Re: 1987 300E aux fan switch? Also temp gauge ?

I just spent time on my E300D 1995... should be similar enough to your car.

Two trigger for the fan... low and high speed. The low speed is triggered by
your accumulator/drier... with either green or red switch... these are
temperature switch. If you jump the two wires together here, the low speed
should come on. If not, then you got problem elsewhere.

The black switch on the top of the accumulator/drier is for compressor...
making sure there is enough pressure to keep the compressor from burning out
due to no refrigerant.

The other trigger is for high speed and that is located on your engine in
the front... two prongs probably with blue color... If you pull this harness
off, the high speed should come on. If not, then you got problem at the
relay. This high speed relay is the green one in the fusebox... usually
should be good as it rarely get kicked on.

The blue relay in fuse box is low speed... This relay can go bad or fuse get
blown. This relay triggers the low speed when the red/green switch wires are
jumped.

If the low speed does not come on... it is most likley the relay is bad...
or wrong colored switch red/green... or simply bad switch. This red/green
temp switch required the refrigerant to be evacuated before replacing.

My problem? I put the wrong colored one in... original is red... and I put
in the green one... and lo and behold... low speed never come on.


.

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