FAQ: Warm/Hot Air on Drivers Side, Cold on Passenger Side

I'm still having center warm problems too, and my servos's appear to work full range (so my earlier post may be bunk)...

So I'm thinking about pulling the center vent cover off, and seeing if I can somehow see into the hvac box...

On my post above, the airflow diagram...If door #2 is not fulling closing off the heater core path, then that would PROBABLY explain the difference in temps??

When I took off the servo which moved door #2, and manual moved that white lever control (the part the servo actually turns) full from one end to the other, I never actually got COLD air from the center vents...it was still coolish...

So I'm wondering if there's something blocking the door from fulling closing, thus allowing just enough air to go into the heater core path and making the center vents warmer than the passenger vents...

I need to investigate deeper how I can have warm center, but cold passenger on the same temp settings, and how the passenger side #2 door (is there one??) may be fully closed, while the drivers side isn't...

Mr.Riviera...thoughts???

I’ve learned a few things from the FSM that may be of use. I was going to wait until I’d gone through my own Riv before I posted but that may be a while yet.

Natsriv’s post of Fri Aug 05, 2011 1:58 on page 5 shows the driver’s side actuators in a photo. Actuator #2 controls the Driver’s side “airmix door” (temperature setting door) which controls the main cabin temperature. There also is a passenger side “airmix” door with its own actuator which is exactly opposite Actuator #2 on the passenger side. This is according to a figure in the FSM which follows the figure that Natsriv posted on pg 5 of this thread.

1) The driver's side and passenger side airmix doors are linked mechanically so that the passenger door follows the general air-mix position of the driver's side. The passenger temperature control then controls the passenger side actuator opposite the driver’s side #2 but its movement is, or should be, limited by the setting of the driver's side actuator. That’s why the max temperature differential of the passenger side is something like -8 / +15 degrees F that of the driver's side.

Bottom line: The FSM states that if you cannot achieve a temperature difference between the driver's and passenger's side that either the passenger side airmix door actuator isn’t operating or the linkage between the two doors has been lost. This would still apply if the temperature were different between the sides and you were unable to change them with the passenger temperature control.

As I’ve said, I haven’t delved into my Riv yet so I don’t know what this mechanical linkage consists of but it’s probably buried within the air handling unit itself and may be a bear to fix.

2) The HVAC programmer keeps track of the position of the doors via potentiometers built into the actuators and I believe those positions are recorded in the programmers KAM (Keep Alive Memory).

3) If you disconnect the car battery the KAM may lose its memory and lose track of the door positions. If so, the programmer will throw DTC-0052 which I guess has to be read with a Tech-1 . I haven’t been able to find anything in the FSM about any “re-learning” procedure that one would implement or one performed automatically by the programmer after power loss.

That’s about all I know about it right now.

Yes, the blue gear in the photo is the potentiometer??

Is it possible that one side closes completly while the other (the driver's side) perhaps closes only partially, since the linkage is preventing it from fulling moving?

if the FSM is correct, couldn't you take the center vent out, and at least with a flashlight be able to see if the driver's side is fully closed?

You're right, it's a bear to figure out and probably fix...

just a thought..not basis in fact...but what if you took the passenger actuator off, and the drivers side. Then moved the passenger side to its hot positon, then moved the drivers side to it's cold positon...would it be colder finally on the driver's side?...I mean if you go to the extreme on the passenger side, would that allow the extreme opposite on the driver's side....

I might add, that after about 20 minutes of cool, my drivers side is blowing cold but never the same coolness as the passenger side.......

Natesriv wrote:

Yes, the blue gear in the photo is the potentiometer??

Is it possible that one side closes completly while the other (the driver's side) perhaps closes only partially, since the linkage is preventing it from fulling moving?

if the FSM is correct, couldn't you take the center vent out, and at least with a flashlight be able to see if the driver's side is fully closed?

You're right, it's a bear to figure out and probably fix...

just a thought..not basis in fact...but what if you took the passenger actuator off, and the drivers side. Then moved the passenger side to its hot positon, then moved the drivers side to it's cold positon...would it be colder finally on the driver's side?...I mean if you go to the extreme on the passenger side, would that allow the extreme opposite on the driver's side....

......

I think, yes, that the blue gears are probably the potentiometer input drivers.

I would think that if the linkage were working properly, that moving the driver's side air-mix door would move the passenger side door in the same general direction, but not vice-versa.
Otherwise, the passenger temperature control could command the main cabin temperature and clearly it's not meant to work that way. I would also think that manually moving the "white lever" that acutator #2 engages that you should be able to get the main vents to blow at maximum coldness and that if that doesn't happen that there is some sort of interference from the coupling mechanism preventing the driver's side air-mix door from closing completely as Natsriv pointed out.

I'm going to be very interested to see the door linkage that the Engineers came up with because I can't really envision it myself right now. I'll probably see it and say "Oh -duh! "

I've had this problem with my 95 since I bought it. Pass side worked perfectly but no heat or a/c on my side. Defroster performance was weak also. This thread inspired me to pull the cover and watch the acctuators the center one (#2) did not move. I pulled it and took the cover off and with a pair of needle nose freed the motor up. Put the excess grease back on the gears, reassembled and put back in. I now have full function including cold center vents and the heat that was missing all these years. Cost, a couple of sore shoulders because I'm too old for that position. But the help from you guys and having this function as designed is priceless. I'd rather be lucky than good in this case.

Another mystery to solve: Driver's side no heat or AC, passenger side perfect when the driver,s side is supposed to be the controlling side ? This doesn't fit my model of how its supposed to work.

brutusk1 wrote:

Another mystery to solve: Driver's side no heat or AC, passenger side perfect when the driver,s side is supposed to be the controlling side ? This doesn't fit my model of how its supposed to work.

Do you mean no airflow, or the temp is always the same, or what?

I was referring to pbrktrt's post above mine which I don't quite understand either.

Oh okay. I don't think there is a "controlling side". There is an interior temp sensor which provides feedback to the head for general temp control. The passenger can request 5 + or - of the target temp. If the drivers side actuator goes whack, the passenger side should still be trying for the target temp (although + or - 5 based on the comfort setting). I am not sure if there is a passenger side interior sensor as well, but it shouldn't be needed if the formula is right.


In my experience, if the passenger sets +5, the drivers side eventually starts blowing - a few to compensate and shoot for the target as the average in the cabin.

to help clarify for all... Deekster and any other "jedi's"...

My FSM often times refers to the "drivers side" center vent and the "passenger's side" center vent...but my center vent's two outlets all blow the same warmer temp.

I'm thinking the passenger side "center vent" is the two next to the radio??

I was wondering the same thing. I think you're probably right. That's what mine is doing too.

what do I have to pull to get to this blend door actuator and replace?

Has anyone found a solution to the warm air on the drivers side when all the servos are working? I even disconnected the blend servo on the drivers side and made sure the arm all the way to cold and it was still blowing just luke warm air on the drivers side and cold on the passengers with the temp set at 60.

This seems to be the $64,000 question - hopefully I'll have time this weekend to tear into it. I've done enough speculating.

Well, if you find out, make sure to let me know. I don't have time to tear it apart for a couple of weeks. My guess is there is some taped on foam strips for sealing the blend doors came loose, or I have a crack in the drivers side door.

Spin wrote:

Has anyone found a solution to the warm air on the drivers side when all the servos are working? I even disconnected the blend servo on the drivers side and made sure the arm all the way to cold and it was still blowing just luke warm air on the drivers side and cold on the passengers with the temp set at 60.

It's possible you have a bad HVAC head, that's probably the next part to replace after you verify all of the actuators are functioning properly. It's possible to repair these units sometimes, if it's a bad solder giving you problems. I found a good used one from moradpartscompany.com for around $50. Also try car-part.com

deekster_caddy wrote:

Spin wrote:

Has anyone found a solution to the warm air on the drivers side when all the servos are working? I even disconnected the blend servo on the drivers side and made sure the arm all the way to cold and it was still blowing just luke warm air on the drivers side and cold on the passengers with the temp set at 60.

It's possible you have a bad HVAC head, that's probably the next part to replace after you verify all of the actuators are functioning properly. It's possible to repair these units sometimes, if it's a bad solder giving you problems. I found a good used one from moradpartscompany.com for around $50. Also try car-part.com

Pretty sure that's not it. I even disconnected the servo and manually made sure the damper was moved to the full cold position. It still blew luke warm air, and the passenger side cold.

That's the same thing my 95 was doing for years. Pulling the center actuator and freeing up the motor has fixed mine. I better clarify, the center one on drivers side. It was the only one not moving during cycling the functions. I now have cold air from all vents and hopefully heat on the drivers side.

brutusk1 wrote:

This seems to be the $64,000 question - hopefully I'll have time this weekend to tear into it. I've done enough speculating.

Can you get at the servo doors by removing the center console?

96RIVMANN wrote:

Can you get at the servo doors by removing the center console?

No need to remove the console, just remove the panel "under" the dash on the driver’s side and the glove compartment for the passenger side.
When my '99 was acting up it was opposite what everyone else is talking about here recently, I had cold air on the driver’s side and warm/hot air on the passenger side. I found the servo right inside the glove compartment to be stuck, freed it up and it took care of my issue.

The reason I ask is because all of my servos work like they should. I just have a hint of warmer air blowing out the drivers side and lower center vents.

Ok my problem is that the "Comfort Passenger Control" seems to not working properly, because when I have warm air coming out of both sides and want to have cold air coming form the passenger side it doesn't work, the servo doesn't move when I use the controller, I replaced the controller from a 95' (used) and it's still not working...

Any ideas? Could it be that both controllers are not working correctly???

Do you know what is the color of the cable coming from the controller that tells the passenger servo to move so I can test it with a multimeter???

Thanks any help will be appreciate it

Not sure if anybody had this problem or not. I didnt see it any where but this is what I have. 1998 Riviera that I put 2 new blend motors in. Now the driver side still doesn't change UNLESS if I turn it to 60 it will go to hot hot. If I turn it to 90 it goes to ice cold. And the passenger works fine all the time. Any ideas before I destroy my dash? lol

Hi guys hoping you all can help. I have a 1995 Rivy SC Most awsome car i have ever owned. But one problem. The heat and air go crazy.Sometimes it works great and then has a split personality.Tonight was typical. i was driving home from raleigh and it was hot so i put on the air. it is the automatic unit with the seperate driver and passenger temp control.Fot the first half and hout it worked great. Thn all of the sudden the driver side goes to heat and the passenger still has cold ac.Sometimes when i turn the system off and on it clears. sometimes not. Tonight it would not fix. so i had to shut if off.I sure would be thankfull for any help or its going to be a long summer
Rick