one last try

[joderest]

Thanks but I think this fault is a software issue of some sort. I had it all reset on STAR last year and it all worked perfectly for a week then failed again.
Issue is...... Start car, select blower to screen, flap does not open. Turn car off, start car again and then flap will open.
The work around does work every time, just have to remember not to switch heater off.

 

[M80]

Have you considered the front SAM for ingress?
Might be worth checking the enclosure for evidence of moisture and spraying the SAM connections with electrical spray (not WD40 that can leave an insulating film).

 

[LostKiwi]

Thanks but I think this fault is a software issue of some sort. I had it all reset on STAR last year and it all worked perfectly for a week then failed again.
Issue is...... Start car, select blower to screen, flap does not open. Turn car off, start car again and then flap will open.
The work around does work every time, just have to remember not to switch heater off.

If it were a software fault it would be a common issue affecting many thousands of cars.

 

[umblecumbuz]

As Craig and Botus.
It sounds very like damp connections somewhere, and the front Sam looks a likely culprit. Damp creates corrosion, especially in soldered joints. This is a fifteen year old car, after all.

Where front Sam's have given intermittent problems, cooking them in the oven has worked for others. Haven't tried this myself because I'm a man - I burn toast in a blink!

 

[joderest]

Thanks all you could be correct.
I think this issue started due to the following......
The plastic vent that goes across the top of the dash, one of the tabs broke off and jammed the flap, the motor tried to move it and rounded out/snapped the little plastic control arm. This then put the motor out. I replaced the motor and repaired the arm that controls the flap, but it would not reset, as i said, STAR reset the limits, but it only lasted a week then went wrong again. I have tried everything to sort it out and failed, all the other flaps work as they should, no issue.
The work around "works" since leaving the fan on lowest setting when turning off, when starting again, every thing works.
I have spoken to a Mercedes diagnostic man, who had no idea what the issue was, he said the heater flaps are controlled by the AAM, and if that was faulty i would have other faults, so he discounted it.