Just bought a nice 96 thunderbird 4.6L with 102,000 miles on it. my air cond works very well, but when i turn on the vent or heater, it turns on the air conditioning. i can change the temp of the air from cold to warm, but in effect the only air or climate control that works in my car is the air conditioner, either by turning on the air, or when i turn on the vent or heater. the dealer who sold this to me says it's probably a 'climate control switch' and to bring the car in, they'll check, and get one from a salvage yard. i searched auto parts and found no such switch specifically or in particular. on another forum a mechanic said the air conditioner or compressor dehumidifies the air whenever the vent is used, so that is what is really happening. anyone know? thanks.

SOURCE: 1998 Ford Explorer a/c not working properly

HI. Here is a complete check list that will help you trouble shot this issue. You will find the problem in one or more of these areas stated below.

1. Check Drive Belts - The air conditioner utilizes a drive belt that supplies power to rotate the compressor, which is basically a refrigerant pump. If the belt fails the compressor has nothing to drive it, inspect and replace as needed to restore operation. If belt is intact proceed to the next step.

2. Check for Compressor Clutch Engagement - Turn the air conditioner to the "on" position and set controls to the coldest setting. Start the engine and allow to idle. Then open the hood and inspect the clutch at the front of the compressor, is it turning? "Engaged" if so, the system has enough refrigerant to activate. If the system is low on refrigerant it will not work properly. In this case an air conditioner recharge kit is needed to recharge the system. If the system is low on refrigerant it could cycle on and off, making a ticking noise. If the compressor clutch is not turning proceed to next step.

3. Inspect for Refrigerant Leaks - If the system has a large leak and no refrigerant remains it will not activate. First test system for a static pressure charge, with the engine off attach an ac gauge to the low side pressure port and check the state of charge. Depending on outside temperature there should be between 50 psi and 80 psi. (Cool and warm). A refrigerant leak detector is needed to inspect for leak, but if you do not have a leak detector there is an alternative method. The air conditioner system is designed to run with oil suspended in the refrigerant to lubricate the system. Check for oily residue outside the system by inspecting all hoses, compressor, condenser, evaporator or receiver drier and replace any component that has failed.

4. Inspect Fuses - Check under dash panel and under hood power distribution center. Replace failed fuses as needed, recheck system. If the new fuse fails when reinstalled a short circuit is present and requires diagnosing with a wiring schematic, follow circuits to locate short, repair as needed and recheck system.

5. Check Temperature Control Vents - The vents inside your car are controlled by a cable, electrical servo or vacuum servo. If the temperature blend door is not functioning properly it will cause warm air from the heater to exit the vents. To check this start the car and allow the engine idle, next turn the blower motor speed on low, switch the temperature control from warm to cold while your ear is close to the vents. You should hear the door move inside the heater box as it swings from open to close. If not, insect for a vacuum leak or a shorted motor in the servo, repair the leak or replace the servo motor.

Bill

• 424 Answers
• Posted on Oct 05, 2009

SOURCE: climate control is on defrost only the auto

Check your vacuum pump located on the right side fenderwell. see if its running. Check the vacuum hose at the hubs for leaks or damage. repair if damaged. check for other vacuum leaks such as the grey hose going to the heater control valve.

SOURCE: 1998 for taurus heater wont blow hot air only cold

you need to check the blend door in the heater box it maybe broken or stuck.the blend door switches between the heater core and ac evaporator to provide a mix of temperature