My '91 190e has a similar problem, although I didn't wash the engine. The Aux fan will come on high even when the engine is cold started and the A/C is off. The A/C has been converted to 134a (before I bought it) and I know that the 134a operates at a higher pressure than the old r12, but would this cause the fan to come on even with the A/C switched off and engine cold??