MY AC BLOWS WARM AIR WHEN GOING UPHILL.WHAT COULD BE THE CAUSE??
Your Blend Air Door Actuator is vacuum operated. The system has a vacuum reservoir and check valve that supply vacuum to the Heater/AC system when there is a low engine vacuum condition such as hard acceleration, hill climbing or towing. Either the vacuum canister has a leak or (more commonly) the vacuum check valve has failed. Look under the hood at the firewall for a single vacuum line running through the firewall and follow it back to the reservoir, check valve and eventually to the vacuum source. The check valve is usually the problem unless you can hear a vacuum leak under the dash with the windows up.
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