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Old 01-01-2007, 11:02 AM
Ron in SC's Avatar
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Location: Charleston, SC
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Question Blend air flap actuator motor problem

Vehicle is 1999 ML 320.

Intermittently I can not turn heat completely off with temperature control knob.

I removed lower dash so I could get a look at the blend air flap actuator shaft and the linkages that attach to it. Right now the linkage moves thru its full range of motion with the heat shutting completly off as it should.

What else might be the source of the problem I'm experiencing? I did have another complete heating and A/C switch unit so I swapped them out and that did not make any difference.

In the photo what is circled in red is the shaft and in yellow is the linkage.

Attached Thumbnails
Blend air flap actuator motor problem-000_0577.jpg  
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Old 01-03-2007, 01:12 PM
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The blend air motor is a common failure on the 1998-01 ML's..
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Old 01-10-2007, 09:58 AM
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Ive been driving around with the bottom part of the dash off and until yesterday Ive not had heat when the temperature control knob was turned all the way to the left. That's the way it should be.

Then yesterday I had heat when it was turned to the left. I looked at the linkage and the arm for the blend air motor was not where it should have been it was positioned to allow some heat. I have no idea why the blend air motor did not return the linkage to the position where it does not allow heat. I have no clicking or other noises going on. Is this indicative of failing blend air motor?
Is problem blend air motor, temperature sensor, something else? Is there a way to test whether or not proper signal is being sent to blend air motor?

If not then I'm thinking it be best to replace both blend air motor and temp. sensor, since I think I have to take evaporator box/case apart.
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Old 01-13-2007, 04:50 PM
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Location: Charleston, SC
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The blend air motor is cheap and easy to replace with the top of the dash off; it's held in place with two small screws. Part# 1638200108. Hope that was my problem. Did not have to remove crash bar or go into heater/evap case. My dealer had these motors in stock and they don't ever seem to stock anything except oil and filters and stuff they know needs replacing because an item has a record of failure.

Below is photo of inside of case that houses blend air motor. The motor is Chinese.
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Blend air flap actuator motor problem-000_0605.jpg  

Last edited by Ron in SC; 01-13-2007 at 08:33 PM.
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Old 01-14-2007, 02:39 PM
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Location: Charleston, SC
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With the new blend air motor installed I turned A/C on with fan on high and turned heat up all the way. Vent air came out hot almost immediately. Then I turned heat knob to coolest setting and vent temp went to cold almost immediately. I think the new motor works smoother and faster than the old one which was working intermittently and sometimes not at all.

I've put everything back together except glove box, that way I can keep and eye on linkages for a while to see if they continue moving as they should when the heater control knob is moved. Hopefully the blend air motor was the problem; only time will tell.

For anyone wanting to do this job I suggest, the following:

--Get Alldata DIY and read the applicable sections. Job is not technically difficult. Keep in mind what Ive done is what Id consider about 30% of dash removal. I did not remove crash bar or heater/evap case from car, nor did I have to disconnect coolant system or A/C system, let alone take the case apart.

--When taking dash apart never lay a fastener on the floor, have system to keep track of them. If you can not remember what goes where put it in a zip lock bag and label it.

--Use a set of plastic upholsry tools for prying, that way you will do no damage.

--If you can not get a part out because it seems stuck you have either missed a fastener or you are pulling on the part the wrong way.

A 1/4" drive battery powered ratchet is helpful for removing all the small bolts, better for limited access areas and fast.
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Old 04-07-2007, 11:22 PM
Join Date: Feb 2001
Location: Lakewood NY
Posts: 85
blend air motor

I am experiencing the same symptoms in my 98 ML320 which you described . How much did the blend motor cost? What part of the dash needs to be removed to access the blend motor?
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Old 07-23-2009, 05:44 PM
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I have experienced this just recently. My wife drives a 1999 ML430 and informed me that the air conditioning was not working. It would not turn on or activate. I found a fuse blown. Cannot remember what it said it went to, but it was a 30A fuse. Anyhow, I replaced it and still the AC did not work. Due to time I put off troubleshooting til later date. The next day my wife said she heard a ticking noise coming from behind the dash. When I turned the temp comtrol to warm the ticking stopped and when I turned it to cool, it started again. This is when I found out it could be the blend air motor that could be causing it from a mechanic friend of mine.

My question is....will this damage/faulty blend air actuator moter being bad cause the AC not to work. Or do I have 2 or more problems at the same time The fan blows, but I do not hear the compressor kick on and the air stays the same temperature feeling.
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Old 06-19-2012, 03:53 PM
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If anyone has more to offer by way of information or schematics in order to remove the top of the dash as opposed to the entire cabin fan assembly i would greatly appreciate it.
Last night i went and removed the covers at the bottom and the glovebox / cubby hole -i am able to see the motor and cam (quickly did a diy to force the a/c ait to flow) the blend air flap actuator motor sits above the crash bar therefor no access my way.
Pls help?

Also the part number for 2002 ML320 Km 220 000
Ps the Youtube video clip appears to be different to my vehicle unless i am suppose to remove the airbag cylinder and work from the bottom up!!!
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Old 09-12-2014, 03:18 PM
Join Date: Sep 2014
Posts: 1
Blender motor

I have been reading some of these threads. The blender motor on my 1998 ml320 was not working. One of the gears was cracked. I replaced the motor but it is still not working. It only works on direction. Is there a controlling switch, sensor, or is it controlled by the main computer? Any suggestions greatly appreciated.

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