I believe I need a blower regulator. I'm tryiing to make sure my diagnosis is correct and I didnt find anything in the archives to clearly check the blower regulator?

Blower worked initially when I got the car then stopped after sitting for a while (weeks) then worked for a bit and now quit.

Checked voltages at three pin connector near drivers firewall - good ground on black, 12V on red, and 1.2v to 7.5v on the yellow so I believe the interior button box is OK.

Removed blower and there is 12.4V at the blower leads but blower doesnt spin. Blower was hard to turn so I lubed bushings with ATF easier to spin now. Brushes dont look worn down to far (have spares). Hooked motor up to a power supply (curent limited 7v 5A or 12v 1.5A) it doesnt turn. Hooked it up to battery charger and it spins right up instantly (charger set at 2 amp setting but probably allows a much larger start up surge).

So I suspect it is the regulator but want to be sure befor I order a $300 part (or get a used one).

Thanks
Paul

Seeing that you have trigger voltage at the reg...

Do this:

The regulator is a switched ground, so if you ground the neg. wire[blu on earlier models/grn on later] at the Bower motor , the motor should come on .[this eliminates the reg. circuit]
If it does , replace the reg.
Also, make sure the motor is not drawing high current, as that will burn out the reg.

Also, make sure the motor is not drawing high current, as that will burn out the reg.
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I have a similar problem. My blower just won't run at high speed.

How do you determine whether the motor is drawing high current, and what do you do if it is?

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)

Thanks Arthur, I jumperd the blue (in my case) wire to ground and the motor spun up instantly.

What should the currant draw on the motor be?

I suspect the dry bushings caused excessive draw and that may have taken out the regulator.

Thanks Paul

I need the chassis/model for amp draw spec..
Also, if it is a late 124 , a common cause for reg failure is blocked air filters ...the reg heat sink can not handle the dissipation w/bad filters ..[94/95 series]

et al ... model/year specs help me on these as the 124 chassis has had many changes through its long vintage...........

Sorry I usually try to include vehicle detail in my messages.

My car is a W124 1992 400E (no air filter)

Is there any difference outside of current draw between filtered and non filtered? Those seem to be the only two motors on W124 chassis when I looked up parts.

Thanks for your help
Paul

I believe the filter system draw spec is 28A/High speed draw and non- filter at 25..
The testing of your blower should be direct connect to bat voltage w/amp meter in series . This will give you true motor draw without the regulator in the circuit and will be an indication of motor condition.
Let it run a while to make sure the draw does not increase as it warms up [ a min or so should be sufficient].
Anywhere around 25 A draw should not be too high for the reg to handle..............

'89 420 SEL - where do I get blower motor brushes?
Dwight

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Dwight

I am getting ready to tackle the 'porcupine' resistor and the blower motor in my W124. I am using used parts. Should I replace the brushes in the used blower motor before I install it?

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David
1986 300E Anthracite + ECodes + MB Mileage Award

I ended up buying some overly large brushes from an Electrical repair shop and grinding them to the right size. A couple of bucks, no big deal.
Dwight

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Dwight

My blower motor won't run at hi-speed in and 88 126 300sel.
Did you ever figure the problem out?

Mine was the regulator. Got a used regulator and blower from Potomac German Auto, via eBay auction

http://www.pgauto.com/

for about $100 shipped. Old regulator tested bad with new (used) motor. New (used) regulator tested good with both motors. New (used) motor had biggger brushes, so installed it and kept original for spare.

.

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David
1986 300E Anthracite + ECodes + MB Mileage Award

My 93 400 E had no fan function it runs fine on the bench. It sounds like it could be the voltage regulator. Where is this located and how is it tested.
How can you tell if your car came with dust filters, mine are not present.

Chris

You need to check a couple of things. If you removed the fan so you can test it on the bench you are 90% to removing the regulator. Its under the plastic where the actual fan motor was mounted. You have to remove several torx screws and then you can get the regulator out. its attached to a large heatsink (frequently refered to as the porcupine - you'll know why when you see it). Its a tight fit but it does come out - lift and tilt.

You will see the connector for the resistor mates up on the firewall on the drivers side. This is a three pin connector. You also need to check voltages here check my first post in the thread for the colors and voltages. This will tell you if it is the regulator or the button box.

Dont know when they switched to dust filters but I believe it was a model year change. it would be in the area of the fan.

Paul

Thank you. This is a great thread. I pulled the blower fan (w/Filters) from 94 E320 and had a shop repair. He did not put in new brushes (unfortunately) even though I asked him to. I had read a thread saying they are only good for 85K miles. He said their was enough brush on them and it ran fine. He did say it was probably the blower regulator that caused him to replace the armature. Your comment on "dirty filters" was probably my answer. The filters were plugged on the 160K miles driven. It looks like I need to go deeper under the blower fan and locate the blower regulator. I do hope Potomac Recycler has one for me because I noted they cost $400. Any other suggestions?