Advice on intermittent AC issue? - The Unofficial BMW M5 Messageboard (m5board.com)

s4kebomb · 29th July 2008, 01:16

My car developed new problem with the AC.
When the car is idle, sometimes the AC stops blowing cold air.
I pressed the AC button (the one above circulation button) off and on again but the AC won't blow cold air, but as soon as the car starts to move again, the AC blows cold.

I tried to see a pattern on when it starts to happen, but as far as I remembered it happens more often during day time when the outside temperature is about 90 and up.

Last weekend it happened once. I went to my friend's house, about 2 hours later I started the car, I noticed the AC didn't blow cold air for the first 5 minutes. I took the car for a drive, AC is blowing cold no problem.

The first time it happened, outside temperature was about 105F, the car was fully warmed up, and I was waiting in the car, AC is on, about 10 minutes later I noticed the AC is not cold anymore, oil temperature goes over 210F, water temperature climbs up to 3/4 mark. Took the car for a little drive around the block and both temperature went down to roughly halfway mark, and AC is blowing cold again.

The only thing I changed on the AC component is the Final Stage Unit. AC blower were acting up so I changed it. This is prior to this current issue.

Has anyone ever experienced this? Any input on what else I need to check?

SSense · 29th July 2008, 01:21

I had the same problem long ago, had to replace a part, dont really remember the name what it was, but it usually comes under the dashboard, you can remove it from the passenger side. Looks like some pointed needles, if i get to know what it was, ill reply you for sure, but that is it.

s4kebomb · 29th July 2008, 01:47

I know what you're talking about.
That is the Final Stage Unit.

I changed that a few months ago prior to this whole problem, I hope it's not a defective FSU that caused this new problem.

Thanks for your reply.

DRM · 29th July 2008, 02:13

1) Your rising oil and coolant temps in hot weather have nothing to do with A/C.

2) Your A/C needs a recharge of refrigerant. This is normal for a 6-year old car. Take it to a good indy shop. It's not expensive.

s4kebomb · 29th July 2008, 02:40

Dan,

I'm not too familiar with AC system, so pardon my ignorance.
Does the refrigerant needs to be completely discharged and refilled?

I checked the refrigerant level using a refrigerant recharge kit from Walmart that has a gauge on it, it says my refrigerant is in the OK level so I didn't filled it up. I know I can't solely rely on the cheap gauge, but at least they should be somewhat accurate.

Now if the refrigerant is the problem, should the AC be not cold all the time then, or at least during a hot day it's not cold at all?
Why does the AC blows cold most of the time and sometimes it blows not just slightly warmer, but really blowing air as if the AC button (button above recirculating air) is off?

I'll pay a closer attention to the AC compressor if it is actually kicks in or not when the AC is warm.

DRM · 29th July 2008, 02:46

Quote:

Originally Posted by s4kebomb

Dan,

I'm not too familiar with AC system, so pardon my ignorance.
Does the refrigerant needs to be completely discharged and refilled?

I checked the refrigerant level using a refrigerant recharge kit from Walmart that has a gauge on it, it says my refrigerant is in the OK level so I didn't filled it up. I know I can't solely rely on the cheap gauge, but at least they should be somewhat accurate.

Now if the refrigerant is the problem, should the AC be not cold all the time then, or at least during a hot day it's not cold at all?
Why does the AC blows cold most of the time and sometimes it blows not just slightly warmer, but really blowing air as if the AC button (button above recirculating air) is off?

I'll pay a closer attention to the AC compressor if it is actually kicks in or not when the AC is warm.

All I can say is your symptoms sound exactly what I experienced. 'Took mine to my indy shop. They checked then added refrigerant (not replace). 'Think it was about $60. That was 3 months ago; no problems since.

IslandS62 · 29th July 2008, 03:29

I've noticed the same issue on my 2001. Once in a while leaving the office the AC will blow warm for a bit...I'll have it recharged and report back. In my experience I bad Final Stage Resistor makes the fan speeds wonky, it does not make the AC blow warm.

Crossing fingers for no leaks, but this is a BMW after all...

s4kebomb · 29th July 2008, 21:13

IslandS62,

I'm planning to get mine recharged too, but if you do it before I do, can you report your progress if it cures the problem or not?

gsfent · 30th July 2008, 01:17

Quote:

Originally Posted by s4kebomb

IslandS62,

I'm planning to get mine recharged too, but if you do it before I do, can you report your progress if it cures the problem or not?

Assuming you will be taking it in, is there any reason you can't get a home kit and add a 1/2 or a full can of r134?
I know you should measure, but I would think a 1/2 can wouldn't hurt and if it improves, you know you are headed in the right direction. Just need to locate the low pressure port, which I assume realoem would show.
Regards,
Jerry

s4kebomb · 30th July 2008, 02:05

Jerry,

I can't do it at home because when I checked the level with the gauge that came with the recharge kit, it was full.

So, I need to have an Indy shop to do the discharge and recharge since discharging refrigerant to open air is illegal.

DRM · 30th July 2008, 02:21

'Went back and looked at my receipt; also called my indy shop for details.

1) System capacity is 40 oz of R134.

2) My indy shop "discharged" the system completely in a sealed loop capture; then reloaded R134 back in.

3) My system took 30 oz additional R134 to completely refill (meaning - my system was down 30 oz; which caused symptoms OP described).

4) Cost was $48 plus 1/2 hour labor.

5) This procedure was done last March; no problems since then.

'Hope this clarifies and helps.....