Bypassing Blower Motor Regulator? - PeachParts Mercedes-Benz Forum

Bill()C · #1 10-16-2007, 10:56 AM

87 300SDL

OK... so I don't have the several hundred bucks right now to buy a new blower motor regulator.

I have no fan whatsoever. I have power going into the regulator with nothing coming out of it to the fan. Anyone know if I'll damage the fan motor if I bypass the regulator? I'm guessing I'll only have one speed if I do but I can live with that for now. Not having defrost in the fall and winter is a pain.

Thanks,
Bill

tangofox007 · #2 10-16-2007, 02:02 PM

Quote:

Originally Posted by Bill()C

87 300SDL

I have power going into the regulator with nothing coming out of it to the fan.

That's not enough evidence to convict the regulator.

Bill()C · #3 10-16-2007, 02:57 PM

I'm open to suggestions... The fan motor does work. The leads TO the regulator are energized, But the leads from the regulator to the fan are not energized. What else should I be looking at?

TIA,
Bill

Jeremy5848 · #4 10-16-2007, 03:08 PM

You certainly could rig up a manual selector switch that would run 12 volts to the fan. By using a multi-pole rotary switch and connecting the fan resistors, you could even have multiple speeds. Wire and switch must be rated to carry the fan current (a couple of amps, I believe).

Jeremy

Bill()C · #5 10-16-2007, 03:20 PM

...or just let it run flat out, which is what I was going to do until I can find a replacement regulator, (which still seems up to debate)... I'm just wondering if this would hurt the fan motor in any way. I take it from your opinion, I'd be OK.

Bill

bustedbenz · #6 10-16-2007, 03:27 PM

not doubting the "couple of amps" - but why, if this is true, is the blower on a 30 amp strip fuse?

tangofox007 · #7 10-16-2007, 03:35 PM

Quote:

Originally Posted by Bill()C

I'm just wondering if this would hurt the fan motor in any way. Bill

The fastest motor speed uses system voltage normally. Only the slower speeds go through the resistor. As long as the power source is fuse protected, everything should be fine.

tangofox007 · #8 10-16-2007, 03:38 PM

Quote:

Originally Posted by bustedbenz

not doubting the "couple of amps" - but why, if this is true, is the blower on a 30 amp strip fuse?

Is the blower motor the only component powered through that fuse?

On the W123, for example, the majority of the ACC system (including the blower) is powered through a 16 amp fuse.

Jeremy5848 · #9 10-16-2007, 03:56 PM

Reference: "Service Manual -- Heating, Air Conditioning, Automatic Climate Control -- Model 123" (dated 1988) page 83.8--600/10 (Climate Control III).

The schematic on this page shows that a 16 Amp fuse in position 'b' powers the fan and most of the rest of the climate control electronics.

I'll put an ammeter on my fan one of these days, see what it draws. My "couple of amps" was not supposed to be an accurate figure.

Jeremy

rrgrassi · #10 10-16-2007, 04:00 PM

My 16 amp fuse kept blowing, and the black plastic in the fuse block was melting. The old blower motor was drawing 26 amps!

New motor and now the circuit pulls 13-15.

bustedbenz · #11 10-16-2007, 04:50 PM

Oops. 123 vs 126 again. Someday, I swear I'll learn to make sure I'm not trying to read 123 posts and connect them to my car.

On the 126, they moved it out to an external fuse (wires go under the fuse box, strip fuse is in a plastic holder bolted to something outside the fuse box itself) because of that very melted plastic issue. Mine burned up this week, melted the whole plastic casing and everything with it.