Howdy.

I have the 'bread box' replacement kit from Mid America for my 89 vette. Before I begin this project (Project 1) I've researched the 'A/C blows hot air' problem (Project 2) and found several threads regarding it.

From what I can tell, during Project 1 I should be able to access the areas where Project 2's problem are. Is this correct? If so I can avoid removing the passenger seat.

Also, if I have to replace the two resistors that others have mentioned burning out, what are there value's? Can I get them at Radio Shack?

Thanks for the help.

 

Well, I don't know about the resistors, hope I don't have to, but removing the breadbox won't help you get to anything as I recall. Does seem like it should, but it don't.

 

Removing the bread box, just gives you better access to the VATS and fuze box wiring connections... other than that, nothing...

 

I like the breadbox..... especially since I have no airbags and my grandson rides shotgun.

 

As for the resistors my local Radio Shack didn't have them. I even took the programmer down 'cause I wasn't sure about the values, but the 2 guys in there didn't know how to read them; don't even think they knew what a resistor looked like.

 

Somewhat doubt your a/c blowing hot air has anything to do with the Programmer (assuming you have electronic air) which is located above the accelerator pedal. Is the compressor coming on? Feel the small pipe just as it enters the evaporator and the big one on top. With the compressor running, both should be colder than the outside air temp and about the same temperature. No a/c is usually because it's low on gas, but if the lines are cold, the temp door may not be moving. It's controlled by an electric motor mounted on the heater plenum, passenger side. It's linkage is held together by a plastic clip and the clip sometimes breaks. Remove the blower module on the evaporator case to observe and verify that the door moves when switching between 60 and 90 on the control panel.

 

What's the point of the breadbox anyway?

 

The door flap is the problem; when I first turn it on it blows cold, then when I start driving I will eventually hear a <sound-effect> 'fuh-wump' and the sound of the air flowing through the vents changes. That is when it starts blowing hot air.

So yes, I believe it is the trap door, and according to thread posts so far the recommended fix is to remove the negative ground, the passenger seat and then bottom cover of the 'dashboard', the ECM (doesn't need disconnecting), then unbolting the two screws holding the motor in.

This is what leads me to believe that the assembly is behind the bread box. I guess I'll just have to start on this Friday night and plan on an all-weekend project. Hopefully it won't be that bad.

Thanks.

 

The reason you can't (easily) get to it (if at all) by removing the BB because there is plastic 'wall/rack' that holds other electronics right behind the BB. I've replaced a few BB's and all you can get to when they are out are these electronics and air vent hose.

There might be a way to remove all the electronics and the plastic piece, but, if you can, it still sounds easier to drop the ECM to get to it. It only took me a few minutes to do both when I replaced an ECM in an '86 .

Good luck next weekend

 

I'm in the midst of trying to solve this "blowing hot air" problem. I've got it down to the blend door in the evaporator; its not moving when I cycle the temp from 60-90 degrees. I followed the shop manual and did voltage checks at the motor connector's tan/blk and yellow wires, and the readings did not vary as they should; they stayed at around 9 volts constant.
Will be calling Chev dealer tomorrow for a new programmer.$$$

 

I went out and did a more thorough diagnostic based on the questions you posted:

1. Yes, the compressor is coming on and stays on; no kicking in and out.

2. The small pipe is hot; the large pipe is ice cold.

3. On the passenger side in the dash is a vacuum switch with an orange hose running to it. When I go between 60 and 90 it opens and closes.

4. I can feel cool, not cold, air coming from under the dash in the area of the vacuum switch when the temp is set to 60. When I set it to 90 the door closes and I can't feel any air at all.

5. The front dash vents are shooting out really hot air.

6. Pulling the vacuum line for the vacuum switch had no impact on the hot air coming from the front dash vents.

 

Orange vacuum line (there should be 2 - one is a bleed to keep the door from cycling) goes to the fresh air or outside air inlet. Normally opened; closed for recirculation of inside air at 60 or 90. Temp door is mechanical - no vacuum involved. If you remove the blower module you can sometimes move the door manually and get it working again.

A funky temp door motor may throw a trouble code. It sends a return voltage to the control panel so that the panel knows it's position. Trouble codes are indicated by a flashing LED above the outside air temp indicator. Access by pressing the outside temp button and pushing, then releasing the Auto button. Advance the display to Mode 8 by pressing the Warm button. Press the Cold button for any codes. 00 is no faults. 01 is a motor fault. It won't set if only the linkage is busted as the control panel still gets the voltage signal.

As best as I remember, The Service Manual voltages are wrong. GM issued a Bulletin correcting it, but I can't find my copy right now. If the battery has been disconnected, the motor goes through a self test so the panel will know it's position and this will effect voltages.

I remove my upper pad, bread box, vent hoses, ECM, hush panel (and anything else in the way) when accessing the heater plenum - probably not necessary, but once I get started, I just keep taking out parts until everything is accessible.

The small pipe, right where it enters the evaporator case should be the same temp or maybe a tad warmer than the big one above it. The rest of the line should be hot. If it's hot where it enters, the orifice is usually plugged up, but the compressor would be cycling on and off. Sounds as if you just have a bum temp door motor or the linkage is busted.

 

To SunCr: Is there a way to hook up test leads to drive the blend door motor open/shut?

 

I don't know, I've never tried it. Motor is pretty simple. Positive voltage on one terminal drives it in one direction; voltage switches to drive it in the other. Inputs (through '89) are tan/black - terminal D and yellow - terminal C. Putting 12 volts to one or the other along with a ground on the opposite should run the motor. You might also have to power and ground the Feedback Circuit. It gets a 5 volt reference from the Programmer on terminal A - red; ground is terminal F - black.

 

Thanks for the info, SunCr. I knew about the tan/blk and yel leads, but I wasn't sure about just applying battery voltgage across it to get the motor to run. Didn't want to burn anything up.
Thanks again.

 

No clue.

 

This sounds good in theory, however if your grandson is wearing his seatbelt and the seat belt allows him to travel far enough to hit the bread box, isn't that wrong?

In other words, in an accident the seat belt should stop the travel of the seat occupant way before hitting the bread box.

I've never liked air bags; at least how they are used in the steering wheels and the passenger dash. That doesn't mean they should not be used, but that they should be engineered differently.

 

Okay. I found an old post that had pics on opening up the small component area on the firewall area (where the evaporator lines go into the firewall) to play with the other air flow door. I could push it with a long screw driver and make cold air come out of the dash. Cycling between 60 and 90 did no good. Put my hand through the bottom of the dash, reached my hand around the motor and found the rod not connected to the plastic clip on the motor. Removed the computer, then the motor and saw the plastic clip would not stay closed. I had purchased a new plastic clip at lunch today figuring even if it wasn't broken it would be wise to go ahead and replace. Here is a picture of the removed motor and clip



Before putting the plastic clip in I re-attached the ground to the battery, turned the ignition on and cycled through the temps. The motor didn't move. I pulled the motor and tried moving the lever with my hand - no good - frozen stiff.

I checked the connector with a volt meter and cycled through the temp and saw the voltage change as I did it.

What's the chance my local Chevy dealer parts dept. is going to have the motor in stock on a Saturday morning???

 

the breadbox was installed originally in the '84 as a passive restraint system. chevy thought that the government was going to implement a passive restraint law, where every car was going to have to have it. but it turned out that they never passed that law, but chevy decided not to change the design until they updated the interior and added airbags.

 

OK!
Let me know!