Its my understanding that the washer fluid is heated as well as the lines and nozzles? Are the lines really heated? When does the system activate?

And how does one test the system form head to toe? With winter coming I want to make sure its working properly and wont cause issues such as excessive battery drain.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Battery Drain ..............
That might be something I 'm experiencing..

If the W126 is like the W124 then the washer reservoir is heated with engine coolant and the nozzles are heated electrically. However, I don't think the actual lines are heated. I think the washer tank may be heated continuously whereas the nozzles are on a thermostat like the mirrors.

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1989 300CE

The washer fluid is heated by coolant flow through a coil in the washer fluid tank, the temperature is regulated by a mechanical thermostat inline with the coil and located inside the tank, its a black device about 3" long. They fail and allow continuios heated coolant flow evaporating washer fluid.

The nozzles are electricly heated and the hoses are electrically heated, they are controled by an electronic thermostat which is located in the hood's rear cross brace underside on the drivers side on the 126 chassis I'm pretty sure. The thermostat is a black plastic rectangle about 1" X 3" long that snaps into an opening in the cross member.

The hoses between the tank and hood nozzles are also heated. There's a small resistance wire in there, take a peek and you'll see it. It's run by the same thermo switch as the heaters in the side view mirrors.

So the thermostat in the washer tank fails? Mine might have, it gets quite hot... hot enough to make the washer fluid steam.

I don't see the system being able to cause any battery drain, it's all run off of switched power so with the key off the system is off. And it doesn't use much power. I seem to recall the service manual saying it all draws under 2 amps.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Thanks VERY much. Thats the info I am looking for. I am going to check things out and test continuity. I saw that access port on the underside of the hood, now I know what its for.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car