2000 Plymouth Neon Air condition don't work

Tiny
DEYA_10E
  • MEMBER
  • 2000 PLYMOUTH NEON
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 67,000 MILES
My car's air condition has stopped from working. Well what it does is that when ever I step on the gas it blows out hot air and when I brake, it blows out cold air, what can it be wrong? Why is it doing this?
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Friday, June 5th, 2009 AT 4:42 PM

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Tiny
RASMATAZ
  • MEMBER
An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that is contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. An identifier should be used to check the refrigerant before the system is serviced to prevent cross-contamination of recovery and recycling equipment.

Possible causes of intermittent cooling in a manual A/C system that might be caused by an electrical problem include:

Faulty low pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If the cutout switch is not reading correctly, it can prevent the compressor from coming on.

Faulty compressor clutch. The magnetic clutch on the compressor requires full battery voltage to engage. If the voltage to the clutch is low, or the clutch coils have too much resistance, or the air gap in the clutch is too great, the clutch may not engage to drive the compressor.

Faulty compressor clutch relay. Check to see if the relay is receiving voltage when the A/C is turned on. Also check the relay wiring and ground connections. If bypassing the relay with a jumper wire or routing battery voltage directly to the compressor clutch makes the A/C work, the relay is probably bad.

Faulty A/C control switch. The switch may be worn and not making good contact when it is turned on.

Some possible causes of intermittent cooling (or no cooling) on automatic A/C systems include all of the above, plus:

A problem in the control module or control head (this usually requires using a dealer scan tool to read fault codes and perform self-diagnostics).

A bad temperature sensor (an ambient air temperature sensor, interior air temperature sensor, evaporator temperature sensor, or sunload sensor). Again, a factory scan tool is usually required to perform diagnostics on the system.
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Friday, June 5th, 2009 AT 4:48 PM
Tiny
CARADIODOC
  • EXPERT
One more thing to try: Under long acceleration such as going up a long steep hill, does the air switch to defrost? If so, replace the vacuum check valve with one that includes a small storage canister. You'll find a bunch of them in the salvage yards or at the dealership. The valve is in a small hose that runs along the firewall just under the rear edge of the hood. The original one is about the size and shape of two nickels. The replacement is about 1 1/4" in diameter and 2" long.

What happens is under acceleration, manifold vacuum is low. In the event of a problem with the vacuum system, the vent motors in the dash are spring-loaded to go to the defrost mode. Your feet might freeze, but for safety, the windshield will be clear. I suspect your temperature door is spring-loaded too and goes to the hot position when you accelerate and vacuum is low. The replacement check valve stores enough vacuum to prevent this from happening.

Caradiodoc
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Friday, June 19th, 2009 AT 6:58 PM

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