There are many potential reasons why an air conditioner compressor in a Cadillac DeVille won't engage. Some problems, for instance, may be due to the compressor's belt or tensioner pulley, the air conditioning compressor's clutch, a restricted condenser or low refrigerant. Knowing some of the elementary troubleshooting and recharging techniques for your DeVille can get the cold air flowing again without having to take your vehicle to a professional mechanic.
Listen to your engine and try to remember any recent noises that you may have heard. A faulty compressor may be signaled by metallic bearing noises. If you have heard loud knocking noises, then a professional mechanic will have to purge the system to bleed the air out of it and refill the refrigerant.
Open the hood on your 1998 Cadillac DeVille and inspect the drive belt that is connected to your compressor. If the belt is frayed, cracked, torn or broken then it should be replaced immediately. Use a socket wrench to loosen the belt by rotating the belt adjuster bolt and remove the old belt. Insert the new belt and tighten it using the belt adjuster bolt.
Check the tension on the compressor's drive belt with the engine turned off. Use a ruler to measure the deflection at the midpoint of the belt when it is depressed. There were three different DeVille models produced in 1998. Models with drive belts less than 12 inches should depress 1/4 inch or less. Belts 12 inches or longer should deflect between 1/4 and 1/2 inches.
Inspect your air conditioner's hoses for leaks, cracks or bubbles. Bad hoses should be wrapped with gaffer's tape as a short-term solution and replaced as soon as possible. Bad hoses have the potential to leak refrigerant and oil, which could cause the compressor to seize up.
Inspect the tensioner pulley's operation with the engine turned on if the belt checks out fine. Turn on your air conditioner to full blast and open your doors. This will prevent the compressor from cycling off if and when it does engage. If the pulley appears to wobble when it turns on, then you may need to either tighten the pulley or replace it if it is damaged.
Put your hands on the two pipes coming out from the evaporator, which is next to the firewall and has tubes leading from the air conditioning system to the car's interior. The two pipes should be cold to the touch. If they are not, then your system most likely needs a recharge in refrigerant.
Puncture the refrigerant recharge can by twisting the hose into the nozzle. Bleed the air out of the hose by twisting the release valve on the can and then twisting it back once you hear the "whoosh" of air expelled from the recharge kit. According to Napa, the 1998 DeVille holds approximately 32 oz. of R-134A refrigerant.
Attach the hose from the recharge kit to the low side fitting, marked with a capital "L," which is located between the compressor and the accumulator. Turn on your Cadillac and crank the air conditioner to full blast. If your kit has a low-pressure gauge, it should read between 25 to 40 psi (pounds per square inch). Use a thermometer to gauge the temperature of the air coming of the vents. When it reaches between 40 and 50 degrees F, then the air conditioning recharge is complete. Turn off the valve from the recharge kit and turn off the car.
