1998 Pontiac Grand Prix GTP, alternator exchanged, battery unhooked and rehooked. Now blowing hot air on passenger side only, regardless of settings on either side.

Archeology currently under way to find owner's manual, but isn't there a trick to resetting the individual climate controls?

The CJ2 air conditioning is equipped with an on-board diagnostic feature which allows the heater-A/C control to detect certain system faults. The diagnostic feature can also be used to display certain data parameters. If the heater-A/C control detects a fault in the system, the man symbol will flash during the first 2 minutes of vehicle operation.

Entry into the diagnostic mode is gained by pressing in on both temperature knobs at the same time for 5 seconds. The following display modes are found within diagnostics:

• The diagnostic pointer

• The diagnostic value

By rotating the driver temperature knob one detent in either direction, the display is toggled between pointer and value. The value displayed is the decimal equivalent of the RAM contents. A 2 is formed using the minus sign and the leading 1 in order to display values over 199.

A diagnostic pointer mode is identified by a minus sign preceding the pointer number. The pointer provides an index, which identifies the corresponding diagnostic value. The Diagnostic Trouble Codes (DTCs) reside under diagnostic pointer -00. The pointer will be set to this position upon initial entry into diagnostics. If more than one code exists, they will be displayed sequentially at a rate of 2 seconds per fault. Rotating the passenger temperature knob will switch the diagnostic pointers. A wrap around feature is provided if the pointer is continued past either end. Other data used by the computer resides under different diagnostic pointers, and may not be of use in observing the system. To exit the diagnostic mode, press any mode button.

Important: A two-digit trouble code indicates the fault is current. A three-digit trouble code indicates a history fault.

For a list of Trouble Codes and their meanings, refer to DTC Table .

Retrieve the codes and post them. I'll see what I can find.

Whoa, thanks. Will relay above to the person doing the actual work. Thanks.

Okay, just as an aside, the following was suggested, and did not seem to work

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Place the ignition switch to the OFF position.
Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
Install the HVAC/ECAS fuse.
Start the vehicle.
Wait 40 seconds for the HVAC control module to self-calibrate.

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I really thought it might be something like that, since it worked pre-battery disconnect and failed after re-connect.

So trying as you said above, pressed both knobs to go into diagnostic. At indication (-00) turned passenger knob. Indicator went to (00) then returned to (-00)

Though not really what you mentioned, driver's knob was turned to indicator (-01) When passenger knob was rotated, indicator went to (10) Driver's knob then turned to (-22) when passenger knob was turned, indicator went to (158)

Was not sure if you needed any of the codes beyond (-00) which apparently was (00) I got from your email that codes on indicators (-01) to (-22) weren't needed.

Any ideas or other instructions?

[This message has been edited by CanyonAg77 (edited 6/29/2011 1:52p).]

FWIW, with my truck, I had to disconnect power for a minute, reconnect, then without touching anything on the a/c yet, run the truck for a few minutes, then turn it off, then run it again and then check the a/c.

Mouth, that's sort of what I thought the reset trick was: Power it down with the controls to off, and re-connect and re-start.

Perhaps before this is all over, someone will tell us how to set the A/C before removing battery power. For instance, would the A/C computer not freak out if you turned the A/C off while running, then switched off the vehicle, then disconnected the battery?

Those numbers aren't showing up on the chart.
I was trying to find the relearn procedure, but '98 model is on the very bottom end of vehicles for which I have complete info. Here is GMs description and operation of the dual zone system on the 98 GP.

Dual Zone Air Conditioning (A/C) System Description
The dual zone A/C system performs the following functions:

• Heating

• Ventilation

• Air conditioning

The dual zone A/C system is controlled by vacuum and electronic circuits. Both electronic and vacuum circuits determine air intake and discharge locations. Electronic circuits also control the following functions:

• Mode operation

• A/C compressor clutch operation

• Fan operation

• Discharge air temperature

The driver may select any of the following functions from the Heater-A/C control:

• Interior temperature

• Fan speed

• One of eight different modes of operation

One of these modes is a fully automatic dual zone mode. In the fully automatic dual zone mode, the system determines the following conditions:

• Air intake

• Discharge locations

• Fan speed

• Discharge air temperature

The system determines these conditions from the following information:

• The temperature that is selected by the driver or the passenger

• Any information that is provided by the system's network of sensors

The passenger temperature control significantly increases or decreases the air discharge temperature on the passenger's side of the vehicle.

The passenger control is on the heater A/C control head. The passenger control is enabled by pushing the DUAL button on the control head.

Is the "dual" button off?

Thanks for your input, I was still hoping it might me a simple reset like

http://texags.com/main/forum.reply.asp?topic_id=1695866&forum_id=46&page=last

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turn the AC off, turn the truck off, pull the climate control fuse (under the hood) for 10 mins, plug in, start truck, dont touch the climate control, Wait 10 mins press auto, wait about a minute, turn temp to max cold then wait a minute, move to middle temp, then hot.

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Those numbers aren't showing up on the chart.

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Here's what another Internet post showed:

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On-Board Diagnosis Mode
The CJ2 air conditioning is equipped with an on-board diagnostic feature which allows the heater-A/C control to detect certain system faults. The diagnostic feature may also be used to display certain data parameters. If the heater-A/C control detects a fault in the system, the man symbol will flash during the first 2 minutes of vehicle operation.

Entry into the diagnostic mode is gained by pressing in on both temperature knobs at the same time for 5 seconds. The following display modes are found within diagnostics:

The diagnostic pointer
The diagnostic value
By rotating the driver temperature knob one detent in either direction, the display is toggled between pointer and value. The value displayed is the decimal equivalent of the RAM contents. A 2 is formed using the minus sign and the leading 1 in order to display values over 199.

A diagnostic pointer mode is identified by a minus sign preceding the pointer number. The pointer provides an index, which identifies the corresponding diagnostic value. The diagnostic trouble codes (DTCs) reside under diagnostic pointer -00. The pointer will be set to this position upon initial entry into diagnostics. If more than one code exists, the codes will be displayed sequentially at a rate of 2 seconds per fault. Rotating the passenger temperature knob will switch the diagnostic pointers. A wrap around feature is provided if the pointer is continued past either end. Other data used by the computer resides under different diagnostic pointers, and may not be of use in observing the system. Press any mode button in order to exit the diagnostic mode.


Important
A 2-digit trouble code indicates the fault is current. A 3-digit trouble code indicates a history fault.


Clearing Codes
Press the A/C mode button in order to clear codes from the heater-A/C control.

Any of the following components may cause malfunction in the temperature controls:

The refrigerant system
The electrical wiring connections
The vacuum connections
Faulty components that have mechanical problems, such as sticking valves
As a part of the diagnostic process inspect the following components:

The refrigerant, vacuum or mechanical systems. Refer to Vacuum Test .
The blower controls. Refer to 66-0 .
The compressor controls. Refer to Cell 67: RPO L36, L67 .
The air delivery controls. Refer to Power and Grounds .
The temperature controls. Refer to Electrical Diagnosis. Complete the diagnostic procedure for the heater A/C control microprocessor.

Make sure to turn the climate control off first, then hit both buttons at the exact same time. I know one time it took it like 5 seconds, the next time it took like 15.Then rotate the left knob until the desired number appears.

Position Description
-00 Error codes Click here for the Trouble Codes chart
-01 (servo position) 103-107 43-162
-02 (servo position) 128 120-202
-03 (servo position) 150 162-194
-04 CJ2 Fan Speed Low=15, 29, 44, 58, 71, 86, 110=High, CJ2 Unit will adjust to other increments as needed
-05 (servo position) 93 88-191
-06 (servo position) -152 00-252
-07 (servo position) 00 0, 34-255
-08 (servo position) -155 00-255
-09 (servo position) 00 0, 23-255
-10 ? 04 04
-11 CJ2 Vent Mode 1=Def, 2=Bilevel, 3=Auto, 4=Lower, 5=Def+Lower
-12 Engine Coolant Temp -60 degrees 80=104, 95=131, 100=140 Peak@135°F
-13 Actual Vehicle Speed in MPH
-14 (servo position) 00 21=0
-15 ? 39 44
-16 Radiator low fan turn on temp -106 207
-17 Radiator low fan turn off temp 196 199
-18 ? 50 51
-19 (servo position) 162-169 40-172
-20 Affected by cabin temp sensor 89 50-172
-21 (servo position) 00 ?
-22 Sunload Sensor -117 LIGHT=126, 218=DARK
To return to normal operation, press the MODE button next to the Passenger temperature knob.

This is a list of the Trouble Codes displayed by the CJ2 Unit.
A two digit code indicates a current fault while a three digit code indicates a historic fault.
Trouble Code Description
00 No System Fault
01 or 101 Inside Air Temperature Sensor Short
02 or 102 Inside Air Temperature Sensor Open
03 or 103 Ambient Outside Temperature Sensor Short
04 or 104 Ambient Outside Temerature Sensor Open
05 or 105 LH Electric Actuator Open or Short
06 or 106 RH Electric Actuator Open or Short
07 or 107 UART Serial Data Line Fault
08 or 108 Solar Sensor Open

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'98 model is on the very bottom end of vehicles for which I have complete info

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Sixth generation ran from 1997 to 2003, so perhaps newer aren't much different?????

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Is the "dual" button off?

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Does it have to be off for diagnostic? Or are you saying in normal operation somethings whacks when dual mode is on?

Dual mode has to be "on" to control the passenger side.

Apparently passenger blows hot regardless of how its control is positioned and even if driver control is set full cold.

Sounds like the passenger side temp door actuator has shat itself.

It is mounted on the passenger side of the HVAC case and can be accessed by removing the glove box.

If you choose to replace it yourself (pretty easy) DON'T plug the connector to the new one until it is installed. If it isn't installed when connected, the actuator will over-travel and strip.

Crud. As said above, could this have to do with the battery disconnect? And if so, where should the A/C be set before disconnect so the computer does not lose it's mind?

And if the car is about to take a trip, can the door be wedged in place until trip is over?

(Redneck duct tape and bailing wire solution, I know)

Most automatic systems will self calibrate. We've seen too many times when a battery disconnect wigs out the a/c system.
If an actuator completely shuts down, it usually needs changing.

If you are in Texas, just take the actuator off and prop that bad boy open to the full cold position and don't worry about it 'til December.

Might do that.

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We've seen too many times when a battery disconnect wigs out the a/c system.

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Sounds like GM has a problem....

And, and thanks for all your time.

One more odd thing...apparently on this car, you push the "dual" button to allow the passenger to set their own temp, and the button lights up. While the original problem was happening, the light would come on and the system would switch to dual control without anyone pushing the button.

Aaaaannnnnddddd.....the problem magically healed itself today.