Okay I just hooked the heater and a/c system up in my 90 project. I know absolutely nothing about how to diagnose issues with this system.

Sometimes while on recirculate the a/c goes from cold to warmer air then goes back to cold. When I select upper vent only and set the temp control to 90 degrees sometimes the idicator lights above the button thats selected starts flashing. The system does indicate outside temps but I've never seen a inside temp displayed (unless its not suppose to)

Another thing I noticed kinda weird is on some heater settings the compressor always is running. Like when its on dash vents and 90 degrees is selected the compressor sometimes runs and then doesnt. The a/c only seems to work somewhat correctly when recirculate is selected and 60 degrees is selected but then it occasionally does the warm air thing.

The compressor always runs so thats not whats causing the switching of cold to warm air. The system seems to switch vent setting fine, turns on and off fine.

Last night for instance I selected dash vent and 90 degrees and yes it got real warm in the car but after say 15 minutes the indicator light started flashing then when I shut car off it stopped flashing but then started again.

Any help getting this system to work right would be appreciated.

 

The reason its flashing is there is a problem/trouble code stored.
A/c compressor will run on all vehicles with defroser on to dehumidify the air to remove foggy windows.There is a way to search for trouble codes by pressing HVAC buttons but,I don't remember off hand how to do it.Even if you find the way you need to look up the procedure for testing so access to all-data or another source will be needed.I hope this helps & other members here will add to this.

 

I assume you have the C68 automatic HVAC system.
I am not an expert on the 90 but you need to check the blend door mechanical operation. There are some rods and holders that break so the air mix door is not controlled properly and may just be flopping around. There is a motor that moves and it is connected to the door with the rods. This is what regulates the air temperature. You will probably have to take some panels off on the passenger side to get in there.

The temp display reads outside temperature or inside set temperature.

The compressor always runs (cycles) except in top vent, and heat (bottom vent) mode.

Here are the codes, see if you can sort out some of the problems.


CODES
You can read the HVAC system diagnostic codes from your climate control unit if your 1990 to 1996 Vette is equiped with RPO C68. To enter diagnostic mode, push and hold the fan up arrow and down arrow at the same time until the LCD shows -00 You are now in diagnostic mode and may select any parameter using the up and down arrows. To see the value for that parameter, press the fan "auto" button.
Note: A minus sign on the display range means to add 100 to the value displayed. So, -155 actually is 255.

Parameter Number Parameter Description Valid Values
0 System Faults
(one of these will be set if your air conditioning controls have an LED flashing) 00=No Faults
01= Temp Door Motor Circuit Fault
02= Temp Door Motor Circuit Fault
03 = Ambient Sensor Open
04 = Ambient Sensor Short
05 = In-Vehicle Temp Sensor Open
06 = In-Vehicle Temp Sensor Short
07 = Solar Load Sensor Open
08 = Solar Load Sensor Short
09 = Low Freon Detected
10 = UART Failure
1 Temp Setting 60F to 90F
2 In-Car Temp Sensor 10 = HOT -130 = 230 = COLD
3 Outside Temp Sensor 10 = HOT -130 = 230 = COLD
4 Sun Load Sensor Max light Max Dark
L98 38 183
LT5 115 -110 = 210
[Notice the solar shield effect!]
5 Ignition System Voltage 0 = 9 Volts -155 = 255 = 16 V
6 Engine Speed (RPM divided by 25)
7 Vehicle Speed
9 A/C System Mode 00 = OFF
01 = Re-Circulation
02 = A/C
03 = Bi-Level
04 = Heater
06 = Defrost
07 = Vent
10 = Manual Re-Circulation
10 Blower PWM 0 = 0 Volts 128 = 14 Volts
11 Program Number 00 = COLD -155 = 255 = HOT
12 Mix Number -155 = 255 = COLD 00 = COLD
16 Coolant Temperature In degrees C
17 Solar Correction 114 = Max light 128 = max dark
30 Stored Full Hot Value 0 to 50
31 Temp Door Travel Range 100 to 200
34 Temp Door Position Requested 00 = Full HOT -153 = 253 = Full COLD
35 Compressor On Time .1 second increments
36 Number Of Times Below Critical Time
37 Software Version Number

 

Lol, pcolt94 beat me to it!

Here is how to enter the diagnostic mode of the electronic A/C controller. Taken directly from the 1990 FSM:

"If a system fault is detected, the LED of the operating mode the system is in at the time of fault detection will flash at a rate of 60 times per second. Fault codes will then be stored.

To enter into the diagnostic mode, the fan 'up' and fan 'down' buttons must be pushed simultaneously for approximately 5 seconds. Upon entry into the diagnostic mode, the LCD will display any fault codes stored by the programmer.

FAULT CODES DESCRIPTION

00...................................... ..........NO SYSTEM FAULTS
01............................TEMP. DOOR MOTOR CIRCUIT OPEN
02..........................TEMP. DOOR MOTOR CIRCUIT SHORT
03...................................... ......AMBIENT SENSOR OPEN
04...................................... ....AMBIENT SENSOR SHORT
05.....................................I N-CAR TEMP. SENSOR OPEN
06...................................IN-CAR TEMP. SENSOR SHORT
07...................................... .SOLAR LOAD SENSOR OPEN
08.....................................S OLAR LOAD SENSOR SHORT
09...................................... .......LOW FREON DETECTED
10...................................... ..................UART FAILURE

While in the diagnostic mode, it is possible to check several different system parameters (circuits or systems). This is done by pressing the fan 'up' or fan 'down' button. Once the parameter to be checked has been chosen, the fan 'AUTO' button is pressed and a diagnostic value is displayed on the LCD.

The following is a list of diagnostic parameters:

PARAMETER DESCRIPTION

02...................................... ......IN-CAR TEMP. SENSOR
03..........................OUTSIDE (AMBIENT) TEMP. SENSOR
04...................................... ........SOLAR LOAD SENSOR

For further diagnosis of ECC system codes, refer to the diagnostic charts in this section. To exit diagnostics, change to a different ECC system mode."

Find out what codes are stored in your A/C controller, and report here what they are and I will send you the troubleshooting page(s) for that code.

You should purchase an FSM, while they are a bit pricey, they are worth it if you are going to do any work/troubleshooting on your vette.

 

All good info, but start with a rebooted processor (Programmer) by removing power for a minute or two - disconnecting and reconnecting the battery is the quickest method for me. Then restart. There should/will be a brief delay (nothing works) while it learns Temp Door Position which it does by moving the door from fully open to fully closed. After that, compressor should engage and all controls should function. If it starts flashing, obtain the trouble code.

 

I've had the complete heater core box out and don't know what you mean by "rods" that the motor is connected to. Mine has the motor mounted right above the blendoor and this electric motor is connected directly to it.

I do know when a cold setting is selected this blen door closes all the way but when a hot setting is set it opens like half way and kinda flutters and wigs out.

 

Ok then, like I said I was not a 90s expert and was not sure just what you had. Now that I know you have the direct motor drive I know what you have. I recently just spent a few weeks on my system working on it. Operation is same as 94 but the programmer is a different type. I documented most of the highlights of my work in a post recently and some might relate to your problem. With out the FSM, I would have never been able to do the detailed troubleshooting that I did. You should at least read (and hummer me) it to get familiar with some of the things I did.

http://forums.corvetteforum.com/c4-t...blem-94-a.html

I am not going to give you any massive troubleshooting procedure as to how I did it but just try to give you a bottom line. There are 3 main pieces in the HVAC system. Control head, programmer and motor. I don’t believe the control head is bad. Either the programmer is bad which drives the motor or the motor is bad.

Now I had a similar problem to yours, it would oscillate when going to heat. In the motor box there is a motor and a rheostat pot that is the feedback voltage for the door position. If the feedback voltage is out of range, it will drive cold, but not go to heat. I had to re-position the gears on the pot to get the correct feedback voltage. After I did that as per the FSM, everything worked. This is not a normal problem in the FSM. I did have an error code of “01” for the motor circuit.

If you have some technical and electrical competence I will email you the pages to work with. If you do, PM me your email, take me couple days. Or you can go out and buy some parts and attack it from that end.

 

This weekend I will pull the codes and let you know what ones are there. Any idea how much the motor cost for this thing?

 

I usually buy used when I can from a local guy here or Ebay. Maybe $50-$60. But I would hate to see you go out right away and buy anything before taking a good shot to find the problem. Having information on where the problem is, is better than throwing darts.

 

Ok I did the key on engine off fan up fan down and 00 was displayed. Could the fact when this a/c system was installed and low on freon be the cause? If thats the cause why is it showing no faults even though the indicator light flash?

 

also I did the advanced diagnostic with the fan up the press auto button. I did this with key on engine off and climate thing set to off position.

But pressing the fan "up" fan "down" thing on shows a "00" I've even waited a few seconds but it always remains "00"

also I should add these were done in the dark and probably 60 degrees outside.

(1) 86
(2) 173
(3) 128
(4) -127
(5) 163
(6) 00
(7) 00
(9) 03
(10) 128
(11) -155
(12) 00
(16) 14
(17) 128
(19) 132
(20) 171
(21) 109
(22) 62
(23) 128
(24) 128
(30) 60
(31) 95
(34) 00
(35) 00
(36) 00
(37) 07

 

Also does anyone know the correct GM part number and name for that blendoor electric motor. I always hear this thing constantly running so I just want to get a new one for it.

 

Pcolt94

I looked at that thread you did and yes my motor looks just like that one

yes this is a C68 car too

 

Jeff
Let me know what part it is you need. I might have it also. I have the heater box out of the same car the controller came from.

Phil

 

Phil can you post a picture of that box so everyone can see how mine is?

 

Yea should be able to when I get home. Will be a few hours before i get home from work BUT I will do it when i get home tonight.

 

Well I bought a new blend door actuator motor and see if this cures my issues. I'm curious why my indicator lights would be flashing yet no codes are stored.

I will let you all know the outcome and if the new actuator helps.

 

I’m assuming you installed the motor and have the indicator light flashing. What you may need to do next is to re-set the system by disconnecting the battery for 30 seconds. This might enable the programmer to adjust itself to the new motor and feedback voltage.

If that does not fix it then try to extract the code again. If there is no code, see if the motor is responding correctly to the temperature control or if you have the same problem.

 

No, I haven't installed the actuator motor as of yet. I just got the thing a few days ago and plan on putting it in next weekend. Probably have to remove the heater core again (for joy)

the system seems to always switch vents correctly depending on which button is selected, and fan works as it should so I dont think this is a head unit issue or controller issue. But like I said with key on and motor not running I constantly hear this blend door motor running maybe the gears in it are stripped or something I dont know.

I do know even when car is at operating temperature it doesn't blow as hot of air as I would think it should. I do know when heat is selected this actuator only opens the blend door about 1/2 way then start doing that occilating movement and sound.

 

What I can see you have a 1990 year car and the motor you ordered is a direct drive motor connecting right to the shaft of the mix door. If you drop the plastic panel (and side panels) above the passengers knee the motor should be visible. It is held on with 2, 7mm screws. One screw is easy with a ¼ “ ratchet, and one is a b***h. I use one of those flat, round, ball ratchet things for shallow places. Only need one screw to hold it for testing purposes.

Once the screws are out, pull straight down, it might be stuck at first. Go easy at first to avoid damage to door and shaft. Squeeze the connector release and it comes right off. Then you can slip the new motor on but pay attention to shaft position. I can only get my motor on in the cold position for some reason.

If you feel you don’t have the setup I have indicated, or I have an error in information, I am speaking from a 94 point of view. I just don’t think you have to pull the heater core or any stuff out.