CHECK AND REFRESH YOUR AC SYSTEM
1 Locate air-con components in your engine bay
Start by identifying the main air con components in the usually crowded modern classic engine bay. Removing plastic covers should reveal a ribbed drive belt from the crankshaft pulley to the compressor, which is mounted low down on one side of the engine. The condenser or air con radiator is often sandwiched against the main radiator. The low pressure port will be used later and shouldn’t be confused with the high pressure port.
2 Check the cabin air filter
The cabin air filter prevents foreign matter entering the car. A clogged filter often causes stale smells from the air con and heater, so fit a new one if it’s dirty. It’s frequently overlooked during servicing.
3 Check the drive belt
The compressor is driven by a ribbed belt, either the serpentine belt that runs the water pump and engine auxiliaries, or its own separate belt. Check that the belt isn’t cracked or frayed and replace if in doubt.
4 Check the compressor
Start the engine and switch on the air con.
You should hear the engine note change as it takes up the load of driving the compressor. Replacing a faulty compressor is a complex job.
5 Air con recharging kit
Kits are available containing an adaptor hose with pressure gauge, plus canisters of a leak sealing fluid and refrigerant. Read the instructions carefully and note expected pressure readings for the next step.
6. Check the pressure
With its valve closed, connect the pressure gauge to the low pressure port. Start the engine and note the pressure reading. Very low pressure suggests that the system requires stop leak compound.
7 Adding stop leak
Stop Leak seals minor leaks and conditions tired O-rings. Screw the canister to the hose adapter and turn it upside down. With the engine idling, open the valve, then close it once the canister is empty.
8 Adding refrigerant
Refrigerant is added in the same way as Stop Leak. Disconnect the empty canister after closing the valve, run engine for ten minutes then recheck the pressure.