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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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Discussion Starter · #1 ·
I'm getting ready (have been for about a year now) to take care of my faulty HVAC system. In preparation for rebuilding the HVAC system and blower motor, I am going to test my auxiliary water pump.So,questions:

1. Does the block heater use the aux. water pump in its heating of the block, or are all the parts involved solely part of the block heater apparatus? (And how does that work, anyhow?)

2. If I leave the aux. water pump installed where it is, then run a lead from the negative terminal of the battery to ground, and run leads from the positive terminal of the battery to the two remaining wires on the aux. water pump, if the pump is working properly, will I be able to hear it running?

Thanks, again, to all of you out there helping my in my plight to get this car 100% mechanically operational for my mother... I could not have done any of this without you. Hopefully the pictures I take of this job will in part repay your kind service to me.

Also, I might be buying another wagon (long story), in which case, the current wagon might be up for sale... what do you think a fair price would be for the wagon in mechanically perfect shape, with some minor rust issues? (I might be able to take care of this all this summer before a new wagon gets in, but then again, maybe not...)
 

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1982 300CD
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The stock block heater is simply a heating element that screws into the passenger side of the engine block. A cord plugs into it, and into an A/C outlet. I believe that there are aftermarket units out there that somehow incorporate the pump.

I have never "hot wired" the pump, but I would assume that it should run if you put power to it.

I remember hearing about putting a fuse in the power line for the pump because when it fails, it can take out the ACC unit. Anybody with details on that? I might get to that sometime soon...
 

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89 Mercedes 300E, 91 Mercedes 300CE, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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Are we talking about the circulating pumps/heaters that go inline the radiator hose? It is quite common to use an oil pan heater,transmission pan heater, block (freeze plug) heater and battery tray heater all together with the pumps I think you're referring to. Really basic on their operation.
 

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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1,993 Posts
Discussion Starter · #4 ·
I'm talking about the thing that Greg put up in the pic... when I plug it in, I hear some sort of whirring... so I thought there might be some pump operation to it...

Greg, and others, I'd love to figure out a way to put an inline fuse into the system, since I really don't want to have to swap in another pushbutton unit if/when(moreso, considering the car is so old) the Aux. water pump goes.
 

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'78 240D 4-speed greasel
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312 Posts
they will make noise but its no problem, what could be a problem though is if there is any air in the cooling system that may pocket itself at the block heater, which could then burn the heating element out.
 

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'82 300D
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I'm talking about the thing that Greg put up in the pic... when I plug it in, I hear some sort of whirring... so I thought there might be some pump operation to it...

Greg, and others, I'd love to figure out a way to put an inline fuse into the system, since I really don't want to have to swap in another pushbutton unit if/when(moreso, considering the car is so old) the Aux. water pump goes.
IIRC it's a purple colored wire that runs to the aux warer pump. Use a 1 amp in line fuse. I have done mine like that.
 

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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1,993 Posts
Discussion Starter · #8 ·
Thanks RR! I'll give that a shot.

To make sure my PBU was actually working properly, I used a length of pipe insulation I got at Home Depot to replace the disintegrated foam part of the tube that supplies suction for the temp reader in the dash... an poof, the temp selector wheel and auto function work perfectly now, with the exception of the leaking vacuum pods and the faulty switchover valve...
 
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