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Automatic Climate Control - Unresponsive - '94 Convertible

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Automatic Climate Control - Unresponsive - '94 Convertible

 
Old 10-12-2013, 05:16 PM
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wingnut_c4
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Default Automatic Climate Control - Unresponsive - '94 Convertible

I know there are a ton of posts on climate control but I haven't yet found one that exactly matches my symptoms.

The panel is backlit but doesn't display anything. I installed a new (rebuilt) panel from Eckler's today (yes I know I am 'throwing parts' at it but it seemed logical).

The new panel does exactly the same thing.

I noticed there is a disconnected plug near the blower fan motor (yellow and grey wire), I found that on the wiring diagram, it looks like it goes between the "ACC Selector Switch" and the "Outside Air/Re-circulation Door Actuator". But I cannot for the life of me find the plug to connect it to. Not sure if that would fix the problem but probably something that needs to be addressed.

So Plan A is to actually fix this...Plan B is to turn the heat on so that at least I can drive it without freezing to death. It's current status is it flows cold air with AC on through the defrost vents. My thought was if I could manually set the temperature control to warm it would last me me until it can be fixed.

From other posts i thought I could access the temperature control door behind the blower fan, I have the blower fan off but the door is not obvious (at least not to me).

Thoughts/Insight?

Thanks!
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Old 10-12-2013, 09:48 PM
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Attached is a pic if the orphan plug, can anyone point me in the right direction ?
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Old 10-13-2013, 03:50 AM
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We need to know a few things first...

What year is the car? That makes a major difference.

Do you have the C60 manual HVAC system or the C68 automatic HVAC system? That also makes a major difference. I assume it's the C68 system since you say it doesn't display anything, which implies that it does have a display.

The temperature door (most people call it a "blend door") is located inside the evaporator housing. You remove the resistor module if you have a C60 system or the blower control module if you have a C68 system and you can see the blend door through the opening. It looks like this (the rusty thing -- 60F position in the first pic, 90F position in the second pic -- those are the C68 positions. Minimum temperature and maximum temperature for C60 systems):





It's possible that your car is different (year?), but on my car the outside air door is vacuum controlled. It's inside the car by the passenger's right foot, so that plug is unlikely to go there.

You could disable the AC compressor. On earlier years it is controlled by the blower module. Later years have a relay. Unplugging the compressor ought to do it.

Check your A/C fuse.

Last edited by Cliff Harris; 10-13-2013 at 03:53 AM.
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Old 10-13-2013, 06:58 AM
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Originally Posted by Cliff Harris View Post
We need to know a few things first...

What year is the car? That makes a major difference.

Do you have the C60 manual HVAC system or the C68 automatic HVAC system? That also makes a major difference. I assume it's the C68 system since you say it doesn't display anything, which implies that it does have a display.

The temperature door (most people call it a "blend door") is located inside the evaporator housing. You remove the resistor module if you have a C60 system or the blower control module if you have a C68 system and you can see the blend door through the opening. It looks like this (the rusty thing -- 60F position in the first pic, 90F position in the second pic -- those are the C68 positions. Minimum temperature and maximum temperature for C60 systems):





It's possible that your car is different (year?), but on my car the outside air door is vacuum controlled. It's inside the car by the passenger's right foot, so that plug is unlikely to go there.

You could disable the AC compressor. On earlier years it is controlled by the blower module. Later years have a relay. Unplugging the compressor ought to do it.

Check your A/C fuse.
Thanks for the reply, it is a '94 Convertible with the C68. I did unplug the AC as a stop-gap, now just need warm air -

Any insight on the orphan plug?
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Old 10-13-2013, 08:13 AM
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Originally Posted by wingnut_c4 View Post
i thought I could access the temperature control door behind the blower fan, I have the blower fan off but the door is not obvious
The blend door ( temp controller as you call it ) is located in the HVAC ducting inside the car
Earlier year shown but the motor that moves the door ( that can only be seen from underneath
the dash ) is in a similar location

IIRC your year has the motor driving the door directly without the linkage shown



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Old 10-13-2013, 10:09 AM
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Did you check your fuses? The backlight and display are on 2 different fuses
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Old 10-13-2013, 06:17 PM
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i do still need to go through the entire fuse box but i did check the one labeled 'AC Control'

Does anyone have a pic of where the Yellow/Grey plug connects on a '94?
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Old 10-15-2013, 05:09 PM
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Ok so I went through entire fuse box and tested every fuse, my interior lights work now (woohoo) but it didn't help the climate control.

I have a service manual and the troubleshooting in it will be very helpful but it seems to start from the control working but 'no cold', 'no heat', etc...

If I'm missing the 'nothing works at all section' please point me in the right direction.

Any help, ideas, or encouragement would be appreciated
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Old 10-15-2013, 05:35 PM
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If I pull the big fuse marked AC my display goes blank but still lights up. That's why I mentioned fuses.

I also got a SYS code on the speedo when I pulled the fuse.
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Old 10-15-2013, 05:42 PM
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Originally Posted by bassackwards View Post
If I pull the big fuse marked AC my display goes blank but still lights up. That's why I mentioned fuses. I also got a SYS code on the speedo when I pulled the fuse.
What year is yours? I didn't see a big fuse (I assume you mean under the hood) labeled AC, I'll look again
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Old 10-15-2013, 05:52 PM
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Mine is a 92 and I meant the largest amp fuse in the panel on the rt side of the dash.
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Old 10-15-2013, 05:54 PM
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Originally Posted by bassackwards View Post
Mine is a 92 and I meant the largest amp fuse in the panel on the rt side of the dash.
Ok - yeah, I checked those and the maxi-fuses under the hood...

Thanks
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Old 10-16-2013, 02:31 AM
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You still need to pull out the blower control module and look at the blend door.

When the ignition is first turned on the HVAC control head moves the blend door fully cold and fully hot to calibrate the extremes. Then it sets the blend door to the position indicated by the temperature setting on the control head. It takes about 15 seconds to do the calibration. You can watch it happen through the blower control module opening. If I have the radio turned off and the blower control module disconnected I can hear the blend door motor doing the calibration.

It's possible that your HVAC programmer has a problem. It drives the blend door motor. It's located above the accelerator pedal. It's common for the resistors to burn up. If one burns open the blend door will get stuck at one extreme. Here's a link with way more information than you need ;-):

http://forums.corvetteforum.com/c4-t...schematic.html

If you scroll down a bit in that thread there is a picture of the HVAC programmer PC board that shows the resistors that get hot.
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Old 10-16-2013, 08:21 PM
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Originally Posted by Cliff Harris View Post
You still need to pull out the blower control module and look at the blend door.

When the ignition is first turned on the HVAC control head moves the blend door fully cold and fully hot to calibrate the extremes. Then it sets the blend door to the position indicated by the temperature setting on the control head. It takes about 15 seconds to do the calibration. You can watch it happen through the blower control module opening. If I have the radio turned off and the blower control module disconnected I can hear the blend door motor doing the calibration.

It's possible that your HVAC programmer has a problem. It drives the blend door motor. It's located above the accelerator pedal. It's common for the resistors to burn up. If one burns open the blend door will get stuck at one extreme. Here's a link with way more information than you need ;-):

http://forums.corvetteforum.com/c4-t...schematic.html

If you scroll down a bit in that thread there is a picture of the HVAC programmer PC board that shows the resistors that get hot.
Thanks I think that will help but right now I am 'totally dead' situation. The controller literally doesn't display anything and the buttons don't do anything (this is a 'new' controller). It is backlit but that's it. I am stuck thinking the orphan plug near the blower motor is related (even if it's not I'm pretty sure it should be plugged into to something.)
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Old 10-17-2013, 02:45 AM
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The only thing I can think of that is in that area is the feedback fuse. It is in the wiring that tells the HVAC control head what speed the blower motor is turning.



Coolant overflow tank level? My car doesn't have one, so I can't look into that.
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Old 10-17-2013, 07:10 AM
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Originally Posted by Cliff Harris View Post
The only thing I can think of that is in that area is the feedback fuse. It is in the wiring that tells the HVAC control head what speed the blower motor is turning.



Coolant overflow tank level? My car doesn't have one, so I can't look into that.
What year is yours? I definitely do not have a fuse there, what is the small box to the left of the fuse in the pic?
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Old 10-18-2013, 02:57 AM
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Originally Posted by wingnut_c4 View Post
What year is yours? I definitely do not have a fuse there, what is the small box to the left of the fuse in the pic?
Mine is a 1986. The fuse normally fits inside that box. I just took it out for the picture.
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Old 02-15-2016, 08:23 PM
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Originally Posted by wingnut_c4 View Post
I know there are a ton of posts on climate control but I haven't yet found one that exactly matches my symptoms.

The panel is backlit but doesn't display anything. I installed a new (rebuilt) panel from Eckler's today (yes I know I am 'throwing parts' at it but it seemed logical).

The new panel does exactly the same thing.

I noticed there is a disconnected plug near the blower fan motor (yellow and grey wire), I found that on the wiring diagram, it looks like it goes between the "ACC Selector Switch" and the "Outside Air/Re-circulation Door Actuator". But I cannot for the life of me find the plug to connect it to. Not sure if that would fix the problem but probably something that needs to be addressed.

So Plan A is to actually fix this...Plan B is to turn the heat on so that at least I can drive it without freezing to death. It's current status is it flows cold air with AC on through the defrost vents. My thought was if I could manually set the temperature control to warm it would last me me until it can be fixed.

From other posts i thought I could access the temperature control door behind the blower fan, I have the blower fan off but the door is not obvious (at least not to me).

Thoughts/Insight?

Thanks!

I know your thread is several years old now, but did you ever find out what was causing your problem? I have a 94 with the same problem...back light works in the climate control, but no display and the buttons don't work. Thanks
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Old 02-15-2016, 09:51 PM
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Is the outside temp sensor hooked up?
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