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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > AC not blowing cold when idling/not moving



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      04-07-2016, 02:44 PM   #23
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If the A/C is working at all, I would not suspect the pressure switch. That is just a safety switch if the refrigerant charge gets too low, to prevent damage to the compressor. All it does is prevent the compressor from coming on in that case.
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      04-07-2016, 04:59 PM   #24
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If you ask me, it seems like the guy you went to doesn't have a clue. Change the compressor?! No.

Did he turn it off auto mode? In auto the car may be blending in warm air.

I would try turning it off auto mode, set the temp as cold as it will go (on both sides), and see if that makes a difference (just for kicks).

Also try this. When the engine cool, turn a/c completely off (push fan lower speed button until the hvac system goes completely off). Start car, listen for the fan. Pop the hood and look at it maybe. Then turn on the a/c full blast (not auto, make sure a/c compressor is on). Did the fan speed up?
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      04-07-2016, 07:36 PM   #25
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Quote:
Originally Posted by patents View Post
If you ask me, it seems like the guy you went to doesn't have a clue. Change the compressor?! No.

Did he turn it off auto mode? In auto the car may be blending in warm air.

I would try turning it off auto mode, set the temp as cold as it will go (on both sides), and see if that makes a difference (just for kicks).

Also try this. When the engine cool, turn a/c completely off (push fan lower speed button until the hvac system goes completely off). Start car, listen for the fan. Pop the hood and look at it maybe. Then turn on the a/c full blast (not auto, make sure a/c compressor is on). Did the fan speed up?
Yes, he turned off the auto mode, put it on the coolest setting (60F), let it run and then measured the temperature. That's when it was 68F that was blowing out.

Also, he took the car for a spin, drove around for about five minutes and then came back to the service. We popped the hood and the fan was not running. At all. Then we held the engine at around 2000 rpm and then the fan came on, not at full speed, but it was on. Probably the engine got hot enough for it to start cooling it.

When the engine is cool, the fan will not come on at all, AC on or off, doesn't matter. But I'll test your suggestion tomorrow and see what happens.

Thank you!

Last edited by Mr. Rothstein; 04-07-2016 at 07:42 PM..
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      04-07-2016, 07:42 PM   #26
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Quote:
Originally Posted by patents View Post
If you ask me, it seems like the guy you went to doesn't have a clue.
BTW, my experience with BMW guys is, everyone has different ideas :P I have had two E46s and now I got the E90, have been driving and DIY-ing simpler things on them for years, often looking for expert opinions from both online and the actual mechanics (the ones with good recommendations and/or ratings), and there are many schools of thought regarding many issues around.

It's like with transmission fluid - there's a school of thought that says never change it, and then there are ones who say change it at 60k, and then there're guys who say change it at 100k. And each and every one of them base the opinion on their own experience, what they've seen. Which is the right opinion, or the correct experience? Who knows.

So that's why I'm asking around here and also talking to the mechanics. I mean, all you here have had different ideas and that doesn't mean any of you is wrong. It's just experience that differs.

That, of course, doesn't mean that I didn't stumble upon a guy who doesn't know his shit. But I have no way of knowing. So all ideas are very welcome
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      04-07-2016, 09:20 PM   #27
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Ha yeah a few posts ago I swore you were low on refrigerant. Now I think it's a fan issue.

Do you have a BMW code scanner to check for stored codes? Also there is a fan diagnostic that can be run with the right software tools.
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      04-08-2016, 12:14 PM   #28
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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.
I'd have to see electrical drawings, but there may be a temperature or pressure switch or transmitter on the condenser that tells the ECU when to turn on the fan. This is to save fuel economy as the fan isn't needed when moving or at low speeds if it's cool outside. It might also tell it spin faster or slower.

On most newer high efficiency home AC systems, the condenser fans operate in this manner. In low ambient conditions, the fan can be made to cycle on and off depending on the set-up for low ambient cooling.
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      04-12-2016, 02:57 PM   #29
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Quote:
Originally Posted by patents View Post
Also try this. When the engine cool, turn a/c completely off (push fan lower speed button until the hvac system goes completely off). Start car, listen for the fan. Pop the hood and look at it maybe. Then turn on the a/c full blast (not auto, make sure a/c compressor is on). Did the fan speed up?
All right, I tried this. The fan was stationary when the car was running without the AC. The moment I turned the AC on full blast, the fan started, too, and went to pretty much full speed.

Quote:
Originally Posted by patents View Post
Do you have a BMW code scanner to check for stored codes? Also there is a fan diagnostic that can be run with the right software tools.
I have a bluetooth OBDII scanner that connects to my phone; I have never had any error codes. Moreover, the guy who did the refrigerant change hooked it up on a computer and also claimed he didn't get any codes.

But yesterday I was driving around and everything was the same as before. When the car is stationary, the air flowing into the cabin went warm again. It wasn't a particularly hot day, but the car is black and it heats up properly when the sun is shining. On the other hand, the temperature sensor that regulates the AC, should also measure the inside temperature, right?

And it doesn't make any sense that when the AC is not on AUTO, the fan starts, but when I want it to hold my preferred temperature in the cabin at 70F, then the fan doesn't start and the cabin gets real hot.

So, do we have any new ideas?

And thank you so much for helping me!
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      04-12-2016, 04:36 PM   #30
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An OBD scanner will not read BMW-specific codes. Unless the mechanic you took it to has the equipment, he might have only scanned OBD codes as well. Our cars are really smart, and it may have an error in memory.

The inside cabin temperature is measured at the hvac controls, there's a little vent, and a tiny fan that blows cabin air into the sensor. Outside temperature is used for at least cycling the compressor in cold weather (I don't think it runs under a certain temp), and it may go into the auto mode algorithm.

If auto mode is off and the a/c is on full blast in manual mode, does it still warm up when you stop?

Have you tried driving around, and when you stop and the air gets warm, getting out and checking the fan?

I'm pretty much stumped. Either the fan is not being controlled properly, or you still don't have the right refrigerant charge. Maybe a faulty pressure sensor is shutting off the compressor. Speaking of, is there a way to confirm when the compressor is actually running at a given moment? It would help to know if the compressor is even running when you stop and the air gets warm.
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      04-18-2016, 05:34 PM   #31
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Quote:
Originally Posted by patents View Post
An OBD scanner will not read BMW-specific codes. Unless the mechanic you took it to has the equipment, he might have only scanned OBD codes as well. Our cars are really smart, and it may have an error in memory.
All right, but the technician who did the AC service connected it up to a computer with BMW software and that didn't give any codes, either.

Quote:
Originally Posted by patents View Post
The inside cabin temperature is measured at the hvac controls, there's a little vent, and a tiny fan that blows cabin air into the sensor. Outside temperature is used for at least cycling the compressor in cold weather (I don't think it runs under a certain temp), and it may go into the auto mode algorithm.

If auto mode is off and the a/c is on full blast in manual mode, does it still warm up when you stop?

Have you tried driving around, and when you stop and the air gets warm, getting out and checking the fan?
Today was quite a warm weather (84F), so I checked out how the car behaved. On AUTO, it still does what it used to do. And when AUTO is off and the AC is on full blast in manual mode, it does still warm up when the car is stationary. I checked the fan and about half the times when the car was stationary, it was off, and half the times it was on, although not full speed. My assumption here is that it still turns on the fan when the engine needs cooling, but it doesn't turn it on full speed when the car is stationary and air is needed for the AC.

Quote:
Originally Posted by patents View Post
I'm pretty much stumped. Either the fan is not being controlled properly, or you still don't have the right refrigerant charge. Maybe a faulty pressure sensor is shutting off the compressor. Speaking of, is there a way to confirm when the compressor is actually running at a given moment? It would help to know if the compressor is even running when you stop and the air gets warm.
Yeah, I am stumped, too :P The bottom line is, it still behaves the same way, whether it's on AUTO or not. But the fan works when it needs to cool the engine; it doesn't when it's only needed to push the air into the AC and the cabin. And it's really annoying to sit in a traffic jam with hot air flowing into the cabin when it's 84F outside.

(I don't know how to check the compressor, I don't even know where it is.)

Any ideas now? Should I look into replacing the fan?

Thank you!
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      04-18-2016, 11:55 PM   #32
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Same issue I am having. Havent been able to track it down, any luck with you?
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      04-19-2016, 09:11 AM   #33
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The fan seems to work fine, maybe it's just not being controlled properly.

As much as I hate to say it, I think you may have to take it to the dealer for diagnosis. We just don't know enough about how the fan is supposed to work and how the computer controls it. And I haven't come across that information online. The dealer (or someone with the right software) can run a diagnostic routine on the fan, but if the fan passes, then you are still stuck. The dealer has the technical resources to figure it out.

Be prepared for the problem to be something you never would have thought of.

Side story: Back in the day I owned a Saturn and I was talking to a service adviser at the dealer. He told me in the early 90s, when the cars had only been out about 3 years, they had a customer whose car was having auto transmission problems. Shifts were late and very hard. Being out of warranty, he took it to a transmission shop and had it rebuilt. Still didn't fix it, so he took it to the dealer, who quickly diagnosed it as a bad alternator. Turns out that the transmissions for those cars were quite advanced at the time and took a lot of power to drive the shift solenoids. No one would have guessed a bad alternator would have anything to do with transmission behavior.

It turns out that in college a buddy of mine had one of those early 90s Saturn models. One day he told me that his transmission was shifting rough and his ABS light was on. He was a bit worried about what could be wrong, but I told him right away he needed a new alternator. So that weekend we changed it out and all was well.
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      04-19-2016, 12:53 PM   #34
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Quote:
Originally Posted by patents View Post
The fan seems to work fine, maybe it's just not being controlled properly.

As much as I hate to say it, I think you may have to take it to the dealer for diagnosis. We just don't know enough about how the fan is supposed to work and how the computer controls it. And I haven't come across that information online. The dealer (or someone with the right software) can run a diagnostic routine on the fan, but if the fan passes, then you are still stuck. The dealer has the technical resources to figure it out.

Be prepared for the problem to be something you never would have thought of.

Side story: Back in the day I owned a Saturn and I was talking to a service adviser at the dealer. He told me in the early 90s, when the cars had only been out about 3 years, they had a customer whose car was having auto transmission problems. Shifts were late and very hard. Being out of warranty, he took it to a transmission shop and had it rebuilt. Still didn't fix it, so he took it to the dealer, who quickly diagnosed it as a bad alternator. Turns out that the transmissions for those cars were quite advanced at the time and took a lot of power to drive the shift solenoids. No one would have guessed a bad alternator would have anything to do with transmission behavior.

It turns out that in college a buddy of mine had one of those early 90s Saturn models. One day he told me that his transmission was shifting rough and his ABS light was on. He was a bit worried about what could be wrong, but I told him right away he needed a new alternator. So that weekend we changed it out and all was well.
Hah. Yeah, interesting anomalies like that happen - and I am no stranger to those either.

A while back I had an E46. During a road trip, the transmission warning light suddenly came on, and the tranny went into limp mode - but not the classical limp mode when it's just stuck in third, but it just yanked really hard when changing gears, especially changing them down. Tried to diagnose it with the help of a friend, but couldn't figure it out.

When I got back from the trip, took it to a transmission shop. Turns out it was the air flow sensor that had given in. That was something so idiotic that we hadn't even thought about that. But afterwards I googled around and, indeed, when the air flow sensor on the E46 goes, it's the transmission light that comes on and it's the transmission that starts to act funny.

All right, thank you for all your help, I might, indeed, just take it to the dealer. Unless someone else here has a sudden flash of ideas?
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      10-17-2018, 05:47 PM   #35
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Did you ever find the problem

Mr. Rothstein, I am having the exact same problem. Did you ever get a correct diagnosis to fix the issue?
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      12-27-2018, 04:04 PM   #36
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I am having the same issue. In my case as the air became warmer a strange sounds appear.
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      05-22-2019, 08:35 PM   #37
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I'm having the same issue. Bump

Did anyone ever solve this? I had an indy replace my fan and the fan control module. It worked for about a week and then no longer. I've heard there could be issues with grounds, fuses etc?

Thank you!
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      06-01-2019, 10:26 PM   #38
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I'm also looking for what the solution was as I am having the same symptoms.
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      06-07-2019, 01:24 PM   #39
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BUMP I'm also having this problem. Fan works and runs when stationary but warm blowing with the a/c set to MAX. Anyone currently working on a resolution?
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      07-11-2019, 07:25 PM   #40
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I'm also having same problem. I wonder if the magnet or air gap is too weak or needs to be adjusted on the air compressor.
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      07-19-2019, 10:27 AM   #41
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Might as well add me to this list. Exact same symptoms.

Driving on interstate I get nice cold air. stop for any period of time and air gets warmer and warmer. Revving engine to around 2000 rpm's does make air a little cooler, but not really cold.

There has to be something specific causing this for so many cars to experience the same thing.
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      07-19-2019, 11:28 AM   #42
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Quote:
Originally Posted by steel609 View Post
Might as well add me to this list. Exact same symptoms. [Actually, YOU are the first poster to this thread this year who DESCRIBED his symptoms (other than warm air instead of cool ;-)]

Driving on interstate I get nice cold air. stop for any period of time and air gets warmer and warmer. Revving engine to around 2000 rpm's does make air a little cooler, but not really cold.
WHAT Diagnostic Equipment/Software do you have access to (INPA, Scan Tool, etc.)?
Do you have Manifold Gauges?
Do you have the time/interest to diagnose the system yourself?

There are MANY reasons why the refrigeration system (Compressor PUMPING R-134a through the Condenser, Expansion Valve, Evaporator and back to Compressor) may NOT function correctly, or air coming from vents may get warmer when you slow or stop.

You, or whoever is going to properly diagnose your issue, need to understand how the system works and have proper equipment/software to read or observe Parameters/ values such as Refrigerant Pressure, Evaporator Temp, Mixed Air Flap Positions, Radiator Fan Speed, Coolant Temp, etc.

INPA or similar Software or Scan Tool can do that, or you can monitor High Side & Low Side Pressure in Refrigeration System with Manifold Gauges. If you have, or want to obtain, any of those tools, I can walk you through tests you can do to try to identify the cause of your issue. Otherwise, simply take the vehicle to any decent A/C shop, as simply trying to replace whatever part someone tells you "fixed" his issue, when NEITHER of you understand the system or how to diagnose it, is a fool's errand.

The 1st suspect (ONLY the first -- there ARE others ;-) when the A/C system cools properly at highway speed, but warms a LOT when slowing or standing still, is Air Flow through Condenser mounted in front of Radiator, due to Radiator Fan or E-Fan NOT running fast enough. There are different things that can cause that, from issues in various sensor wiring/connectors, etc. which tell the DME when/ how fast to run the E-Fan (such as Engine Coolant Temp Sensor or Refrigerant Pressure Sensor), to E-Fan wiring/connectors or the Integral Fan Control itself.

So FIRST, determine at what % of Maximum Speed your E-Fan is operating when A/C is on at idle. If you have NEVER paid much attention to your E-Fan and the noise it makes, trying to GUESS what speed it is running at is NOT a good idea. Proper Software such as INPA, or Scan Tool, connected to your OBD II Socket, can tell you precisely what that speed is.

If you have INPA, or any BMW-specific Software or Scan Tool that can to Activation of the Fan, or monitor actual E-Fan speed while monitoring Coolant Temp, you can get a good idea of whether or not your E-Fan is operating properly, or whether slow speed is causing your "warm vent air" issue. HINT: the E-Fan is responsible for Heat Transfer via rate of air flow through BOTH the Condenser & Radiator, when vehicle stationary. Just monitor E-Fan speed with engine idling and A/C on MAX.

If you want to try to do an "initial diagnosis" yourself, just of fan operation, let me know & I'll suggest some first steps. Otherwise, find a competent A/C shop.

George
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