The heat control has been flaky for some time, and as things cool down it's getting more critical. Just the lightest touch on the control wheel would make it cut in and out. (The monovalve LED I added some time ago is really crucial for this kind of diagnostic.) Today I finally made some time and removed the ACC panel. I removed the potentiometer from the PCB and opened it up. It's custom, no way to come up with a replacement, except out of another unit. I cleaned it out, and used DeOxIt fader spray on it, and did a very light wire-brushing of the circular tracks and the sliding metal fingers. According to my meter, the resistance change is smooth, with no intermittency. We'll see if this works any better. While I was there I added another LED, this one for showing AC energization, behind the center button. I used the other LED from the same toy, but used the blue side for this function. I used another 680 ohm resistor from the junk box, and hooked the series combination between the X1-7 (Klima) pin and power. Also, one of the two illumination lamps was intermittent, so I replaced it with a new one. All this took a little over two hours. On the test drive today it behaved well, but as it was a warm day nothing much was proven. The next cold morning drive should be more definitive.
-- Jim _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
