Car clinic: Is long-term storage OK for my new Audi Q5, why does Seat Altea's climate control blow hot and cold, and can I ditch my BMW 320d's run-flat tyres?

The Car Clinic experts

THE DEALER
Jason Dawe is our used-car expert and has appeared on Top Gear and the Morning Show

INSPECTOR GADGET
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory.

Q. When I ordered my new Audi Q5, I was told it would arrive in March with a 14 registration plate. My dealer now tells me it will be delivered in early January. He’s happy to hold on to the vehicle until March 1. Will it harm the car to be sitting around for several months?

AC, Peterborough

Some dealers, keen to get your money in the bank, would have put you under pressure to take the vehicle early, but yours has said he is happy to hang on until the arranged delivery date.

Many new cars sit around for a long time waiting to be sold without suffering any harm. The eight weeks or so it will take for your Q5 to come out of the factory, into the dealer’s stock and then onto your driveway is actually faster than normal. Cars manufactured in the Far East, for example, and transported to Britain by ship can be in transit for many weeks and then stored in compounds for months before finally finding their way to a customer.

JD

Q. The climate control on my 2007 Seat Altea often blows alternate bouts of cold and warm air rather than a steady mix of both. My garage has carried out a diagnostic check but found no fault. It is getting worse — is there anything I can do?

PS, Norwich

Carrying out a diagnostic test will not get to the root of every car-related problem. We spoke to the experts at automotivecoolingservices.co.uk  who said it was most likely that the temperature control motor was failing to move a flap to the correct position. The engine management system records only that the flap has moved but not how far, which may be why the test found no fault.

Air-conditioning flaps act a bit like mixer taps, opening a certain amount to allow hot air to mix with cold in the right ratio to achieve the selected temperature. In your case a flap could be sticking, sometimes opening too much so that you get too much hot air, sometimes too little so the air remains cold. The replacement of the flap and motor would cost between £80 and £100, plus about two hours’ labour.

DP

Q. I would like to swap the run-flat tyres on my BMW 320d for conventional ones. To spread the cost, would it be safe to change the two rear tyres first and change the front two at a later date?

RT, Stockport

Run-flat tyres are designed to resist collapse if punctured, allowing drivers to continue on to the nearest garage rather than having to call a breakdown company or change a wheel by the side of the road. They also provide protection against blowouts.

Their biggest drawback is that they tend to give a harder ride than conventional tyres. If one is punctured, the car must be driven at a reduced speed —usually a maximum of about 50mph — for no more than 50 to 100 miles, depending on the make. Most manufacturers advise against repairing run-flat tyres, as the sidewall may have been badly damaged by the time the car has made it to a garage.

The industry safety body Tyresafe advises against switching from run-flats to conventional tyres, as does BMW, arguing that your vehicle’s suspension, steering and braking have been set up to work in conjunction with run-flats. However, a spokesman for BMW did agree it was feasible.

National Tyres also does not recommend the change but will carry it out if asked. It adds that mixing the two types of tyre on one vehicle would be dangerous.

If you opt for conventional tyres, as well as replacing all four at once, be sure to match the size and specifications of the originals, and check for insurance implications. For future punctures an aerosol sealant such as Tyreweld (£9.99, halfords.com) is a cheap option.

Alternatively, a BMW space-saver wheel and jacking kit costs between £368 and £391 (the price depends on the model and the year) from alloywheelsdirect.net. There’s no spare-wheel-size hole under the boot floor to store it in, though.

DP

Got a car problem?

Email your question to carclinic@sunday-times.co.uk, or write to Car Clinic, Driving, The Sunday Times, 3 Thomas More Square, London E98 1ST, with a daytime phone number, your address and as much detail about your car as possible. We can’t reply personally, so please don’t send original documents or SAEs. Advice is offered without legal responsibility.