Will someone explain how aux fan works, on my 93 Mercedes 190e in the morning when I turn the a\c on the aux is not on, it comes on about 20 minutes latter.. at first I thought it was because it was low on freon .so I top it off.this morning. still 20 min after start up then it finally came on. . I check my w 140 and its the same way .but I'm still a little confused about the aux fan to how it really works as far as the drier switch high and low relays. will someone please explain to me how it works I really do appreciate everything you guys do thanks you very much.

It's an "auxiliary" fan. This means it is an additional cooling mechanism to the 'normal' cooling fan. The aux fans kick on when the engine temp reaches a set point (I think maybe 100-105C?) - above what the normal fan might be able to achieve. There's really no connection of the AC and the aux fans - other than, there is more 'pull' on the engine when it is engaged. Hope this gets you thinking in the right direction.

Someone step up and correct me if I'm wrong...

__________________
Dale

Ok.. Thank you sir.

Wrong, the aux. fan should operate when the high side of the compressor rises. If it doesn't operate, the high pressure switch on the drier/receiver will shut the compressor off.

With gauges connected to the ac system, at idle in park, you can watch the high pressure rise, the aux. fan turn on to cool the condenser, and the high side pressure will drop.

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Ok thanks that's what I thought.