longer blows hot air but it’s only lukewarm. Both my great mechanics are stumped (one an A/C shop, another my 10+ year favorite). I am driving in a California heat wave in my black car w/black interior with all windows open. Any ideas???

There’s not a whole lot to an AC. Are you sure they aren’t taking you for a hot ride?

The one part I don’t see they’ve replaced it the compressor.
It is hard to imagine them not being able to troubleshoot that, tho: you put a gauge set on it, start the engine and watch the pressure. Whatever is read on the low and high pressure lines should be within a certain number and ratio. They must have done that.

A/C problems are difficult to diagnose over the net without knowing what static pressures are, both high and low side pressures, etc.

Making a huge assumption here, but if the A/C system pressures are about where they should be, if the evaporator outlet is cold, etc, etc. then maybe there’s a problem with the blend door. The blend door is what shunts air through the evaporator or heater core as the case may be.

The part about replacing the condenser twice is a bit suspect though.

I’m with ok4450 on the blend door.

I agree with OK4450 as well. Weird how that hasn’t occurred to them before replacing all those parts.

Yep, step #1: FIND A NEW SHOP. Look for one specializing in a/c, all systems are pretty similar. A ‘defective condenser’? Only if it’s leaking or plugged, I’d think, and no need to replace to diagnose that.

thanks all for your speedy replies! the first denso air compressor had an issue with the oil levels it was shipped with, thus the replacement. so i got a new compressor, AC dryer, AC expansion valve, and THEN the heater control valve. the A/C shop is a great one that is among the 46 BMW shops recommended right here on Car Talk…but the blend door sounds like a whole new possibility – so I will definitely ask about that. BTW they have not charged more $$ for all the extra work so I don’t feel ripped off, only amazed that these mechanics can’t figure out the problem! will update after they check the blend door – thanks!

oops – i meant they replaced the COMPRESSOR, not the condenser!! sorry about that!!

Now at least that makes some sense, but odd they replaced the compressor without it solving the problem.

ok, new wrinkle: just spoke in more detail with my longtime mechanic who replaced the heater control valve. he said it COULD be the blend door (and would have to take a bunch of stuff apart to get to it to even check it out) but now he says that when he checked the A/C pressures after all the work, they were STILL off: low pressure should be 30-40 and won’t go below 72; high pressure should be 280-350 and won’t go above 200 or so. So he’s isolated it to a problem with the pressures, but has no idea WHY this is happening. He knows the A/C lines are clear; the compressor is a brand new Denso (not remanufactured) – so NOW I ask you all: what could be causing this issue with the pressures? Sounds like if we solve that, we solve the temp issue!

Hi side gauge is between comp and expansion device so Pressure should be maxed due to restriction from debris. It is not. So, freon must be low or compressor must be weak. Cooling fans running on low or off should produce even higher pressures.

I would have to respectfully disagree a bit and say that 300 and up PSI is not acceptable. Normal highs are in the 225-250 range with lows in the mid 30s being the norm.

Based on the pressures provided that would normally point to a weak air compressor but it’s been replaced with new. If the old compressor was trashed and the system was not thoroughly flushed before installing the new one it’s possible for contaminants to ruin the new compressor.
At this point I assume the system was flushed and everything is fine in that regard and hopefully the correct amount of refrigerant oil was added to the new compressor.

Next in line would be an expansion valve that is stuck open or open too much. Following that is that the system has air in it from not being evacuated properly or the system has a leak and the pressures currently seen are due to compressed air rather than refrigerant.

For what it’s worth, the low side pressure is roughly equivalent to the evaporator temperature with the evaporator being the part that gets cold. So 72 PSI is roughly equivalent to 70ish degrees and that of course, will cool nothing.

Thanks for your post, all good to know. Expansion valve is new and not stuck open, and the system has been checked & rechecked for leaks. May have to explore the blend door possibility next though I hate to put more $$ into this problem…

I wished that I could be of more help but a blend door will barely have any effect on the system pressures at all.

That 200 and 72 is the problem, Refrigerant relies on a pressure drop to become cold and that pressure drop is simply not enough to cool properly. Something is amiss for sure.

Another vague possibility could be that the compressor is short-cycling; meaning that when it engages it’s cutting off far too soon. One would hope this would be caught if the case and is definitely noticeable.

What is temp of evap outlet line? The line may be buried. Don’t know BMW routing. But it will go from evap to comp inlet. With a receiver/accum usually

hmmm. not sure. i am passing all these tips on to my A/C guy & my mechanic, hoping we can get to the bottom of it. spoke to them today & they confirmed it is not short-cycling. we all know it’s the pressures but nobody knows why (yet!)

Hallelujah! Just picked up my BMW after its sixth visit to the shop (#5 with my AC guys) and they finally cracked the mystery. It dawned on him that the AC drier could have too much oil. So he took it all apart again, blew out all the lines, put in new compressor #3, new valve, and upon inspecting the drier, saw that the ‘desiccator’ it comes with had too much oil soaked into it…so with all new everything, this time it worked. I am cool! Thanks all for your input – I left a long note for both shops Sunday eve with your ideas & tips and I think that really helped…