LCD temp control display

My A/C/heating control panel LCD display quit working on my '95 LeSabre so I got a replacement from the junk yard. I took the old one with me to be sure and get one that matched. It operated just fine for about a week. Now, It operates fine on start up: Temp and function is shown. I can even change the temp setting from the steering wheel, but after a few minutes the 9 panel buttons blink randomly, about a second each. The system then goes into a “default mode of just the front defrost/windshield blowing air. Restarting the car tends reset the system but the random problem returns after a few minutes. I can still change the temp setting from the steering wheel button. At least the number display changes. The passenger control on the door does not seem to be affected, but I cannot operate the rear defroster. I checked for loose connections but did not find any. The connector seems to fit just fine. I did disconnect the positive cable to reset any codes during the installation. Anyone have a suggestion? Thanks!

My A/C/heating control panel LCD display quit working on my '95 LeSabre so I got a replacement from the junk yard. I took the old one with me to be sure and get one that matched. It operated just fine for about a week. Now, It operates fine on start up: Temp and function is shown. I can even change the temp setting from the steering wheel, but after a few minutes the 9 panel buttons blink randomly, about a second each. The system then goes into a “default mode of just the front defrost/windshield blowing air. Restarting the car tends reset the system but the random problem returns after a few minutes. I can still change the temp setting from the steering wheel button. At least the number display changes. The passenger control on the door does not seem to be affected, but I cannot operate the rear defroster. I checked for loose connections but did not find any. The connector seems to fit just fine. I did disconnect the positive cable to reset any codes during the installation. Anyone have a suggestion? Thanks!


Did the replacement come from one of these models?
BUICK LESABRE 1999
BUICK LESABRE LIMITED (1995 - 1998)
BUICK PARK AVENUE (1995 - 1996)
BUICK PARK AVENUE ULTRA (1995 - 1996)
BUICK RIVIERA (1996 - 1999)

They should all be interchangeable.

Without seeing an electrical diagram the only things would be connections. It might be the ground buss in the door frame on the driver's side where several dash area items ground. Some of those have lots of corrosion probably from cars in wet areas or with lots of snow carried onto carpet into that area by feet.

I had a 93 that would lose control of the manual HVAC and door locks because that ground buss was corroding.

Thanks for the reply. The replacement actualy came out of a '95 LeSabre; same part number on the display unit as the original defective one. It seemed to work fine for about a week. Even this morning it displayed the correct outside temp. Where exactly is the ground buss you mentioned. I can check again for loose connections. There is not much extra wiring so moving the display unit around is knda difficult once the connector is attached. Again, thanks for the help

Thanks for the reply. The replacement actualy came out of a '95 LeSabre; same part number on the display unit as the original defective one. It seemed to work fine for about a week. Even this morning it displayed the correct outside temp. Where exactly is the ground buss you mentioned. I can check again for loose connections. There is not much extra wiring so moving the display unit around is knda difficult once the connector is attached. Again, thanks for the help

I sent you a PM on the site here. Check your messages at the top.

You might, might have problem with the programmer box (the computer box on the corner of the heater) that sends signals. But I'd put it low on the list for now.

You might have a problem with the double battery cables on the positive. Turn the heater OFF with the key ON to park it before disconnecting.

But if it were the cables at the battery, I'd think you'd get other symptoms of wandering battery voltage due to corrosion between the two that bundle together into one red plastic end.

Have you put the old control unit back in? The wandering lights in the new one makes me think it may be defective.

Before you disconnect any battery cable, the ignition should be turned on and the A/C controller should be turned off; then you disconnect the negative cable first! Your system has a fault and it may be in a relearn mode, it may reset eventually, or it may not. If you have a fault that continues to be present, it will not reset. If the system detects no further faults, it will restore normal operation after about 50 ignition cycles.

You may have vacuum issues and you need to check the vacuum canister and vacuum lines from the intake manifold to the programmer. IIRC, the black line which goes to the inside (passenger side dash) has a coupling where it changes to a purple line. Check vacuum at this point also. If vacuum is present (with engine running) to the programmer, I would suspect that the vacuum block located at the programmer and going the vacuum actuators may have an obstruction. The multi-line vacuum block could be blocked, or you could have a vacuum leak going to the actuators. You can test the vacuum actuators, with a brake bleeder vacuum pump to see if they are operational. The rear defroster is a separate issue and may be related to the controller. Check voltage from the relay to the grid.