[Lood]

I just replaced my blend air motor after a year of tick tick. Installing the new motor I tested it and found that it does not move through the whole range. It moved to the full heat position and would not return from there no matter what the control was set to. I decided that the controls must be bad so I ordered and replace the AC controls. Same result, motor moves and stay in the full heat position.

Out of desperation I opened the old Blend air motor and started playing with it. I noticed that once it moves past a certain point towards the full heat position it just continues to move and will not return. After experimenting with the old motor I found that I can change the gear position so that it hits the stop before it reach the point of no return. Once I set it like that I only had 90 deg movement in the motor. I did the same to the new motor and it now operates although only partially but I have heat and full AC. Neutral position on the control is now to the left of the white bar on the control.

I figured that it has something to do with the stops not being set correctly but without the dealer's software who knows.

Has anyone had this issue before or am I the first one to encounter this?

 

[Witek_M]

Sounds like you have temp sensor signal missing. What year is ML?

http://www.benzworld.org/forums/w16...air-blend-motor-still-no.html?highlight=blend

 

[sgtpepperaut]

yeah i got sick of this too....put a "rod" over the level and drilled a small hole in the glove box. "manual override"

ohh and yes i encountered it but i doubt my solution will help you... from what i could see was that the flap was actually position to the furthest position in the back on the motor tried to keep going. So i just didnt set the temp control to minimum but to two three clicks above that and the clicking was gone and cold air was still blowing...

i know its a ghetto fix but you can barely see it and it costs me about 30 minutes and a thick coathanger..

 

[43sqd]

It's apparent that you have tinkered with the wrong thing (new actuator motor). The way these motors work is after it receives a signal for heat , the motor will operate in that direction UNTIL it senses a stop, either by the full travel of the door or by touching the white levers. Then when you request A/C the polarity to the wires is reversed, making the motor rotate in the opposite direction.

With the motor removed from the heater box, but the electrical plug still connected, the motor, when actuated, will revolve in that direction FOREVER, until you turn the key off or the battery runs down.

Therefore, the old motor and the new motor are working perfectly. If when you took apart the old motor, if neither of the white plastic gears were not cracked, then it was perfectly good. But now you have realigned the new motor to the wrong position. What made you think that the new motor was faulty?

Your ticking sound is probably being caused by one of the white actuator legs, shown in the photo below, being cracked or there is a foreign object blocking the full travel of the air door. But now you will have an additional problem with the new motor not being geared properly.

 

[Merzatt]

I hope the A/C control mechanism was not too expensive. It should not be replaced unless all of the actuators are acting dead or someone opens the unit and finds burnt circuit.

It sounds like the rail mechanism became stiff and motor is unable to move the rail in one way. Actuator motor senses the resistance and thinks that it reached the end therefor stops. When you removed the actuator, were you able to move the rail freely by hand? In fact, this might be the main reason why it is so common for these actuator to give up.

PS. please update your profile.

 

[Lood]

I hope the A/C control mechanism was not too expensive. It should not be replaced unless all of the actuators are acting dead or someone opens the unit and finds burnt circuit.

It sounds like the rail mechanism became stiff and motor is unable to move the rail in one way. Actuator motor senses the resistance and thinks that it reached the end therefor stops. When you removed the actuator, were you able to move the rail freely by hand? In fact, this might be the main reason why it is so common for these actuator to give up.

PS. please update your profile.

$30 on eBay not to bad. This motor went to the stop and no matter what you do it stays in the full hot position. It is my daily driver so I drove it with the new motor and it stayed hot no matter what, AC on full recycle the air blend motor stayed in one position. Max hot. I had trouble getting air at my feet and now with the new controls that works fine so the control was on the blink I think. Rails moved freely. Remember if I stayed within the 1/4 movement the motor worked fine. As soon as I exceed the 1/4 turn towards the hot side it runs away to max hot that is it no return. It might be the stop setting I am sure it can be set by the Dealer. It is a 98 with high miles so for now it works even though the neutral position is towards the AC side. I even checked the temp sensor pumped some hot air on it no luck the motor stayed there.

 

[Lood]

Sounds like you have temp sensor signal missing. What year is ML?

http://www.benzworld.org/forums/w16...air-blend-motor-still-no.html?highlight=blend

It is a 98. I don't know about the temp sensor the full AC should over ride it right. Once the motor goes on the run to the hot side there is no stopping it and nothing returns it.

 

[Lood]

It's apparent that you have tinkered with the wrong thing (new actuator motor). The way these motors work is after it receives a signal for heat , the motor will operate in that direction UNTIL it senses a stop, either by the full travel of the door or by touching the white levers. Then when you request A/C the polarity to the wires is reversed, making the motor rotate in the opposite direction.

With the motor removed from the heater box, but the electrical plug still connected, the motor, when actuated, will revolve in that direction FOREVER, until you turn the key off or the battery runs down.

Therefore, the old motor and the new motor are working perfectly. If when you took apart the old motor, if neither of the white plastic gears were not cracked, then it was perfectly good. But now you have realigned the new motor to the wrong position. What made you think that the new motor was faulty?

Your ticking sound is probably being caused by one of the white actuator legs, shown in the photo below, being cracked or there is a foreign object blocking the full travel of the air door. But now you will have an additional problem with the new motor not being geared properly.

Ok so the old motor had a cracked gear. That caused the ticking. I installed the new motor and it worked fine on the AC side it was only when I turned it to the heat side that it ran away. It is my daily driver so I had to drive it for a few days with the new motor installed before the new controls showed up. It stayed hot all the time even with full AC on. I first played with the old motor until I understood that it needs to hit the stop before it runs away. Once I had the old motor under command of the controls that is when I changed the new motor to do the same. All I really did was change the stop position manually. I am sure one should be able to set it; actually the dealer should be able to. If not there is something else causing it I just don't know what. I can reset the motor to factory setting. I have it marked on the gears. It is just the first time I encountered this with a motor control.

 

[Witek_M]

It is a 98. I don't know about the temp sensor the full AC should over ride it right. Once the motor goes on the run to the hot side there is no stopping it and nothing returns it.

Up to 11/99 ML320 has simple analog system that compares voltage in two loops. One formed by in car temperature sensor and blend air flap motor feedback resistor. Other by temperature knob resistor. When voltage is equal motor stops. There is no override, there is no digital diagnostics, there is no stop learning.

 

[Lood]

Up to 11/99 ML320 has simple analog system that compares voltage in two loops. One formed by in car temperature sensor and blend air flap motor feedback resistor. Other by temperature knob resistor. When voltage is equal motor stops. There is no override, there is no digital diagnostics, there is no stop learning.

Thank you. This is handy information. I check and post what I find. I will start with the temp sensor.
My wife reminded that it happened also when the ML was only a few weeks old. The dealer fixed it but I don't know what it was. I checked with the dealer but they do not have the detail. It was paper back then.
Thanks you for the information.

 

[kck7]

I hope someone responds although this thread is a little aged...

I have ticking sound. Took apart the glove box area and pass. airbag and got the motor out, hoping I could flip the wheel over and save the $$. No dice, the white wheel is cracked although it has a fairly good grip on the spindle (but I can see where it is not as firm as it should be, hence the slippage at higher motor speed, ie the cold part of the dial). I did flip and try but it actually made it slightly worse (faster ticking). I guess I will buy the whole motor.

Two major questions that I hope someone can set my mind to rest on.

1. I did not disconnect the air bag as i could not figure out how. Frankly I am afraid of accidentally (no pun intended) activating it by touching, pulling on or tampering with the wrong thing. I did disconnect the negative terminal of the battery before doing any of this work. Can the airbag be disconnected (ie detached from the car) and then reconnected? That sensor wire doesn't behave like your typical wiring harness. Can it be taken out and put back together?

2. Is there a correct orientation of the white lever that mates to the motor? In all the messing around the white lever came out and I don't know whether I put it back correctly. (eg full front, middle, or rear of rotation cycle?)

Again, I have the jitters about the airbag, because it can be very dangerous at close quarters and even if it's not, the cost to replace it would be way high I assume. If you can tell me a little more about this aspect it would be very much appreciated.

 

[jtlimburgh]

Actuator Motor

It's apparent that you have tinkered with the wrong thing (new actuator motor). The way these motors work is after it receives a signal for heat , the motor will operate in that direction UNTIL it senses a stop, either by the full travel of the door or by touching the white levers. Then when you request A/C the polarity to the wires is reversed, making the motor rotate in the opposite direction.

With the motor removed from the heater box, but the electrical plug still connected, the motor, when actuated, will revolve in that direction FOREVER, until you turn the key off or the battery runs down.

Therefore, the old motor and the new motor are working perfectly. If when you took apart the old motor, if neither of the white plastic gears were not cracked, then it was perfectly good. But now you have realigned the new motor to the wrong position. What made you think that the new motor was faulty?

Your ticking sound is probably being caused by one of the white actuator legs, shown in the photo below, being cracked or there is a foreign object blocking the full travel of the air door. But now you will have an additional problem with the new motor not being geared properly.

I'm a new member here so please bare with me. I'm just wondering how hard it is to get to this actuator motor to be replaced? I cannot use the AC right now because now matter how I turn the temp knob, the temp does not change. But I can hear a ticking sound under the dash but it goes away once in awhile. Any info will be greatly appreciated...

 

[abpfischer]

It's apparent that you have tinkered with the wrong thing (new actuator motor). The way these motors work is after it receives a signal for heat , the motor will operate in that direction UNTIL it senses a stop, either by the full travel of the door or by touching the white levers. Then when you request A/C the polarity to the wires is reversed, making the motor rotate in the opposite direction.

With the motor removed from the heater box, but the electrical plug still connected, the motor, when actuated, will revolve in that direction FOREVER, until you turn the key off or the battery runs down.

Therefore, the old motor and the new motor are working perfectly. If when you took apart the old motor, if neither of the white plastic gears were not cracked, then it was perfectly good. But now you have realigned the new motor to the wrong position. What made you think that the new motor was faulty?

Your ticking sound is probably being caused by one of the white actuator legs, shown in the photo below, being cracked or there is a foreign object blocking the full travel of the air door. But now you will have an additional problem with the new motor not being geared properly.

Hi

Is the air blend motor number 29 in the attached diagram?

I appreciate any help that you can give.

 

[Noodles]

Nope, it is 53. Follow the arrow as to where it mounts on top of the whole unit.

 

[43sqd]

Here's a live shot of it. Remove the glove compartment and switch the controls from warm to cold and you will see that the operating levers do not move (they should).

You will have to remove the top portion of the instrument panel which is not very difficult. Don't let the instructions scare you. Pre-order the Blend Door Motor but when you receive it do not try to move it manually. Install it as is, part #163 820 01 08. Check with dealer for correct application.

Only order the Blend Door Motor from the dealer or an on-line dealer, as you don't want to install a faulty motor and have to do this job twice.

http://www.benzworld.org/forums/w163-m-class/1417771-diy-thread-collection-5.html#post4763314

 

[Maytag]

i'm going to be doing this procedure next weekend. Two questions, please:

1. I'm really hoping I diagnosed mine properly, since I already bought the new actuator. I accessed it (sort of) by removing the back of the glove-box. There I confirmed that the levers were not moving, but since I needed a defroster, I tried to force it to move; it wouldn't. I eventually disengaged the actuator arm from the lever by prying upward on it until it pulled out of the slot on the lever. The door then moved freely wherever I wanted it. But the arm on the actuator would still not move. Does this sound like a bad actuator? Or do I have an electrical issue TO THE actuator?

2. Somewhere on this forum, I know I saw a step-by-step on removing the top of the dash for this procedure. But now I can't find it again. Can someone point me to that?

thanks!

 

[43sqd]

2. Somewhere on this forum, I know I saw a step-by-step on removing the top of the dash for this procedure. But now I can't find it again. Can someone point me to that?

When you select a thread to show your problem, you should read it first. The link is in post #15.

 

[Maytag]

When you select a thread to show your problem, you should read it first. The link is in post #15.

ok... tail firmly between my legs.... I didn't see the link, only the image in post 15.

thanks for your help. :bowdown:

 

[idahombz]

Here's a live shot of it. Remove the glove compartment and switch the controls from warm to cold and you will see that the operating levers do not move (they should).

You will have to remove the top portion of the instrument panel which is not very difficult. Don't let the instructions scare you. Pre-order the Blend Door Motor but when you receive it do not try to move it manually. Install it as is, part #163 820 01 08. Check with dealer for correct application.

Only order the Blend Door Motor from the dealer or an on-line dealer, as you don't want to install a faulty motor and have to do this job twice.

http://www.benzworld.org/forums/w163-m-class/1417771-diy-thread-collection-5.html#post4763314

Where would you recommend to order the part? Autohausaz okay? Thanks as always!
the old ML problems are so predictable and consistent. I guess if I fix them all i can last the SUV to half million miles. 98 ML @ 171k miles.

 

[43sqd]

Where would you recommend to order the part? Autohausaz okay? Thanks as always!
the old ML problems are so predictable and consistent. I guess if I fix them all i can last the SUV to half million miles. 98 ML @ 171k miles.

parts.com has it cheaper than Autohaus. Check how much are both are with shipping.

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