Car ac compressor clutch

How to detect the air conditioner compressor clutch failure

Diagnosis of the part is carried out in several stages. As a first step, you need to check if the clutch activates when the air conditioner is switched on. The diagnosis procedure is dependent on the drive belt length.

If your vehicle uses a long belt to drive auxiliary units, adhere to the following instructions:

1. Turn off the ignition.
2. Shift the transmission lever to neutral.
3. Disconnect the connector of the wire harness going to the clutch, and apply voltage of 12V to it. If the component is serviceable, you should hear a peculiar click that indicates its activation.
4. Disconnect the power supply from the connector.
5. Start the engine.
6. Again apply 12V to the wire that is going to the clutch. The sound of the compressor activation  indicates its good working order.

If a short drive belt is installed on the car, the procedure is as follows:

1. Turn off the ignition.
2. Rotate the pulley on which the belt moves by hand. It should rotate freely.
3. Apply 12V voltage to the wire going to the clutch. If the component is serviceable,  a much greater effort will be required to rotate the pulley by hand.

You will need a multimeter for a more comprehensive diagnosis. With its help, you should measure resistance between the component terminals and check for breakage in the component winding. Then check if the power is supplied to the part by measuring the voltage between the corresponding terminals of the power supply wire. Next, measure the clearance between the pulley and the pressure plate. It should be 0.35-0.65 mm on the average.

If in your vehicle the thermal protection device is located outside the coil housing, you should inspect its operability too. For this purpose, disconnect the device from the clutch and measure the voltage at its terminals.

You may identify that the air conditioner compressor clutch requires to be inspected by the following symptoms:

• the air conditioner does not switch on;
• windows mist up  in sunny weather;
• corrosion is visible on the clutch pressure plate surface;
• while driving, abnormal sounds are heard from the engine compartment;
• the rubber components of the unit have melted on the surface.

Causes of the air conditioner compressor clutch failure

One of the most common part malfunctions is the pressure plate wear due to incorrectly adjusted clearance: if it is smaller than required, then, even with the compressor off, the plate and pulley wear out. The slippage of the plate in relation to the pulley can also result from too high pressure in the air conditioning system, or from jamming of the compressor bearing, which also leads to accelerated abrasive wear of the assembly components.

Increase of the gap between the plate and the pulley is also provoked by slackening of the spring. A too long distance impedes the action of the electromagnet upon the clutch pressure plate, which causes the latter to stay inactive after the compressor is switched on.

Often the clutch malfunction is connected with the bearing freeplay, because of which the  pulley inner surface starts chafing against the electromagnet housing. The parts temperature rises, which results in melting of the surface of the insulation layer of the magnet winding,  and in the winding burnout.

The clutch bearing premature wear is often caused by the dust boot destruction, which makes the assembly components exposed to moisture and dirt. The temperature drop that occurs, for example, due to the water ingress onto the heated surface of the part is also hazardous to the bearing.

Repair of the air conditioner compressor clutch

The part repair generally involves replacing faulty components: a bearing, an electromagnet, or a pressure plate. These works, if you have the appropriate equipment, are easy to be carried out by yourself. Some service stations offer the service of winding a new coil of an electromagnet: in such a case, repair is only possible to be made by specialists.

Replacement of the air conditioner compressor clutch

It is advisable to entrust the component replacement to professionals, since during the procedure there may be a necessity to dismantle the compressor, and this work is quite time consuming. But if you have relevant experience and a set of appropriate tools, installation of the air conditioner compressor electromagnetic clutch will not cause you any difficulties. The sequence of steps is as follows:

1. Unscrew the central nut of the unit, retaining the clutch with a special wrench.
2. Remove the clutch plate and the adjusting shims. When reassembling, the number of shims can be increased if necessary.
3. With the help of round-nosed pliers, remove the pulley retainer ring, and then the pulley itself.
4. Remove the coil bolt, remove the clip ring.
5. Install new components in the reverse order, replacing the retaining rings.