Car clinic: Disputing a yellow-box PCN, fault-checking a noisy air-conditioning unit, problems of a shiny dashboard and a sluggish Mitsubishi Carisma

Your motoring problems solved

The Car Clinic experts

Tim Shallcross used to train AA patrols to fix cars. Now he advises the Institute of Advanced Motorists.

Nick Freeman is a solicitor who runs a legal practice in Manchester and specialises in road traffic law.


Q. I have been sent a penalty charge notice (PCN) after being snapped by a camera at a yellow box junction. I set out to cross the junction only when there was sufficient space on the other side; however, as I crossed, a car overtook me and pulled in front, which meant I could not entirely clear the yellow lines. Do I have grounds for an appeal, or is it just a case of: if the camera gets you, you’re done?

TS, Sheffield

A. If your vehicle (or a part of it) has stopped in a yellow box junction, an offence has not necessarily been committed. There is a contravention only when you enter the yellow box junction at a time when stationary vehicles already present would cause you to have to stop in the box. In other words, the exit you are driving towards needs to be clear before you enter the junction. If circumstances change after you enter the box — as you claim — you have grounds for an appeal.

It is important to note that the authorities must be able to prove that the contravention was committed when you entered the box.

The PCN will contain instructions about how to make representations to your local authority, and about a subsequent appeal should it reject them.



Q. I can often hear a groaning noise coming from somewhere in my VW Golf. It sounds a bit like the snoring noise our cat makes, and seems to disappear when I turn off the air-conditioning. What could be causing it?

JM, Farnsfield, Nottinghamshire

A. When you turn on the air-conditioning, an engine-driven compressor (sometimes called the air-con pump), the engine cooling fan and the heater fan should all start up. Any of these could be making the noise. With some careful listening, you should be able to work out which one.

The trick is to make each part run individually. First, turn off the air-conditioning, start the engine, switch the heater fan to each speed setting for a few seconds and listen. If there is no groaning noise, you know the problem is not with the heater fan.

Now turn the air-conditioning back on. Both the compressor and the engine cooling fan will start to run. Wait and listen. If the groaning noise begins but then fades after a couple of minutes, the problem is probably with the compressor, because this component is automatically turned off after a few minutes’ operation. If the groaning noise is continuous, it’s likely to be the engine cooling fan that’s at fault, because with the air-con on, this component runs all the time.

In the case of a compressor fault, make sure your mechanic checks its drive belt. It could need adjusting or replacing, which is much cheaper than replacing the compressor itself (about £70, against £500).

Get the air-conditioning system checked as well — low refrigerant level caused by a slow leak can make the compressor noisy. This needs special equipment, so you cannot do it yourself, but lots of garages now offer a check and top-up service — sometimes known as air-con re-gassing — for about £50.



Q. As part of my job, I clean and drive a Jaguar XJ hearse. A company director has told me he wants the dashboard to be “gloss shiny”. I am worried that this will cause too much reflection on the windscreen and could be dangerous. Is there any sort of law relating to dashboard shine?

GP, Bridport, Dorset

A. There is no law or regulation governing how brightly the dashboard is reflected in the windscreen. Regardless of this, anything that makes a dashboard more shiny risks causing distracting reflections in the windscreen when the light comes from certain angles, and should be avoided.

I suggest you demonstrate the potential problem to your boss by placing a sheet of white paper on top of the dashboard and inviting him to see the effect of the reflection for himself.

A compromise would be to offer to use a matt-finish cleaner specifically designed for dashboards. Simoniz matt dashboard wipes cost £3.99 for a pack of 20; CarPlan Complete matt dashboard cleaner costs £4.99 for a 500ml can (both at The latter also contains UV protection to guard against fading and cracking.



Q. For the first mile of any journey, my 2000-registered Mitsubishi Carisma runs poorly and lacks power. It feels as if it is not firing on all cylinders. What could be behind these sluggish starts?

SW, Cardiff

A. In older Carismas, dirt and oil deposits can build up in the throttle body (the part that moves to control engine speed when you press the accelerator). Clean the throttle body or, if you’re unsure, ask a garage to do so. It’s easy, cheap (it would take a garage no more than half an hour) and a good idea on a car of this age. Use a good carburettor cleaning spray — the best thing for removing tar-like deposits — such as Frost carb cleaner (£4.60 for a 500ml can;

However, the symptoms you describe are more likely to be caused by tar build-up on the ends of the fuel injectors. The Carisma was one of the first cars to feature a direct petrol-injection system, in which the petrol is sprayed straight into the combustion chamber at the top of the cylinder. This helps the fuel to burn more efficiently, but the petrol must be sprayed in a specific pattern, which is achieved by precise engineering of the spray holes in the ends of the injectors.

All petrol contains traces of tar-like heavy oils, which, over time, can clog these spray holes and reduce engine efficiency. The effect is particularly noticeable when the engine is cold and at its least efficient.

The simplest way to clean the injectors can be to go through a couple of tankfuls of an “advanced” petrol, such as Shell V-Power or BP Ultimate. Although claims about these fuels giving increased mileage and power have been disputed, they certainly contain powerful cleaning additives.

If after two tankfuls there is no improvement, consider having the injectors removed and cleaned and the spray pattern checked by a specialist. Expect to pay about £60, plus a couple of hours of labour.




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