Fig. 12.4. Electromagnetic clutch of the compressor drive: 1 – elastic element of the disk; 2 – clutch pressure plate; 3 – driven clutch disc; 4 – bearing; 5 – inner bearing race; 6 – working surface of the pulley; 7 – pulley grooves; 8 – electromagnet winding; 9 – electromagnet body; 10 – electrical connector block.
An air conditioner compressor is a complex, high-tech unit. Many units of the compressor pump section are manufactured using selective assembly. Therefore, manufacturers do not supply components for repairing the compressor pump section for retail sale. The only compressor unit that can be repaired in a garage is the electromagnetic drive clutch (Fig. 12.4).
When operating a car, compressor clutch failure is a very common malfunction. As a rule, the bearing of the 4th pulley begins to deteriorate first.
The cause may be incorrect tension of the drive belt, water getting in when driving through a deep puddle, slipping of the pressure plate and, consequently, overheating of the bearing, etc. As the problem increases, play begins to appear.
When the play reaches a critical value, the inner surface of the pulley begins to rub against the surface of the housing 9 of the electromagnet coil during rotation. As a result of friction, the parts heat up, and the insulation of the winding 8 of the coil begins to burn out. An electrical short circuit occurs, and the electromagnet fails.
In the most advanced cases, the bearing jams and the inner race of the 5th bearing rotates on the landing neck of the compressor cover. After this, the compressor has to be replaced, and this is a very expensive repair at specialized services.
To avoid unnecessary expenses, pay attention to unusual noises when the air conditioner compressor is operating during routine vehicle inspections. If you suspect problems with the pulley bearing, remove the drive belt (see Checking and replacing the accessory drive belt) and turn the pulley by hand. The bearing should rotate evenly, silently, without jamming. There should be no axial or radial play.
If necessary, replace the bearing without waiting for it to completely fail.