My auxillary fan is wired to the horn - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 04-22-2010, 05:30 PM Thread Starter
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My auxillary fan is wired to the horn

Just bought a 1970 280S. The auxillary fan was wired to the horn so that it came on with the ignition and is always on. This is a little annoying. I guess the car might have had some overheating problems but after disconnecting this it runs at a good temp. I can't find the original connections that I assume goes to the temp switch on the thermostat housing, so my question is- can I just wire the fan to the AC compressor so it only comes on with the AC? It works when i touch it to the two wires at the top of the compressor. I am assuming the fan is only needed to keep the condenser cool.

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post #2 of 3 (permalink) Old 04-22-2010, 05:56 PM
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To answer your question, yes it is possible.

The question is, do you really want to? I would try driving around the city in stop/go traffic for 1/2 hour and see what happens to the needle. if its still ok, then having it come with the compressor sounds reasonable.

Former MB: "Miss Juliana" - 1972 280SEL 4.5
Current MB: 2013 C250
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post #3 of 3 (permalink) Old 04-25-2010, 01:21 PM
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On most engines of that vintage there was a 100 degree C switch that turned on the Aux. fan. There is a sensor somewhere on the engine (mine on my M110 is on the cylinder head on passenger side. I have converted my whole cooling system to the electric fan system. My Aux. fan now comes on anytime the A/C is on or when the engine temp. gets over 100 C. I replaced the Aux. Fan with a larger 16 in. fan that, I am sure, has a higher CFM rating than the stock one. My stock engine driven fan was replaced by a thermostatically controlled (185 degrees F) 14 in. electric unit.
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