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Old 11-23-2012, 02:36 PM
bustedbenz's Avatar
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Join Date: Feb 2007
Location: Lexington, NC or Boone, NC
Posts: 2,272
Climate Control / Blower Regulator Questions

I'm trying to get my thoughts organized for a few upcoming climate control repairs and realizing I need to get a few "fundamental" things straightened out first.

1. Am I correct in saying that the "porcupine" (an electrical device with a spiny heat sink on top of it that resides in the plastic blower motor housing) is singlehandedly responsible for varying the blower motor speed, based on voltage input from the CCU? In other words -- there are no other components involved with controlling the blower speed, other than the CCU, the porcupine, and the fan itself?

2. Am I correct in saying that the "fire hazard" resistor coil under the hood in w126 and w123 cars, was REPLACED by the porcupine? In other words, if I have a car that uses a porcupine regulator, it absolutely, positively, does not also have a resistor pack under the hood to start a leaf fire? And, likewise, if I DO have the coils under the fuse box (my '82 300SD does have this, I've checked) then it does not also have a porcupine; the devices are mutually exclusive because they do the same job two different ways.

3. How many of my MB's are equipped with an "Auxiliary" water pump, which as I understand it, helps to circulate coolant while the engine is at idle to promote better heating? 1982 240D with MANUAL climate controls, 1982 300SD with CCU, and 1987 300SDL with CCU. I've never done the add-a-1-amp-fuse trick to the aux pumps on any of mine yet... do all of them need it or does the 87 have some kind of self-protection that the earlier ones lacked? (I saw a reference in a previous thread on aux pumps that said something to the effect that 86+ don't toast themselves the same way that 85- do. Trying to confirm or deny.)

Thanks, folks. Just trying to get a few confused thoughts straightened out on which ones I've got and how they operate. (And what all needs to be on my to-do list.)


"What could possibly go wrong?"

~Michael S.~ -
1986 M-B 300SDL, retired due to rust and electrical problems. Donated engine to:
1987 M-B 300SDL, odo dead. New project.
1982 M-B 240D, odo stopped at 308,000
1982 M-B 300SD, 175,000
1989 Dodge Ramcharger, 87,000 - 4wd, 318
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