Help required to diagnose ACU problem with 1979 Shadow 2 please. Immediately on start there is a rapid and very loud "dat dat dat dat dat" from dash. If I shut ACU off until coolant temp is warm I can shut the noise off by moving the upper temp selector to full cold and them moving slowly warm until noise starts again. The point at which the noise starts gradually moves to the "warmer" side of the temp selector, but not to the pont where normal operation can be restored. There seems to be an unsual amount of activity from the servos and the rear screen demister has failed. I suspect the upper servo, but could be upper sensor chain? Any help greatly appreciated.
Shadow II Upper Servo Failure
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5 comments
Paul, It sounds like a problem with the AC servo. The servo sits on the gearbox tunnel behind the vertical section of carpet below the centre console. If you remove the carpet you will be able to see the servo. We suggest that you do this in order to try and identify exactly where the noise is coming from. The gears inside the servo are plastic and tend to crack with age so these may be the cause of the fault. We also recommend turning the AC off with the engine running to see what happens as the actuators close down. On either side of the servo are two circuit boards - the boards are identical and just clip into the servo so it may be worth swapping them to see if this makes any difference - if the heater matrix (which is located above the servo) has leaked then the water may have damaged the circuits on the boards. Good luck.
Thanks for the very helpful reply. It looks like the gears have stripped. I can see the lower flap moving when changing the lower temp wheel but the upper flap doesn't move at all even though the servo motor is running continuously, obviously trying to make the flap move. The noise comes from one of the solenoids rapidly making and breaking contact. I swapped the circuit boards but it made no difference. I guess I am up for a new set of gears of a complete recon unit. Thanks again for the advice.
Paul,
We can supply a reconditioned unit for £450 or a used one for £250. If you would like one sending please confirm the VIN of your car. Thanks.
One final question (I hope!) can you tell me which servo module controls which servo please? I think the drivers side module (on a RH drive car) controls the upper servo and the passenger side module controls the lower servo. Is this correct?
Paul
Yes, the reply that you have given is correct.
Many thanks
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