1999 ML430 - Air blend motor
#1
1999 ML430 - Air blend motor
Help! The vehicle was blowing only cold air. I read through the forum and replaced the air blend motor, but it didn't fix the problem. I am able to get hot air by manually moving the mechanism, so I know heat works.
The air blend motor will only move one direction, until it bottoms out and locks up the gears. I have verified that the motor will turn both ways when I reverse polarity using a 9V battery. I'm wondering if the problem is with the sensor on the back of the hot/cold dial. There are two wires coming off of it but both read 0V no matter what position the dial is in. Any help would be appreciated. Thanks.
The air blend motor will only move one direction, until it bottoms out and locks up the gears. I have verified that the motor will turn both ways when I reverse polarity using a 9V battery. I'm wondering if the problem is with the sensor on the back of the hot/cold dial. There are two wires coming off of it but both read 0V no matter what position the dial is in. Any help would be appreciated. Thanks.
#3
When I first installed the new motor, I attached it to the plastic linkage piece and installed the 2 screws before I turned on the power. After I was unable to get the motor to switch the air door with the dial, I took the screws out, and I have been applying power as the unit is uninstalled.
#4
MBWorld Fanatic!
When I first installed the new motor, I attached it to the plastic linkage piece and installed the 2 screws before I turned on the power. After I was unable to get the motor to switch the air door with the dial, I took the screws out, and I have been applying power as the unit is uninstalled.
Those motors should not be bench tested because it loses its indexing.
How did you know to which pins to supply voltage and ground to?
How were you able to move this?, Explain..........I am able to get hot air by manually moving the mechanism,
After replacing the motor, did it operate the same as the original?
Did you replace the motor by removing the dash or through the glove compartment?
Last edited by Maj. Dundee; 11-03-2019 at 07:30 AM.
#5
How did you know to which pins to supply voltage and ground to? - I applied the voltage directly to the motor, which has only two pins. The connector input appears to be 5 V, but the voltage on the motor was measuring between 8 and 9 V.
How were you able to move this?, Explain..........I am able to get hot air by manually moving the mechanism, - The linkage that moves the actual flap, which connects into the motor. Actually, when I removed the old blend motor, the flap returned naturally to the "hot" position, but I am able to put it in either postion by moving the linkage manually. I primarily mentioned this to provide the information that the vehicle is producing warm air. The problem with the old motor was that the gears were "jammed" holding the linkage in the cold position. The failure mode on the old motor may have been that the motor wouldn't run in the reverse direction because if I reverse polarity on the old motor, it doesn't work at all. The old motor will only run in one direction.
After replacing the motor, did it operate the same as the original? - It did not act exactly as before. It would attempt to move to the "cold" position, but it would only move maybe 20% of the way.
Did you replace the motor by removing the dash or through the glove compartment? - I took the dash off, so I can see the entire mechanism.
Those motors should not be bench tested because it loses its indexing. - I was worried that the indexing was off on the new motor. Curious, when a new motor is received, what position does it arrive in? Hot or cold?
At this point, would you recommend getting another new motor to try?
How were you able to move this?, Explain..........I am able to get hot air by manually moving the mechanism, - The linkage that moves the actual flap, which connects into the motor. Actually, when I removed the old blend motor, the flap returned naturally to the "hot" position, but I am able to put it in either postion by moving the linkage manually. I primarily mentioned this to provide the information that the vehicle is producing warm air. The problem with the old motor was that the gears were "jammed" holding the linkage in the cold position. The failure mode on the old motor may have been that the motor wouldn't run in the reverse direction because if I reverse polarity on the old motor, it doesn't work at all. The old motor will only run in one direction.
After replacing the motor, did it operate the same as the original? - It did not act exactly as before. It would attempt to move to the "cold" position, but it would only move maybe 20% of the way.
Did you replace the motor by removing the dash or through the glove compartment? - I took the dash off, so I can see the entire mechanism.
Those motors should not be bench tested because it loses its indexing. - I was worried that the indexing was off on the new motor. Curious, when a new motor is received, what position does it arrive in? Hot or cold?
At this point, would you recommend getting another new motor to try?
#6
MBWorld Fanatic!
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With a good motor installed you should not be able to move the linkage. If you can that means that one of the wheels in the motor is broken. Where did you buy it?
I believe it arrives in the heat setting.
If the two levers are not damaged, then I would get a quality motor. Dealer charges approx. $190.
This is OE part, the same exact one from the dealer.
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