Bad blower motor regulator wanted - Page 3 - PeachParts Mercedes-Benz Forum

Brett San Diego · #31 05-24-2007, 07:40 PM

I have to resurrect this discussion. What was the final result here? Jim, Ken, Did the home brew regulator work? Is it the final conclusion that an existing regulator is unrepairable due to the epoxy potting compound or due to lack of availability of the required electrical components?

Brett

KenP · #32 05-24-2007, 08:52 PM

This is a coincidence! Haven't been active on the forum for a bit, but was passing thru while looking for some wheels for the wifes E320.
Anyway, the module can not be repaired. Its all potted in epoxy.
You can buy components that will approximate its operation but the heat issue remains. Its really a pretty crude way of controlling the flow of current through the blower assembly. MB should hang their heads.
I fussed with it for a while trying to get the linearity and start up voltages right, but ran out of patience after a while. The components are not rare in any way, but they need to be ordered from commercial sources...who have significant minimums for orders. I spent way more than a new regulator would cost and still wasn't happy with the result.
So, yes it can be done. No, I wouldn't bother.
KenP

JimF · #33 05-24-2007, 09:04 PM

I've been corresponding with another 'fix-your-regulator' person, named "Dexter".

He has gotten one to go but it has the 'offset' problem, as shown in post#22. He also put the blower motor in the collector ("Rload" represents the blower motor in the "emitter") and so he has the 1.4 - 1.7 volt offset (where nothing happens) but he says it works other than that.

I agree w/ KenP that the mechanical configuration is a tough-nut to crack. So much so, that it's not worth the trouble.

wbain5280 · #34 05-25-2007, 12:00 AM

If your any good at breadboarding electronic circuits, try this one. It's much better and the fan will run better too.

http://www.uoguelph.ca/~antoon/circ/pwm555.html

from:

http://www.uoguelph.ca/~antoon/circ/circuits.htm

and general Model RR circuits

http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

Pulse with modulation

http://home.cogeco.ca/~rpaisley4/Throttles.html#8

JimF · #35 05-25-2007, 10:59 AM

Quote:

Originally Posted by wbain5280

If your any good at breadboarding electronic circuits, try this one. It's much better and the fan will run better too.

http://www.uoguelph.ca/~antoon/circ/pwm555.html

With the use of the NTE2389 and a "large" heatsink, it almost works! The ref ckt's input drive level is wired to the 50K pot that when adjusted, constantly reconfigures the "2/3Vcc" and "1/3Vcc" levels required to get the correct PWM output. Unfortunately, the drive voltage from climate control module, N22, is just a DC voltage so the input drive voltage requires some 'modification'.

So this ckt actually is more complicated than the "darlington" transistor version since there's more parts required. However, if properly configured, it would NOT have the "offset" problem, which is good news. However, Q1's power dissipation can not be ignored so you still have to properly heat sink that transistor (FET).

Brett San Diego · #36 05-27-2007, 04:26 PM

Thanks all. Appreciate the responses. So what exactly is the failure mode of the original regulators? Is it the heat issue that kills them to begin with? Is the main transistor just burning up?

Brett

JimF · #37 05-27-2007, 05:12 PM

Never took one apart . . but I just was given a 'dead' one . . . so based on external measurements, the transistor is shorted. The heat is pretty intense due to the power dissipation so I'm sure it suffers "thermal fatigue" similar to how a fuse suffers "metal fatigue" and it finally opens.

rogerjones1 · #38 08-15-2008, 11:49 PM

Was anybody able to build a regulator based on the information in this thread.

Also, does anyone have the specs on a 1997 E420 blower motor. I am thinking of constructing a regulator using MOSFETS.

Roger

JimF · #39 08-16-2008, 11:42 AM

That one source I mentioned in post#33 has but I never saw a completed picture . . .

A company called "Unwired Tools" used to make a regulator but recently recalled all of them b/c . . . you quessed it. . . they got too hot. We (Pat @ Exclusive Motors and I) did test one and it got really hot.
Link: http://unwiredtools.com/products.shtml That product has been removed!

They used a variable power system similar to that employed by "Carver" in his power amps; the power rail is variable and continually moves based on the audio input signal. This means the transistor (or FET) output stage never has to dissipate large amounts of power if I'm not mistaken. They were more expensive than the standard replacement regulator.

Mine died about 7 years ago and the replacement is still going strong. As KenP said, it's probably not worth the trouble.

PS: check out this post by wbrian63;
Unwired Tools Recall

wbain5280 · #40 08-17-2008, 12:31 AM

Try this circuit for model railroad engines using PWM.

http://home.cogeco.ca/~rpaisley4/Throttles.html#8