Clutch Slippage

Tip of the Week… Clutch slippage is a common cause for clutch and or compressor failure. The heat created when a clutch slips can damage the pulley bearing and weaken the compressor shaft seal. During any service work to the a/c system always check voltage to the clutch coil and air gap between the hub and pulley to prevent slippage.

Clutch slippage

Tip of the Week… Clutch slippage is a common cause for clutch and or compressor failure. The heat created when a clutch slips can damage the pulley bearing and weaken the compressor shaft seal. During any service work to the a/c system always check voltage to the clutch coil and air gap between the hub and pulley to prevent slippage.

Compressor Clutch Problems

If the compressor isn’t turning, make sure the magnetic clutch engages when energized. Underlying problems here may include a bad relay, fuse, wiring problem or a defective clutch. If the clutch fails to cycle on and off when the A/C is turned on, jumping the clutch lead with a jumper wire from the battery will show if the problem is in the clutch or elsewhere. If the clutch engages, the problem is the clutch power supply (relay, fuse, wiring, switch or control module). Refer to a wiring diagram and work backward toward the battery to find out why the voltage isn’t getting through.

Many A/C systems have a low-pressure cutout switch that prevents the compressor clutch from engaging if system pressure (the refrigerant charge) is too low. This is designed to protect the compressor from damage in the event of a leak. So if the clutch isn’t engaging, check the refrigerant charge and the cutout switch. The clutch air gap is also important for proper clutch operation. If the clearance is not correct, the clutch may slip and burn or not engage at all. The specs can be found in a service manual along with adjustment procedures. Generally speaking, most clutches call for a 0.015 to 0.040 inch press fit clearance.

Clutch Slipping & Overheating

Possible Causes of Ac Compressor Clutch Slipping and overheating:

Liquid slugging -will cause high shaft rotation torque. This inhibits rotation of the armature plate and leads to slipping.

Contamination on friction surfaces – will diminish the coefficient of friction between the two mating surfaces and result in slipping of the armature.

Low voltage to the field coil – causes a reduction in the strength of the magnetic field of the field coil.

System overpressure – will cause high shaft rotation torque. This inhibits rotation of the armature plate and leads to slipping.

Engine harness defective connection – may result in insufficient current being applied to the field coil.

Finally, recharge the system with the recommended amount of refrigerant and compressor oil. Don’t overcharge and don’t add too much oil. Check cooling performance before returning the vehicle to the customer, to verify that everything is working properly and that the new compressor is doing its job.

Ounce of Prevention

Never use compressed “shop” air to leak or pressure test an A/C System. Under certain conditions, pressurized mixtures of R134a and air are combustible. In addition shop air will inject excess moisture into the system.

Tip of the Week – Clutch Slippage

Clutch slippage is a common cause for clutch and or
compressor failure.  The heat created when a clutch slips can damage the pulley
bearing and weaken the compressor shaft seal. During any service work to the a/c
system always check voltage to the clutch coil and air gap between the hub and
pulley to prevent slippage.