Can anyone help me with a set diagnostic first steps to see why my cold A/C only blows out the floor and defrost vents, no matter which blend door button I push. 1987 Fiero GT, v6- 5sp-- w/ factory air cond. ? New owner, I've had the car two months.
It could just be an easy fix. There is a plug that controls the motor for that airflow that goes to the bottom you can see from the passenger side footwell. Its sits in the middle , mine was cut. Had to rewire a new plug.
An answer to Patrick's question will help the diagnostic process. The direction of airflow is determined by flaps in the air-ducts (below and behind the dash) which are moved by motors controlled by the push-buttons for Heat/Vent/Demist/Norm/Bi-level etc. These flaps ought to move to direct the air to screen, dash-outlets or footwells whether the a/c is on or off.
A common problem that seems to come with age (I have the same issue in my '88 Formula) is that the little motors don't work too well. Sometimes they stick and the flaps don't move. Sometimes for some reason the flaps only move (you can hear the whirr-clunk) when you first turn the ignition on, and pushing the buttons while you drive along has no effect. It sounds as if your HVAC flaps are "stuck" in the position which directs airflow to screen and footwells rather than to the dash-vents.
I don't have an easy fix to suggest. Access to the motors and flaps seems to be difficult, and it's not easy to figure out where and how to spray WD-40 or similar to ease matters. Maybe other forum members will have solutions to offer?
These flaps ought to move to direct the air to screen, dash-outlets or footwells whether the a/c is on or off.
Exactly. IMO, mentioning A/C only serves to muddy the waters in regards to air not being directed out of the dash outlets.... unless for some reason this only occurs during A/C operation.
[EDIT] It's probably worthwhile being made aware if the heater/HVAC unit is A/C equipped or not, as there may indeed be some slight differences in the hardware.
[This message has been edited by Patrick (edited 05-31-2020).]
AC/Heat control board Switches operate 2 motors. 2 motors route air to outlets. control board or motor(s) problems cause the above. See my Cave, Heat & AC
Note: Board has 2 small "Coins" that limit power to the motors. (NTC or PTC Thermistor I believe) If fried, the motor connecting to it have problem itself or w/ door(s) they moves or dead.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
First of all to the Ogre: Thanks for the write-up. Next Saturday I'll start in checking stuff with a lot more confidence, and a lot fewer false starts down the "is this the place I need to work" path. To SpadesLuck: I hope you are right. It is a new to me car in April, There was no need to use the a/c other than a couple of minutes at the car lot to see if it worked. I know the compressor works, I think the blend doors worked then. I added a performance sound subwoofer and a bluetooth phone radio, so I had that area apart and could have pulled something loose. (DOES ANY HAVE PICS of the blend door electric connectors?)
FYI to all (thanks for the suggestions) the fan motor control works normal. there is never any change in the blend door/airflow behavior. No clicks/whirls/etc. at start up, no sounds across the entire HVAC button row, no sounds when I shut off the engine, and nothing I do from the drivers seat (or elsewhere) causes a change in the airflow path (stuck on blowing out the defrost vents, windshield and both side windows)
Thanks again, on Saturday I'll crawl into the floorboards with at least some idea of what I am looking for. I'll keep you updated.
...... the fan motor control works normal. there is never any change in the blend door/airflow behavior. No clicks/whirls/etc. at start up, no sounds across the entire HVAC button row, no sounds when I shut off the engine......
This information is a bit puzzling. My analysis might be simplistic, but I'm trying to be methodical. It seems that either
(a) the electrical buttons on that panel are faulty and have bad - or no - connections to the things they are supposed to control; OR
(b) the controls in the dash panel are fine, but the motors that move the vent-flaps are dead, or the flaps themselves are stuck in one position.
If (a) is the problem, how come the fan-speed control works normally? (it may of course actually be wired as an entirely separate unit). And how does the a/c actually kick in - since that is activated by the Max/Norm/BiLevel buttons? Is the a/c permanently on? Does the "Off" button work?
If (b) is the problem (and the fact that the fan-speed control works suggest that at least some of the controls are OK) it should be possible to switch the a/c on and off, even if the direction of the airflow can't be adjusted between screen, dash vents and footwells.
Seems to me the next step is to try to narrow down whether the fault is electrical and with the buttons of the control panel unit, which is easy to see and - I would think - to remove/replace; or whether the problem is with the motors and flaps down in the ducts behind and under the fascia - where the issue could be electrical or mechanical.
Originally posted by br1anstorm: If (a) is the problem, how come the fan-speed control works normally? (it may of course actually be wired as an entirely separate unit).
The blower fan works independently of the buttons.
Feeding information into the diagnostic forum team while waiting for Saturday to come around.
In regard to electrical behavior of my HVAC control buttons. Any of the three AC related buttons (Max. Norm, B/L) will activate the AC compressor. Pressing the OFF or any of the non-AC buttons (vent, HTR, defrost) will turn the AC off. Regarding the fan, Lo, 2, 3, Hi all run the fan as you would expect them to, in any of the six button settings. The Cold---Hot slider seems to be working, (Cold air comes out of the defrost vents) but hard to know exactly since we have never had dash vent airflow and a long enough ride to prove it in the real world.
I think that answers all current questions from "the team". We are one day closer to diagnostic Saturday. Thanks for the help. I'll do my best to photo the process on Saturday.
Hi guys, I just stumbled across this on one of the FB Fiero forums: (poster's name withheld by me) "Fieros have no motorized actuators for the heater system, that's New school tech, lol... All Fiero AC control valves are vacuum actuated, like pretty much every gm vehicle from the 60's thru the mid to late 80's... The GMT pickups were some of the first gm vehicles to get electronic actuators for the heater controls..."
Everyone else I have heard from talks electrical actuators. What's up?
------------------ John E Stark
[This message has been edited by JohnEStark (edited 06-12-2018).]
Hi guys, I just stumbled across this on one of the FB Fiero forums: (poster's name withheld by me) "Fieros have no motorized actuators for the heater system, that's New school tech, lol... All Fiero AC control valves are vacuum actuated, like pretty much every gm vehicle from the 60's thru the mid to late 80's... The GMT pickups were some of the first gm vehicles to get electronic actuators for the heater controls..."
Everyone else I have heard from talks electrical actuators. What's up?
Someone is an idiot. And yes if you're going to state it that matter-of-factly and be that wrong you deserve to be called an idiot. Fieros don't use ANY vacuum actuators in the HVAC system. The non-AC cars use two cables to open and close doors in the HVAC box to select between vent, heat, and defrost (top slider cable) and cool or hot (bottom slider cable); The AC cars use the push button head unit, which controls all the vents with actuators except the blend door, which uses a cable. No vacuum lines.
HVAC for AC equipped cars from the factory service manual
1984 Pontiac Fiero Factory Service Manual - Page 1B-4 AIR CONDITIONING
quote
SYSTEM COMPONENTS-CONTROL
Controller
The operation of the A/C system is controlled by the switches and the lever on the control head. The compressor clutch and blower are connected electrically to the control head by a wiring harness. The blower circuit is open in the off mode and air flow is provided by the four blower speeds available in the remaining modes. Cooled and dehumidified air is available in the max, normal, bi-level and defrost modes. Temperature is controlled by the position of the temperature lever on the control head. A self-adjusting cable connects this lever to the temperature valve which controls air flow through the heater core. As the temperature lever is cycled through its range of travel, a sliding clip on the cable at the temperature valve connection will assume a position assuring that the temperature valve will seat in both extreme positions. Temperature valve position is independent of mode selection. The temperature cable attaches to the top side of the air conditioning module. The systems fresh air valve and heater/defrost valve are operated electrically, thereby eliminating the need for vacuum control valves and lines
Heater Only Controller - Note only electrical connectors for the fan speed switch and a 2 pin connector for face illumination, and cable attachment points
A/C controller - a single cable attachment point for the blend door, a large electrical connector, and the same smaller connector for the fan speed switch
RWDPLZ: This is awesome support for what I am facing. On Saturday I'll have my tablet computer set to this thread next to my wrenches while I start the process of disassembly for diagnosis/repair.
I am fairly confident the blend door actuators are not working, but why? and what will I need to do to make them work?
Any advise on how to get to them? how to test them? Your pics show me what I am looking for, but I feel kind of like Indiana Jones at the door of the Temple of Doom!
The Mode Door Actuator is the one that controls when air comes out of particular vents, Item 51 in the exploded diagram above. It's right behind the radio.
Here's a video showing where it is and how it works:
Try putting your hand on it while you press the different control head buttons and see if you can feel the motor and gears moving. If not try unplugging it and cleaning the wiring terminals at the actuator and connector.
1) RWDPLZ's posts - complete with pics, diagrams, video and crystal clear advice - are awesomely good. Great respect! That post (or this thread) should be made a sticky or put into a tutorial section;
2) I wish I had a spare HVAC assembly out on my lawn to experiment with and explore!
3) It's certainly looks like a royal pain in the a** to access, maintain or repair/replace those motors, actuators, levers and flaps. I'm just praying to the god of all automobiles that the control mechanisms in my own Fiero carry on working (more or less well) for a while longer......
[This message has been edited by br1anstorm (edited 06-12-2018).]
Saturday a week ago I took out the radio, the console cover and worked on the A/C blend door. The process took two days, the report can be short and sweet. I now have cold air coming out the dash vents. Using "Ogre's"wiring diagram I determined the blend door actuator worked. I sanded and cleaned the contacts, I think it actually works, but with cold dash air working I'll leave the buttons alone until fall when A/C is not critical to enjoying the car. Thanks again everyone, especially RWDPLZ and Ogre. BTW, The center tunnel in the frame swallowed a 1/4 socket and a short 1/4 drive extension. Trying to get it back was 1/2 my total work time. Gave up and reassembled with it in there. To my surprise, there is no rattle!
RWDPLZ, thank you so much for compiling this information here, I had battled with my 86 GT blowing in default mode (a little air out of every vent at once) for years now. It's nice to visually see the diagrams explaining every little detail and even nicer to know only one of the motors controls airflow direction!
Only one thing left to sort out: how to remove an entire HVAC box from a parts car. I tried like heck at a junkyard last year and I am really quick at dissecting Fieros, but this one stumped me, despite a very in-depth attempt at disconnecting anything I could see and reach.
The two pictures of the unit you posted still leave me wondering what was preventing it from full removal.
RWDPLZ If you have this unit, can you count teeth on driven gears? (Drive gear on motor etc doesn't matter.)
CLICK FOR FULL SIZE
Guessing Big gear bit hard to count but think has 39 teeth, can't see small gear under motor so say 10. I get 390 rev's in on motor to 1 rev out. (seem Camera had problems compressing 1 part of big gear because very low contrast in one section.)
On the bottom of the big gear is the "switch" that stops for each selection.
Warning: Because of high gearing, If you jammed the output then even that "weak" motor can break whatever is weak. Is likely part of why used PTC Thermistors in the control board to reduce power to them as motors tries to draw more amps trying to prevent breaking. In short, Get PTC hot = more resistance. To limit motors they spike resistance and "shutdown." (Likely Faster the Breaker used in Gen1 HL motors.) Most Temp sensors in Engine are NTC types, hotter resistance drops w/ more even Ω curve.
CLICK FOR FULL SIZE
Not sure Thermistors are in Ground or Common side to the motors. Don't have real board layout now and FSM isn't exactly the same.
Plus If you have a AC Bulb dim/blown, Don't count thinking is just the bulb/socket... On top of dimmer problems, The wire here just pop out of the cold/weak solder joint to take pictures. Won't surprise me if the board have other crap joints and part of why motor control "fix itself" just plugging in/out connections etc. Crap joints can kill the whole system or just 1 part of same. I didn't see markings to give away likely subcontractors that make the board like obvious maker and patents on chime unit that have same problem.
The Mode Door Actuator is the one that controls when air comes out of particular vents, Item 51 in the exploded diagram above. It's right behind the radio.
Here's a video showing where it is and how it works:
RWDPLZ, have you been able to remove the Mode Door Actuator for the housing? I have tested mine, and it appears not to be functioning. I know from the video it has a clip holding on the two linkage rods, but it seems nearly impossible to remove that clip, and probably as impossible to put it back together again.
How in the He.. did you get the blend door motor out ? I know they say to remove the heater core cover and reach through the vent opening with your right hand to disconnect the 2 arms BUT I can not get my hand in that opening.What am i missing ?
