MichaelFuentes

I have a 2003 SL500, my blower motor was working sporadically, so I replaced the resistor/regulator and now the blower motor runs only on high speed and I still have no control with the fan speed control dial.
Question: Does the ECU need to be reprogramed to except the new Resistor/Regulator or do I have a different problem?

P.S. I also replaced the AC Heater Climate Control module and still no change.

Aussiesuede

When the climate controls are set to AUTO, does the fan speed adjust itself, or does it still just run on high all the time? If the fan speed operates normally in Auto mode, but stays on high when not in Auto mode, the culprit could be the fan spped control knob as it's a very common problem. Over time, gunk builds up on the spindle, and the pickup doesn't get to see a clear metal contact. In some cases, simply rotating the knob from low to high quickly about 50 times will clear the gunk. But whe that doesn't work, you have to dismantle the knob and clean in manually. I realise this might not be your problem, but wanted to offer up something that's both free and easily checked. Unfortunately I don't have an answer re ECU reprograming.

MichaelFuentes

Thanks Aussiesuede for your response.
Setting controls to AUTO have no response, however, with the car off and pressing the REST button, the fan does work and blows air.
When I reinstall the original resistor/regulator, I can drive around for a few hours and the blower with eventually come on and work perfectly, but when I shut the car off and immediately turn it back on the blower motor with not come back on.

I did replaces the entire AC Heater Climate Control module, which includes the "fan speed control knob", with no change, so that rules out dirty contacts.

I'm starting to suspect there's another sensor that's going out that affects the blower motor. I need to do some more research.