QUESTION -- Our Camry's air conditioner started "blinking" on and off last year. I took it to the dealership but by this time the air conditioner began working again. The mechanic told me that a component part was not sending the message for the air conditioner to come on but they could not check to see which component it was unless it wasn't working, so I was to bring it back when it quit the next time. It worked fine all the rest of the summer. This spring, the air conditioner blinked a few times and quit totally. I called the dealership and after several calls back and forth we were assured it was the compressor and it had to be replaced - for $500 for a reconditioned one. This was diagnosed on the phone. I was in the car yesterday on a short trip, tried the air conditioner and voila it worked and remained working. We feel there are two totally different explanations here and if the compressor is shot why does it start working again? Is the dealership just guessing? They want to put the compressor in but we are going to postpone this work at least until we get a few more answers. We would appreciate your opinion.
ANSWER -- It is extremely rare for a compressor to malfunction intermittently. Usually when this happens, it is due to debris in the system sticking under one of the check valves in the pump. This reduces the compressor output but doesn't stop it working completely. From your description, I don't think there is anything wrong with the compressor and I am not sure how they diagnosed this over the phone. It may be just a guess, but I don't think the correct one.
To check out the system, first check that the compressor is operating. Turn the air conditioning on and look at the drive hub for the compressor when the engine is running. The pulley around drive hub will be turned by the drive belt. If the compressor is engaged, the drive hub will also be turning. This means there is at least a minimum charge in the system and that the controls are requesting compressor operation. The compressor is actually controlled by the engine computer through a relay.
Next, a set of pressure gauges should be installed on the system to determine the operating pressures. A low charge would indicate low pressures and this can cause the compressor to cut out. A low pressure switch is used to protect the compressor from operating without a charge, but a slightly low charge can cause the pressures to be low when the engine compartment is cool and yet still have enough pressure to allow the compressor to operate when temperatures are warmer.
A scan tool can be used to check that the computers are receiving the correct signals for compressor operation, but an intermittent problem might not show up. An inspection of electrical connectors to the compressor and relay in the engine compartment might show up a loose connection and would be worth the effort if everything else looks good.
My initial impressions are that the refrigerant charge may be low or that the low pressure cycling switch may be malfunctioning. The compressor would be the last thing I would blame, if it is turning.
QUESTION -- I have a 1997 Mercury Villager minivan with 158,000 kms on a 3.0 litre V6 engine. When the engine is cold, it hesitates slightly but run perfectly fine within a minute. The dealer narrowed down my problem to a sticking idle air control valve and recommends that the valve be replaced at a cost of over $600. I would like to know whether the sticking valve could be removed and cleaned or lubricated instead at a far lower cost. Please advise.
ANSWER -- Although I have taken the idle air control valve from these vehicles apart to clean them, it has been with very limited success. There are several moving parts inside the valve, including a small planetary gear set. These parts are in motion much of the time we are driving a vehicle and do wear. Even after carefully cleaning them (don't clean inside the actual electric motor) the parts have still worked intermittently. A new valve would be the best solution. The price does seem a little high, so it would be worth a few phone calls to check on it. Surprisingly, dealer parts pricing on many parts has been some of the lowest lately, so this may be the best you can do.
Jim Kerr is an experienced mechanic, instructor of automotive technology, freelance journalist and member of the Automobile Journalists' Association of Canada.
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