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Climate Control
Assorted notes for fixing interior climate control components.
System performance
To get the most heating or cooling performance from the climate control system, avoid running the blower on high speed. You'll get more heat from the system sooner because the lower speeds give the air more time to pass thru the system. Same thing works for AC. On high the blower moves the air so fast that it spends very little time in contact with the heater or evaporator.
If you're having trouble getting heat from the system and everything in the cooling system seems ok, the heater core may be air locked. Try bleeding the heater core as described in the cooling system article.
Beyond that the heater core may be full of either internal or external trash.
- Leaves and other junk may have built up in the heater box. This can be very dangerous. If this garbage gets against the blower speed resistor, it's been known to catch on fire. (Several forum members have had this happen!)
- Internal trash is most often the result of failing to maintain the coolant. If flushing won't clean things out then it's usually easier to replace the core instead of trying to get it cleaned or repaired.
(I'm not covering AC performance here. There are too many things to go wrong with that system.)
AC/Heat Mode Actuators
The Fiero is somewhat unique in it's use of a Servo Motor system to operate the dampers in the AC/Heating unit in the passenger compartment instead of more traditional vacuum motors. These electric devices are controlled by a set of push buttons mounted above the radio.
Servicing the actuators is straightforward. Either it works or it doesn't. If it fails to stop at a particular position, it could be a control switch, or the actuator. Generally though an actuator will fail either by the motor spinning with no resulting change to the dampers, or it won't spin at all.
Which motor does what?
The actuator behind the radio is the busy one. That one controls flow to all the system's outlets. The one that is buried under the system is used only when the AC is set to Max. It opens the recirculation door. Of the two, the one behind the radio is the most likely to have a problem.
Testing
You did check the fuses.....
There are three ways to test for problems in the electric duct control system. The easy one is to swap a known good set of controls but this is difficult to impossible for many people... So what else can be done?
Option 1
If you have an extra control set, just plug in the control board to test the motors.
If you are borrowing the controls from another car, just move the board with the buttons. To get the board loose, remove the aluminum cover then remove the three screws that hold the board. (One thru the board and two thru the metal bar for the buttons. Sometimes they aren't all there... Don't worry about that.)
Just using the board will save you from having to mess with the temperature slide(s).
Option 2
This test will assume all the wiring is ok. No one is likely to screw with the motor wiring but anything is possible.
For this one, you need to pull out the control head and disconnect the large connector from the control board. (Leave everything else hanging out of the way.)
| Motor | Terminal | Wire Color | Mode |
|---|---|---|---|
| Mode | D | Tan | Defrost |
| F | Purple | Bilevel | |
| J | Lt Blue | Vent | |
| M | Red | Floor | |
| Recirc | E | Gray | Fresh air in |
| L | Yellow | Recirculate | |
The table above shows what terminals in the control connector you will need to test each motor.
Connect a FUSED 12V source to the terminals above (One at a time) and see if the motor stops at the correct position. If the motor doesn't turn or fails to stop then the motor is bad. If the motor does work and stop at the right spot then the control board is bad.
The 12V source should be fused for 1-2 amps. The motors only draw about 150 milliamps.
Option 3
This one can be used to test a mounted motor or a loose one. If you are testing a loose motor, be careful the arm doesn't pinch you. That arm has more torque than you might think. The table below lists the terminals on the motors.
| Motor | Terminal | Wire Color | Mode |
|---|---|---|---|
| Mode | A | Black | (Ground) |
| B | Tan | Defrost | |
| C | Lt Blue | Vent | |
| D | Purple | Bilevel | |
| E | Empty | ||
| F | Red | Floor | |
| Recirc | A | Black | (Ground) |
| B | Yellow | Recirculate | |
| C | Gray | Fresh air in | |
Terminal A on the Mode motor is the one farthest from the corner of the case. I think the Recirc motor is the same but I've not seen them. They are so hard to get at I can't test the one in my car.
Ground the A terminal and connect a FUSED 12V source to the other terminals one at a time. The motor will run for a bit then stop at the correct position. If the motor doesn't turn or fails to stop then the motor is bad. (If you are testing a loose motor, just make sure it stops at the same spot each time you power a particular terminal.)
Again, the 12V source should be fused for 1-2 amps. The motors only draw about 150 milliamps.
Service
I've never had the motors themselves apart. Haven't run into a dead one yet... It may be possible to fix one but don't hold your breath over it.
The Actuators are a real pain to get at. One is located behind the radio and has 2 linkages inside the duct. The other is under the ductwork with the crank facing the driver's side. This one is very uncomfortable to reach.
To remove Actuator behind the radio, unplug the control cable, and then remove the two hex head screws. After the screws are out, Carefully lift the Actuator away from the heater box until you take up the slack. Find some small locking pliers, forceps, or even string and hold onto the linkages. If you drop the damper links they will be an absolute shit to get a hold of again later! Continue to support the actuator while you do this!
There is a flat steel spring clip on the end of the actuator crank pin. With a pair of forceps, or needle nose pliers, rotate the clip so you can pull it off then CAREFULLY pull it off. Forceps, and locking pliers, are preferred for this since they will lock and hold the clip securely. DO NOT lose this clip! You might need it later if you didn't get one with a new unit or dropped the clip when harvesting the used unit you are installing.
The tricky part is getting the links back onto the replacement actuator. If you dropped the links then good luck to you, if you locked onto them like I just told you to, then you're made. Put the links back onto the crack in the order they came off! The links will only fit one way on the Mode motor's crank!
The actuator under the duct can be reached, with great difficulty, by crawling under the dash on the driver's side. This one only has one linkage. The clip and link are easy to deal with. I'm not sure how it's screwed to the duct. There is a small metal bracket. I can't see if you take the motor off the bracket or if you take the bracket off the duct. Neither one will be easy.
Temperature control
The temperature control slide uses a push/pull cable. This cable attaches to an arm on the top of the duct below the left speaker. This rarely goes bad. If it doesn't work most of the time you've snapped the pin on the slider or gotten something hung up on the cable or in the heater box.
Fan Speed Control Knob
Warning! The heater blower switch knob is held in place by a small "rolled leaf" spring. Be careful taking the knob off, as this spring is sometimes loose and can fall out of the knob. If you lose it the knob won't stay on the shaft without adhesive. If you must glue it on I suggest you use silicone as it can later be removed if need be to service the switch, or replace the knob.
The button fell off...
The buttons on the AC/Heater controls are not actually attached to the switch stems. Two little ears on each button are the only things that keep them from falling out of the controls. Sometimes the ears break off the button and then the button either pops out more than the others or pops out entirely.
The easiest fix is to put a little RTV silicone inside the button and slide it back on the stem. If the button hasn't come out completely you'll need to pull the control set to get to the back of the button. Make sure the button lines up with the others and then leave it alone until the Silicone sets.
I recommend RTV silicone for this just in case you ever need to take the things apart for some odd reason. If you use another glue, use something that sets slowly so you have time to line up the buttons. Don't use super glue!
Heater Core
The heater core on cars with AC is replaced according to the instructions in the Haynes book but removing the cover can be a bit tricky. Here are a couple things that make the cover easier to deal with. (This might apply to non-AC cars but I've never seen one.)
Take the Chime socket off its bracket. The ones that face right are held by 2 screws. The ones that face down are held by one screw and the other side is sort of wedged onto an ear on the bracket. Let the whole thing hang by the wires.
The top screw is hidden under some insulation. Take out the speaker and slide your hand forward along the top of the cover joint until you feel the boss. The other three screws are pretty easy to find. There's only one screw on each side of the cover.
If you loose a screw and can't find a replacement then leave the top hole empty. The other three hold a spring against the heater core and help seal a gasket in the bottom of the cover. (The gasket is supposed to help contain leaks in the core. It doesn't always work.)