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Pontiac Bonneville Heating/Cooling Problems



  • I did try the calibration you suggested and it's not working. Although I discovered if I follow the calibration you gave me after the thermostat starts to register it will blow warm air and get warmer as the engine temperature rises. On occaision this method doesn't work until I shut down the car and restart it. Could the failure of the actuator arm have caused the vehicle to shut down and loose all power? I guess the next step is to look at the actuator arm. Will get back to you after I get a chance to observe. Thanks again for the tips.
  • My wife has a 98 bonneville se and the heat is not working. It worked fine last week but the other day it would not come on. I played with the knobs and switched it over to air conditioning and all of a sudden it started to blow even switching back to heat. Defrost, floor, upper body, they all worked. Now this morning it would not work no matter what I did. I thought first maybe fuses or relays.Even a heater core but I had one go out in a berretta and the floor was soaked. You can hear it pressurize when you switch it from defrost to heat but blows nothing. What could be the problem?
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    A question. Are you saying the blower motor does not work--there is no sound of rushing air and you can't change the speeds and hear the motor change?

    If so, there are two possible problems besides a blown fuse.
    #1 is the blower motor is dying. Try tapping, gently, on the bubble shape housing for the blower motor on the firewall behind the motor with the ignition on (engine off) and the blower speed set to blow. If the vibration starts the blower, then most likely you need to replace the blower motor. AFtermarket stores have them. It's about 5 screws and a connection to replace.

    #2 is that the blower control module for the automatic speed system or the resistor pack for the manually controlled speed system is acting up. The automatics are a power transistor that often acts up by varying speeds from normal, not working, staying on after car is shut off. It's called a blower control module and is above the blower motor on top fo the air channel the blower feeds into on the firewall. The Relay Center above needs two screws removed at the ends and it has enough slack in the wires to move up a couple inches and allow better access to two screws.

    #2 for manual systems is the blower resistor pack has one of three resistor coils blown. OR, important, the contacts for the electrical wires are burned. Try wiggling the wires around the resistor pack with the blower turned on. See if it makes contact there. The blower resistor is same place the automatic control module is located.

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

  • I also have a 97 Bonnie and currently experiencing this problem - and not for the first time. It has happened before and this time was brought on by replacing my dead battery. When it happened previously, it went away all by itself. Talked to the service guys at local GM dealer. It was explained there are 3 computers that ccontrol HVAC. One of them has not reset causing the temp to flash. When it resets, heat will return.

    I have found out Pushing buttons at power up doesn't help, taking the temp from max to min to max to min doesn't help, you can't see the HVAC codes on OBDC unless you have a special HVAC diags computer and A/C will work normally.

    Unless you want to spend mega bucks on new computers, you'll have to wait it out and carry a few lap blankets in the car.
  • HELP ME!!! Bought a used digital control unit, put in new thermostat. Blower works, no leaky heater core.........NO HEAT

    18 degrees and no heat and add 2 boys under 5.......and their Mom. I need help............and heat
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    Is the engine heating up fully? Is the temperature gauge going to the normal setting for full temp? The thermostat may not be closing. AFter driving for 10-15 minutes, the upper radiator hose should be too hot to hold for more than a few seconds.

    Then are both radiator hoses fully hot with the blower motor running? If the core is clogged with crud from the coolant in a radiator that has goop from not being changed enough, the flow through the core may be less than enough to heat the air when air is really cold. If one hose is cool, that may mean the flow is low and the blower air is taking all the warmth out of the coolant.

    Or the electric actuator may be not cycling for full heat. I assume you have a manual control system without digital temp readout and you do not have passenger temp control.

    From what I can tell from forums, the blend door for how much air goes through the heater core on a Bonneville is controled by the upper actuator, the red circle in this picture. The white arm to the left of it is the actuator arm. Some actuators lose calibration and come crack a gear inside so they slip.

    Did you change the battery recently? Did you turn off the heater with the key on so that it Parks before disconnecting the battery? IF not people seem to report problems afterwards.

    Some have dropped the glovebox door forward and through that opening say they can see the upper blend door arm. They attached a coat hanger to it and used that to move the blend door to HOT, until they can replace the broken actuator. You can take off the plastic layer under the passenger side of the dash and look up to see the actuators.

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

  • Thanks to whomever said to set the heat at 60 and wait til it flashes and then adjust up. This is working. With 199k on it, I don't want to spend any more than I have to to keep it going.

    Appreciate the help. :D
  • Ok, hello all. I think my bonne is a 98. Its an automatic tanny, no digital temp read outs for hvac and not dual temp control.

    the first issue is that sometimes the fan does not come on. Turning the car on and off, and turning the fan speed controls does nothing either. SOmetimes when i'm driving it will come on, and sometimes if a shut the door hard enough it will aslo come on. If i read through this forum thoroughly it is likely because of a loose or flattened connection. As a temp fix it says i can use my toe to tap against the under part of the dash close to the firewall, and on the passenger side. Can someone confirm this for me. Also, what is the permanent fix for this?

    2ndly, the hvac system does not seem to put out the proper temperatures. In the winter it will warm up the car, but only after about 20mins or more and the air coming out is warm, not hot. Same is true in the summer with the AC, it will be slightly cool, but not enough to cool the car.

    I'm a novice as far as car repairs go, but am good at following instructions, and have a father who is willing to give it a go as well. I dont think it is the actuator because i don't get hot or cold, unless its possible for the acuator to be stuck in the middle?

    Any help would be most appreciated.
  • Hey, Just wanted to get your opinion on my similar problem...

    98 bonnevile se, changed the battery 2 months ago, 1 month ago heat started to act funny...I can start the car in the morning(letting it idle for like 15 min) and it will blow hot air and heat up, but then when I get in and drive the air goes cold...also if I don't start the the car and just drive it, it never gets warm...

    The blower works, tried the resetting the knob trick with no change...

    Also sometime when I slow down the battery needle on the gauge drops like 3-4V and the oil presser gauge drops...not sure if this is a similar problem or what...

    car has 150K on it and would like to get as much out of it as a in upstate NY I need the heat...any suggestions???
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    The question is about the motor and thermostat? Is the motor being forced to heat up by the thermostat? After 15 minutes of driving with ambient above 25, the upper radiator hose should be too hot to hold more than a few seconds with a bare hand.

    Then both radiator hoses should be hot even with the blower on high. That tests if the flow through the radiators is open.

    If the thermostat hasn't been replaced for 3 years, I'd change it to be sure it's trying to stay closed to force the motor to heat up. If it's cold enough outside, the engine may not be able to stay at 195 losing heat to the air from the motor and through the heater core. You might try partically blocking the radiator with something to slow down the air flow.

    Then you are ready to check to see if the blend door is putting all the air through the heater core. You'll have to check the movement of the electrical actuator on top of the heater box inside the car.

    But the odd thing, is that many of these problems follow a battery change where people don't turn off the heater before turning the key to OFF so that it goes into park. Or something related.

    Your car is a manual temp control from what you said or didn't say: it doesn't have a digital readout?

    You really need to get under the dash and watch the movement of the actuator linkage on the heater box that moves the blend door.

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

  • I bought this car cheap because the former owner was sick of driving a cold car. Read this forum and went right to the vacuum connector and removed it. Spliced those vacuum lines back together using the recommended 1/8th inch hose pieces as was discussed earlier and VOILA!!, everything now works as it should! Replaced a few rotted vacuum lines under the hood as well.

    Once pulled apart the nipples in my factory connector were found to be very soft and apparently had caused all of this car's ac/heater problems too.

    Thanks, guys!

    Tom in Michigan.
  • kevin27518kevin27518 Posts: 3
    I had the problem with my display flashing. I also had change my battery during the past few months. I have found a simple fix!

    1. Locate your outdoor temperature sensor (open the hood and look down in front center of the radiator)

    2. Disconnect the wire from the sensor. It just unplugs at the connection.

    3. Start the car (no outdoor temp) turn the ECC on the inside temp flashed as it did for me before.

    4. turn the car off after about a minute or so.

    5. Reconnect the temp sensor and start the car and GOOD GOD no flashing light and the heat and a/c works!!!

    I can't remember if I turned the ECC off before turning the car off, but I think I may have. Try it both ways if you need to.

    It has been about 2 months or so since I did this and it's still not flashing.

    Tech told me that you have to have the ECC off when you remove the battery so that this does not happen again
  • I dont remember when it all started but my bonne wont put out any cold air. Ive got adequate r134 refrigerant but still no cold air. When I turn the A/C on and turn the temp all the way down I can hear the compressor kick in. My temp display flashes on the ECC also. My mode controls aren't working properly either, seems only to come out at the floor and defrost vents. One last thing, when I travel on the highway everything could be off and im still getting hot air out of the floor vents. Really sucks in this hot weather!
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    Couple of questions are have you checked the flow of air out the defroster to see if that air is COLD after it's run a while.

    Have you checked to be sure the compressor is turning in the middle part while the motor is running and AC controls trying to engage it?

    Have someone switch the AC on while you're watching that compressor belt running and see if the middle part with the three strips starts moving?

    IF so, are the tube going into the AC unit back by the firewall both cold? With the outlet one to the dryer unit colder than the inlet? IF so you have a good charge of freon.

    Check the front of the firewall around the heater blower motor for broken plastic that's letting in air from the hot engine compartment. Some have had trouble with the plastic there breaking from age and heat.

    Your AC digital readout is flashing for some reason. Most of the time it's low freon OR it's a bad actuator motor on the doors inside.

    I'm betting freon. Was the compressor running when you measured the freon pressure on the low side?

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

  • I ran it for awhile and still heat coming out. I haven't visually checked the compressor but the oil pressure gauge goes up when I hear it kick in. Yeah the a/c lines get cold. cold enough to condense water on them. Ill have to check the plastic cover later because my wife took it to work. Where and what does the actuator motor do? The freon pressure was about 50 PSI at an ambient temp of 85 degrees.
  • kevin27518kevin27518 Posts: 3
    edited May 2010
    Try the fix from message #163 and see if that helps
  • tried it.... no luck.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    edited June 2010
    If you have a dual temperature controlled system, you have two actuators, one on top of the HVAC box for the passenger and one in the programmer that sits next to the HVAC box. I would expect one of them to be working...

    But. Take off the hush panel underneath the dash on passenger side and take off the glovebox door, if you can.

    The bottom one, a white arm of plastic snapped onto a rod with grooves, should be all the way in to the left.

    Top actuator and bottom actuator arms circled...

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

  • i have a 98 sse...and ive been experiencing electrical problems for some time...bout last winter i had no heat due to a bad blower motor moduel... i replaced it with 1 from a junk yard and it was working fine...but i would always hear a kind of vaccum noise coming from the passenger side even when the heat or ac was off...and about a few months ago i noticed that my battery was being drained... ive replaced my battery and my alternator is excellent...i have to unscrew the negative on my battery daily so it doesnt die on me...and i can still hear that vaccum noise...especialy when i rescrew the negative and start my car...does anyone know what the problem may be...i would greatly appreciate any advice possible
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    Is the motor running when you hear the vacuum noise?

    Take off the underdash cover and actually listen closer to find the source to see if it's the black tube coming through the firewall to the right.

    If it makes the noise without the motor running and with the key on, see if one of the two actuators that are electrical is running. They have a little electric motor that moves the arms to adjust the vents. The top one cracks a gear and the motor might be running trying to adjust. BUT it should turn off when the key goes off because there's no power to it. I'd have to check the factory service manual but I believe that's the case. What happens if you press OFF on the AC controls while it's making the noise?

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

  • greasemokeygreasemokey Posts: 2
    edited June 2010
    when i press the off button it goes off...but i can still hear the vaccum noise...i have the electronic temp control so when i start my car it flashes on and off...and when i turn my car off to run into a store or something and come right back..when i start my car i hear the vaccum noise_my temp control is flashing_and my battery is some what drained...just might have to pay that $85 per hr to see what the problem is...damn
  • nocargtxnocargtx Posts: 5
    Got 98 bonneville digital ac controls and ac works but air comes out only two places--windshield and floor. Changed dash control and vac programer and still same issue. Any ideas???? Is there a default and air comes top and bottom and no where else when there is a problem in the system?
    Thanks for any help!!! :(
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    Let me remind others to diagnose the problem before replacing parts.

    Three possible problems:
    Bad electric controls from dash controls?
    Bad plastic connector on programmer box?
    No vacuum from under hood?

    The default for no vacuum is that the doors in the heater box are left in defrost mode (which bleeds some air to the floor) so the windshield can be cleared for safety.

    There is a common problem with the plastic connector on the corner of the programmer in cars of your era. The plastic softens and sucks shut when vacuum goes through each of the 5 little tubes. There was a black plastic nipple inside the connector that is often blamed.

    Bypassing that connector with little tubes to carry the vacuum from the internal plastic tubes to the external ones (different colors in some cases) will fix the problem.

    I have read a couple people with no vacuum from under the hood. The plastic tubing starts next to the big brake booster hose on the back of the upper intake manifold. There are soft rubber connectors, people said, connecting the hard plastic tube. The soft rubber vacuum hoses can deteriorate after 10-12 years of heat and aging. Check the connectors for cracks, hardness, or holes. There will be connectors at the upper intake, at the T just in front of the accumulator for the AC (take off the relay cover over the MaxiFuse center), and at the connector on the reservoir under the fender in front of the passenger tire. Check that cannister for cracks. If you pull of the hose, then reconnect and run the motor, removing the hose should give you a good whoosh as air rushes in to fill the vacuum.

    If the AC control is bad, most people say it just is obviously dead or crazy.

    My testing for vacuum, was run the engine, then turn it off and leave the key ON. Switch between various settings on the control panel. After a few seconds you'll hear the vacuum diaphgrams sucking in to move the doors. Also you can remove the hush panel on the driver's side, and when you switch the controls, you can feel the vacuum diaphgram move with your fingers on the engine side of the diaphragm. The back of it is open so you can feel whether the thing moved. You'll have vacuum for about only 30 seconds or this if your hoses under the hood are all okay.

    There are 3 vacuum motors. One above the accelerator slowly closes to give recirculated air taken in from above the driver's feet.

    One closes off the floor opening and forces air upward to the dash or defroster openings. This one also has a second vacuum tube. When these are working, it leaves the floor vent partly open for windshield and floor with lots of air to the floor but air going out the defroster.

    The remaining vacuum motor operates a horizontal axis door that closes off the flow to the defrosters; this forces the air out the dash vents because the floor vent is supposed to be closed off.

    To verify that the blue hose to the defroster door was getting vacuum, I switched the hose to another vacuum diaphragm and felt that motor move closed when AC dash was asked for.

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

  • nocargtxnocargtx Posts: 5
    Thanks for your reply--have changed some elements mentioned and also have vac to the junction connector. Did not check to see if connector was open. I have no vac coming out any of the other tubes to the various actuators on the main box. I only know my source of vac to the connector from outside is good and open.
    My main programer box was replaced last year--the lever plastic gears were stripped--it works fine now. Temp changes from cool to hot as it should. My temp light fashes since replacing vac programer.????
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    edited July 2010
    > only know my source of vac to the connector from outside is good and open.

    TAke a long piece of plastic tubing or rubber vacuum tubing. Connect it to the black incoming vacuum and connect it to the blue tube's connector for the dash vents. See if it will pull that diaphgram closed. That would check for full vacuum power in the black line going to the programmer box.

    I know of one person who said they were able to get the plastic coupler apart and open up the holes successfully. I would just jumper it with tubing from inside to outside.

    The only odd thing is you're getting none of the vacuum motors to work.

    >light flashes

    Does your car have a separate electrical actuator on top of the HVAC for the passenger side air blend door? Is that motor stripped or not working? Is it plugged into the main programmer box?

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

  • nocargtxnocargtx Posts: 5
    My car does not have a seperate act. for passinger side--has one program box with act arm at top of box and it works OK as best I can tell. Temp goes up and box switches and goes other way and temp changes.
  • Fixed the dern thing--cut vac lines on the two part connector and connected them with small black hose to by pass factory connection and everything fine--works like it should. Apparently the connector does not seal tight enough for vac not to leak.
    Wife has cold air like it should be and life is better!!!!
  • bahappebahappe Posts: 5
    Could you please provide me a graphic of this because I need to check and probably change one or more of the actuators. IT would be of great help.
  • imidazol97imidazol97 Crossroads of America I70 & I75 Posts: 22,311
    Of what do you need a graphic? The HVAC box showing the upper actuator for the passenger air and the lower which is part of the programmer box?

    What is happening with your car? Maybe that will tell me what you need to check?

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

  • bahappebahappe Posts: 5
    The air works on the passenger side but not on the drivers side. I removed the glove box and hush panel and checked to see if both of the actuators were working and both of them were. I then assumed that there must be actuators on the driver's side. I then went to the driver's side and removed the hush panel. Looked up in there and it appeared that there were 2 actuators in the middle of the console. I looked to see when i turned the A/C and Heat on if the little silver circle was moving and on the actuators. One of both of them appeared not to move either way except when I shut down the car and turned the car back on... When A/C was heat still blowed out the drivers side was still hot and cool on the passenger side. Please advise. I guess i really may not need a picture after all...
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