86 420 sel engine wash, now no AC
 

After washing my engine a/c compressor won't engage and the low speed of auxiliary fan runs all the time. I searched here and read a suggestion that a temp sensor on the left front of the engine could be the problem for the aux fan. Could this be the problem? Is it on the intake or front face of the block? Has someone else had this problem? Thanks

Well, I solved my own problem. I found a temp sensor mounted in the thermostat housing. When I unpluged the two wire side of it (There is a separate 1 wire conector) while the engine was running, the aux fan quit running and the ac came on. I can't understand why this temp sender could be affected by an engine wash. No cracks- it looks good. Anyway, tomorrow I will replace that puppy and all should be well. I hope . I will report back since I started this thread, maybe someone else can benefit.

That's the 105/115 switch. At 105C one wire gets a ground signal to turn on the aux fans. At 115C another wire gets a ground signal to cut the compressor. Maybe water pooled on the switch and grounded the wire the cut compressor wire. Or the plastic housing has gotten brittle with age and water seeped in.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD