Heater problems, passenger side blows cold air, drivers side blows warm air. Dual control under passenger side dash not closing door inside heater box. Fuse? Where is it. 97 STS
Optional Information: 1997 Cadillac STSAlready Tried: I've checked the fuses under the hood on the drivers side with a test light .All the ones that are powered up with the engine running have power on both sides. I don't have a owners manual so I don't know which one if any are for the heater controls. Everything else works as far as I know at this point. It just happen the last Friday as I was driving home from work, And don't you know the temperature was dropping down into the mid teens. Right when you really want to go outside and ---- with your car. I know that there are fuses on the back side of the rear seat if I go through the trunk but I didn't know if any of those control anything to do with the heater. I wouldn't think they would. But? The dual temp. control light Blue/red on the dash work I could take a test light and see if there is power being supplied to what looks like the motor that moves that rod back and forth that goes inside the heater box but when it Quit working the control on the dash was not lit and we don't usually touch it.
Most new cars use a computer to control these doors, and there is no separate fuse to each one. Very common is an internal failure of the stepper motor gears inside the door actuator itself, and this requires replacement of the actuator.
You may try to remove the actuator you see that isn't moving, and then manually move the door yourself by turning the exposed shaft. Sometimes the door itself becomes jammed or broken, but it is not a common problem. If you can turn the door yourself, see if heat returns. If so, then it is definitely the actuator.
I'm not sure if this will apply....I don't have access to the service information here, but I can dig into it a little more at the shop tomorrow.
Many dual zone systems use a heater core that has two separate passages...one for either side of the car. Look under the hood, near the firewall and locate the heater hoses going into the cabin. If there is more than two, start the car and let it run until warm...make sure all the heater lines are hot. If not, it may be in a heater control valve, or blockage in the heater core itself.
If the problem happened all of a sudden, then I would look for a mechanical failure first before suspecting the heater core.
When you changed door position manually, did the temperature coming from the ducts change? IF this is a motor actuated door, you shouldn't have been able to move it without removing the actuator first. And there is more than one actuator in that casing. Are you sure you are looking at the right one?
Now wait. Were not done. Let me check the heater core ? cores. First of all though, I did manage to reverse the condition when I turned down the temp. control to 60 and turn up the dual control to high heat for the passenger side. I got heat out of the passenger side and cold air out of the driver side. And to answer your question about the actuator. It did change temperature.from heat to cold out of the drivers side I know there's heat in the box. I can feel it coming out of the little seams.
Now to go back to your latter idea. I am wondering about your discription of the heater core. In the back of my mind in the very beginning when this started.
When the temperature here drops down in the teen.s 12 degrees Burrrrrrr. It takes a lot more heat to make you feel warm. I can tell in my heating bill. Maybe it had a lot more to do with the day we were having. But IT doesn't make sense that I can't get both sides to put out max. heat on high demand.
What about disconnecting the battery and resetting the computer? It's late tonight and I've got to go to work tomorrow. I'm going to go out and look at the possible of that dual heater core. maybe that side is restricted but it felt like a lot of heat was coming out of the Passenger side when I turned down the main temp. control and turned up the Pass side dual temp control..
OK, I did some digging on your system...let's start from the beginning. Here's what I want you to do....
First, disconnect the negative battery cable and let it sit for fifteen minutes. Then reconnect your battery, turn the key to the "on" position for 3 minutes...this lets the computer recalibrate the doors and perform its self diagnostic function.
Now, let's see if the computer sees a problem. You are going to put the computer in diagnostic mode by following this procedure:
Turn the ignition "on". Press the "off" and "passenger warmer" buttons at the same time, then press the "lo" fan speed button until you see "ACM?" displayed on the control display. Now press the "Hi" fan speed button...you should now see "ACM Codes?" in the display. Press the "Hi" button again...any stored codes will be displayed. Let me know what numbers show up, if any.
This system uses a single heater core and two independent doors. The doors should work in unison in all modes EXCEPT "Dual zone"...so try MAX Heat in any position OTHER than Dual Zone and let me know how that works as well.
The two rubber hoses you saw are for the heater core, and the two aluminum lines are for the air conditioning system. Another possibility if you are getting heat from BOTH sides is a thermostat that is not closing all the way when it should. I personally use an infrared temperature gun to measure the temperature of the heater hoses going into and out of the heater core. This can tell me real quick if the coolant just isn't hot enough to begin with or if there is a restriction to flow in the heater core itself.
If you decide to take it to a shop, use the Shop Finder feature on this site to find a good one:
Let me know how you make out...one way or the other. Take care...
Hang in there...