1996 Mark VIII, No heat and intermittent AC

[Maroon8]

I feel bad for posting about this when there's so many open posts but I'm new here and can't seem to find anything outside of 97-98 years, I've done the test on the HVAC unit (can't remember name for it) and it came up with code 2 for the blend door though I can here the motor turning during the test. As for the A/C, when it's set it will take some time before it's felt (from 5-30 minutes if it wants to work at all) when it does work it usually stays on but will fluctuate from cool and cold as I drive. does anyone know of a sure way to test the Actuator?, From what I can see the actuator in my 96 looks different from the 97-98.

 

[driller]

On the 96, it's not a 'blend door' but technically known as an AC Air Temperature Control Door and is completely different from the infamous 97-98 blend door.

A/C Electronic Door Actuator Motor

The A/C electronic door actuator motor (19E616), is located on the inboard side of the A/C evaporator
housing (19850) and is connected to the A/C temperature control door.

* Its function is to move the A/C air temperature control door on command from the control assembly.
* The A/C electronic door actuator motor contains a reversible electric motor and a potentiometer. The
potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to
indicate the position of the A/C air temperature control door.
*A 5 volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates
the position of the potentiometer. The exposed value of the actuator wiper voltage is sent to the
control module and matched with the wiper voltage of the module potentiometer.
*The printed circuit board then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the control module wiper voltage.

There is an extensive troubleshooting section for the system starting with the EATC unit self test. Diagnostic Trouble Code "02" displayed during diagnostic procedures indicate the AC Air Temperature Control Door cannot reach desired position. Troubleshooting is then directed to "Pinpoint Test B".

Pinpoint Test B tests for the appropriate EATC DTC then follows through by first testing the actuator motor by disconnecting both electrical connectors from the EATC and applying battery voltage to the appropriate pins on connector C2.

* Operate the A/C electronic door actuator motor in both directions using a 12 volt battery. The
following pins may be jumped to use the vehicle battery. Make sure the ignition switch is in the RUN
position.

Jumper 1: Pin C2-24 (BK 57) to Pin C2-21 (DB/LG 249).
Jumper 2: Pin C2-24, (BK 57) to Pin C2-22 (O, 250).

Further testing involves testing resistances in the EATC module assembly and continuity between the EATC and AC electronic door actuator motor.

It should be noted that replacement of the AC electronic door actuator motor requires a calibration routine be performed for the system to function properly.

I highly recommend obtaining the 1996 model year specific service manual and EVTM for diagnosing such systems. So much on the 96 models is uniquely different from the earlier years of the Gen 1 Mark VIII and of course the 2nd generation Mark VIII.

 

[Maroon8]

On the 96, it's not a 'blend door' but technically known as an AC Air Temperature Control Door and is completely different from the infamous 97-98 blend door.



There is an extensive troubleshooting section for the system starting with the EATC unit self test. Diagnostic Trouble Code "02" displayed during diagnostic procedures indicate the AC Air Temperature Control Door cannot reach desired position. Troubleshooting is then directed to "Pinpoint Test B".

Pinpoint Test B tests for the appropriate EATC DTC then follows through by first testing the actuator motor by disconnecting both electrical connectors from the EATC and applying battery voltage to the appropriate pins on connector C2.


Further testing involves testing resistances in the EATC module assembly and continuity between the EATC and AC electronic door actuator motor.

It should be noted that replacement of the AC electronic door actuator motor requires a calibration routine be performed for the system to function properly.

I highly recommend obtaining the 1996 model year specific service manual and EVTM for diagnosing such systems. So much on the 96 models is uniquely different from the earlier years of the Gen 1 Mark VIII and of course the 2nd generation Mark VIII.

Perfect, I didn’t think there was much of a difference between the 96. Do you have any recommendations where to get the service manual from?

 

[driller]

Do you have any recommendations where to get the service manual from?

Helm Inc., the OEM source no longer publishes manuals for the Mark VIII but you should be able to score a set off eBay.

 

[Maroon8]

I’ve gotten my service manual, the motor turns both directions with the jumped pins but doesn’t stop, is that normal?
also test B4, is this testing the EATC itself or is this the connector on it?
Lastly B6 says the actuator connector is accessible but I’m having trouble finding it, does anyone have pictures or been able to reach it before?

 

[driller]

I’ve gotten my service manual, the motor turns both directions with the jumped pins but doesn’t stop, is that normal?

When you jump the pins on connector C2, you are grounding the motor drive circuit and it will not stop until you disconnect the ground. In operation, the feedback potentiometer indicates the position of the AC Temperature Control Door and it is commanded to move by grounding the proper motor drive circuit and stopping where directed by disconnecting the ground.

also test B4, is this testing the EATC itself or is this the connector on it?

This is testing the A/C Air Temperature Control Door Actuator potentiometer through connector C1.

Lastly B6 says the actuator connector is accessible but I’m having trouble finding it, does anyone have pictures or been able to reach it before?

I assume "accessible through the glove compartment" requires removing the glove compartment. The actuator should be to the left of the blower motor, probably accessible to the left of the glove box opening. This is the best I can do... a screenshot from the manual: