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2002 Bravada heater problem

For the last year or so the heater has been acting up on this car.The temperature/blower controls on this car are mounted on a small panel in the center of the dash. The center knob is temperature, with an "auto" (blue dot) position on the left side, and a red dot detent position on the right side. The right hand control knob directs from where the air will blow and also selects AC, heat or defrost, and the left hand knob controls fan speed.

There has never been a problem with the air conditioner if that matters. However I honestly don't know if we ever really tend to select a particular AC temperature or are just happy when it gets "cold".

For the last year or so the only way it was possible to get heat or hot defrost was to turn the temperature control, the middle control of the three all the way to the red indent position on the right. The heat or defrost would be on full and you could set blower speed and that was ok. After a few minutes it would get too hot. Then you would have to turn the temperature knob slightly to the left just off the detent to get it to stop blowing hot. It would then gradually cool off until you would have to turn the knob full clockwise once again to the detent to get it to start blowing hot again. There was no temperature "control" to speak of. The temperature was either hot or cold. The blower speed control always worked normally as does the other control which directs and selects AC and where the air will blow through, as well as selects defrost.

We use this car for short trips in the Winter and since the heater and defroster were both functional this has been no real problem. However last night we went for a ride. It was raining and in the forties and misty. No matter what we tried, the heat and the defroster blew cold until the last two miles of the trip home. Engine temperature according to the dashboard gauge looked to be normal. But Winters can get cold here in New Hampshire and this is only the beginning, and so even if it was once again the "either on or off" scenario we must have heat and defrost working again consistently to some extent.

I am an electronics technician and so I feel that I have a good shot at fixing this if I were to try, however the problem is I do not understand exactly what is happening in this temperature control arrangement. I don't mind if it were to work once again either on or off but we must get it working before the really cold weather sets in. Can someone please help me with a little "theory of operation" discussion here? Thanks for any replies. Lenny.

Reply to
captainvideo462002
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The Bravada uses an optical encoder and a stepper motor on the temperature door. The detent position bypasses the control and applies power that opens the blend door wire open. The motors have been known to fail. Sometimes you hear them cycling open/closed (this shows up as a constant clicking from behind the dash) the other common failure is loss of control such as you have.

Not hard to replace the motor BUT you have to pull most of the dash to get to it easily.

Reply to
Steve W.

Is it possible to get to this door and just jam it open in such a way as to get heat and defrost all the time for this Winter?

Reply to
captainvideo462002

Not easily. There are two different doors, one for each side.

OR a possible thing to try would be to take it to a dealer. Have them try to recalibrate the actuators and control head. It seems like it is working but not under proper control.

It would point out where the problem lies as well.

Reply to
Steve W.

Steve Its strange but sometimes the heat works fine on the detent position that is. I asked my wife if she's heard any clicking when the heat is not working and so far she is not certain but doesn't think so. The other night when I was in the car with her and we noticed the problem I didn't hear any either. We did have the radio on so maybe we masked it but I don't know. But from your last post it sounds like if you set the temp control to the right hand detent position, regardles of the condition of the variable temperature portion of this assembly, (which as I said previously hasn't worked for awhile), should you get heat even with a bad variable control? Does the fact that I'm not getting heat in the detent position coupled with the fact that we have heard no clicking, narrow this down some? I was thinking perhaps a bad variable control but if the detent position takes that out of the equation then what does that seem like? Thanks, Lenny

Reply to
captainvideo462002

If it is intermittent the problem is probably a bad solder joint or bad contact at the actuator motor.

The system is supposed to bypass a bad control when you turn the control all way. BUT that also supposes that the motor is operating properly.

Personally I could never figure out what was wrong with the old cable units! Other than they made automatic temperature control difficult.

Reply to
Steve W.

Steve I'm going to check this situation out further and I'll let you know what I find. I definitely agree that there are few things simpler than a cable....I really wouldn't mind having that system right about now. I just don't understand the implementation of all this failure prone technology in all our products today. Do we really need to be nagged by a refrigerator that tells us in a "soothing" female voice that we're low on milk.? Isn't that why we got married? Lenny.

Reply to
captainvideo462002

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