Hi all, been working on the A/C on 280se 71 3.5 v8 and finally got the compressor to switch in (large relay had rusty spot inside) but I still don't get the aux fan to start??

I had a look at the two switches that turns on the a/c and noticed a loose wire so checked out the two knobs the blower switch had round pole connectors and all were connected the right switch (temp?) has three spade conectors and there is no where where this spare (blue/blask stripe) wire goes is it just a spare? I did hower notice (terminal #3) had a empt spotr where a connector could have been? can anyone confirm the terminals on this switch?

Anyway the green compressor light comes on when the blower is switch on but fan doesn't kick in? is there a way to test the A/C?

thanks guys.

If I remember correctly on my 72 280SEL 4.5 the fan engaged depending on A/C head pressure not the mere fact that the compressor was on. The fan was energized by pressure in the system. On my 81 300CD the fan only works I believe to stabilize engine temperature regardless of A/C compressor engagement. Never hear or see the aux fan on in the winter even tho the auto climate control has the compressor engaged 80% of the time. Verify what signal engages the fan. Dont assume the compressor engagement is the signal.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.