It reminds me of an old electric train set I have. Over the years, more and more current is required to move the locomotive, presumably because of dust and dried-out lubrication in the motor.
I did observe something interesting:
Since the first 90-degree days last week, the A/C would oscillate from cold to warm, with refrigerant pressure ranging from 06 to 28, and evaporator temps from 46 to 84 -- coldest/highest pressure intervals when stopped at traffic lights (engine ~600 rpm) and warmest/lowest pressure intervals on highway ( engine 2,000 rpm+) The cold air was never constant; it always oscillated.
Today that changed. While waiting to meet a client I idled for about 15 minutes and the car stayed comfortably cool the whole time, with no warm/cold oscillation. Evaporator temps varied between 49 and 55 and refrigerant pressure fluctuated from the high to mid teens. Aux fan readout showed voltage fluctuating from 10 to 21, and they were indeed spinning.
Standing at the driver door looking at the CCU, I could hear the fans spin faster or slower as displayed voltage rose and fell. There was a delay of about five seconds between a voltage display and the corresponding change in fan speed.
After some reflection I realized that instead of running the A/C on Auto as I usually do, I had manually set the blower fan to max. When I reduced the blower speed three levels, fan voltage dropped to 3.2 and fans stopped spinning (visually checked). After increasing blower speed to max, voltage rose to 21 but the fans did not move -- until after I toggled the EC off (red light on, fan voltage 3.2) and then back on (red light off, fan voltage 21), after which fans resumed spinning, the compressor engaged, and the constant cooling resumed.
This behavior suggests a connection to the blower motor regulator but I have never hard of such a thing, nor does it seem to make sense. I cannot, however, ignore what I observed.
Quote:
Originally Posted by Diseasel300
Bearing noise = toast. Not sure about the W210 fans if they can be serviced or not. I know the 126 can be serviced by drilling out a couple of rivets. My fan ran, but howled like a banshee. New bearings shut it right up and been fine ever since. 3.2V may or may not be enough power to break the motor free, assuming it actually is providing 3.2V. I guess you'll find out with the new fan.
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