Well, I'm about to rejoin the ranks of W124 400E owners for the second time (I bought the first one about 2004 and actually it will become a parts car).

Anyway the new one is exhibiting classic blower regulator symptoms - I know how to test (Actually created a thread on that way back when) and I have a new motor that may have all of a week on it. My question is about regulators.

In the past I have bought used ones - shying away from the $$$$ for a new one. I think I remember new ones for $300+. Anyway new ones with heat sinks now look to be ~$250 with porcupine and ~$210 new style (I know I need the porcupine but I have spares so I could swap the heat sink.

More interesting is searching on the part numbers shows them available for ~$80 to ~$150 as either just the electronics and wiring which you must attach to your own heat sink, or an obvious aftermarket heat sink.

So the question - Finally - has anyone tried any of the new low cost regulators? Good, bad, indifferent???

Thanks
Paul

In theory one should be able to rebuild the regulator as most of the time is just set of resistors and one or more of the resistors tends to die.

I've never opened one up before but I'd wager you could verify the bad resistor, and replace it with a suitable unit from Mouser/DigiKey/Newark/Allied

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From my reading (and I'm no electrical expert having a ME background not EE) Mercedes uses current limiting to control motor speed. So there are some active electronics in the module - still no where near $200 of components.

On further reading it looks like the W140 (and early W210) blower regulator has the same functionality (albeit different wiring). It looks like these can be had for ~$30-150, what would be necessary is to cut their 4 pin connector and replace with a W124 harness. It looks like the W140 part's 4 pins are

1) Red (large gauge) - hot to motor
2) Red (small gage) - hot to regulator
3) Black - ground to regulator
4) yellow - variable volt to regulator

Output from regulator is one large gauge blue

So it looks like you could make your own harness for a w124 - 3 wire harness (really just splitting the red hot wire into two leads);
red - directly to fan and a tap off to the regulator
black and yellow go to regulator
and the blue output also goes to the fan motor

Anyone know if this will work - searches don't give any definitive answers that I could find.

Paul