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Pontiac Bonneville Heating/Cooling Problems



  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    I think you have bad vacuum in the motor or a leak under the hood.

    Check the vacuum hoses around the motor? Do you hear a vacuum leak?

    Check the reservoir behind the front wheel underneath. Cracked? One line on it good connection? When you shut off motor and go to it to pull off, there should be a strong vacuum whoosh for 15 seconds or so when you pull off the hose.

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

  • jd0754jd0754 Posts: 3
    Thanks a bunch, I'll keep you posted, I am going to have guy that's a Mr. Goodwrench at a dealership around here look at it hopefully this weekend. One more question though, when I finally get the air to come out of the center vents when you shut off the engine it closes the door to the center vents immediately so when you restart the car you will have to wait another 5 minutes for the air to come out of the center vents again, caused from losing vacum?
  • Greet'ins all!
    2002 dual control..excellant AC from driver's side...FULL BLOWN HEATED air from passenger vents.
    All fan speeds operational
    All modes operational

    But the AC just cant quite do its job fighting with the blistering hot air coming from the passenger vents...even shutting the vent louvers off, the heat still forces its way out some and also out of the windshield defrost vents.

    Not a freon problem it a bad control? Or can it be a vacuum hose / actuator arm?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    There are several actuators on the driver's side of the HVAC box. You'll have to try moving different controls and watching for the axle on each one to turn. I'll bet you'll find one isn't moving. It might be stuck--or-- dead.

    There have been a few reports of failed electric actuators all along with these H-bodies.

    I can't tell you which actuator is which function. I'll have to see if I have a labelled diagram. My guess is start testing for movements. You'll have one for recirculate, mode choice, driver's temp, passsenger's temp?

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

  • Thanks, that was it! FIXED IT! After removing the glove box I found a small moterized gear reduction box was stuck...I removed it and manually rotated a shaft that must control an air mix door. I could manually go from full hot to full cold easliy. After opening this small moter/gear box...abut the size of a cigerette pack...I was able to lube and it started working again..the dual system works just great for now!
    ...reading through all these posts really helped!
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    Great! Thanks for coming back to post what worked for you; that will help others know what to test or look for if they have a problem.

    >I could manually go from full hot to full cold easliy

    Was that on top of the HVAC box?

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

  • breez22breez22 Posts: 1
    Ok i read through all the post's, and i just got my car back from my mechanic. i've gotten some great info on this my blender door was stuck on the hot side. The mechanic moved it to the cold air side. I have not tried much but this gives me some great ideas. I would like to know does the actuator actually rund the blend door? Are the 1999 models actuator in the same spot on to as the 1997 that the pictures were on? Thank you in advance.

    Have to thank you for the advice. Got the freon topped off and the system is working great.

    Still working on finding the leak (had a dye included with the top off just to see if we can find it), but worst case, I can spend $30 topping it off couple times a year. Definitely worth it, and better than spending a bunch of time and money on suggested fixes from the repair shop that sounded like a whole lot of work for nothing.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    only if you find an actual leak location would I consider repair. Then I'd do it only if the leak was more than once per season. There are some sealers that I read about people putting into their system as a do or die.

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

  • ok ill try to explain this the best i can when you start the car sometimes the ac will work great then out of the blue it will start blowing warm air sometimes when it does that you can put it in netural and rev it and it will blow cold but only sometimes
    sometimes it will switch by itself to ac off and pushing any buttons on the switch will not help it just stays ac off now when it first started this you could push the seat memory switch on the door and it would turn the ac back on but now it wont now its like if it is on its on and it may stay on for a second or untill u shut the car off then again it may just switch to ac off and start blowing warm air again to no avail it now seems that if it starts blowing warm air and the ac off is not lit and you put it in nutural and rev it it will make it say ac off and the door switch now seems to do nothing for the help of turning it back on as well im just not sure where to go with this problem i have a very extenstive background in autos but nothing like this have i ever seen please help soon
  • oh also not sure if this is related but the speedo stopped reading correctly as well sometimes it is just off sometimes it will go to like 20 or 40 and stay there other times mostly it will just stay on 0 however the heads up display reads correctly all the time all other gauges seem to be fine just the speedo the odomittor and trip all work yesterday my wife drove it to work it stayed off almost all the way it did switch to ac for like 5 mins after she shut the car off and started it but then the ac off lite came back on and stayed that way till she started it 12 hours later on the way home??
  • 2000 Bonneville SLE
    Dual Climate Electronic controls
    I have read through this thread a few times and have tried several things. First, I topped off the freon but to no avail. Then this afternoon I checked the bleed doors and they were fine. I found 2, one on either side of the main console in the back. I found where they were, then I played with the thermostat to watch how the actuators reacted. I then removed the actuator units and manually turned the doors, just to double check they were opening/closing the door to the min/max.

    So now I'm stuck. What else could it be?
  • I have a 97 Bonneville Se with an acceleration issue related to the A/C-Heat blower vents. When you are running either a/c or heat and accelerate, the blower vents on dash switch over to the defroster vents until the acceleration stops. It then goes back to working normal. There is no issue with hot changing to cold or cold changing to hot, just vent change over. This system is a standard turn dial controller without digital functions. Any suggestions? I believe it is a vacuum issue but cannot seem to figure out where. I even had the dealer charge me for 6 hours of labor to say they could not find anything. Needless to say, I do not use that Pontiac dealer for anything anymore. Any help would be appreciated.
  • I can give you a suggestion in regard to the change due to acceleration. Your programmer (which does nothing more than select vents) works off of pneumatic pressure (or vacuum more correctly). It gets its vacuum from the intake manifold. Therefore, when you accelerate, manifold pressure drops. Now, this is the way the system works everyday in everyone's car. Why this loss of vacuum is affecting your system more than it should be is a mystery to me, but its the only thing I can think of. Try tracking down the vacuum hose and see if there is a partial leak. My hose was on the front of the engine on the driver's side, and mine was leaking too. On my car the hose went thru the firewall on the driver's side.
    Maybe this will help. Good luck.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    Ralph's on the right track.

    Your unit uses vacuum to control the diaphragms that are inside the car. Each of these diaphgram motors is a rubber/plastic diaphragm that can tear or crack and leak air in which makes the vacuum the programmer (switch that controls the vacuum) ineffective. There are four of these on the driver's side of the dash. There is a plastic cover under the dash taht comes off with a few screws.

    You might have a leak in one of the diaphgrams, but you say it occurs in AC or heat. Those use different diaphragms.

    So back to basics. Your tube for the vacuum comes off the top of the motor (take off the plastic gray cover over the top by removing the oil filler tube--grab with hand and twist to unscrew the spout not the cap). Then look on the back firewall for the 1 ft diameter brake booster. Follow the big tube from it to the motor. Right next to that is a little plastic tube coming out. That's your vacuum line to the inside.

    That line may be cracked, aged, rotted and leaking air in near the motor due to heat.

    Follow that line to the passenger side (it goes in a bundle of electrical wires) and you'll find a connection at a Y where one line goes to the inside of the car and the other goes to the front of the car under the fender to a small plastic tank. That tank may be cracked and leaking in air.

    There is a one-way valve in the line from the engine. It goes in a bundle up behind the alternator then the plastic line goes up over the accumulator and downward behind the wheel well. The valve is right there in a rubber section of the line. It in the line toward the motor and keeps air from going from the motor into the passenger compartment side. That valve may not be working any longer. That would let lower vacuum from the motor add air to the passenger side when you accelerate and the motor loses vacuum because you've opened the throttle plate wide.

    There have been a few comments about leaking air around the upper intake manifold where it bolts to the metal lower intake. But you don't mention any rough running at times or fast idle, which would be symptoms if the upper were twisting and leaking air in at certain temperatures.

    Something to try is run the motor and turn it off. Then leave the key ON and push buttons to select different settings on the HVAC unit. With my 1998 I can do that for about 20 seconds or more of listening to the vacuum motors pull the different plates in the box to change the air flow. If yours does not retain vacuum in the storage tank under the front fender enough to do 5 or 6 change cycles that might indicate a leak in a tube after the one-way valve such as the tank at the front or a part inside the car.

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

  • cmazeocmazeo Posts: 6
    Just bought a 2000 bonneville from an auction and the hvac doesnt work at all. No display in the window. Buttons dont light up. Checked the fuses under the hood and under rear seat. None are blown. Had a mechanic scan but no error codes for the hvac. Gotta few other problems too but this is the main one. Thans for any help.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    You may not have found all the fuses. The head unit may not be working. It may not be plugged in. Please wait and I'll check my 03 service manual for fuses tomorrow morning. Hopefully it's just a fuse.

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

  • cmazeocmazeo Posts: 6
    ok thanks, The interior lights on the unit do come on but not any of the lights on the buttons ( defrost, auto, rear, display... etc) . You mentioned the head being unplugged .. not sure what the head is but if it was unplugged would it affect the interior lights on the unit ?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    In the rear fuse block,
    #33 HVAC
    #34 Ign 3
    #25 Pass MDL

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

  • cmazeocmazeo Posts: 6
    #33 and # 34 checked out good, #25 has no power feeding the fuse at all. Thanks
    ..............also I pulled the unit out and checked the connector in the back where it slides in for power using a grounded probe light and I had pwr on about 4 of the leads on that connector. That unit is hvac unit is really flimsy.. I think I'll try and find one at the salvage yard and replace it .. maybe that's the problem.
    will let you know ... thanks
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    You might want to check ebay and other used books for a Helm factory service manual for your Bonneville. Helm does the authorized manuals. has them available new. It sounds like you might get your use out of it troubleshooting.

    You said your car was the automatic temperature control... because you said you couldn't see the readout. I didn't check the manual unit.

    Odd the passenger door module wouldn't have power. Do the windows and power locks work on that door?

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

  • cmazeocmazeo Posts: 6
    No, the power lock or window doesnt work. The window was stuck in the down position and I ended up powering up the motor in order to get it to go up. Will be checking on that service manual though.. thanks.
  • cmazeocmazeo Posts: 6
    Ok I screwed up. I thought I was using the ground post checking for battery on the fuses but actually I was using a positive post near the fuse panel. I rechecked the fuses the correct way with the car running and not running. Fuse # 33 and # 30 had no power car running or not. I traced # 33 and found the wire (brown) was spliced into 2 other brown leads. I tied a hot lead to the other brown leads and started the car. The hvac unit works fine. The blower motor has a loud hum and weak air flow but at least I am getting close to fixing the problem. Thanks !!!! again for your help... Checked on ebay for manual... I'll be buying one from there. Thanks again.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    >Ok I screwed up.
    Welcome to the club. At least you didn't "break" anything being backwards. I tend to break things that weren't already a problem.

    This is what the factory service manual looks like and it is two manuals. This one is the Helm manhal.

    try searching for combinations of factory, service, bonneville, pontiac, and see if you come up with some that aren't completely labeled.

    Helm manual for GM

    Try searching for combinations of factory, service, bonneville, pontiac, and see if you come up with some that aren't completely labeled.

    here's one under 2000 bonneville service manual (no word factory) and it's $5 current bid 20 hours to go and $15 shipping.

    link title

    here's one for $9.99 and 9.99 shipping bid current.
    link title

    Make sure both manuals are there.

    I didn't look under Pontaic without the bonneville word...

    As for the circuits, I think studying the manuals will help.

    Check the cabin air filter intake for the blower motor. If there's a filter it may be stopped up. See if the blades for the fan rotate freely while you have the filter out (you can easily see the blades when you're servicing the cabin filter out on the firewall.

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

  • cmazeocmazeo Posts: 6
    I ordered a set of service manuals from ebay today.... cost about $ 27 with shipping. Should be here in a few days. Thanks again for the help. Will let you know how everything turns out. There are a few things wrong with the car .. so this should help.
  • rockohrockoh Posts: 2

    Man, you gave me the whole breakdown. Thanks dude, and I will let you know how it works out. I have been kind of busy so I just got a chance to look at the website again, but I am glad I did. I'll get back to you after my investigation.

  • I own a 1997 Bonneville - it heats the inside at start up - couple of minutes later - it turns on the air - two mechanics are left shaking their head - while saying I have never seen it do this before, have you - what was the cause?
  • I own a 1997 Bonneville. My heating does not work correctly since I had a total loss of power. I had removed the battery to charge it then put it back in. Since this happened I had a technician test the battery and charging system, both tested okay. He said the loss of power was caused by a badly corrodid battery terminal which he replaced. The control is temp controlled and when I set it for heat it just blows cold air. Some times shutting the vehicle off and restarting it corrects the problem. The other thing I have noticed is the Temp indicator flashes 2 to 3 minutes then stays on solid, this happens every time the car is started. Is there something that needs reset to correct this problem or is this an indication of some kind of component failure? The technician could not find anything about the flashing temp indicator and suggested I take the vehicle to a dealer for service.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,072
    My guess from a distance is that when you disconnected the battery, you did not turn off the AC unit first by turning the key ON and then shutting off the AC with the off button.

    You might try moving the temp all the way cold for a minute and then put it all the way hot for a minute and see if it's able to recalibrate itself.

    Otherwise you may have a cracked actuator gear. The actuator is a little electric motor that moves a lever that is the temperature blend door inside the heater box. If the gear is cracked, it slips on the axle. Therefore the programmer box doesn't know that the arm isn't moving even though the electric motor thinks it is moving it.

    You may take off the plastic panel above the passenger's legs. Take off the glovebox door by removing screws along the bottom hinge. Then watch the white plastic arm sticking out of the heater box connected to the actuator motor on top of the heater case.

    On Pontiacs those actuators are supposed to be difficult to get to the two screws holding it on.

    There may also be an actuator moving an arm on the bottom of the HVAC case that is from an actuator that's inside the programmer box. Does your car have separate controls for passenger and driver temperatures?

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

  • I do not have seperate controls for driver and passenger, just the main control on the dashboard above the radio. I didn't know that you need to shut off the AC before removing the battery. I will try the recalibration first and let you know if that works? Thank you for your response to my problem.
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