Possible heating issue with ML270

[Joderest]

Hi All
I say possible, as not looked into anything yet as no time, here's the story...
ML has been fine, but i have noticed that during this cold weather of late its taking a time to get up to temperature, so have put a possible thermostat replacement on list of things to do. It still reaches about 85, but takes a while.
Yesterday, leaving work and going home, it was slow to warm up, and did not turn heater on until it was at about 40, had slight heat as would expect, but then noticed NO HEAT TO WINDSCREEN, blower not getting there. Every thing else was fine. About a mile from home, started blowing on the screen again. Wife used it last night and said it appeared fine.
This morning, very cold, drove off to work and waited for engine to warm up before using heater, but even at about 60, no heat at all into cabin. Turned blower off, turned temp control to cold, re turned it all on again and hey presto, heat as normal, all vents working, no funny sounds, no clicking or anything like that.
So, i do not know if i have a problem looming, or these vehicles do have a glitch in cold weather. Funnety thing was, our Mini stopped blowing on top speed during the really cold snap, bought a new regulator and cabin filter, but as weather warmed up, started to work again and has been fine since.

Any Thoughts ????

 

[skippyjasper]

I'd replace the thermostat first and then see if the internal heating resolves itself.

 

[Joderest]

yep, i accept that, but i have heard that Mercedes heating systems are prone to "mishaps", and if i have to strip the dash it would be in warmer weather. Its due for service in a couple of thousand miles at 40,000, so may well do the "stat" then.

 

[Stratman]

yep, i accept that, but i have heard that Mercedes heating systems are prone to "mishaps", ..................................

Not as much as they're prone to knackered thermostats

 

[wu56Shoozz]

Drain the system when doing the Thermostat. Put heater settings on HOT Make sure the nose of the car is high up like on ramps, then using the garden hose fill the system from the top hose first, filling the block then the heaters and allow to flush for a small while.. then repeat from the bottom hose. Then place the the bottom hose on secure and start to fill up the system (making sure the thermostat was replaced) add in your antifreeze, and continue until water appears out the top hose. Secure top hose and fill. Leave cap off and start engine, continuing to top up with antifreeze. Leave idling until warm letting all air bubbles out and replace cap and your good to go.
This way your feeding the block and heater first and avoiding any airlocks...

 

[Joderest]

I accept I will have to do stay.
I think I have the dreaded motor servo flap issue. The windscreen air flow seems cycle, air flow one minuet then none, then air flow then none.
I suspect the arm is knackered. Are these plug and play or do they need to be reset on star for their position. Or is there a reset procedure I could try.
I can feel work and money coming on.
Part number I have is A2038201642. Does anyone know if that is correct. Is it possible just to buy newcontrol arms and reset motors.

 

[Joderest]

Could any one see if part number 1638301033 is still available and how much.
That is the control arm

 

[wu56Shoozz]

It would appear so, at about £25 notes...

Can you provide a photo of the offending item??

 

[Joderest]

Erm, no but if they are £25 for a tiny bit of plastic, it's going to be repaired. It's no problem to wire and bond it.

 

[Joderest]

OK, I have stripped it down to the offending item. It was as expected, the windscreen defroster flap motor actuating arm was split, so motor was just spinning.
I do not have time to find a new one, I have attempted a repair and resolve. It it all works I will do a long update on getting it out and repair.

 

[wu56Shoozz]

If you could show me or Photographed it we could of looked at machining in aluminum - problem solved permanently.

 

[Joderest]

To be honest it would have to be cast due to shape. There is a design fault, as it should have been in a stronger material to resist breaking, but then it would break motor if flap jammed
Oh well.
I will try and take pic, but I am a bit dodgy at it

 

[Joderest]

Ok, I have given up.
After spending the best part of eight hours stripping out the car to get at the flap servos, repaired the arms, tried to zero motors, put it all back together, charge battery (went flat because I forgot about interior lights). The result is the same, no blower to windscreen.
Hence taking to auto electrician Friday, I know when I am beaten.

 

[Joderest]

UPDATE
took this to auto electrician, he put his scanner on the car which will allow him to reset flap motors, whilst in test mode, all was working ok, as soon as he exited the mode, it went back to cycling again ( open/shut/open/shut)
His verdict was that the motor is knackered and has gone so far out of limits, will not reset, so new motor only way to go.
New Motor was £140, and it does not come with the actuator arm, appears thats another£25, and none available this end of the country, they could get one by next weekend, oh hang on , that's Easter, so following weekend.
Odd thing is, actuating arms on my Merc are black plastic, replacement ones are white nylon type plastic.
I will be making mine as strong as possible and re installing to save time. The auto electrician explained to me that its all to do with the load that the ECU detects on the motor as to where it stops and where it starts, all way above my head.
So i have to take the whole lot out again which, in short, involves
Under dash off, foot rest out, foot brake lever out, auto transmission ecu out, other large wiring block out, remove large metal mounting plate, and then by laying in footwell, working round all pedals, you can reach the three screws that hold the motor.
Pig of a job

 

[Joderest]

I should also mention...
1) Mercedes say that its a part not often bought, only 5 in last two years, which i find hard to believe.
2) Mercedes say its always the motor, there are second hand arms on e bay, guess what, they are split the same as mine !!!!!

 

[Joderest]

Has someone got an electronic brain?.
I still cannot understand how these motors know there limits. When the guy had car on scanner (autel I think) it showed all the motor values, and showed them moving, but there was nothing to really reset, just a test. It was odd that while on test the defrost flap motor behaved itself, responding to heater as it should. When came out of test mode went back to moving on its own.
I am concerned that when I install the new motor I have nothing to reset. Auto electrician said it should zero itself.
I am a spanner man, nuts and bolts I understand, this I do not.
Anyone with some thoughts.

 

[sturgeon]

Anyone in your area that repairs/rewinds electric motors? Might be a cheaper option.

 

[Joderest]

Sturgeon.
No, it cannot be repaired, as a sealed unit. I have already bought the replacement, i just cannot understand for the life of me how it works. I am more than capable of removing old item and putting new one in, but, what position does it go, flap open, flap closed, ignition on, ignition off, what do i select on heating controls etc etc etc.
My brain hurts !!!!!!!

 

[sturgeon]

What a pain! Different flap, different car, but does this give you any clue, when he actually installs the new motor?

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[Joderest]

Thanks for that, well it did seem he just plugged and played.
I am still not convinced, its all electrickery to me. Perhaps a magic wand would be the way forward.
Going to strip it out tomorrow morning and reassemble Monday morning ( working late shifts) so will let you all know.