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Buick LeSabre Heating / Cooling



  • When I start my 94 LeSabre Limited, the A/C fan will not come on 99% of the time. The Dual Automatic Control will be dark, no lights at all. After driving about 5 minutes or so, the fan will begin to start then stop several times before finally coming on. The control head will then show the blinking set temperature and the Dual and Defrost lights will be on. The air is now blowing out of the windshield vents. If I repeatedly and in rapid succession press the Auto burtton, the air will eventually come out the dash vents. Is there anything I can do to try to fix this? The buttons on the passenger control have to be pressed repeatedly to move the indicator. On the main control, the buttons must be repeatedly pressed to take effect.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    edited September 2010
    Your problem might be a defection head unit or control unit on the dash. I would suspect, however, a ground problem. Are you in a wet climate with snow or lots of rain that carries into the car and wets the carpet near the door as the foot drags over it?

    I think the AC control grounds at the buss that's under the door sill plastic right where your feet go into the car. It's bundled with other cables and wrapped with tape. They corrode. You might try hitting against that area when the AC control won't work and see if things make connection.

    Does anything else not work at times, like the power door locks?

    The blinking could just be a reaction to having the power go on and off as the connection is made.

    AC units are the same for 92-94 leSabres and 91-94 Park Avenues. You might pick up a couple from a junkyard and see if they work better. They should be an easy removal after pulling the plastic trim off the front of the dash.

    You might also have a problem with the blower motor control module which changes the voltage to the motor to vary speeds. This replaced the resistor in older cars with set speeds. It's a power transistor and some circuits. Follow the power leads from the blower motor. It will be close by and will stick into the tunnel where the blower motor pushes the air; the air movement cools it. These sometimes fail with odd speeds compared to the 6 or 7 speeds manually selectable. Sometimes they keep the blower motor on even when the key is turned off, draining the battery.

    You can connect the blower motor directly to battery power and a ground with a fuse to see if it runs fine at full speed. Motors wear and stick and do funny things with age and detrioration.

    The air flow direction may be similar to the problem with the connector on the programmer box on the corner of the HVAC box under the dash. The vacuum sucks the soft plastic closed. It usually happens to the dash vacuum tube that closes off the air to the defroster to make it come out the dash front. If the air won't come out the dash at first, see if it's coming out the defrost.

    I can give a link for bypassing the softened connector if you find that's what's happening. It also could be just poor vacuum due to rotted or cracked vacuum lines under the hood or a cracked vacuum reservoir tank that's losing vacuum. When there's no vacuum the unit go to defrost direction for safety.

    This message has been approved.

  • Thanks for the reply. I failed to mention in my original post that I have had 3 control heads in this car ... 1 was even purchased 'new' from an AC-Delco parts distributor. I am beginning to doubt it is the Control head. When the system is off, there is no exterior temp display - with any of the heads that were in it. Truly, it is as if there is no power to the unit then all of the sudden it comes on. The control is the same as the 91 - 94 Park Ave? I dont think that there is a fan motor issue since the fan does run. Is there any way to test the control head? Thanks again.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    You have had three new control heads in it. I doubt it's the control head.

    I'd check at the buss ground connections. I would take a look at the one of the left--check my pictures I linked. They're not hard to get to.

    My 93 had started occasionally losing control of the heater (manual AC) and the system reverted to defrost and the AC turned on. Probably the default was the compressor on. The lights on the head did stay on. At the same time the door locks would quit working. Then after a while driving or after parking the pair would start working again at the same time.

    I never got to troubleshoot it by checking the buss: my wife made me trade it for a pretty red 03 leSabre when they came out with a pure red again.

    If you are enough of a cobbler, it would be interesting to connect to the power lead of the AC head and use an LED light to show when it had power and when it didn't have power.

    OR I think take the ground wire for it and parallel a 2nd ground lead along with the other and see if that eliminates your symptom.

    I think you're into a diagnosis stage here.

    The only other thing I can think of is the ignition switches might have a separate contact that's worn and is making and breaking contact. I never have physically checked to see how many different contacts are in the ignition switch--that's the actual switch down on top of the lower steering column and not the key cylinder at the top.

    I do know a few people have had them wear out with certain things dying while driving, but I can't remember if that was the car cutting off motor-wise or if it was accessories.

    This message has been approved.

  • I finally got around to looking at the control board and you where correct there were 4 pink colored round not square 120 ohm resistors that had signs of excessive heat and they basically unsoldered themselves thanks for the fix. Working like it was new.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    >round not square 120 ohm resistors that had signs of excessive heat a

    Thanks a lot for posting back about what you found. It lets me know I steered someone the right way and lets people reading know what worked if they have the same symptoms you had.

    Thank you.

    This message has been approved.

  • jj14jj14 Posts: 2
    It seems like im having the same problems most 94-98 lesabre owners are having..I need help!

    First off I have the digital control w/ passenger side climate control as well..

    When I start my car the ac/heat control unit will blink for about 30 seconds..when its blinking nothing but cold air will blow in the winter and nothing but warm air will blow in the summer...when it finally stops blinking in the winter on the driver side will get heat, the passenger side will be ice the sumer the drivers side will get air sometimes and the passenger side will be hot...

    I have been told that it is the AC heat programmer by a local shop and I have also been told that it is a blend door actuator by my mechanic..these are 2 big differences..also when I turn the key (without the motor on) i hear what seems to be my blend doors moving while the ac/heat programmer is blinking...

    I have read many forums and it seems to be the actuator but I dont know which actuator to get..I have a friend whose parting out a 94 lesabre so I could just get it from there if I knew which one to get
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    edited December 2010
    I can tell you I've had the same symptoms. The HVAC box under your dash uses vacuum actuators to change the path of the air flow. But it uses electric actuator motors that move wire rods and move doors inside the box to change the temperature by moving blend doors that make more or less air go through the heater core for heating.

    You can take off the hush panel under the passenger side dash. It has about 3 screws holding it to the front of the dash and two little nuts that hold it to the firewall above the carpet.

    You can then see if you are able to lie on the floor the actuator on TOP of the HVAC box with a metal rod that attaches to a white plastic arm that moves the door inside the box. If you can move that arm with about the force to move a library book sliding it on a formica countertop, the gear inside the actuator is cracked. That lets the gear slip on the gray hub. It's the gray hub that moves the metal rod. I took mine out, disassembled the actuator, glued the nylon gear to the hub, and put it back in after drying overnight. So far it's working. Note that the gray hub and arm outside the actuator box has a tab that operates in a slot of about 180 degrees. That limits the movement; be sure to keep the tab in that slot.

    This is the HVAC box with the actuator circled on top. The bottom actuator goes to the programmer box and is for the passenger. You should be able to turn the key ON and operate the temps on the controls and make those actuators move. You may be able to tell the top one slips on the hub.


    The actuator looks like this:


    If you glue the gear in place, consider the gear's movement range so that the crack is not in the movement allowed.

    Replacement actuators are available at different stores and I am thinking the actuator is in the $50 range.

    Some have snapped the wire rod out of the white plastic (just push backwards--it snaps into a groove) and held the heater vane in place with a coat hanger to manually move the temp door.

    Better access to the repair site can be had if you take off the 6 screws along the bottom of the glovebox hinge. It all drops down and you've got great access.

    Good luck. Hope this info helps. You do not need a programmer box. I am 99.99% sure you'll find you can watch the actuator slip or make it move by pushing on the metal rod.

    This message has been approved.

  • Thanks imidazol97: Thanks for the great experience sharing & photo. That's very helpful since I have not yet gotten to the underside of my car.

    Thanks for sharing
  • sed55sed55 Posts: 3
    How much for the digital control out of the '94. I need to keep on trying them until I can finally get one that a) turns on all the time and b) changes when I press the button. Mine I have to pound on the buttons to get them to change and forget about any temp changes with it. I have not been able to get a viable cause other than to kerp on throwing controls into it. I have tried three already. This is a '94 LeSabre.
  • jj14jj14 Posts: 2
    Thanks for the detailed instructions!!

    I have looked at rockauto and looked at the actuators. I have a CJ2 code for my buick so I need the part #16141822 which is, like you said, in the $50 range...

    my question is..if I get my mechanic (who also said I needed a blend door actuator) to fix this, will I be able to get hot heat on both the driver and passenger side in the winter, and cold air on both sides in the summer? Also, will this eliminate the blinking on my control unit?

    Again thanks so much you have no idea how much I appreciate it! :)
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    >I be able to get hot heat on both the driver and passenger side in the winter, and cold air on both sides in the summer? Also, will this eliminate the blinking on my control unit?

    I can't be there to diagnose, so I can't guarantee.

    If you watch the movement of the actuator arm when you change the settings for driver side from cold to hot, you should be able to tell it's not moving the full range due to slipping. When moving, you should be able to push your finger against the rod to help it move one way or the other. And that should give you full heat or full cold.

    That was my diagnosis. I could move the arm with moderate finger pressure. Many Pontiac owners have had the same problem. Theirs is harder to get to the two screws holding the actuator in place because of the placement of dash and shape of the instrument panel.

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  • atxcaratxcar Posts: 3
    Looking through the threads I think my heater / AC control unit is bad, but would like a second opinion before replacing it. It's a 1993 Buick LeSabre, Custom with the non-digital control with push buttons that are supposed to light up; a slide lever for the heat control; another slide switch for the fan; and a rear defog button. Not a dual unit. Seems to be AC Delco part number 15-71887, oem 16145214.
    The car is fully maintained, but with high miles (100k+).
    At the moment, it wants to run the the AC through the defrost, but I can push the button to go through bi-level and it will do so with cold air for a while (time varies). I cannot turn it off by pushing the "off" button. None of the buttons seem to respond properly, and it seems to switch between settings randomly with the air flowing to that selection. Sometimes the buttons light and sometimes they do not.
    Initially I had to fix a ground disconnect at the battery and another loose (smoking) ground at the top, middle of the firewall between the relays and big fuses. I also had the AC system recharged. Prior to the ground fix, the buttons would light up in a circular pattern, switching the controls as they rotated. At least now that has stopped. The driver side interior ground seems good too. The car did have an aftermarket alarm in the past.
    The AC does blow cold and I can move the temp lever to have it blow hot.
    The problem is not being able to turn it off and not being able to select where the flow goes properly.
    Any other ideas or suggested tests? Could it be vacuum or the reservoir? The other part by the glove box?
    If odds are that it's the control, which other makes and models would have the same control unit? 91-94 Park Avenue? What else? These things seem to be getting harder to get.
    Thanks for your help.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    It does sound like the electrical control unit in the dash might be at fault. You say you're cleaned the ground on the driver side under the carpet under the door sill? There also is one on the passenger side. I do not know WHICH one is the ground for the heater AC unit.

    I do know my 93 had started losing control of the heater. It would go into AC mode with the compressor running and the power door locks would not work. I did not get to isolate which ground was the one before we traded it for a newer leSAbre.

    The dash control unit is for 92-94 leSabres and Park Avenues including Ultra according to RockAuto--when you click on the blue linked number it shows all vehicles using that part.

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  • atxcaratxcar Posts: 3
    Thanks for the second opinion. I was lucky enough to find a used control unit from a similar 1992 LeSabre in a nearby salvage yard for $50, ready to go. Swapped it out and the problem is fixed.
  • advent70advent70 Posts: 4
    edited August 2011
  • Hi all

    I have 2004 Lesabre Limited with about 89K miles. Has run flawlessly since purchased new. Now experiencing lack of heat in passenger cabin, and noticed recovery tank was low. Refilled to proper fill line, heat returned, but now noticing heat is ebbing again. Believe heater core is clogged. Car engine temp is fine, all running OK otherwise.

    What are the proper steps to get to the hoses to perform a heater core flush? Is a garden hose sufficient?

    Second, if I go to this trouble, should I go ahead and replace the thermostat? If so, does that imply a drain and refill of the system, or can I get by just replacing the thermostat (even if I might spill some coolant along the way)?

    Any other tips/hints appreciate.d
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    edited October 2011
    If you get enough heat part of time, then core is not clogged.

    Pull the dipstick and look at the color of the oil. It should be relatively new looking or dark, depending on how long it was changed. If it looks chocolate like a milky look, there may be coolant getting into the oil due to leaks at the intake manifold gaskets, the EGR tube inside the upper manifold, or the gasket at the throttle body on the end of the upper intake. Coolant in the oil is something to be taken care of quickly, not in a month or so. Coolant in the oil damages the metal of the bearings. The oil with coolant needs to be gotten out and replaced with fresh, even cheap oil, until you get the internal leak fixed.

    Look for drips under the car after it has been driven and well heated and shut off.

    First, with engine cool check the coolant in the radiator. Use the radiator cap to check the level of coolant--not the reservoir. Fill the radiator to the top. Before putting the cap back on, check the underside of the cap for a gooey substance. If there, clean with a small brush and dish detergent, such as a toothbrush. The little disk on the underside of the cap should move free. That's what lets the coolant back into the radiator when it cools, but keeps the pressure in as it heats up.

    Run the car for 10-15 minutes when you go somewhere, then with car parked speed the negine at 2500 rpm for 10 seconds or so, let idle for a few seconds and repeat 4 more times. If you can put the front of car higher than the driver seat on an uphill slope like a driveway that is better. That should get the air out of the heater core according to the service manual.

    Then after car cools check to be sure the radiator level. Fill again if necessary. All this time, keep the level in the coolant in the reservoir between the cold and hot marks.

    Now check the level of coolant in the radiator and the reservoir after several days. If it has gone down again and there are no obvious drips, then look for leaks at the water pump, the plastic elbow at the lower intake manifold to the bracket of the idler pulley for the belt, and at the hose connections. Do this with a flashlight and right after the car has been driven hot and shut down so there's pressure in the radiator so you're more likely to see coolant dripping.

    When the level in the radiator drops a little, air gets into the heater core and less coolant coes through. That means less heat. Often when the engine speeds up, the heat will improve and will drop off at idle.

    There are a couple of other things to ask about, but it's important to establish if you have a leak outside or an inside leak first. Then we can worry about the current coolant.

    This message has been approved.

  • atxcaratxcar Posts: 3
    Hi Soonerdew, since you topped off your system and the heating worked it indicates that coolant was circulating through the heater core and it is not plugged. Check your level again, most likely it is down again and needs more. If that's the case, your system has a leak in it somewhere and you need to fix it. Check the level in the radiator too, not just the recovery tank.

    If the levels are good, it may now actually be plugged. Two heater hose lines come through the firewall so to flush the heater core disconnect them and use your hose to push water through. If it doesn't go through, it's plugged and you may need to replace the core, which is quite a bit of work.

    Good Luck
  • There are no leaks of any kind on the vehicle. The garage floor (where its parked every night) is bone dry.

    I will top off the radiator as you suggested and see if that affects the heating situation. Just to be clear, the heating isn't intermittent; a partial refil of the reservoir restored the heater to normal condition, but now (about six weeks ago, or so) the hot air temp has dropped again. Your air in the system description sounds apt.

    The manual indicates replacement of the thermostat requires draining the system, but it would seem I could replace it with the engine cold and risk losing/spilling only a relatively small amount of coolant. Does that makes sense? Would be much easier on the wallet to change it myself, and besides I have no faith in nearly any of the local GM dealers not to gouge me with unneeded/extranous repairs.

    Is a true cooling system flush a good idea? I've done it once already with this vehicle a few years ago, around 30-40K miles due to the stories of sludge related to DexCool, but was hesitant a 2nd time as I wasn't convinced a frequent high-pressure flush opposite the normal coolant flow didn't at least risk damaging something.
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