My car is still like that, I just got use to it so it dont bother me. It blows a warm air after about 15 minutes, on the drivers side. My solution was starting the vehicle about 20 minutes before I go somewhere

So that'* four members that have reported the same symptoms: etalk, 98bonnie, Twister97, and 95bonne. Not an isolated incident. Worth figuring out. It'* gonna happen again.

Can you check to see if both heater hoses are hot when this hot pass / cold driver occurs? Normal operation in winter will be one hose hot, the other just a little less hot as some heat has been removed through the heat exchanger (heater core) to the passenger cabin. If both hoses are hot, the problem is definitely in the ducting. If one hose is hot and the other cold, that would indicate low or intermittent coolant flow through the heater core. That could be caused by low coolant, or a plugged core, or, I suppose, by a malfunctioning water pump.

Do impellers ever come loose from the shafts on water pumps? I've never seen that, but that would cause low or intermittent flow.

Thanks for considering this issue, Bill. I'll check the heater hoses in the morning and post again.

The heater was fine last cold season and the a/c worked fine all summer and does now. The first I noticed this phenomena was a few weeks ago when this cold season started. At first I thought it was just slow warming up, even though the gauge said 190 degrees.

Thanksgiving is when I first realized there was actually a problem. My passenger, who is normally cold-natured, complained about it being too hot at about the same time that I was just beginning to feel like I wasn't going to freeze to death. Her comment led to me putting a hand in front of the passenger vent and being extremely surprised at just how hot the air streaming out of it was. Both of us then made comparisons from side-to-side on the dash vents, defrost vent and floor vent, finding what I've stated here to be fact: cold on the driver side, very hot on the passenger side.

The only thing done to the car regarding any of the heater components is that about six months ago, around June, the upper radiator hose developed a small pinhole leak. When I replaced the hose, I also flushed the system and added new antifreeze. Checked the levels several times afterward, topping it off once. It has never leaked and is still full to where I topped it off six months ago. I also checked the radiator this morning when I checked the overflow and it, too, is full.

The temp gauge hangs exactly where it always has, around 190, except for when it warms up some, maybe 205?, when idling for awhile in traffic. It cycles back down to 190 once moving, which shows that the thermostat and water pump are performing as expected.

I don't leave anything on the dash while driving, so there is no probability that trash may be causing something to stick in the ductwork. Certainly nothing is partially blocking the ductwork. When the fan is set high enough to judge airflow, it seems equal to both sides.

The A/C blows cold out of all vents. The heat mode blows very hot air out of the two passenger side dash vents and cold air out the two driverside vents at the same time. Blows the same way, hot and cold, for the defroster vents and for the floor vents.

Before reading all the posts on this subject, I had considered that possibly a main duct feeds a dual duct that splits the air in two directions, to the passenger side and the driver side, and that the door is possibly jammed halfway open, allowing the heat only into the passenger side. With further thought, this doesn't really make a lot of sense because of two facts: the amount of air flowing when the heater is on is equal on both sides, and the a/c blows equally cold on both sides.

As Twister97 implied in his post, the car will eventually warm up, but it is only from the hot air on the passenger side circulating through the cabin. I seldom drive more than a few miles at a time and the car doesn't "feel" like it warms up at all. (But the gauge says it does

Thanks to everyone for your interest in solving this dilemma. I, like most of you seem to be, absolutely abhor being totally dependant on the dealers and at their mercy.

95bonne

Well, I inspected the 97 dash I have downstairs, pics from the parts cars and a 95 manual and could find nothing that would explain the problem. Over the summer, I noticed that the cold air from the AC was noticibly cooler on the passenger'* side. If I opened up the glove box the passenger'* seat was blasted with cold air and the driver'* side received less and warmer air. I suppose that the restriction of the glove box vents can help equalize or come close to the same amount of airflow in both areas. Since I don't really drive the car in cold weather, I don't have any heater experiences to share that will help any further than already discussed.

I can't seem to find any duct pics of the 97 but here'* a couple from the 93.

was under dash today. there r 2 air doors that r side by side one for driver and one for pass. at bottom of the air box with a little plastic bolt on piece that seperate the 2 . took the plastic piece off. there is a door in each opening that works on vacuum both doors did open up when i move the selector switch. i let car get hot stuck hand in pass. side hole would almost burn u.hole left to it was only warm air . looked up by gas peddle and saw plunger type diaphram not opening big air door that RANDMAN 1 shows in picture as i tried all the selections on the selector. there is no vacuum going to this plunger what so every. traced it back to selector setting controller where there r 4 or 5 colored coded tiny vacuum hoses going to switch. so i hope its just a selector switch that is bad .will get onefrom junkyard tomorrow and let you know . Thanks for all your help . Tim

For the life of me I can not understand what the heck you are saying.

Just for clarification, air temp is controled electrically by the air mix actuator and the air flow direction is controled by vacuum. There should be 5 different colored vacuum lines:

1) Violet - source vacuum. Comes from the engine, through the firewall and in to the HVAC programmer.
2) Orange - outside air/recirculate. This is the line that goes to the diaphragm pictured above. This should open and close as you select and deselect Recirc on the control head
3) Blue - defrost control. If no vacuum is present in this line, the air is directed to the defrost (windshield) vents. If there is vacuum present, the air is directed to the dash vents.
4) and 5) White and light green - bi-level control. This controls bi-level air flow such as defrost and floor or dash and floor operation.

I know the one he'* referring to. And on the 95 I had there was a receipt from previous owner about air mix doors..but that was cold all the time.

Keep us up to speed...this is a new one.

Great job, Tim!

This may be wrong, but what I understand 98bonnie'* message to say is that under the dash, he found that there are indeed two air passageways on the main air duct. One is for the passenger side and one is for the driver side. He removed a bolted-on piece that separates the two passageways and found that each passageway has its own vacuum-controlled door. Both doors did open when he moved the selector switch.

He let the car get hot and stuck his hand into each passageway. The passenger side was very hot, but the driver side was only warm. Up by the gas pedal he saw a plunger-type diaphragm that was not opening the big air door (shown in Randman1'* picture) as he tried all the settings on the selector switch. There was no vacuum going to the plunger at all.

He traced the vacuum hose back to the selector switch and found 4 or 5 tiny color-coded vacuum lines on the switch. He'* planning to get a selector switch at a junkyard and will let us know if it works.

Based on Tim'* input, I just talked with our local Pontiac service man. Why was I not surprised when he said that "we" had never heard of this problem, that it could be one or more of two dozen things like vent-doors, switches, actuators, wiring, etc? Of course I would have to leave the car with them forever so that they could go through it and track down the problem (@ $65 an hour?). He also said that the heating duct system was electrically controlled, not vacuum

I talked with the parts man and he said that the selector switch (for a 95 model) is about $22, but that the vacuum lines don't go to the switch. They go to a separate vacuum controller (forgot what he called it), which sells for about $13. Neither part is stocked and are order-only.

Tim, if a new switch doesn't solve the problem, I have a few questions if/when you have time. If it does work, the questions are pointless

You said that there was no vacuum at the plunger-type diaphragm when you tried different selections on the selector switch. Does this plunger/diaphragm control a door that opens only on the driver side? Can the door be manually manuevered so that we can, at least, get some heat 'til we solve this thing?

Does the vacuum line run to the selector switch or does it go to a separate vacuum control unit that is controlled by the selector switch?

Is there source vacuum at the switch or the vacuum-control unit?

What color-code is the diaphragm line?

Thanks so much, Tim, for taking the time and effort to share your experience with us. And thanks everybody for helping us get this resolved.

Bill, I checked the heater hoses after driving 3 miles to work. The temp gauge showed 150? degrees at the moment. Both of the hoses were about the same temperature and felt pretty warm, but not like HOT.

It was 16 degrees this morning when I cranked the car and turned on the defrost for the iced-over windshield. After about 10 minutes of running, I walked out of the house and immediately saw that the windshield was beginning to thaw on the passenger side but was still solid on the driver side :( How unusual!

I surely look forward to hearing what you learn today, Tim!

Jim

Ok...sounds like you guys are getting into the programmer rebuild issues many saw in the spring. Cover me...I'm going for the link.

The topic is for a different resulting problem, however the programmer rebuild may be part of the issue. Although I didn't get all that you did from the post.

It'* long..it'* a pain..but I'd suggest reading the whole thing and following the links.

http://www.bonnevilleclub.com/forum/...29&highlight=A

The air mix door that controls the amount of air that passes through the heater core and thus controls the temperature of the air passing into the distribution box is electrically controlled.

The flaps for the ducts that control the flow of air for the dash outlets, foot outlets, and defrosters are all controlled by vacuum motors as outlined by Randman, above.

The puzzling part of this problem is that we don't know of any flap that separates passenger from driver side in any of the ducts.

I am beginning to wonder if the problem may be in the heater core itself. That it may become partially blocked so that either one side or the other is warm and if the flow of air through the core is sufficiently laminar, then one side of the car gets hot while the other does not. It is hard to imagine laminar flow in the distribution box, but it is more difficult to imagine a flap fault that would not also cause a significant difference in air FLOW from one side to the other.