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Pontiac Bonneville Heating/Cooling Problems



  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,705
    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.

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  • 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 & I75Posts: 17,705
    > 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.

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  • 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 & I75Posts: 17,705
    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.

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  • Thanks for the email, going to try the ext. temp. probe.

    Your suspicion of the actuator motor at fault makes me think how come it all works fine, I mean I can use the control system to work the vane, until the
    exterior temperature in the control panel starts to flash that it all goes Hay Wire.... maybe thats how that got started!

    I like your mention of the other forum, my thought exactly but the vane moves all the time, once you have waited for the ext. temp. from flashing set the vane to max again then it all works fine using the control panel, so it makes it hard to connect to it and allow it to move by it's self.

    By the way there is a another controller at the bottom which does not get stuck when the ext. temp. flashes in the control panel
  • asierasier Posts: 1
    Were you able to get your heater/AC fan working?
    Cost? I really need your help on this!

    Ted Applegate
    Dayton, OH
  • I have a 1998 bonneville si I don't know if it will be the same but I had the blower motor control module replaced. The part was around $200.00. It's working fine now. Hope this helps.
  • Was wondering if disconnecting the ext. temp. probe worked or not. Let me know what you tried or how you did it, if you would. Sure glad to know I am not alone with this problem, thanks for every ones input.
  • I tried disconnecting the ext. temp. probe and that did not solve the inital problem, all it did was kept the ext. temp from being displayed on the digital controller display. However, I have gotten my heater to work a couple times now by warming the car up good then with the heater on max heat 90*. Then I use the temp control button and drop it to 60*, at that point the AC light comes on, I then power OFF the digital controller then back ON, increase the temp to 90* and I get full heater control. Not sure if this will continue to work but so far so good.
  • What is the dual control system and how would I know if I have one? Are you talking about the controller under/behind the glove box as one, and the digital display controller as the second? If so, that's what my 96 Bonneville has. I can get my heater to work most every day now but it is not consistent. As I have mentioned in other postings, sometimes it's as simple as dropping the temp to 60*, powering down/up and raising temp. But this doesn't always work the first time. I would like to pursue what you suggested about the gears slipping on the hub. Was wondering if anyone, with this very problem, has actually inspected their nylon reduction gears and whats the easiest way to get to them? Is it necessary to remove the controller again behind the glove box? I always have a hard time with the top wire terminals on this controller and would rather avoid removing it again if possible.
  • dmx6dmx6 Posts: 7
    I have a 98 Bonneville SLE car that the a/c works great but no heat! Set temp on the auto control panel to 90 and still no heat. Cut car off wait few seconds start up--have heat for few seconds and then back to full A/C. Temp reading flashes on controller and goes out then reads ok.--but no heat. Common thread might be changing battery--mine worked OK till I replaced battery. Anyone know how to reset system or if it even must be reset? My wife had previously complained about delay in getting heat before I change battery---I have been having trouble with positive battery cable having corrosion because battery had a leak at the side connection (reason for battery change). If these things are this sensitive then someone should have an answer. Cold wife makes for serious issues!!! HELP!!
  • Okay, I have read all 38 posts under this topic and I am having the same issues. I have a 1995 Pontiac Bonneville SSEi and I just recently replaced the battery. After that, I too only have heat for a few seconds when I turn it on, then it goes out. If I turn the car off and restart it, there is heat again, and then the process starts over. It is currently 6 degrees here in Colorado and I have two small children who need to be warm! Please help me figure this out! It does sound like we are all having the same issues after battery replacement. Keep the posts coming, guys! I desperately need your input! Best Regards, Angela
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,705
    >getting heat before I change battery---I have been having trouble with positive battery cable having corrosion because battery had a leak at the side connection (reason for battery change).

    have you checked your battery cables below the connector at the battery? I assume you have the double cable going to the positive... have you cleaned between them to bright metal? Have you cut down into the plastic convering the copper cable to be sure the corrosion hasn't eaten into that part as well? I have read about people having the battery acid eat into the cables. I have even heard an extreme case where it wicked through the cables down tot he other end at the starter...

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  • Hello. I'm not sure if this information was for me or the other guy... but I changed my battery because it was just weak. I had several garages test it and tell me it was weak and wouldn't last me the winter. Then one day my car wouldn't start. So, that's why I replaced it. There was no leakage or corrosion present. This is so frustrating. It seems everyone is having the same problem with this make and model--you would think there would be recall information out there somewhere. Thanks, Angela in Cold Colorado!
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