Ml270. Rear heater blower not working

[Joderest]

Hello, wonder if any one can shed some light on this issue.
Rear heater controls seem to work, meaning lights move and I can hear stepper motor working.
The blower motor does not work at all. Front systems seem to work ok.
I took top of center arm rest and checked the multi plug there, seems ok, checked fuse, seems ok. I doubt if the motor has been used much as old owner did not carry passengers.
Do the motors just die?. What sort of job is it to change?.
Any help would be great, I did have all old faults cleared a couple of weeks ago, no heater type fault code seen.

 

[Joderest]

ok, i have now done some digging and wonder if anyone can shed some light on the questions. The fan in the consul does run, when ignition is switched on it powers up and can be adjusted for speed, but after about 30 seconds it stops and will not turn on again, until ignition is off, then back on. The switch on the heater controls will turn it off, but not back on. I have had a look at the centre flap actuator, and when turning on ignition, does not move, also when using the rear fan turn off switch, it does not move, i think i can hear the motor running. Hence i think i have a damaged control arm, which i will need to fix. However, if you move the flap with your finger, very little resistance, so i wonder if the flap is stuck and the insert in the heater box is snapped off.
QUESTIONS
1) is there some sort of micro switch, or sensor that will shut the rear fan motor off if it does not detect the flap open, or no movement of air from the flap.
2) does the flap motor have a sensor or micro switch that when flap open, will send power to the fan motor.
3) It appears a simple job to remove said motor, except for one screw up behind the plate that holds the gearbox electrical connection, i can see one 7mm bolt, is it a case of removing this bolt so the plate can be swung aside so that access to the third screw is given.

Has anyone done this job, where can the updated insert for flap control be found, i did find a part number, but it did not give a clue where i can buy from.
Any help, no matter how small would be good.

Thanks

 

[Joderest]

I really do not understand this system at all

The rear blower works for about a minute
when car first turned on. You can increase and decrease the fan speed during this time, move air from face vents to floor. Then it slowly dies and shuts off. Will not run again until car switched off, left for a while, then turned back on and process repeated.
I know I have to fix flap opening motor\ arm. What am I missing here. Why does it shut off on its own.
HELP

 

[grober]

02 ML500 Rear Air / No Output - Mercedes-Benz Forum

 

[Joderest]

i saw that tread, but again, there is no real reply as to why fan motor runs for a minuet, then stops.
must be a common type fault

 

[grober]

Having had a quick look at the circuit diagram the culprit might be the Rear A/C electronic blower regulator. Perhaps it starts up- a component overheats and it shuts down? There appear to be entire assemblies for sale [ motor plus flap plus regulator?] on EBAY for little money £20-30----- might be worth a punt? I suspect the regulator is the small rectangular metal unit on the rear of the unit?
Rear Heater Blower Motor-Rear-A1638300308-(Ref.603) 01-05 Mercedes ML 270 W163 | eBay

 

[Joderest]

Thanks for that, sadly I feel you may be correct, I was trying to avoid taking out centre console, oh well. Need to fix flap motor first.

 

[Joderest]

Update.
Well, was going to look at flap arm first thing this morning, however, wife's Mini had issue with fan on constantly. So used my new icarsoft MB2 tool in OBD2 mode, gave fault on temp sensor, changed sensor, cleared fault, all good. Tool has now paid for itself.
Got the flap motor arm out, very fiddly. It was split, so used fiber glass resin and pulled it back together with wire, good as new. Refitted, now I know why arm split. The motor runs all the time, opens the flap, closes the flap, then a few seconds later, opens the flap, closes the flap. There is some sort of fault there, as watched it for 5 minuets and it did not stop. So I am sorry to say, I reverted to type. Waited for the flap to be in open position, then disconnected motor, bit of tape on the connector. No fault codes showing, there is a bit of airflow to rear.
Now just got to fix the rear blower motor which has a fault. But it can wait.
Thanks for every ones help on this

 

[Joderest]

UPDATE
I have taken GROBERS advice, and bought another unit off e bay, £19.00 delivered !!!!. Arrived yesterday. Took it apart this morning, cleaned and oiled all moving parts, including motor shaft, disconnected motor from rest and gave it a direct 12 volt feed, it ran well for a couple of minuets, so appears the motor is sound.
I will not have the time to fit it for a couple of weeks, but will update when i have. I have seen more than one post on other sites regarding same issue, so seems something on the unit has is prone to a fault.
I will post when installed and if it fixed.

 

[Joderest]

Got round to taking console out and fitting replacement heater unit. Bit fiddly but easy job.
All back together, fan now runs without fault and warm or cold air delivered to rear as it should.
Bear in mind replacement cost £19, PO had dropped money behind ashtray and centre console, it just kept giving ¡¡¡¡¡, in the end it added up to £18.20, so total cost to me was 80p, result.
Just one more fix today which is defeating me at the moment, water ingress, but have an idea on that, and will update thread.
This one done now.