2000 BMW 323i wont cool at idle

[jwestfall]

I have a 2000 323i sedan which has about 85000 miles on it. Recently the AC began to blow warm at idle. At 2000 RPM the air cools down to 55 or so with an outside temp of 98. So it is fairly comfortable until traffic slows me down. The local mechanic put gauges on it -on the low side 90psi at idle, 55psi at 2000RPM. The high side was up there but I dont recall the reading. He first thought it might have been overcharged. However this car has never had its AC system opened. It is all original. When I told him this he said I had a weak compressor. The compressor is not making noise and it is cooling well at higher speeds. I checked the Auxillary fan and it is blowing air over the condensor. Got any ideas? help is appreciated.

[Tom Greenleaf]

If you have the history it's NOT overcharged, as per your post. Fan must be working well and condenser clean and free of junk. Best I can say right now with the info at hand,

[jwestfall]

I noticed when I hold the gas pedal down for about 1500 to 2000 RPM the aux fan speeds up considerably. I think this could be the reason my AC cools better. What do you think? Why would the BMW auxillary fan run at different speeds?

[Tom Greenleaf]

I'm not a beamer tech but the fans should be full blast with A/C request in almost any car.

[Trotsky]

I noticed when I hold the gas pedal down for about 1500 to 2000 RPM the aux fan speeds up considerably. I think this could be the reason my AC cools better. What do you think? Why would the BMW auxillary fan run at different speeds?

I'm no A/C expert but I know about BMW's. The BMW auxillary/electric fan is a 2 speed unit:high/low. It runs at low speed when A/C is turned on. Runs at high speed when coolant/engine reaches a specific temp.

So it sounds like the fan speed is switching from low-high when you rev to 1500-2000(increasing load) therefore enchancing cooling.

[jwestfall]

So you think the fan and or fan controller (whatever that is) may be bad?

I played around with it this afternoon with temperatures in the 90s. With a hot engine, I held the RPM at 2000 for a few minutes; then I got out of the car and listened to the fan. It was clearly slowing down but in steps every 20-30 seconds. It would slow a little more each time. By the time it was down to a slow speed which I could barely hear. It was still moving air from touching the radiator. Keep in mind the car never overheats. The temperature gauge stays vertical. Is this fan bad?

joe

[The Transporter]

Aside from what the electric fan is doing, is the viscous engine driven fan engaging? It is quite common for the coupling to fail, when stationary, I would expect this to be engaged a fair amount of the time given your ambient temperature.

When this fan is not engaged it is possible to grab and spin the fan against the direction of rotation, but when engaged, it will make quite a distinct whoosh sound (And make a mess of your fingers)

[DNT]

Lets get a set of guages on this vehicle and then take the water hose and spray the condensor with the car at idle, if your compressor is good the pressures should pull down on both sides to normal levels, if your compresssor is weak the low side will stay up close to where it was and only the high side will drop significantly. If compressor proves out good you most likely have a problem with the electric fan either the controls or the motor itself. You really need a control schematic like from ALLDATA or similar to see what controls are built into the system. Some compressors exhibit the high low side pressure symptons at idle when going out without producing any noise. Have you had any other work done on this vehicle recently? Just out of curiousity I would verify that the fan is turning in the correct direction you just never know with these things LOL.

[jwestfall]

Thanks for the idea. The pressures do come down to normal with the water hose on the condenser. I guess I need to focus on the fan. It seems to run at a very low speed most while I am at idle. I noticed that it speeds up when I run the engine up to 1500 to 2000 RPM. Then is seems to step down to slower speeds gradually. It doesnt seem to be a 2-speed type fan. Anyone know anything about the fan controls on a 2000 323 manual sedan? I would think the fan should scream at idle with the AC on and 95 degree heat.

Thoughts?

[Guest]

Change the clutch on the engine driven fan...Hope this helps.

[jwestfall]

Well this particular model does not have an engine driven fan. There is only one electric fan located between the engine and the radiator / condensor. My dealer was confused too, because there are several different configurations for this car depending upon year, transmission, etc.

Joe

[Tom Greenleaf]

Dealer confused! You need a new dealer! A call to BMW customer service wouldn't hurt either. Try NOT to use bad language, best,

[The Transporter]

My mistake, the year 2000 E46 was indeed fitted with an electric puller fan. in place of the more usual pressure switch as on earlier vehicles there is a variable pressure sensor which allows the speed of the cooling fan infinately up to its maximum speed. This sensor reports to pins number 2,7 and 10 on the large plug on the back of the AC control module. The fan motor is controled from the Engine Control Unit which feeds a module which is part of the fan.
To add to this set up the compressor is a Denso 7SBU16C which is a variable displacement unit which can make diagnosis entertaining, I think that we shall need some pressures because if the compressor was not giving us adequate head pressure at idle, then the fan would have no need to run at speed

[Tom Greenleaf]

We are all here to help you get thru this - I think you know that, Tom

[jwestfall]

Well I bought the Bentley manual for this car as a starting point. From what I can tell this car will report error codes from the air conditioning computer which can be read by the dealer. However, I thought an error code would generate a "check engine light". I have no indication of this kind. Does this mean that there is nothing wrong as far as the computer is concerned? Or are there error codes which do not give an indication.

FYI, the temperatures are running in the high 90s with high humidities.

[The Transporter]

Although I can't comment on US spec vehicles, but an ac fault in a European spec car will not cause the engine fault light to come on, assuming that it has detected any fault at all. We still need those pressures, you see if the compressor is not performing correctly, then the fan will run at a speed to suit the head pressure, in such a case then there would be no fault found.

[jwestfall]

the low side was 90psi at idle, 55psi at 2000RPM. The high side was up around 200psi, but I dont recall the reading. THe local mechanic said my compressor was not working properly. The compressor cools to 35 F at highway speeds with temperatures outside 85-90 F. Also the compressor makes no unusual noises. Ideas?

joe

[Tom Greenleaf]

This is getting confusing The pressures are normally taken at 1,500 rpm not 2,000. You low #s are way too high if compressor is staying on and high # is a bit low. Out put temp of 35F at speed is too low! That's too close to icing up your evaperator.

You said that the pressures were normal with water on the condenser but didn't post the pressures. Are you convinced that your pressure and temp measuring is accurate?

If the water test made it work properly than it really suggests a problem with the fan for condenser.

A low reading of 90 !! You shouldn't have any cooling at all!

Maybe it's just me - but this doesn't make sense??