How do I know when it's time to get a new roof for my convertible?

Q. I have owned a 2007 Audi A4 convertible from new. The folding roof is sticking when I try to open it, and the fabric is beginning to wear. Can I get both problems fixed or is it time for a new roof?
AS, Radlett, Hertfordshire

A. In common with most modern cabriolet roofs, the A4’s is a complex piece of electromechanical engineering. It has a lattice frame, and sensors that feed data to the ECU, the car’s electronic “brain”, which controls proceedings via three motors and a hydraulic pump.

Clearly, you have to solve the opening problem before progressing to the wear on the hood itself. We spoke to a specialist in convertibles, Cayman Auto Services (caymanautos.co.uk), which said that it sounds as if one or two potentiometers — a sort of motion sensor — is out of sync and is confusing the ECU. These can normally be adjusted without the need for replacement; if this is all that is required, the cost would be included in Cayman’s standard diagnostic fee of £72.

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Once the mechanism has been sorted, try Soft Top Reviver (£33.25 a litre plus £4.50 carriage from Renovo; renovointernational.com) to remove the marks on the hood. After treatment, make sure you keep the hood dust-free because dust is in effect millions of tiny, gritty particles that can act like sandpaper as it opens and closes, further damaging it. And always leave the car with the hood up rather than folded down.

If you do need a new roof, you can get one up to original spec from Carhood Warehouse (carhood.com) for £505. Fitting isn’t easy for an amateur, so the company’s £725 fitted price will probably appeal.

INSPECTOR GADGET
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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