[Maytag]

Hey y'all:
I've used the search function, and have found some _similar_ issues, though none are exact. But they've helped me come up with a couple things to check.
I'm hoping for a little help from y'all with more experience?

'99 ML430 with 210k miles, in very good running condition. I've owned this car for 3 years and 90k miles. Have never had trouble with the heat before. This has been a very warm summer (obviously!) but the temp on the dash-gauge has remained consistently in a zone that seems quite normal. Possibly related would be the idler-pulley that went on me two weeks ago, flinging the belt off at highway speeds. The belt actually flipped around enough to break the fan shroud, but everything else seemed intact.

This morning, went to use the heat for the first time in 6 months, and it won't get warm. There seems to be NO CHANGE in air temp, no matter the position of the control dial.

Coolant level is good. Temp gauge reads normal. I reached-in and grabbed the heater-core discharge hose (where it connects to the aux pump) and it is warm to the touch (though nowhere near as warm as the radiator hoses, for instance). I'm working, so I haven't reached all the way in to feel the supply hose for the heater core yet.

I've searched around this forum, and I'm looking at two places to start my troubleshooting:
1. Blockages in the heater-core supply hose.
2. Blend-door motor.

Does any of this ring bells for anyone? Am I on the right track here? Anything obvious I'm missing?

 

[43sqd]

This is a classic Blend Door Motor problem that occurs when the seasons change.

Because of non-use, switching back and forth, once in a while (summer, switch to heat every couple of weeks and do the same during winter, switch to A/C) will prevent keeping the actuator in a dormant state.

If you have a few tools and a little mechanical ability, this procedure is not difficult at all.

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

 

[Maytag]

Wow! Thanks for that!
I do have the tools and aptitude to perform the described procedure. But let me first ask:
Is there a way to double check the diagnosis, to definitively determine that this is indeed the problem, before i tear open the dash?

 

[43sqd]

Wow! Thanks for that!
I do have the tools and aptitude to perform the described procedure. But let me first ask:
Is there a way to double check the diagnosis, to definitively determine that this is indeed the problem, before i tear open the dash?

Yes there is but you will have to remove the center console to access N19, which is required for testing.

 

[Maytag]

allright.... it's snowing here... and I need a defroster. But I haven't had time to get to this yet.
Is there a way that I can manually move the blend door to heat, without tearing everything apart today? I'll get to the procedure this weekend.

 

[Maytag]

43sqd;
I'd like to perform the test that you have detailed above. I noticed today that the illumination of those dials has also quit. I would like to rule-out an electrical problem before I replace the blend-door motor.

But I'm not savvy when it comes to the technical bulletin you posted. I understand where that connector is, but I do not understand what to do with it. Am I measuring voltage between pins 8 & 9? and looking for it to change from <1v to 11-14v? (I'm only guessing at what I'm seeing there)

Help?

And what would make the panel illumination go out just on those three dials?

 

[Black3]

One bulb lights all three dials.

The number is 27 something I think and you can get it from Amazon or a big box for about half or less what it costs at the dealer. It is under the center knob and you need to go to the local hardware store and get six inchs or so, as little as they'll sell you, but at least about six inches, of silicone tubing that will fit sorta tightly over the bulb. So, get the bulbs and go to the hardware store and get some tubing that fits. You then use the tubing to remove the old bulb and install the new one. There, I just saved you a hundred or two at the dealer.

The rest of the problem is above my pay grade.

 

[43sqd]

Am I measuring voltage between pins 8 & 9? and looking for it to change from <1v to 11-14v? (I'm only guessing at what I'm seeing there)

Yes that's exactly what is supposed to happen. Move the dial in small increments and then wait to see if it registers and then move t the next, etc.

For the dials not illuminating, pull out the center dial and you will see the bulb that must be replaced.

 

[emmie319]

Maytag, yes there is an easy way to see if it's the air blend flap/motor without tearing everything apart. I had this issue and posted this, hope it helps....
Had put this off for awhile because it was winter for one, and because the first time I took out the glove compartment to take a look for some reason I just wasn't seeing the air blend motor. So, today (getting hotter here in Vegas), I decided to take another look. To others...after you remove the glove box only which is just a few...4...I believe screws and disconnect the glove box light, just slide it out. If you reach in on the left top side and pull down the cloth backing just enough to see inside you will see a white plastic lever mechanism. Now for the really good part.....I now have ice cold air and didn't spend one penny, mess with an air bag, take off any part of the dash, radio etc., I simply turned the climate dial...which did absolutely nothing.....except!....allow me to manually move the white plastic lever to the opposite position thus switching me from hot air to ice cold air. I will probably replace the air blend motor at some future time but for the summer I have cold air and if need I can take the glove box out at winter and switch to hot air...and although I haven't tried it yet there is a small possibility that I may be able to remove the air blend motor without doing anything more than I've already done (small hands...and don't you believe the rest of that myth). Now on to my new issue which I believe to be the torsion bar bushing clicking issue.

 

[Oeschj]

Now on to my new issue which I believe to be the torsion bar bushing clicking issue.

Replace them with the $29.00 dealer part and replace in 2 years or BoschBrakes custom bushings and never replace with unlimited lifting ability.
20 min change out.
Issue solved.

 

[Maytag]

I actually did the same thing last week, and moved it to hot until I get more time.
However: I was not able to just move the lever. I had to first disconnect the actuating lever from the crank/lever on the motor. The motor itself would not move.
So I would guess that this is definitely my problem, eh?

Maytag, yes there is an easy way to see if it's the air blend flap/motor without tearing everything apart. I had this issue and posted this, hope it helps....
Had put this off for awhile because it was winter for one, and because the first time I took out the glove compartment to take a look for some reason I just wasn't seeing the air blend motor. So, today (getting hotter here in Vegas), I decided to take another look. To others...after you remove the glove box only which is just a few...4...I believe screws and disconnect the glove box light, just slide it out. If you reach in on the left top side and pull down the cloth backing just enough to see inside you will see a white plastic lever mechanism. Now for the really good part.....I now have ice cold air and didn't spend one penny, mess with an air bag, take off any part of the dash, radio etc., I simply turned the climate dial...which did absolutely nothing.....except!....allow me to manually move the white plastic lever to the opposite position thus switching me from hot air to ice cold air. I will probably replace the air blend motor at some future time but for the summer I have cold air and if need I can take the glove box out at winter and switch to hot air...and although I haven't tried it yet there is a small possibility that I may be able to remove the air blend motor without doing anything more than I've already done (small hands...and don't you believe the rest of that myth). Now on to my new issue which I believe to be the torsion bar bushing clicking issue.