AC Fan weak ... need a blower regulator?

[aliquis]

Well, three weeks or so into my ownership of a 1995 S320, I still love it, but it's definitely testing my patience. Warning lights, jammed seatbelts, and today's problem. No buyer's remorse yet, but ...

Today the AC fan seems to have given up the ghost. The AC still runs cold, and there is air moving through the vents, but there is no change in volume of airflow when moving the fan speed wheel. Judging from other posts I've found, I would say that I'm running at about 25% full potential air volume. It's getting hot here in SC, so this is a problem. I diligently searched the forums and discovered the excellent post about replacing the blower regulator at

http://www.peachparts.com/Wikka/W140BlowerMotor

So ... before I spend close to $300 on this part (my wife is beginning to think that I'm having an affair, the way I'm hiding credit card slips), I'm hoping that I can get some help on diagnosing that THIS is the problem, and thus the part I need to replace. I'm only marginally competent when it comes to things electrical (but I DO have a multimeter, so that's something), but I am completely intrepid when it comes to taking things apart and giving it a try . So thanks in advance for any help.

Tom

[aliquis]

So in the few days that I've been living with the problem described above in my first post, I've noticed some other "symptoms" that I hope can help others help me diagnose this problem.

1) It seems like the drop in fan/blower "speed" is related to temperature. In the morning, when it's around 60-70 degrees, the fan seems to work OK ... I can dial it up to "MAX" and get a lot more air volume than at "AUTO" or "MIN". And I get variation through the dial ... so it's working OK.

2) Now, it could be that the relevant temperature is ENGINE temp, since the fan seems to loose the ability to run at MAX power (or any speed other than weak) after I've been driving for a while.

3) When it's hotter outside (80-90), the fan seems to stop working (i.e., the situation I describe in my original post) sooner.

4) Whenever I start the car up, I get short time when the fan blows full power. This is maybe for 15-30 seconds. This seems to occur regardless of the engine/outside temperature.

Does this help in anyway? I would be VERY grateful for any thoughts!!

Tom

[per]

Before you do anything else, you should check the airfilter for the A/C.

[aliquis]

Well, I solved the problem, I think. Running the diagnostics in the post at the link in my first message sort of suggested that it was the blower regulator. I never did get a voltage on the disconnected blue lead, which is sort of weird, but with the blue lead connected, I was getting around 3V when the fan ran (for a short time) at MAX and then around 9V when it dropped down low and became unresponsive to the dial.

Replaced the blower regulator with a Kaehler aftermarket part. Talked to a guy at another board who told me he's had less problems with this one then that Behr. It was also only $159 at Bimmer Specialist. And it comes "preloaded" with the heat sink grease, so you don't have to guess about how much to apply.

One word of advice if you do this yourself. Be sure you attach the regulator's red and blue leads to the motor BEFORE you connect the 4-pin connector on the regular to the vehicle wiring harness. I did it the other way around first (meaning the red lead is carrying 12.4V from the battery), and got an almighty spark when I touched it to the motor terminal. Don't think I caused any damage (all the voltages checked out OK), so I disconnected the 4-pin connector, connected the leads, then reconnected the 4-pin connector and everything seems OK. But I did end up with a check engine light afterwards and had to go to AutoZone to get it cleared. Guess I sent a surge through the system that tripped a code. Rookie mistake, I know ...