It's a good idea to troubleshoot the AC system in your Toyota Celica before each summer. Problems that may arise are usually fairly simple to diagnose, whether it is an issue with faulty AC controls or a damaged fuse. Before taking your Celica in to an AC mechanic, there are a few troubleshooting steps you can run through on your own.
Turn on the electric blower fan and AC (with the engine running) to check if any of the AC controls are damaged. If the controls are loose or difficult to move, have them replaced. If you do not hear or feel the fan turn on, a fuse may have blown, or the fan itself may be faulty.
Check the fuse box for any blown or damaged fuses. The fuse box in the Toyota Celica is to the right of the console on the passenger side beside the cigarette lighter. Pull off the small panel and read the diagram for instructions on how to identify the fuse connected to the AC system and the capacity it takes. If the fuse is broken, replace it with another of the exact same amperage rating. For Toyota Celica's produced between the years of 1996 and 2005, the fuse purchased should be a 10-amp mini-fuse. The Celica line was discontinued in 2006.
Start the engine and check the two heater hoses under the bonnet. The heater hoses protrude from the firewall and are about the thickness of a garden hose. The firewall is the metal division that separates the engine compartment and the passenger compartment. Place your hand on the two hoses. They should both be warm to the touch. However, one should be noticeably cooler than the other. If it is not, it could mean that the valve control is bad. Have a qualified mechanic investigate this further, as the valve control may need to be replaced.
Turn the AC up to the highest setting and check under the bonnet to see if the magnetic clutch connected to the AC compressor engages. If it does not spin, this could indicate that the system is low on refrigerant. Have a mechanic refill the system. If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch may be defective and need to be replaced.
Inspect all the AC hoses for any leaks. If you notice an excessive amount of green, oily residue on the hoses, they may need to be replaced.
Turn the engine off and check the AC system for adequate pressure. Remove the black caps from the service ports on your Toyota Celica's AC unit. Screw the blue hose to the low-side service port and the red hose to the high-side port. The test gauge has both a red pressure monitor and a blue monitor to read the pressure. A normal pressure reading should be between 50 and 80 psi. If the reading is not in this range, it could indicate a leak. Have a qualified mechanic investigate further for you.