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Pontiac Bonneville Heating/Cooling Problems



  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    Why would you replace the blower motor? If it runs on the 3 lower speeds, that means the fan motor is okay.

    Notice there is a separate circuit for the highest speed due to the high current draw. IIRC it has its own fuse in the relay center under the hood. AND it has its own relay. Either of those may have failed. The relay is in the relay center under the hood.

    If you are able to do some electric troubleshooting, test for power on the purple line to the blower motor when the fan switch is on HIGH and the key is ON. You probably are getting 12 volts on the other 3 speeds and then when you switch to HIGH, the voltage drops to zero.

    The cover for the relay center comes off easily. I do not know if there is a diagram in it showing which large fuse goes to which circuit. You may have to test each of them for 12 volts on both poles.
  • Thanks for the help I can definately do a voltage test to the blower motor,,Is the motor under the dash or under the hood? Or should I just check it at switch?? Thanks again WM
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    Blower motor is on the firewall center behind the engine. It has a round cover with 5-7 screws holding it in. Follow the leads from the motor up to the top of the air passage that carries the air from the blwoer motor.
  • Thank you again it was the fuse and its working. Now Im having trouble with the engine shutting off intermitent. I think it may be the ignition switch because I can wiggle it and it will come back on. How does the switch come out, do I have to pull the steering wheel or is there an easy way to change it,,thank you again . I'm a motorcycle mechanic and working on cars tends to make me crazy
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    edited April 2012
    The ignition switch itself is on the top of the steering column under the dash. It's linked to the lock cylinder at the top by some kind of rod. Many people think it's up at the top with the lock cylinder.

    Several H-body posters have had problems with the switch. Check for it and look for a 5% discount code that goes into the "where did you hear about us" box.

    To replace must not be terribly difficult from what folks in Pontiac forums have said. That's as long as you can get your body in there between the door frame and the seat or lie upside down on the seat and hang over down onto the floor. I worked under there on the diaphragms for the HVAC control valves, but I didn't check on how the ignition switch looked.

    Part #80
    I suspect you need to disable the air bags to do this.

  • Hi,
    I have a 96 Bonneville and got the a/c fixed a few summers ago and then it went out again the next summer. I don’t want to dump a ton of money into it but it allows heat in on the floor board all the time. When i turn the blower on i can switch between floor, vent, and defrost, but when everything is off heat pores in from the floor board making summers miserable. What can i do so that when the unit is off no air comes through any port?
  • Hi,
    I have a 96 Bonneville and got the a/c fixed a few summers ago and then it went out again the next summer. I don’t want to dump a ton of money into it but it allows heat in thru all vents, floorboard vent, and defrost at all times. When i turn the blower on i can switch between floor, vent, and defrost, but when everything is off heat continues to flow in thru all vents though the blower is off. Please help!!!
  • I have a 96 Bonneville with 200K milage and have been experiencing the heat issues that evidently many other bonneville owners have suffered. (i.e. the system closes the blend door after about a minute of operation and only cold air comes out after that).

    Reading through all the various discussions on this particular issue (and trying all the various solutions offered), I've come to the conclusion that it's something that is a) quite common to this particular heating system, and b) even if I replace all the electronic parts (have replaced the "head unit" already), there's no guaranteeing this won't happen yet again.

    So, my question here is simply how do I go about disconnecting the actuator motor (hopefully without damaging it) to where the blend door stays in the "heat position"? Any pictures would be GREATLY appreciated!

    Thanks in advance for any and all help offered!


    Tom, aka Cold in Allentown, Pa :(
  • By the way, just so we're on the same page so to speak, this is a picture of the dashboard...

  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    Most likely your actuator has had a gear inside crack which reduces the pressure fit it has on the axle which extends out of the actuator to actually push and pull on the rod to the blend door.

    The Buick has easier access to this actuator than the Bonneville due to a different design of the dash. Some had pulled the glovebox door forward so they can see through to the top of the heater box or removed the door. There is a view to the rod which has a brace rod in the path but there is a hole in the brace allowing a view of the rod. They have actually ducttaped (IIRC) a clothes hanger wire to the rode to be able to manually adjust it, i.e., keep it from moving on its own.

    The actuator can be removed by two screws and disconnecting the electrical connector, but space is tight. Use methods to avoid dropping the screws or losing the sockets if they come off your wrench.

    Here's a link: link title
  • Thank you VERY much! The link you provided gave me the clue to look through the inspection hole behind the glove box...


    The actuator rod is (barely) visable through the left (drivers side) hole which I circled in red.

    Here's a close up, although, I couldn't get my camera to focus on the rod itself.


    It was a simple matter to take some bailing wire, loop it around the actuator rod end, pull it towards the passenger side of the glove box (which opens the door for heat evidently), and tie it off. That will keep my wife (not ot mention my marriage) warm for the winter. :)

    To actually get at the actuator motor looks to be a real challenge and if my 200k Pontiac makes it through the winter at all, MAYBE I'll attempt to replace it come spring.

    Thanks again!
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    I took the slipping actuator off my leSabre and used superglue between the white nylon gear and the gray plastic axle to hold it. I figured if it didn't hold, I just remove it again and replace. But the car has nearly 200,000 miles and I never know how long I'll keep it.
  • This is great timing! My 96 Bonneville SE has 135K & has the same post battery replacement/ACC issue as mentioned by "tgonya". I have just replaced the thermostat & heater issues not fixed (wish I had been on here 1st). The dealer diagnosed it as the A/C Programmer & $700 for the part just today. Not going there! Will try the Air Mix Actuator recommended by "imidazol97" & pictured by "tgonya". Thanks a bunch guys! Will let you know the outcome.
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    If you do anything that disrupts power in your car, use the key ON and turn the HVAC controls to OFF and let the unit shut down. Many people think that when the unit is left mid position and then power is restored it breaks the gear or forces a slipping as it does the startup movements to max heat and then max cool to locate the positions for the computer. This may only apply to the auto control unit, but I'd shut down the manual unit too to protect its actuator.

    I'm really glad that something I've learned from the past adventures with my H-body and reading other's posts has helped someone here. I appreciate it when someone comes back and says it did help.
  • Hi, I've owned this car since new. A couple of years ago the blower started working intermittently. I would set it and it would come on when it wanted to. I have noticed that it would seem to speed up as the engine RPMs increased. That makes me think vacuum leak. I just put up with it, but now it has it has pretty much ceased to function, though it did come on last weeks for a couple of seconds. I had frost on the windshield so I had it in the defrost mode. Eventually, the warm air rose on it's own and partially cleared the windshield. I don't think I have a heat issue, just getting the fan to work. Does anyone have any ideas?
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    What kind of HVAC system do you have: manual or automatic with digital readout.

    If it's the digital readout, you have a blower speed module that can fail in strange ways. Or it could just be the blower motor is failing. The motor is about 5 screws on the firewall on the back of the engine compartment.
    The blower speed control module is above the motor sitting down into the air path for cooling.

    The Relay Center above that is held in by two screws and can be raised if they're removed for easier access to the two screws hold the BCM in place.

    If you ahve the manual system it's most likely the blower motor. Intead of the module, the manual system has a resistor pack for changing speeds.

    The motor can be tested in place with a fused lead from the battery to the purple wire. You have to also provide a ground for the black wire.
  • I have the auto digital as pictured in Post #221. So, if the motor doesn't work with the test lead, I'm looking at replacing the blower speed control module? Are these parts available at most auto supply stores?
    Thank you very much for your help. I'm going to get on this this afternoon.
  • imidazol97imidazol97 Crossroads of America: US 25 & US 40Posts: 19,422
    > the motor doesn't work with the test lead

    No. If the test of the motor using a fused power wire from the positive battery terminal to the purple wire and a ground to the black wire makes the motor run just fine--at full speed--, then you _probably_ have a blower control module problem.

    They are available from, and various box stores, along with the recycling yards. Depends on how much you're willing to fuss over it from recycling, such as the pick-and-pull yards.
  • 1howard1howard Posts: 1
    edited February 2013
    I am amazed how long this thread has been going. This has to be a design weakness in the Pontiac. I had the same problem but it could go either way, hot in the summer, cold in the winter. I didn't want to work on the problem by having the dealer throw my money at it. The fix I show has been in place for at least four years (just checked, can't believe it was May 2005) and almost always works. I concentrated on the nylon pivot for the control arm and use that to move it back and forth from hot to cold. When it is working changing the temp from hot to cold you can see the arm moving if the glove box door is open.

    I upgraded the arm to metal from wood several years ago. There are times it jams to the right (cold) and I don't want to force it. Usually turning the climate control off completely will allow me to move the arm. Fortunately the car is narrow enough to reach the arm while driving w/o dropping my cell phone, spilling my coffee or losing my donut. :-)

    Here are some pictures and description that may help you understand what I did, but not necessarily motivate you to do it.
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