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Pontiac Bonneville Heating/Cooling Problems

I have a 1993 Bonneville SSE. I was not getting any heat. I sent it to a local garage and they replaced the temp sensor and the programmer. The mechanic said that it wasn't the problem and is stumped on why there is still no heat control. The mechanic is stumped with the problem and rigged something so now the heat doesn't shut off. Does anyone know what this could be?????


  • I have a 1998 Bonneville that the battery died in last week.
    I replaced the battery as alway removing the negative cable
    first then the positive. put in the new battery hooking up the
    positive cable then the negative. when I started the car I noticed that the temperature that displays on the climate control screen was flashing. It flashes for about a minute then stops. The air conditioning works fine but if you turn the temperature up to 80 or 85 so it should be heating it does
    switch the air from the dash opening to the floor openings but the air is cool not hot. If you turn the heat all the way up to max (90) and shut the car off and restart it then the heat will work but if you lower the temp till the air conditioning comes back on and then raise it again you get cold air again. Any Ideas ? Thanks

  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    I've read about this before. I'm not sure if it's specific to Bonnevilles of applies to Olds and Buick as well. There's procedure for calibrating the programmer and parts associated with it.

    I'm guessing... that turning the temp all the way to 90 degrees and let it sit for a minute or two and then lower the temp to 60 and let it run for a few minutes, it should get the settings for the movements on the control arms again.

    I'll check my factory service manual for 98. Gimme a day. Someone else may have it quicker.

    People who have had this problem said it corrected itself after a while.

    Just a thought, are the terminals at the battery clean of corrosion? Is the double connection on the positive clean between the two cable ends? That causes a lot of problems.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • I will try what you said about turning it up to 90 and down
    to 60 Thanks. If you could check on the procedure from your
    service manual that would be great.

  • I tried running the temp up to 90 and down to 60 and
    also tried unhooking the battery cables and touching them
    together for a couple minutes to drain any stored power and I
    still can,t get heat. Any idea's- Thanks

  • I have the same problem with my pontiac it is a 1996. I just had the air pump replaced and the controller started to blink and I have air conditioning but no heat. If you find out anything about your car please post and let me know what you did to fix the problem. Thanks Jeff C.
  • The fan on my 1998 SSE works when it wants to. If I leave it on it'll turn off and on as I drive. Doesn't matter what mode or if its AC/or heater. I've changed the blower motor, changed all the fuses, swapped the relay swith with a different one. Does anyone know what my problem is?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    Most likely it's the blower motor control module. It's the equivalent of the resistors that are in manual heater control cars in the old days. It sits on top of the box near the blower motor. You have to loosen the one or two bolts holding the relay center that's above the heater box there to get it out of the way. It's held in by a couple of screws and is a circuit board. Often they fail in the on mode and the blower won't shut off. Ours failed on a 98 where it would go on and off and operate at funny speeds different than the regular 6 speeds settings that can be picked.

    I was told they're available at Advance Auto as well as dealers,, Or even as a pull from a junkyard.

    You should follow the power wire from the blower motor and see it goes to the module to help find the module. You can tap the power wire and check the voltage to ground as the blower motor slows or stops and see the power dropping that's coming from the module.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • jhaas5jhaas5 Posts: 1
    I had the same issue with my 1998 SSEI Bonneville. I replaced the blower motor control module, which is located in the pictures as directed.
    It worked out wonderfully.
    I pulled the part from a junkyard, for $10.
    Thanks for the advice.
    Please post more if this has solved anyone else's issues.
    Thanks alot.



  • I replaced my blower motor control module. I have air conditioning or het coming out of defrost orm follr vents only. Why doesn't it come out the center vents?
  • Sorry about the previous question....

    I did replace the blower motor control module but have no air coming out the vents in the center. It only comes out the defrost or lower vents.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    You likely have a problem where the soft plastic connector that joins the 4-5 plastic lines for vacuum inside the programmer box with the lines coming from the heater box and the car's vacuum (purple) has thin black plastic that was inside the connection and softens with age and blocks the flow of vacuum.

    If the rest of the controls work as in defrost which is no vacuum to any of the control motors, and heater works which blocks off the air flow with a motor vane at the bottom of the box, you most likely have the AC vent problem.

    The easiest fix is to take out the programmer, or gain access, and cut out the connector and join th internal plastic and outside with 1/8 inch rubber gasline pieces or slip aquarium tank line over the two ends to join them.

    At least one person said they were successful at taking apart the rubbery plastic connector and punching a hole through the black nipples that collapsed and putting it back together. But usually the plastic has soften and sticks together, pulling apart in chunks.

    I can send pictures to your carspace email account of the piece you're looking for. Is it an automatic temperature control system?

    A good check to be sure the vacuum motor works is to switch a vacuum line from another one of the vacuum units to the one for the AC vents and switch the controls until that one operates with vacuum through the line.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • Yes, it's an automatic temperature control system. The pictures would be helpful. This is getting to be a very expensive adventure.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    I got about 6 inch of 1/8 gas line from a NAPA store when looking for a size that would slip over the 1/8 outside diameter hard plastic line used in these cars. It was free from their scrap box.

    The programmer sits on the corner of the heater box and has two screws holding it on. It is possible to remove the cover by unsnapping the two clips holding it in. But I'd take it loose to have more freedom.

    Click on the pictures to see larger views. The black plastic under the passenger side has about 5 screws total holding it in place to quiet sound from under the dash and firewall. The glovebox has about 7 screws on the bottom hold its hinge to the bottom of the dash.

    Then you have a good view. The large bundle of wires into the programmer can be removed, but I don't remember if you have to do that. Make a list of the colors of tubes inside the programmer mating up to the different color coming out of the plastic connector. Cut one tube that goes to the AC and reconnect it or cut all 5 tubes.

    Remember someone said there's an aquarium air tube that fits over the outside of the 1/8 inch plastic.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • My blower motor would intermit stop working. It would work in the morning, not at noon, but then later in the day. This sounds crazy, but the longer you drove it, the more chance I would have of it working.

    I am having the same problem but is becoming less intermitt and more permanent. I have noticed that it blows stronger when driving and less when stopped. I have also noticed that it will stop and start while going over bumps. What do you guys think, I do not have automatic temp control.
  • I have an 1989 Park Avenue the tranny went out of , I pulled the blower motor control module out of. The cooling fins as I call them were about an inch shorter but the numbers on the sensor were the same. My heating and A/C are working fine. I thank you for your help and the money you surely saved me.
  • I am a new member and see the same problem that I have with my 96 Bonneville posted but no answers to the problem. Has anyone the answer to why my heater will work sometimes and not others. I took it to the dealer and the diagnostics said the problem was with the "heater & a/c programmer". They said $700 and change for a new one so I found one at a salvage yard for $175 anyway, after changing out the programmer I still have the same problem. The display will flash and nothing but cold air will blow most of the time. I can switch the air flow from floor to dash and defrost ok, but most of the time I have no heat. I did replace the battery a short while ago, would this have anything to do with it, need calibration maybe? Its very cold right now here in Michigan can someone please help me?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    #1: Is your radiator full (not just the reservoir tank). Open the cap, when COOL, and look. Low coolant means the heater core gets an air bubble--air doesn't transfer heat.

    If it is low, fill. Run car until fully hot and speed up motor to 2500 for a few seconds and repeat this 5 times to push water into heater core and get the air bubble out.

    #2: If radiator full when running motor is hot, are both heater hoses hot even with blower running at full speed. If one is cooler that means there's not enough hot water flowing through fast enough to deliver hot air from the fins. The water is getting cooled by the air going over the fins and won't deliver hot air. Both hoses should be hot.

    Are you saying that the blower speeds work okay? One problem is the blower control module which is like the resistor coils for old blowers is an electronic unit on the auto temperature control models. It sits on top of the air box next to the blower motor under the hood. The relay center needs to be loosened (1 or 2 bolts) and raised to access it. Available at Advanced Auto, etc.

    The programmer sometimes loses its settings when batteries are changed. It's best if the heater is turned off before doing anything like that. When you installed the new programmer did you have to connect a rod from the programmer that was white plastic (yellowed) and snapped into a metal threaded rod coming out of the heater box? IF so, the heater should have been on full heat and the unit have time for the actuator inside the programmer to pull all the way to hot and then you pull the metal rod to the right and snap the two together.

    See if you reach under the dash and unsnap these rods, if you move the metal rod left and right you can control the heated air temperature. If not you might have a partially blocked heater core. But usually it's the evaporator core mentioned blocking up with debris.

    I am assuming yours is auto temperature control and is like my 1998 leSabre. I replaced programmer with a 95 Buick programmer when I messed it up correcting the vacuum tubing block problem that cars from 97 on seem to develope.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • Thanks for the input Keith. I think you are on to something with the air pocket and blocked heater core idea. But I checked my radiator and resevoir but both levels are fine. However, the fluid is brown and looks very dirty with some solids. Also the hoses going to the firewall are not the same temp. One is much cooler and like you said appears to have a partially blocked heater core. I am going to take it after lunch today and have it flushed and re-charged, I sure hope this works and will post again with results. Feel free to advise more if need be. Thanks again for your help with this matter. Mike
  • No go, still no heat! Took Bonneville to garage and they took a look at the coolant and said it did not need to be flushed. Had the oil changed and then we spent the next 15 mins with the engine running and radiator cap off trying to get the air out of heater core. Had some bubbles but appairently did'nt get it all out because its still cold air blowing out. What I don't understand is why do I have perfect heat when I shut the car off for just a few seconds and start it back up. I will get hot air for about 20 seconds then the digital display starts blinking and the air goes cold??? Anyone have ideas? It's still very cold here in Michigan!
  • Mike,

    I have a similar problem with a co workers '98 Lesabre. I am going to try the module first. She is getting off and on heat so I am not thinking there is a water problem. Obviously, I will check the inexpensive things first. I will let you know what works.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    Without seeing the car myself it's hard to guess where to try next. But the radiator hoses not being almost the same temp with the heater blower running on high moving air over the heater core makes me believe you have a clogged heater core.

    I just read where an Impala owner took off the hoses to the heater core and flushed water backwards through the core. And globs of goop came out. I suspect the core can be blocked by gel from bad antifreeze as well as blocked by leakstoppers that people can pour in. The tubes through the heater core are so tiny they are easily blocked.

    If you are able to take off heater hoses somewhere and back flush do NOT put a hose nozzle right on the hose.Your house water pressure is 40 pounds and above. The cooling system never goes above 15-18 or so. Always shoot a stream at the end of the hose; messy but safe.

    The other thing I don't like is that you do get hot air for 20 seconds. But that could come from the heater core getting hot as you've shut off the air flow over it which cools it down since the water flow is blocked. So that slug of hot air around the heater and the hot water in it give heat at first.

    I'd like for you to take off the hush panel under the passenger side and lie on the floor and look for the white nylon rod that mvoes the main air vane for heat control. If comes out of the programmer box which sits vertically and moves horizontally on a little threaded rod in and out of the heater case. For full heat it should pull all the way to the right -- I think. You can tell by unsnapping it and manually moving the metal rod portion.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • mulinmulin Posts: 1
    I am experiencing the same on a 95 Pont Bonneville. I have replaced the programmer as well as the control head. I have also felt the blend door when the programmer was out and the door moves freely. The repeatable symptoms are that when the mode is set to blow defrost and floor at 90deg temp within 1 min or so the A/C indicator will turn on and the temp starts flashing then the blend door is commanded to go to a luke warm setting. You can actually watch the link rod moving the blend door. If you shut the car off, even just for a few seconds, the blend door returns to the warm air setting, upon restart, and the process repeats. Both heater hoses are hot, coolant is full, and any air that might have been in there has been purged. The key here I feel is that the A/C light comes on, clutch does not engage though, and the blend door actually moves to a cold air position.
  • Thanks to all the contributors to this thread. I had this problem on my '96 Bonneville SE. No one local had the part and I wound up ordering it from I was very impressed with their service - same day shipping and a genuine Delco part.

    Thanks to the contributor who took the pictures as well. The Blower Control module is a little hard to spot. Once you remove the fuse panel (two bolts - one is easy, but the one inside the casing is a little more difficult to remove. Thankfully I have a part retriever with a magnetic end), the module is easy to remove - three screws hold it in place. Disconnect the positive battery terminal before you do any of this. I had pulled the 30 amp fuse earlier because the failed module caused the fan to run at high speed even with the ignition off. Replacing the module fixed the blower problem.

    Thanks again to all who contributed to this thread !! :)
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    > Disconnect the positive battery terminal before you do any of this.

    Remember to remove the negative cable first. And always turn off the AC and other accessories before doing that. Some have connected problems with AC units starting after replacing a battery.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

  • Very good description mulin, that is 100% exact correct symptoms of my Bonneville too! Sure wish you had the answer though. I am going to keep trying some of the suggestions given and will certainly post my findings if you will do the same please.
    Thank you guys for your input.
  • You guys i have the same problem with a 98 Buick Lesabre the car has a control panel for temp, ac, fan, heat location, recir,etc. and a passenger control panel. My problem is with the ext temp flashes for about 30 sec the blend box above the control unit goes back to AC location manually pushing it back makes all the heat it can and now the the temp adj on the control panel works fine going from 15c to 32c, it all works fine as long as I don't turn key off because it all goes back to the start.

    I tried holding the auto temp button on a restart until the exterior temp stops flashing and the blend box moves back alittle and stays there, changing the temp from 32c to 15c and back works to where it stoped by holding the auto temp button but moving the blender box by hand to it's hottest position
    it will now give me full temp control from 15c to 32c. Don't turn key off because it all goes back to the start.
  • Just wondering are there any new developments on this duplicate problem that Mulin and I are having with the symptoms listed on posting #23? One thing that was not mentioned and that is, if I park my car in my warm garage over night and let it warm up for 10 or 12 minutes the heater will work fine. My problem is the cold parking lot at work. Still very cold here in Michigan, HELP!.
  • Did anyone find a solution to this problem. I am having the exact same issues on my 96 bonneville. heater works when it wants to, if I put it in the garage overnight and warm it up it works fine but once it is shut off and restarted it blows hot for a bout 20 seconds and then blows cold air, occasionally it will kick into the heater mode any suggestions
  • I'm up in Canada just 10mi from the Vermont border.
    I went to see a mechanic who as the computer tools and the 98 Buick has no codes for AC. to old he said try a new temp control panel or the rheostat in the blender box might be at fault. I would like to know where the exterior temperature probe is located maybe disconnecting that probe would solve the problem because it all works fine for the first 2 min until the ext temp flash's in the control panel.
    I still manually flip the blender box control by hand to the full position after the ext. temp stops flashing,after every restart, I'm lucky it's right behind the glove box, I made it so the glove box opens right up or falls open
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 21,507
    The external temperature probe is on the front of the radiator on the vertical support post that holds the hood latch on the cross piece in front of the radiator. It's about the size of your thumb.

    I suspect the problem is the actuator motor that moves the blend door, if you have the dual control system. I've seen pictures where the electric motor and the nylon reduction gears break. This causes them to slip on the hub that does the indexing as the motor moves the gears to change the vane setting. Then the unit realizes it's not working right and flashes the control light on the dash to indicate a fault.

    I believe it takes a special reader, a Tech II, to see what the heating system computers are doing.

    Someone in another forum connected a clothes hanger to the door control with duct tape so he could control it from the glove box area. By looking down through the glove box you could see the arm for the vane.

    2015 Cruze 2LT, 2014 Malibu 2LT, 2008 Cobalt 2LT

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