I am having a couple of problems with the climate control on an 89 coupe. I can not get it to enter into diagnostic mode, and it does not receive a signal to the air mix door module from the control unit.

To attempt to enter diagnostic mode I am depressing the rear defrost and the fan increase buttons as per the service manual. It states that once into the diagnostic mode I should be able to change modes using the warm button. I have tried this a number of times, using different time frames and methods with no success. What am I doing wrong?!?!?!?!?

The reason I am wanting to enter diagnostic mode is to attempt to figure out why I can not get the mixing door to operate.

I am not getting a response to initiate motor movement.

I desoldered the motor from the board, and it operates flawlessly when I apply power, in both directions.

I have 5 volts coming into the module via. the red wire, and verified the ground to the black wire.

The green wire (position feedback) is sending a signal back to the control unit (varies with position, seems to operate correctly). But, I can not get a response from the control unit to send voltage to the door control via the tan/blk and yellow wires.

Any advice?

Thanks-

 

To enter diag. mode on a 89.

Press the Ext. Temp. button.

While pressing the Ext. Temp Button, press the Auto Fan button and then release it. Then release the Ext. Temp. button.

a -00 should appear. - indicating what Mode is displayed.

Mode 1 is Program number
Mode 2 is in vehicle thermistor
Mode 3 Ambient correction
Mode 4 Blower number
Mode 5 Outside thermistor
Mode 6 Feed back pot position
Mode 7 Calculated door position
Mode 8 System faults
Mode 9 Ratiometric feedback position
Mode 10 Full hot position
Mode 11 Full code position
Mode 12 Software version

To change Mode # press the Warm button.
To see the value in that Mode # press the Cool button.

A system fault is indicated by a flashing indicator. If there is a problem with the ambient sensor, in
vehicle sensor, or the feedback potentiometer, the Ext. Temp. indicator will flash for about 60 seconds,
upon ignition ON. The flashing indicator will reoccur upon ignition ON until the system problem has been corrected.

If you disconnect the battery and reconnect it, the system will recalibrate and move the door from one extreme to the other and then position the door and stop. The blower motor also comes on and you can manually turn it off. Takes about 30 seconds.

 

To enter the diagnostic mode, push and hold the fan up and down arrows at the same time for about 5 seconds.

The display should show "-00".

Push "Auto" and the display will show any fault codes that are stored in the computer.

00-Not used
01-Temp. Door Motor Circuit Fault
02-Temp Door Motor Circuit Fault
03- Ambient Sensor Open
04- Ambient Sensor Short
05- In-Car Temp Sensor Open
06- In-Car Temp Sensor Short
07- Solar Load Sensor Open
08- Solar Load Sensor Short
09-Low Freon
10-UART Failure

 

My car will not enter diag mode with the normal buttons but it does enter diag mode with the vert buttons. Kind of odd I thought. My FSM lists both methods for my year.

 

I only know of the one method - as described - through '89. After that, info is also accessible with a bi directional scanner via the CCM link. Anyhow, what is available in these earlier Years is generally minimal and a door problem is better diagnosed by disconnecting and reconnecting the battery, then turning the ignition to run and with the Controls on Auto and your ears and eyes trained on the motor - see what it does. If nothing, remove it and apply an external voltage and ground to the motor which will confirm or rule it out. Assuming it works, and the Controls light up correctly, repair (there is or was a Tech Tip) or replace the Programmer.

 

Here is a picture of the two methods that are in my '88 FSM. I found it odd that my coupe needed to use the 'vert procedure.



The OP couldn't get the normal procedure to work either. Is this a FSM error?

 

I don't know if it's wrong as I don't have Bulletins for the '88 (which is the most likely place for GM to fix mistakes in the Manual). Do know that if there is a code - it'll be flashing below the Outside Temp Readout. The monitored parameter - for the door - is simply voltage on the return. If it's there, the Panel doesn't record a code. The rest of the faults are for the Themistors and again, it's looking for voltage and doesn't have the capability of determining whether it's the right/wrong amount. Can't say I've ever seen a problem with them (Inside and Outside Temp Sensors) on these early Years. The motor door is usually fine too - it's either got a broken link or the Programmer isn't sending the signals to move it (burned up resistors if I remember the Tech Tip correctly). Eyes and ears work best (for me) in dealing with this part and since I'm fairly dangerous with a soldering iron, I'd be replacing the Programmer if it wasn't working.

 

I had a similiar situation a couple of years back. It turned out to be the programmer; two resistors were burnt out. I took the programmer to a radio repair shop and they replaced the two resistors. A total cost of $3.00 plus coffee. There used to be a post on this particuar issue.

 

I found the site. Hope this helps.

http://www.batee.com/corvette/acrepa...oard/c68.shtml

 

I have tried all the methods mentioned above, along with a few others, and even tried asking my ole' faithful "Magic 8Ball" (which keeps telling me "ask again later") and I still can not get into the diagnostic mode.

Everything else operates correctly on the climate control system.

So, I am beginning to think that I must have an internal programmer problem. (as mentioned in above replies)

I am basing this on the fact/s:

(1)that I can't get into diagnostic mode, and
(2)I do not have a signal from the controller to the air mix module.

The programmer seems to be the common denominator.

Not to mention, I think I have had just about everything else apart on this car over the years, so, I might as well do a lil' bit o' exploratory surgery and see what makes this baby tic.

I'll report back with my findings.

btw... thanks for all the ideas and input. and for the link to the c68 info, awesome!!!!!!!!

 

I had problem with my '90 Climate control unit;

1.) Have you pulled the fuses as indicated in the owners manual?
2.) Have you disconnected the negative terminal on the battery
waited 5 minutes then re-connect.
3.) Possibly the ECM!

Hope this helps

 

'89 and below works a little differently and there is no ECM/CCM interface (other than a low voltage signal to the ECM for idle/WOT control). The Processor is the Dash Controls. You can erase memory by disconnecting the Battery or the Courtesy Clock Fuse (?). Hook the battery back up and it should start moving the door so that it can learn it's position. Takes 30 seconds or so, during which time nothing - compressor - blower - maybe the Outside Temp Readout (may show minus 32) is going to work, but it's the easiest way I know of to start your troubleshooting.

 

well... i cracked open the control unit, and found 2 large resistors (135 ohm) on the board that had been hot and the solder joints were cracked. so, i desoldered them, compared them against one another for consistent operation at different loads and temps to verify they worked correctly, then, soldered them back in.
and...

BINGO!!!!!!!! success!!!!!!!!!!!

everything operates without a flaw. getting the mix door re adjusted was kinda tricky. turns out, that if the door rod is just a bit outta wack the motor will constantly try to achieve the correct position as it is reading the feedback from the pot in the mod. eventually, i was able to get it just right, and the control unit stops the signal when the motor rotates to the max cw or ccw position. you sure wouldn't want to have one of these outta adjustment, otherwise, i think, it would burn itself up. the control unit will constantly send a voltage of 5-9v to the motor, looking for the correct pot signal.

thanks for all the info from everyone. couldn't have done it without ya!!!!!!!!!!!!!!!

now, all i have to do is get the car back together, and ima on the road again!!!!!!!!

btw, i still am unable to get into diagnostic mode... im not overly worried about it, as it all works now, but, still kinda curious what the deal is. i tried all the methods mentioned above, and no luck. oh well. i guess ill cross that bridge when i get there... should i ever need it.

brian

 

Nice work GM would probably replace the works and charge you in excess of $1000

 

Nice Job? Congratulations on the easy fix!!!!

 

Replacements are/were about 100 Bucks or so - though looking at The Last Detail, they no longer list it. I know the '96 is unique and costs something north of $500, but more often than not, that Year has a problem with the vacuum harness hookup - it isn't the motor signal. Anyway, I've got a spare somewhere.

 

Looks like I'll be swinging over to your house for repairs!

Fine job dude!

 

Where is the programmer on an 89?

 

The programmer is located on the drivers side, just left of the brake pedal, screwed into the firewall. It is approx 3x6", black in color with two connections; a vacuum harness and an electrical harness.

 

Ok, I'll pull mine out and look at it for the hell of it. It looks like I'm having door issues.