I just diagnosed mine as bad when I got the proper voltages at the regulator but not at the 3 pin firewall connector.

Does the new assembly come with the 3 wire plate connector or just the big aluminum heatsink? If it's just the aluminum heatsink, I was wondering what can go wrong with this thing? Since they're so expensive I was hoping I could clean it up to maybe solve any heat dissipation problems it may be having.

Anyone know how these things "fry"?

TIA!

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

"Does the new assembly come with the 3 wire plate connector"

Yes it does. I think you have no choice but to R&R.

__________________
Reno

'93 300E 4Matic
'98 Nissan Altima
'00 Yamaha Road Star Silverado

This a pic of a new one as it comes for a 126 chassis. It has a three conductor molex connector with a firewall grommet and two female spade connectors one on a red wire and the other on a blue wire. The aluminim part is a heat sink sometimes called a "porcupine", the electronic device is probably a transistor, SCR, or a triac of some sort.Three wire probably go to the semiconductor and the other two are probaly a thermo senseing device to prevent a meltdown, that may be the nature of your particular failure from the looks of it.

It appears that the semiconductor is controlled by the Automatic Climate Control unit (push button unit in the dash) which turns the switch on and off at various frequencies to control the motor speed using PWM (pulse width modulation) or something like it. The semiconductor in the black box mounted to the heat sink appears to have failed by the heat damage evident on the aluminum. You might want to consider having the ACC checked before connecting a new expensive part to it, it is probably unlikely that the control signal caused the failure but you never know burning up a new one would be a hard way to find out!

The best bet is probably a bone yard for a used one, get a couple they will ether work or not, good or bad, no in between. You might be able to open the black plastic and find out if the switch is an industry standard part and replace just that, might want to start a rebuilding service when you see the prices for a new replacement part!! Good Luck!

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Regulator meltdown indicates high blower current draw..
[ brushs/bearings]

Thanks guys, I'll check the amperage draw after I replace the worn brushes on the blower motor, before ordering a new one. This is the original though on car with 235k miles so I wouldn't be surprised if it's gone south.

I think I saw 20 amps max full speed? Does that sound about right? I'll hook it up to a battery in a bit and report back.

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

Specs I have are from 2 -28 A. , depending on V to trigger of regulator. [ low to high speed]
But keep in mind that this spec is for total draw from the entire circuit [ blower/regulator ].
I would think your 20A- straight blower/battery voltage [ no reg.] would be fine...

Mine fried as a result of :

W124 Climate Control Mystery

Voltage was correct at regulator from push button control box, but fan was on high at all times. The new regulator is not cheap, but it does include the heatsink and is easy to install once you remove the wiper motor.



1987 300D (176,000 mi)
2001 CLK 430 Convertible (18,000 mi)

I had the same part replaced recently...it comes complete (no choice) and it's puzzlingly expensive! (350$cdn)...especially considering a new blower motor was only 200$

The thing to be aware of is that there are different variations of of this regulator on a 300E, I was told, ( natch mine was the $$ kind) and the other variants are quite reasonable (1/10th the $$$) Check it out, first.

CB