126 Blower Motor not working.

[420benz]

With the key on i am getting power to the BM.I pulled the two wires off the BM and put 12v to the motor and it works fine.Confused.

[420benz]

What is the black thing called behind the regulator where the two wires from the BM come from? Does it control the amount of volts to the BM?

[duxthe1]

Sounds like a bad regulator to me. They're basicly a heavy duty FET. They can fail so that they will show voltage at the load but not supply any current.

[420benz]

Originally Posted by duxthe1

Sounds like a bad regulator to me. They're basicly a heavy duty FET. They can fail so that they will show voltage at the load but not supply any current.

This is a very expensive part. How can i be sure that it is bad?

[Arthur Dalton]

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mb-4--0sel-Climate--Control&yearid=1989%40%401989&makeid=MB%40%40MB%40%40X&modelid=420%2DSEL%2D001%40%40420SEL&catid=R%40%40Climate+Control&subcatid=R2022@@Blower+Regulator&mode=PA

See the red and blu wires that goes to the blower??
Jumper wire from the blu to ground ..if that gives you high fan, reg is suspect.
But you see that 3 wire plug?..that should have a yellow wire that is variable V from ther Control Panel..that is what triggers the regulator and if no V there , the problem is not the reg.
You should have 12V ay the red also.

[420benz]

Originally Posted by Arthur Dalton

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mb-4--0sel-Climate--Control&yearid=1989%40%401989&makeid=MB%40%40MB%40%40X&modelid=420%2DSEL%2D001%40%40420SEL&catid=R%40%40Climate+Control&subcatid=R2022@@Blower+Regulator&mode=PA

See the red and blu wires that goes to the blower??
Jumper wire from the blu to ground ..if that gives you high fan, reg is suspect.
But you see that 3 wire plug?..that should have a yellow wire that is variable V from ther Control Panel..that is what triggers the regulator and if no V there , the problem is not the reg.
You should have 12V ay the red also.

I will test it tomorrow.

[Ferdman]

420 benz, not sure if your 420SEL has a 30-amp strip fuse on the driver's side shock tower. It's enclosed in a small black plastic case and has a philips head screw on either end. Typically the strip fuse develops a hairline crack which results in the blower motor not working. If you loosen the two screws it will be obvious if the strip fuse is cracked. If so, replace it.

[420benz]

Originally Posted by Ferdman

420 benz, not sure if your 420SEL has a 30-amp strip fuse on the driver's side shock tower. It's enclosed in a small black plastic case and has a philips head screw on either end. Typically the strip fuse develops a hairline crack which results in the blower motor not working. If you loosen the two screws it will be obvious if the strip fuse is cracked. If so, replace it.

Arthur informed me about that fuse.I did remove it and it is ok.Too Bad that would be too easy. Thanks

[420benz]

Tested Blue wire to ground"nothing"
Tested three wire plug.Yellow"nothing"-White 7.6v
Green/Black 12v Note:With the BM cover off and the key on with both red and blue wires attached to the BM The fan turned very slow.That was this afternoon. I just tried it again and nothing.

[420benz]

I don't even know what the problem is yet.

[Arthur Dalton]

When I say to jumper the blu wire to ground, I am not saying to unplug that wire and take it to ground. You place a jumper on that wire and ground the jumper. That by-passes the Reg.
If the fan does not turn when you do that, then test the red wire for 12v at the BM.
If it still does not work, spin the fan blades at the same time .
Grounding the blu wire is the same as bringing 12V direct to the fan motor ..if NO, then the BM is faulty.

[420benz]

Originally Posted by Arthur Dalton

When I say to jumper the blu wire to ground, I am not saying to unplug that wire and take it to ground. You place a jumper on that wire and ground the jumper. That by-passes the Reg.
If the fan does not turn when you do that, then test the red wire for 12v at the BM.
If it still does not work, spin the fan blades at the same time .
Grounding the blu wire is the same as bringing 12V direct to the fan motor ..if NO, then the BM is faulty.

With both wires connected to the BM and jump blue wire to ground the BM runs at hi. speed.I also get 12v at the red wire.Sorry i misunderstood you.

[Arthur Dalton]

>

I knew that, so I re-worded it.
Anyway, that eliminates the BM and points to the Regulator.
But , before changing that, make sure you have the Var V at that third wire, as that is what triggers the Reg.

I mention that wire as yellow, but it may be a different color b/c I do not have the schematic for your model. The 124 uses yellow.

That 3 wire feed plug should have a ground, [ neg] a 12V Hot [pos+] and the third will be the Var V from the Control Panel.

If you have 12 V from the plug pos and ground and Var V on the other wire
and ground..then you need a regulator.

[420benz]

Originally Posted by Arthur Dalton

>

I knew that, so I re-worded it.
Anyway, that eliminates the BM and points to the Regulator.
But , before changing that, make sure you have the Var V at that third wire, as that is what triggers the Reg.

I mention that wire as yellow, but it may be a different color b/c I do not have the schematic for your model. The 124 uses yellow.

That 3 wire feed plug should have a ground, [ neg] a 12V Hot [pos+] and the third will be the Var V from the Control Panel.

If you have 12 V from the plug pos and ground and Var V on the other wire
and ground..then you need a regulator.

New test confermed i need a regulator.Thanks Arthur and every one for all of your help.

[Arthur Dalton]

Those reg are expensive, so many guys [ if the car is aged and not worthy] just put a toggle sw on that blu wire to ground and run high fan only...at least you have something to heat up with.


I had a friend bring me his older Benz one day , and when I jumped in, there was a household light switch, metal box and all, mounted to the dash.

I said. " Regulator gone, Huh ???'
He said , " Yeah...How did you know that ???????????? "

I said. " Well ..... I didn't see any 4 foot florecents hanging from the head-liner "