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Discussion Starter #1
The blowers to my windscreen and other blowers around the dashboard stopped blowing but the two blowers below worked fine. All displays on controls were fine and the fan was functioning also. After a week or so I booked the car into a garage for them to have a look and would you believe it, before the car went in, it all blowers started to work again and continued working for a couple of weeks. The top blowers failed again while the blowers below continued to work perfectly. I booked the car into the garage again but after having a preliminary look said they had never seen this particular problem before and asked to have the car for several days to investigate. They are planning to do a very long and I believe costly investigation as they have no clue as to the cause of the problem and have never seen it before. The car is low milage 55000 and not driven very much - not sure if that is significant. I have seen lots of problems with the fan and all blowers failing on thr forum but none like the problem I have described. Because the blowers kicked into life again after the initial failure, there may be a bad electrical connection which could be very difficult to find. I am reluctant to let a garage loose on the car without understanding more about what the problem could be. Before booking the car in I would be really grateful for any help or information from anyone who has experienced the same problem.

Many thanks
 

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The car has only one blower but the hvac system has 5 motors that move the flaps within the heaterbox to distribute the airflow.
Each motor has its own little job to do.
Replacing the motors is a dash out job.
But if you are saying that the blower is behaving badly then the problem might be the final stage resistor aka the hedgehog.
 

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Discussion Starter #3
Thanks for your response edber. My feeling is that it is extremely unlikely that three motors are failing at the same time but maybe there is a part or wire that is common to all motors that is failing but I have no idea where this could be. The blower seems to be working fine as the heat & cold air are blowing as you would expect out of the two bottom flaps.
 

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Its the heater control unit that tells the motors what to do,so maybe that could be playing up.
 

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Discussion Starter #5
I had a closer look at the control unit and there appears to be a bad connection with the M-bus 3 pin connector. If I toggle it and push it in very hard all the blowers start to work. However, the connector is in as far as it can go and I think one of the wires is not making a proper connection. As the connector is a bit worn looking and very stiff, I will order a new one and have it fitted which I think may resolve the problem. I am having trouble getting a new connector so I would be grateful if anyone can advise on a supplier who may have the part.
 
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