and what does it do...also what wouldn't work if its fuse were missing? the area around the fuse holder is severely melted and there's no fuse there. while i was installing the external fuse holder/fuse for the blower motor, i noticed that someone had already installed two additional fuse holders. one of them went to fuse #4, and i couldn't tell about the other one..it could have gone to the aux. fan fuse for all i know

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1985 300D Turbo "Eunis"

Its intended to provide extra cooling/air movement for the AC system when sitting in traffic and the like, essentially its temp-activated extra cooling for when the engine fan is moving too slow or isn't enough.....mine rarely ever runs, usually only sitting in traffic when its real real hot out.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

hmmm...would a missing fuse for the aux. fan cause the ac system not to work? like if different ac components are wired in series?

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1985 300D Turbo "Eunis"

I am pretty sure the Climate Control unit, the A/C clutch, and the aux fan all use a different fuse.....I could see the A/C not working "as" well without the aux fan, but I wouldn't see it not working at all. I think its only supposed to use the aux fan if it detects temps at which extra cooling would be needed. The A/C clutch also shares a fuse with the Tach....and a couple other things..... and I think it'd be obvious if the climate control unit itself wasn't working/getting power....otherwise I don't know. I think the A/C should work mostly fine without the aux fan working/having a fuse.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

On most models the aux fan is activated by excessive high side pressure. In other models it is by high side pressure OR high engine coolant temp.

If you watch ac gauges when the aux fan kicks on you see a dramatic decrease in high side pressure. That protects the ac from dangerous excessive high side pressure. If you live in a mild climate, the car could run its whole life without kicking on the aux fan.

Good luck,