Q. During a valeting of my 09-plate Mercedes S 320 CDI, the rear headrests were lifted to the up position to allow cleaning behind them. Now they will not go back down. My dealership reckons that the vacuum pump has failed. Should the pump have been checked during servicing? BS, via email
A. Checking headrests is not part of the service schedule. We spoke to a Mercedes specialist, George Fraser (www.georgefraserltd.com), which confirmed that there was no manual override for the automated rear headrests. They are vacuum-operated by an electric pump mounted behind the seats, which also powers several other items, including the fuel filler cap.
The company says it would start by putting your car onto a computer diagnostic system to ascertain exactly what the problem is, because in its experience it is rare for the pump to fail.
That means the odds are good that the pump simply needs a reset — at a cost of £78. Cross your fingers: if the pump really has failed, it’s expensive to replace, at as much as £1,200 including installation. DP
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory – read more from Dave here.
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