My auxilary fan won't come on via the water temp switch on a 1982 300D Turbo . I found an open circut between the water temp sensor and the relay. The circut beteen the AC temp switch is good and works. Is there another connection or resistor that I'm missing? My wiring schematic only goes to 1980. Did MBZ change something again that worked fine to begin with?

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

On an '82, the fan operates only when the refrigerant switch on the receiver/drier closes. Coolant temp is not a factor in the fan operation. The temp switch near the thermostat is a lock-out switch for the blower motor.

The thermostat switch locks out the interior fan motor? Why!!!!!!!!!!!!!!?

__________________
1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

In the "heat' mode, it prevents the blower fan from running until the coolant temp rises enough to provide warm air.

So that means I can put another sensor in on the thermostat housing and have the best of both options The old world and after climate control. Living in the hills the temp will get up to 100 while climbing long grades. Depending on thermo-fan clutches is always scarry.

Thanks for the info. I'm off to the temp switch catalog and then to the machine shop. This modification could only wear out an electric fan, well maybe some alternator brushes too.

thanks again

__________________
1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

It would be a lot easier to control the aux fan relay with a manual switch. But that fan is really more of an air conditioning component that a radiator cooling fan. I seriously doubt that it's going to make much difference when it comes to engine cooling.