Question on BMW 3-Series AC

Greetings!!!
My BMW is a 1997 M44 318is euro version 4 doors.
This is the A/C issue. When the car is moving the A/C cools up great perfect, when I stop at a light and the engine idles the A/C will reduce noticeable the cool air. The blower maintain the same air flow all the time, it doesn’t varies if the car is running or at stop.
I noticed that if I go to neutral on the automatic transmission and I rev the engine to about 1000RPM the A/C will begin to cool up perfectly.
This scenario started suddenly sins the A/C was in a perfect working condition before I noticed this issue again.
Any ideas or suggestion would certainly be appreciated…
Thx for the broad help!!!
Cheers


__________________
This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW Air Conditioning Maintenance and Upgrade

[Wayne 962]

I think on your car there is an auxiliary air fan that is placed in front of the A/C condenser. If this fan has failed, then you will get the symptoms that you have experienced. This is because the condenser will be working only by using the air that is pushed through the fan by the engine fan itself. The 5-Series has this aux fan in front of the condenser, I'm pretty sure that your car has one too. I would check and see if it's operating properly.

- Wayne

[eztuner12]

Good morning Wayne,
1st thank you for your answer & needed help...
My car came without an A/C condenser auxiliary fan, only the radiator cooling fan which is electronic, not belt drive, located between the front area of the engine and the radiator and it seems to be working in order.
Any other suggestion that you think I should look into?
I would like to remark that when I stop the car & go to neutral on the automatic trans and rev- up to @1000 RPM the A/C will cool perfect as if the car was running.
Again thx for the help and for any other suggestion it may come thru. I’ll be here
Have a great day!!!
Richard

[Manolito]

My daughter complained that her car blew warm air at stoplights, and we traced that problem to a failed relay on her electric fan. If your electric fan is turning on (low speed) whenever the air conditioner is on, then the next suspect is the compressor. The compressor may be failing to develop adequate pressure at low RPM, but if it sounds healthy, perhaps the problem is just lack of refrigerant.

These cars are remarkably particular about how much refrigerant they contain. Just a few ounces too much or too little and efficiency drops off dramatically. It is tough to get the amount just right without evacuating it and refilling it from scratch. To get it just right, you have to monitor the pressures and fill it until the pressures correspond to what they should be for the outside temperature.

What most of us do is use the low-side meter that comes with the refrigerant kit, and add refrigerant just a little at a time until it starts to blow cold, and then we stop adding. Not optimal, but functional.

[eztuner12]

Hi Manolito & Wayne
Last night I spend some time investigating my A/C issue and notice that when the car is loaded “Stop. no running” with light on and A/C on, any time the cooling system fan turns on the density of the head light including the interior lights, dash board too goes low, at this very moment is when the A/C cools less, as soon I rev the engine to @ 1000 RPM the lights density goes higher and the A/ C starts cooling again. I think this scenario can help you to pin down my A/C issue.
Thx and sorry for all the bother, I‘ll be here for your reply.
Cheers,
Richard

[bostogrun]

I think you said your car doesn't have an auxiliary cooling fan, only the electric fan, right? Are you referring to the electric fan with curved blades in front off the radiator? Are you saying you don't have a fan on the water pump pulley?

Did you or a previous owner remove the primary cooling fan and install a fan removal kit? if so you would just have one fan in front of the radiator. It's also possible that someone installed what are called under drivepulleys which would turn the components slower to increase performance. This can sometimes lead to undercharging at an idle because the alternator is not turming fast enough to put out 13.8 volts which will result in draining the battery which could account for dimming the lights. BMW's use two drive belts, a serpentine belt for the the ps pump, alternator and water pump. The a/c pump runs off a separate belt that is driven by the same hub as the crankshaft. If an underdrive (smaller diameter) pulley was installed it cpould be actually turning the a/c pulley too slow at an idle explaining the drop in performance. I had had the same problem in my Z28 Camaro. I installed uderpdrive pulleys and started to have all sorts of charging problems and frequent dead batteries, especially prevalent in cars with security systems. I remedied the problem by buying a $210 Optima Yellow Top Battery.

I am not saying that this is your problem, maybe I am little out there in left field but I would think that if your a/c were undercharged it would consistently blow tepid air?

[eztuner12]

Hi bostogrun
Thx you so much for your time & help!!!!
I got this car new from the local BMW dealer, the only mod that has been done, was by me when I installed the DASC. The only fan this car has from factory is the primary cooling fan between the front engine area and the radiator and it is an electric fan that turns on periodically. There is no auxiliary fan between the condenser and the BMW kidney shape front grills. The car is a German Version; here is the VIN # AS71156. It is a 1997 e36 318is sedan, with only 35,000km @ 21,875 miles, I barely used this car.
The drive belt from the engine was changed for the one the longer one that came with the DASC kit, same as one pulley from the engine (2.5 Idler Pulley Non-spacer Side lip removed) which substituted the OEM idler pulley. The engine idle is perfect runs about 800 RPM at its lowest. The A/C belt & pulley are the OME. The battery goes for about 2 years or more with no problems. Perhaps a stronger battery would solve the issue as it did to your Camaro Z/28. Do you have any idea of the battery Volt and Amps I should use?
The battery it has now is 12v. 50Ah, perhaps a 12v. 65Ah would do the job and my A/C would perform as it should under 1000 RPM. Just a thought!
BTW. the A/C is well charged and the compressor is working perfectly, as they where inspected about 15 days back.
Again thx
Cheers

[bostogrun]

I am not wayne, I am forum participant. If you are only getting 12 volts you got a
problem. I dont know your model. Does the same belt drive the alt and a/c.

Think at least 13.5 volts with the engine running

[bostogrun]

Whats a DASC? Why did have to change a belt for it.

[eztuner12]

bostogrun, sorry for calling you Wayne, I was confused…
The car came with two separated belts, one smaller for the A/C and the regular serpentine drive belt. In order to spin the Downing Atlanta Super Charger (DASC) pulley, the kit included a longer serpentine drive belt.
I would go and check up my battery Voltage this weekend.
[IMG][/IMG]
In the pic you can see the DASC front pulley with the drive belt.

[bostogrun]

That supercharger has got to have something to do with it. Any time you introduce an aftermarket component you always have an unintended consequence. When I put headers on my Camaro, I had a problem with burning up plug wires. My guess is that the blower is adding drag that is slowing the alternator too much at idle. You might have to experiment with different sizes pulleys.

[eztuner12]

bostogrun
The car has the supercharger for about 3 years; this scenario started about 2 months ago or less
The car ECU computer shows no codes what so ever thru the diagnostic tool….
It is just that the A/C decreases coolness when I stop the car, ones it runs again or on stop I rev the engine to about 1000 RPM the A/C cools up perfectly. At nights I noticed the head lights intensity, as well as, the panels light drop at the same time the A/C decreases coolness, all happens when the radiator cooling fan turn on, today I went thru more observation and noticed the RPMs drop from about 900 to 800 when the radiator cooling fan turn on as well.
The DASC is design specially for these car it use lots of the OEM parts, it is a perfect fitment and no modification is done to the electrical system, transmission nor engine what so ever. I have other friend they have installed the supercharger and they are not experimenting this issue, same as I for the last 3 years since I installed the SC to my car.
Thx for the interest in helping, any suggestion or ideas would be very welcome. I will check the battery volts during the weekend; if I can find my multimeter or at least remember to hum I borrowed , as they say “stupid is who borrows a tool but even more stupid is who returns it back, LOL.
Cheers
PS. I will check on the alternator too!! It must be @ this area, alternator or battery I guess, as you guys bring it up.

[coolbear1]

I apologize in advance for not reading the entire tread before answering but I didn't see anywhere that you put a set of gauges on the car. The guages tell so much, there is really no use trying to diagnose the system beyond the obvious without this information.
Put a set on and give me the pressures on a warm day at idle, and 2000 RPM and I may be able to help. At least we can rule out some of the guesswork. The supercharger has nothing to do with it. As long as the RPM's are there, and the air across the condenser coil is adequate, the A/C doesn't care what you add to the engine. Your problem sounds simple, but without information about what the refigeration side is doing, the rest is just guessing.

[bostogrun]

I thought he just put the supercharger on.

Your right he needs to put a manifold pressure gauge on to see what he high and low side pressures are. They should be something like 150 high 28 low?

[eztuner12]

Hi there coolbear1 & bostogrun
Sorry for my ignorance about the mentioned gauges, can you please tell me of which gauges are you referring too???
If you are referring to the A/C R134a refrigerant pressure, I recently took the car to a BMW authorized shop in line to check if the system was missing R134a, in order to see if this was the problem. At the shop they did find out that some refrigerant was needed so they fill it up to specifications, they also did some test on the compressor and some other equipment of the A/C system and all came out that they were in perfect conditions, as well as working fine, but they did not mention anything about the air across the condenser coil, maybe they didn’t check on this. Do to the outcome they told me they should go into further search of the car, if I wanted to, in order to pin point the issue, but I told them, it would be on another occasion, they are extremely expensive when they go into this kind of investigation.
I do have another shop specialized only on Mercedes Benz, Porsche and BMW that has a lower rate per hour of labor and original parts are even less costly then the authorized BMW shop, they even accept me to bring my own parts. I can take the car to them as I have done before for inspections 1 and 2 and minor jobs on this and others BMW’s I owned. I have 100% confidence in them, they have done mayor work on a previously owned Porsche I had, with great success, perhaps they can check up this pressure test you are suggesting, certainly I would save $ and time If I tell them what I need to be done in place of letting them do what they want or to go into searching for the problem.
Again, thx so much for the broad help and suggestions.
Cheers
PS. BTW, the first post made by Richard (guest) is me eztuner12 Thx…

[eztuner12]

Hello again...
Battery voltage is perfect 13.5v and the a/c refrigerant is perfect too
So any other suggestion for a possible solution on my issue???
I hope there is…
Thx to all....
Cheers

[bostogrun]

How about the a/c condensor is it clean or full of dead bugs? If the condensor is plugged your a/c performance will drop.

[eztuner12]

Hi there bostogrun
Looking into my primary radiator cooling fan I notice that when this one comes on the electric fan motor sparkles as if there was an electric false contact, is this normal?
The condenser is clean absolutely. As I explained if I’m on a light stop and rev the engine to about 900/1000 RPM the A/C will cool up perfectly even if the primary radiator cooling fan turns on.
I definitely will do the A/C refrigerant pressure test myself, yesterday I was on my engine bay and try to remove the A/C refilling valves covers, And they totally seemed like they haven’t been removed for a while so I’m figuring out that the BMW shop did not did the pressure check. It has happened before with them.
This issue must be @ the refrigerant or voltage, I guess, definitely will check this myself as soon I get my gages back, or go to another shop to be inspected, second opinion.
Lately it came to my mind the “expansion valve”, do you thing this could be the case?

[bostogrun]

Dont go to the shop, go to Harbor Frieght and buy the two dialed manifold gauge for $40.00. For less than the price of one trip to the shop you will set for life not to mention wasting time taking it to the shop and waiting. Then hoping that take mercy on you and don't rob for too much.

You really can't check the a/c properly without a manifod gauge. those cheap ones usually attached to a disposile bottle of refrigerant only read the low (vacume side) The nozzles are different sizes so even an idiot could not mess it up.

With the engine running and warmed up and the a/c on 100% you should have 28lbs on the low side and 150-180 on the high side. Just Google diagnosing AC probelms and you should get a troubleshooting guide. For example: no cooling with equal pressure on both sides means a failed compressor. Too low of pressure on both sides could mean low refrigerant.

You seem like a smart, resourcefull guy so get cracking. Rememeber these are not problems rather teachable moments as a result of this problem you have learned a lot about a/c, enhanced your knowledge of charging systems and learned a lot about the interactive nomanclature of many components.

I believe a partially blocked expansion valve would cause too much pressure on the low side and not enough on the high. The expansion valve is like a squirt gun nozzle that allows pressurized liquified coolant to vaporize before it enters the evaporator. I am not totally sure so I think you need to do a liitle research on the symptomolgy. Minnesota is a not real big A/C State.

[A930Rocket]

I didn't read the entire thread, but a quick thought came to me with the supercharger.

The system might be turning the fan and alternator slower. This forces the alternator to turn slower and put out less. It also turns the cooling fan slower, bring less air across the condensor.

An underdrive pulley anywhere on the sysytem will only exacerbate the problem.

Good luck!