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      03-29-2016, 02:51 PM   #1
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AC not blowing cold when idling/not moving

Hi,

My AC is not blowing cold air when the car is stationary - i.e. stopped at lights, parked etc. All fuses are fine. Traced the problem to the cooling fan, meaning it does cool the engine, but doesn't increase its speed when the car is stationary, i.e. doesn't generate a strong air flow into the AC.

Is there a sensor of some sort somewhere that sends a message to the fan from the AC when it needs to increase speed and maintain the cold air flow into the cabin? If so, where is that sensor and can it be easily changed?

Or could there be another issue that I'm not thinking of?
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      03-29-2016, 03:30 PM   #2
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So you are saying that otherwise when you are driving, the AC is actually working as normal with cool to cold-ish air from vents.?
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      03-29-2016, 03:36 PM   #3
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Sounds like it may be just low on refrigerant.

When you are driving, do you get equal cooling on the left and right side outer dash vents when the temp is set even?

If you are stationary, and you rev the engine to 2000 RPM, does it get cold then?
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      03-29-2016, 03:42 PM   #4
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Originally Posted by PichaDis11 View Post
So you are saying that otherwise when you are driving, the AC is actually working as normal with cool to cold-ish air from vents.?
Yes, that is correct.
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      03-29-2016, 03:43 PM   #5
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Quote:
Originally Posted by MightyMouseTech View Post
Sounds like it may be just low on refrigerant.

When you are driving, do you get equal cooling on the left and right side outer dash vents when the temp is set even?

If you are stationary, and you rev the engine to 2000 RPM, does it get cold then?
Yeah, when I'm driving, the cooling is equal when the temp is set even.

Haven't tried revving the engine to 2000 when stationary, will do right away.
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      03-29-2016, 03:55 PM   #6
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Quote:
Originally Posted by MightyMouseTech View Post
If you are stationary, and you rev the engine to 2000 RPM, does it get cold then?
So, when I'm stationary and I rev the engine to 2000 rpm, then yes, the air gets cold. Does that mean it's low on refrigerant?

However, the cooling fan still doesn't speed itself up - or course it might be BMW has some sort of algorithm that manages that without me noticing it.
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      03-29-2016, 04:05 PM   #7
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You are just low on refrigerant. Not very low mind you. I find it never really gets cold while just idling. Just how the system works.
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      03-29-2016, 04:24 PM   #8
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Originally Posted by MightyMouseTech View Post
You are just low on refrigerant. Not very low mind you. I find it never really gets cold while just idling. Just how the system works.
All right, thank you. Do you think I could refill it myself, using one of those refill cans I've seen advertised on TV, or should I go have the AC system serviced?
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      03-29-2016, 04:32 PM   #9
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Quote:
Originally Posted by Mr. Rothstein
Quote:
Originally Posted by MightyMouseTech View Post
You are just low on refrigerant. Not very low mind you. I find it never really gets cold while just idling. Just how the system works.
All right, thank you. Do you think I could refill it myself, using one of those refill cans I've seen advertised on TV, or should I go have the AC system serviced?
I would not put that stuff in my car. That stuff is flammable, and if any tech ever hooks up an evac machine with that stuff in there, it could explode and possibly kill the tech.

Get it serviced properly.
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      03-29-2016, 04:32 PM   #10
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Quote:
Originally Posted by Mr. Rothstein View Post
All right, thank you. Do you think I could refill it myself, using one of those refill cans I've seen advertised on TV, or should I go have the AC system serviced?
While my E91 hasn't had any refrigerant issues, my E46 did and was very, very sensitive to either being under or over filled. I'd take it to a good A/C tech.

Tom
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      03-29-2016, 05:52 PM   #11
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Quote:
Originally Posted by Mr. Rothstein View Post
Hi,

My AC is not blowing cold air when the car is stationary - i.e. stopped at lights, parked etc. All fuses are fine. Traced the problem to the cooling fan, meaning it does cool the engine, but doesn't increase its speed when the car is stationary, i.e. doesn't generate a strong air flow into the AC.

Is there a sensor of some sort somewhere that sends a message to the fan from the AC when it needs to increase speed and maintain the cold air flow into the cabin? If so, where is that sensor and can it be easily changed?

Or could there be another issue that I'm not thinking of?
Is there any air flow from your vents? If you put fan on high, is air moving?

Blowers tend to go bad, as the water tends to drip on them. You can try greasing them, but it's better to replace. Replacement is easy (15 min), but it will set you back about $170.
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      03-30-2016, 12:01 AM   #12
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Should be fine to top off. Make sure you opt for only r134a and no stop leak crap. Burp the line before you connect it to the low pressure side. Use a meat thermometer and place it in the center vent on max cool. Let the can flow and rev the engine to 1200-1500 rpm and watch the temp drop to about 20 (do some research to check this number) under ambient temps and you're done.

Source: shade tree mechanic that has replaced a compressor and has topped off a few cars.
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      04-01-2016, 07:34 AM   #13
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Quote:
Originally Posted by W37V View Post
Is there any air flow from your vents? If you put fan on high, is air moving?

Blowers tend to go bad, as the water tends to drip on them. You can try greasing them, but it's better to replace. Replacement is easy (15 min), but it will set you back about $170.
Yes, there is proper air flow from the vents, that is not a problem. The only issue is that when the car is standstill, the cold air turns warm, i.e. turns into outside air only. Once I start moving again, it restarts blowing cold.
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      04-01-2016, 08:23 AM   #14
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Quote:
Originally Posted by Mr. Rothstein View Post
Yes, there is proper air flow from the vents, that is not a problem. The only issue is that when the car is standstill, the cold air turns warm, i.e. turns into outside air only. Once I start moving again, it restarts blowing cold.
Check your fan - by the radiator. See if it's working - seriously.

In some cars there is a fan that kicks in when car is at idle to move the air over cooling element. If the fan dies, ac doesn't work while stationary while it works while the car is moving.
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      04-01-2016, 09:06 AM   #15
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Quote:
Originally Posted by W37V View Post
Check your fan - by the radiator. See if it's working - seriously.

In some cars there is a fan that kicks in when car is at idle to move the air over cooling element. If the fan dies, ac doesn't work while stationary while it works while the car is moving.
Well that's where I started my post, actually :P

The fan does not speed up when the car is idle, BUT it does work and cool the engine in general. Hence my theory that maybe there's a special sensor that takes information from the AC system when to turn on the fan, and that sensor isn't working.
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      04-01-2016, 10:51 AM   #16
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Quote:
Originally Posted by Mr. Rothstein View Post
Well that's where I started my post, actually :P

The fan does not speed up when the car is idle, BUT it does work and cool the engine in general. Hence my theory that maybe there's a special sensor that takes information from the AC system when to turn on the fan, and that sensor isn't working.
Ooops.

Maybe the fan is not spinning hard enough to provide sufficient airflow? Maybe the condenser /evaporator is clogged up? Have you tried cleaning them to see if that improves anything?

---------------------

have you looked at the system at realoem?
http://www.realoem.com/bmw/enUS/part...BMW-328i&mg=64
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      04-01-2016, 01:26 PM   #17
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Quote:
Originally Posted by W37V View Post
Ooops.

Maybe the fan is not spinning hard enough to provide sufficient airflow? Maybe the condenser /evaporator is clogged up? Have you tried cleaning them to see if that improves anything?

---------------------

have you looked at the system at realoem?
http://www.realoem.com/bmw/enUS/part...BMW-328i&mg=64
The condenser/evaporator is the thing that lets the condensed water out? Where do I find it so that I could clean it?

Because, that actually makes a lot of sense as I do, on occasion, get moldy smells in the car, as if the condensed water were stuck somewhere and rotting. (Yeah, that was the part I forgot to mention earlier :P)

So where do I find the condenser/evaporator and how exactly do I clean it?

Thank you!
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      04-01-2016, 02:57 PM   #18
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The condenser is the thing with fins that looks like a radiator that is in front of the car. The evaporator is the thing with fins that looks like a radiator that is in your dash.

The issue is that with reduced airflow through the condenser (when you are stopped), you don't get sufficient heat transfer to condense the refrigerant OR you don't have enough refrigerant and not enough condensation takes place with low airflow.

I do not know how our cars manage the external radiator/condenser fan. In one of my old cars it had a fan secondary fan that came on when the a/c was on or if the coolant temp rose above a certain temp. I doubt your fan is the problem, since it's operation is all electronically controlled. The car knows the a/c is on, it should speed the fan accordingly. I bet if you sit at idle long enough, and it's hot outside, the fan will speed up. That will tell you that it's working. I doubt it has any sort of a/c sensor beyond just knowing that the a/c is on.

It wouldn't hurt to visually check the condenser for obstructions (dirt, leaves, dead bird, etc.) that covers the fins.

As mentioned, I bet you are low on refrigerant. But don't totally discount a fan issue, it just seems like it's working. I really don't know if it's supposed to increase in speed with the a/c on.
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      04-01-2016, 04:22 PM   #19
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Quote:
Originally Posted by patents View Post
The condenser is the thing with fins that looks like a radiator that is in front of the car. The evaporator is the thing with fins that looks like a radiator that is in your dash.

The issue is that with reduced airflow through the condenser (when you are stopped), you don't get sufficient heat transfer to condense the refrigerant OR you don't have enough refrigerant and not enough condensation takes place with low airflow.

I do not know how our cars manage the external radiator/condenser fan. In one of my old cars it had a fan secondary fan that came on when the a/c was on or if the coolant temp rose above a certain temp. I doubt your fan is the problem, since it's operation is all electronically controlled. The car knows the a/c is on, it should speed the fan accordingly. I bet if you sit at idle long enough, and it's hot outside, the fan will speed up. That will tell you that it's working. I doubt it has any sort of a/c sensor beyond just knowing that the a/c is on.

It wouldn't hurt to visually check the condenser for obstructions (dirt, leaves, dead bird, etc.) that covers the fins.

As mentioned, I bet you are low on refrigerant. But don't totally discount a fan issue, it just seems like it's working. I really don't know if it's supposed to increase in speed with the a/c on.
Thank you!

Checked the condenser (or the thing with fins in the front - of which there appears to be three - a smaller, a medium behind it, and then a big one behind that), no other obstructions than a couple of dead bugs. I can't see in front of the smallest fin-ny thing because that's immediately behind the spoiler. But the rest seems to be clean.

Dunno how to access the evaporator, though (I'll google around).

But, if I do sometimes smell mold, then I would assume there's (also) a problem with the condensed water flowing away - or is it a related problem, to either the condenser or the evaporator?

Thanks again!
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      04-01-2016, 07:52 PM   #20
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Here's somewhat an update.

I changed the cabin air microfilter, and while doing it, sprayed some stuff into the aircon to eliminate the moldy smell (I read about it somewhere). I also cleaned up some sort of air holes on the sides of the cabin air filter (on the left and the right, there are some holes, I don't know what they do, but they were all covered in tree leaves, so I cleaned these out. Anyone know what they are for?).

BUT, when I had the aircon on for about 10 minutes to let the spray go through the system and later ventilate the car, the cooling fan didn't come on AT ALL. It did nothing.

On the other hand, I meanwhile fixed something on my wife's car (not a BMW, it's a Crown Vic), I turned on the AC on that one and it turned the cooling fan on almost IMMEDIATELY.

I perfectly understand that a mechanical beast like the Crown Vic and an electronic tender machine like the BMW are completely different animals. So therefore my question is, I guess, could the BMW, at least in theory, regulate the air flow differently, i.e. without the need to turn on the cooling fan while the car is stationary? OR, does it mean there is a problem with the cooling fan itself so that it doesn't turn itself on to push the air into the cabin?

Because, the whole time I had the BMW air con on while ventilating it, the air flowing into the cabin was not cold, it was just the outside air.

However, I know the cooling fan works because I've seen it work to cool the engine/radiator, and I recently did a 1,600-mile road trip from Atlanta to Miami and back, in hot weather, during which the car did not overheat. But the moment I stopped the car, the air con air went from cold to warm.

I don't know if anyone can make anything of what I just said, but I'm keeping my fingers crossed And I thank you in advance!
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      04-02-2016, 01:01 PM   #21
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You can't get to the evaporator. It's not the problem, so don't worry about it.

Older cars simply turn on the cooling fan when the a/c is on. Like I said, I really don't know BMW's logic. I suspect since it's a single cooling fan, there is some more complicated control logic. But the fan works. I really don't think there is any sort of sensor failure.

Also keep in mind that with the a/c on auto, it may be cycling the compressor, or it may not be warm enough outside for it to come on.

I think the next step is to check for proper refrigerant charge.
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      04-07-2016, 03:35 PM   #22
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Okay.

I had the AC serviced and the refrigerant recharged.

But the mechanic was as confused as I was about the cooling fan not coming on. We agreed that I'd drive around for some time and monitor its behavior, and see what happens on a hot day, whether it comes on on full speed or not when the AC needs the air flow.

As of now (it's 67F outside, not too hot), it hasn't gotten hot in the car, but when the car is standstill, the air flow still isn't cold. The mechanic turned the AC on 60F and measured the temperature and said it was about 68F.

What the guy also said was that if it's not working properly now, then the next step would be changing the pressure sensor to make definitively sure it works, and then monitor what happens. And if nothing changes, the next thing he'd do would be the AC compressor change. He also said that the fan should be working normally, since it is cooling the engine, so he doesn't suspect it's the fan itself that is playing tricks.

Does all that make sense to you, gentlemen? Should I follow the mechanic's advice and if it's still not working properly, have the pressure sensor changed? Or what do you make of all that?
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