Still working on HVAC

[QB93Z]

I solved the problem with the AC blowing out the defroster all the time. (separate thread.) It was a vacuum source tubing problem. The air blows out the correct vent for each mode of the HVAC Controller.

Now, after replacing the failed Heat Blend Door Motor, I get heat when the temperature control is set low (60 degrees). The hot air blows out the AC vents. And I get no heat when the temperature control is set high (90 degrees). The not heated air blows out the floor vents.

When I select Defroster Mode on the buttons, warm air blows out the defroster.

I have verified that the Heat Door Control Motor works and moves the door. By removing the Blower resistor module, I have visually verified that the heat door moves when commanded by the AC Controller.

Any ideas?

Jim

[Roadster]

Jim, could any of the following, the inside air temperature sensor, the outside air temperature sensor, the sun load sensor, the CCM are not functioning properly therefore giving a false reading to the HVAC programmer?

Or could it also be possible that the temperature door is opening in reverse than what it should be? The door should be in the closed position when you are running the AC, thus preventing air from blowing across the heater core. That would possibly be why you are getting hot air on a cold setting if that door is open. And that would also explain why you are getting cooler air on heat demands if the door is closed where it should be open.
Depending on what temps you are selecting for the defroster, I would suspect that the temp door would also have an effect on how cold or warm the air is coming out of the outlets.

[QB93Z]

The problem with the Heat Blend Door motor is that it is running backwards for a 1994 car. The replacement I installed came out of a 1991 ZR-1. It turns out that in the 1991 and prior HVAC system, the Heater Blend Door Motor mounts on top of the HVAC distribution plenum. In 1992 and later, the motor was moved to the bottom of the plenum, so it is upside down, and operates backward on a 1994 and later car.

The good news is that the motor on the bottom is much easier to access. In a 1991 and earlier model, access to the motor requires disassembly of the entire air distribution plenum. (Visualize Heater Core replacement.)

The failed Heat Blend Door Motor shows evidence of corrosion to the internal parts. I suspect that condensation in the evaporator, (the AC cooler), collects in the floor of the plenum and can enter the motor.

I have ordered a proper replacement motor. To be continued...

Jim

[S.hafsmo]

Did you not have an early programmer laying around? Maybe swapping it would fix it?
I'm kinda hoping it won't, as I just ordered a circuit board from a 92-93 programmer to test in my '90. If the change in MY 92 you mention above originates in the programmer, I will probably see the same problem you are currently having.

[QB93Z]

Did you not have an early programmer laying around? Maybe swapping it would fix it?
I'm kinda hoping it won't, as I just ordered a circuit board from a 92-93 programmer to test in my '90. If the change in MY 92 you mention above originates in the programmer, I will probably see the same problem you are currently having.

I have a used programmer from a 1991. Since I was able to corrected my "Programmer" issues by repairing the vacuum source tubing, I didn't have to figure out if the wrong year Programmer would work for 1994, I set it aside.

Just for curiosity, how were you able to get the programmer out? I spent at least 2 hours on my back under the dash and could not get mine out.

Jim

[S.hafsmo]

Having the unit out of it's mounts, I moved an electrical connector that was attached to the underside of the steering column, togeter with attached cables, out of the way (zip-tied), gaining somewhat good access to the programmer (metal knee plate removed).
The big problem is obviously the push-on nut (washer?) on the vacuum connector. I was probably laying on the floor of the Z for at least a couple hours before I got it out. Managed to jam it in a way that gave a bit more access, and used a small flat screwdriver (2-3mm wide) that would fit between the hoses, and under this washer, prying one of the sides up a bit. With a slight gap between the washer and the connector I was able to grab it straight over the top with a needle nose plier, and after a hundred attempts and sore arms, it pretty much just broke off.

I've seen some have been able to rotate it, and screw it off like a nut, but mine was reluctant to do so.

This 91 programmer you have laying around, is that something you would consider to sell?

[secondchance]

The problem with the Heat Blend Door motor is that it is running backwards for a 1994 car. The replacement I installed came out of a 1991 ZR-1. It turns out that in the 1991 and prior HVAC system, the Heater Blend Door Motor mounts on top of the HVAC distribution plenum. In 1992 and later, the motor was moved to the bottom of the plenum, so it is upside down, and operates backward on a 1994 and later car.

The good news is that the motor on the bottom is much easier to access. In a 1991 and earlier model, access to the motor requires disassembly of the entire air distribution plenum. (Visualize Heater Core replacement.)

The failed Heat Blend Door Motor shows evidence of corrosion to the internal parts. I suspect that condensation in the evaporator, (the AC cooler), collects in the floor of the plenum and can enter the motor.

I have ordered a proper replacement motor. To be continued...

Jim

This is some great info! I hope I don't need this knowledge down the road but...

[QB93Z]

Having the unit out of it's mounts, I moved an electrical connector that was attached to the underside of the steering column, togeter with attached cables, out of the way (zip-tied), gaining somewhat good access to the programmer (metal knee plate removed).
The big problem is obviously the push-on nut (washer?) on the vacuum connector. I was probably laying on the floor of the Z for at least a couple hours before I got it out. Managed to jam it in a way that gave a bit more access, and used a small flat screwdriver (2-3mm wide) that would fit between the hoses, and under this washer, prying one of the sides up a bit. With a slight gap between the washer and the connector I was able to grab it straight over the top with a needle nose plier, and after a hundred attempts and sore arms, it pretty much just broke off.

I've seen some have been able to rotate it, and screw it off like a nut, but mine was reluctant to do so.

This 91 programmer you have laying around, is that something you would consider to sell?

Yes, I will sell it. How about $150 plus postage. If it doesn't work, I will buy it back minus postage.

I bought it in case I needed it and to have it on the bench to look at while I was trying to get my system working. What is the failure/problem you are working on?

Jim

[QB93Z]

This is some great info! I hope I don't need this knowledge down the road but...

You know me, I always approach problems as learning opportunities.

Jim

[S.hafsmo]

My climate control unit is just dead, showing - -- and is un-responsive. Apparently it's a fault code for lacking data transmission between programmer and controller. I've replaced /checked/re-soldered most components on the programmer board to no avail. My last attempt was ordering a NOS circuit board for a 92-93 from Kurt White, but I haven't received it yet. If it turns out not to work, I'll be in the market for a 90-91 programmer. Hopefully I'll find out soon. I'll just have to make my girlfriend move the solenoid board from the old programmer to the new, and test it in the car before she goes to Cuba the 10th of March. I myself am currently in Africa/Angola, and won't be able to do much fault finding until I get home in early April.