AC only blows on passenger side

[ragman60]

My 1999 Buick Regal GL has 70,000 miles and I was checking the battery connections and disconnected to clean some corrosion from connection. Evidently the WRONG thing to have done.The next morning driving to work the two driver side vents had warm air coming out and I thought the air conditioning had gone out. When I started home in the afternoon I stuck my hand to the middle passenger side to check them and cold air was coming out. Great I have air conditioning! I checked both vents when I got home and cold air was coming out from both passenger vents.

I have the Automatic Temperature Control and I checked the Dual Control and it is off. Fan works correctly on manual and automatic. Manual with fan gets same thing "cold passenger and warm driver side". I have checked all fuses inside and under hood and all are good. The larger cooling fan fuses or relays under the hood I could not check.

Does anyone have an idea what to do? I think it is something simple and don't want to take to a Buick Dealer and pay an arm and leg. Thanks for your help.

[BNaylor]

I've heard of that happening on some Regals with the ComforTemp Climate Control. However, simply disconnecting the battery or working on the cables should not cause the problem. When you go to manual mode and press air flow are all the positions working correctly like windshield/floor, mid/floor, mid, floor? Are front, vent and recir working?

When you press Dual are you getting proper temperature control (up/down) for the driver's side?

BTW - When you disconnect the battery the digital climate control system recalibrates itself for some reason. 1999 models are subject to HVAC logic controller problems within the head unit. After checking above disconnect the battery negative cable for a short period then reconnect and see what it does. A lot of times the problem will disappear and it will start working properly.

[ragman60]

All of the manual mode and air flow are working good and all of them work the same way with warm air on driver and cold air on the passenger in each of the different air flows. Front, vent and recir are all working also. When dual is pressed the owners manual said it only controlled only the passenger side and the regular thermostat was for the drivers side in this mode. Yes for Dual the temperature for the passenger side does change to warmer for warmer and cold for cold. With Dual engaged the drivers side stays with the warm air coming out. All controls are working in order as far as I can tell......

I also disconnected the battery as you suggested and it did not change anything. My car seems to not have anything with LOGIC involved, ie HVAC logic controller problems. Is there anything else that I might try. Are there vacuum leaks or electric relays that may not be letting the air flow flapper or baffler change air direction. Thanks for your help again!

[BNaylor]

Based on your feedback it looks like the problem is narrowed down to the climate control unit or the driver's side temperature actuator. Since all of the controls and vents are working I would rule out a vacuum or vacuum leak problem. The accessory vacuum comes off of the intake manifold and that appears to be good. It is the plastic line that you see routing around the battery, inner fender, and then into the firewall. Needless to say there are no other relays. The driver's side temperature actuator sounds out of position allowing hot air from the heater core to blend with the cold air from the A/C evaporator. The actuator is motor driven based on where the driver's side temperature control is positioned. The temperature actuator in question is located to the left side of the center of the dash. You will have to remove the kickpanel to access it. To give you an idea of how it works, open the glove box and look to the upper left. You will see a round electrical component with wires attached (passenger side). As you move the temperature control for the passenger side you can see the center move and probably get an audible motor whirring type sound. This is controlling a blend door in the lower part of the HVAC assembly. This will give you an idea of how the driver's side is supposed to work although it is more difficult to access.

The problem with certain 1999 Regals with digital climate control is when battery is disconnected the unit attempts recalibration and the temperature actuator may not close completely. Then a component in the logic controller board contained within the climate control unit goes bad. Later model Regals supposedly have an improved climate control unit.

Hope the info helps and good luck.

[ragman60]

Thanks bnaylor for all of your help.

I disconnected the battery a second time Saturday while washing the car but turned the Automatic Control off before I shut the engine off. Pulled it into the garage afterward without turning the Automatic Control on at all. It sit until I drove it to work this morning. I drove my other car to church yesterday to have some air. When I turned it on after pulling out of the subdivision this morning, I now have air conditioning coming out of both driver and passenger side vents. Evidently it did recalibrate this time.

Thanks again for your help!

[BNaylor]

Originally Posted by ragman60

Thanks bnaylor for all of your help.

I disconnected the battery a second time Saturday while washing the car but turned the Automatic Control off before I shut the engine off. Pulled it into the garage afterward without turning the Automatic Control on at all. It sit until I drove it to work this morning. I drove my other car to church yesterday to have some air. When I turned it on after pulling out of the subdivision this morning, I now have air conditioning coming out of both driver and passenger side vents. Evidently it did recalibrate this time.

Thanks again for your help!

You're welcome. Being persistent pays off. It is good to know next time the battery is disconnected for servicing that the procedure may have to be run more than once.

Thanks for the feedback.