Scope -
One of the most common problems with the roof not working is due problems with the convertible top Roof Flap Servos (RFS). If your top suddenly stops working, or doesn't open or close all the way, or if the windows stop working correctly odds are good one or both of the RFS is to blame. At this point you will need to run a fault scan with either an OBDeleven or Ross Tech VCDS to identify the fault code. (More on VAG software friendly OBDII devices here).
I have tested the OBDeleven and while it can be used to find and display a roof-related fault codes, it does not have the ability to run the Adaptation (Output test) to clear the faults for this problem. You can read more about OBDII diagnostic devices here.
If the top is still working as it should and there are no faults in Address/Control Unit 26 Auto Roof, then you can still go ahead and perform the servo cleaning as described below. However, if a fault has been registered, it will require a VCDS to run the Adaptation (Output test) in order to clear the fault and get the top working again.
Note - The term "Adaptation" comes from the Workshop Manuals, when in fact, the VCDS requirement is to run the Roof Flap Initialization which is listed under the Output Tests. This performs a cycle test to make sure the component is within operating parameters and then clears the faults.
NOTE - A downloadable PDF file for these instructions are available here.
![Image]()
![Image]()
Overview -
The RFS has two primary components; the left and right motors (V381 & V383) and the corresponding potentiometers (G596 & G597). When energized, the motor drives the potentiometer main gear which moves the servo arm and ball link to raise and lower the flap. At the same time, the potentiometer sends a real-time position signal to the J256 Convertible Top Operational Control Unit (CTOCU) so it knows if the flap is open or closed. In the event the servo gives a false or out-of-tolerance reading (implausible signal), the CTOCU will lock out the E137 switch (center console roof switch) which will prevent the top from moving to avoid a collision between the top mechanism and the flaps.
Think of the potentiometer like a dimmer switch; turn it one way the light gets brighter, the other way, the light gets dimmer. This is because the voltage changes as the dial is rotated. In the same way, the roof flap potentiometer provides the CTOCU with a high or low value so it "knows" if the flap is up or down.
For a more detailed explanation on how the convertible top works including Measurement Blocks, Fault Codes and Adaptation, click here. Also it's worth reading through Self Study Program 391 linked here.
The Cause of the Fault -
Over time, the grease inside the servo housing can migrate from the gears onto the potentiometer and gunk-up the electrical contact between the circuit board the little copper "fingers" on the contact gear. When this happens, a false signal or "implausible signal" can be generated which will result in intermittent operation of the top or no operation at all. While some service centers recommend replacing the flap servo, this doesn't always solve the problem since even new servos can eventually end up with grease in the potentiometer too.
![Image]()
![Image]()
![Image]()
Purpose of the Adaptation -
When a fault has been registered, the Adaptation has to be performed to allow the CANBUS to establish the new max and min values of the potentiometer. Unlike a normal on-off switch which only has two positions, the potentiometer has a range of positions. The Adaptation allows the CANBUS to "learn" the new expected values for Group 001, Blocks 3 and 4 which should be between ~42 and ~184 as it moves the RFS potentiometer. This is why simply clearing the fault won't make the problem go away even if you've clean up the servos since the out of range values are stored until the Adaptation has been performed.
Fault Scan for Soft Top Diagnosis -
After running an Auto Scan, look under Address 26 Auto Roof. Reported roof flap faults might look something like this:
Address 26: Auto Roof Labels: 8J7-959-255.lbl
Control Module Part Number: 8J7 959 255 B
Component and/or Version: 256 VSG TT H14 0110
Software Coding:
Work Shop Code: WSC 00000 000 00000
VCID: 3E73D87369826EEEA6F-806B
4 Faults Found
- 02000 Switch Position*
008 - Implausible Signal
- 00830 Convertible Top Control Module (J256)
004 - No Signal/Communication - Intermittent
- 03246 - Sensor for Canopy Flap; Left (G596)
008 - Implausible Signal
- 03247 Sensor for Canopy Flap; Right (G597)
008 - Implausible Signal
*This refers to E137 Convertible Top Operating Switch located in the center console.
In this case, the J256 Controller (P/N 8J7-959-255, located in the trunk) received an unexpected signal from the flap servos G596 and G597 and doesn't know if the flaps are up or down or somewhere in between. To avoid a possible collision between the top mechanism and the flap, it deactivates the E137 switch in the center console. When this happens, you can expect to see "Soft top cannot be used" displayed in the DIS.
Getting Started on Repairing the Servos -
CAUTION - Before removing the RFS from the vehicle, It's a good idea to place a towel down inside and around the area under the RFS. This will help prevent anything from falling into the "abyss" as recovering a dropped screw or bolt will be not be fun!
NOTE - These instructions are for both the left and right RFS. However it's recommended you only remove and repair one at a time to avoid mixing up the left one with the right one. If you remove both RFS at the same time, it's a good idea to mark the case and the arms "L" and "R" so you know which goes where. The left and right servos are exactly the same part, it's just flipped for left or right operation. However if you look carefully, the arms are different so don't mix them up.
GETTING HELP - Since this topic has been coming up more frequently as the Mk2s continue to age, rather than addressing each and every Forum members post, I have created a Q&A post just for this topic. If you have any problems or questions about how to do the RFS R&R, please post them in the link below -
www.ttforum.co.uk
Tools You Will Need -
• 10-mm socket
• T-20 Torx driver
• Business card, old credit card, stiff paper stock or an old aluminum soda can
• Isopropyl alcohol and/or electrical contact cleaner
• Paper towel, cotton swabs and/or soft brush
• Ross Tech VCDS for clearing error codes and performing the adaption of the flap motors. As noted, no other OBDII device, including OBDeleven, has the capability to perform the necessary Adaptation and fault clearing.
1 - Accessing the Roof Flap Servo
1.1 - Open the convertible top so it's in the stowed position. The procedure for manually opening or closing the top can be found here.
1.2 - Disconnect the ball-link from the flap and secure it to the clip on the underside of the flap so prevent it from getting damaged.
1.3 - Use a pencil or marker and draw a circle around of each of the four bolts. This will help you realign the bracket when you reinstall it later.
1.4 - Unscrew and remove the four 10-mm bolts holding the Flap Assembly.
![Image]()
2 - Removing the Roof Flap Servos -
2.1 - Unscrew and remove the three T-20 Torx screws and remove the RFS.
2.2 - Disconnect the RFS plug.
2.3 - Remove the RFS from the vehicle.
3 - Opening the Roof Flap Servo Case -
NOTE - Before opening the RFS case, use a white hobby marker and make a line on the arm and case so you can be sure the arm is re-installed in the correct orientation when you put them back together. See the photo in the Trouble Shooting section below for reference.
![Image]()
3.1 - If present, remove the Audi product sticker.
3.2 - Making shims: Shims will be used to keep each of the clips released during this step. You can use a business card, an old plastic hotel key or even strips from an aluminum can. Cut seven strips 1/4" wide x 1/2" long
3.3 - Wedge the shims into each of the seven clips to disengage them. Use care as you don't want to break them!
3.4 - Once all the clips have been shimmed, release the two small retaining clips on either side of the connector. Use a small flat screwdriver and starting at the plug socket gently pry the two halves apart. Then work around the two halves to separate them.
![Image]()
4 - Remove Servo Arm and Disassemble Potentiometer
4.1 - Once the RFS is open, you will see the three major components; the Motor, the Contact Gear and the Circuit Board. The Contact Gear and Circuit board are the two halves of the potentiometer. There are two traces on the circuit board and three copper "fingers" on the Contact Gear.
4.2 - To remove the Contact Gear, press the corner of the Servo Arm Axle inwards (arrow) and push the entire axle down and out of the Contact Gear. NOTE - Use caution not to put pressure on the Contact Gear as there are three very small contacts on the other side of the Contact Gear.
4.3 - Once the Servo Arm has been removed, remove the Contact Gear.
4.4 - Turn the Contact Gear over to reveal the contact "fingers. The circuit board and fingers are now ready for cleaning.
![Image]()
5 - Cleaning -
5.1 - After removing the Contact Gear, carefully remove excess grease from the three Contact Fingers. Be very careful not to bend or damage the fingers!
5.2 - Remove all excess grease and clean the circuit board traces (black concentric circles).
5.3 - Remove any excess grease from the back-half of the Servo Case.
6 - Reassembly -
6.1 - Verify the Servo Arm orientation to the RFS case using the white lines you marked previously, and ensure the position of the arm is aligned correctly.
6.2 - With the Servo Arm in the correct position the Contact Gear is ready to be installed with "fingers" down against the circuit board.
6.3 - Press the Contact Gear fully onto the Servo Arm Axle. You should hear a "click".
6.4 - Align the front and rear cases and press them together. Ensure all clips are fully engaged.
6.5 - The RFS is now ready to be reinstalled in the vehicle.
7 - Installation of the Servo to the Flap Assembly -
7.1 - Connect the Servo Motor plug.
7.2 - Align the Servo Motor with the three screw holes. NOTE - Be sure to align the Servo Arm External Axle with the hole in the frame.
7.3 - Insert and tighten the three T20 Torx screws.
7.4 - Re-install the Flap Assembly with the four 10-mm bolts. (Tighten to 5-Nm).
7.5 - Connect the ball-link to the flap.
VCDS Adaption of the Flap Motors -
If there was a fault registered, an Adaptation must be performed or to the roof will not function. When performing repairs/replacement of the Flap Servos, it's necessary to use a VCDS to run an Adaption. If you just clear the faults and you don't run the Adaptation, the roof won't work.
For more information on the Adaptation and VCDS Measurement Blocks, take a look at the link below -
www.ttforum.co.uk
[Select]
[26 - Auto Roof]
[Output Tests - 03]
[Select] Selective Output Tests
[Choose]Convertible Top Flap Initialization
[Start]
Note - At this point, the top is fully open and in the stowed position. When you hold the convertible top switch, the top will NOT fully cycle as you might expect. Instead, it will start to move the flaps, and then stop. At which point you release the switch and then hold it on again. The flaps will move again and stop. This will have to be repeated anywhere from 20-40 times until the flaps are all the way down so the top is in the fully closed position.
Now you can run through the full close cycle. As you did to lower the flaps, you will have to do this over and over (on-release-on-release) for the entire cycle to close and then open the top. This will take about 5-7 minutes. It's a good idea to have the engine running to keep the voltage up during this process.
Be sure to operate the Convertible Top throughout a complete Close/Open sequence BEFORE exiting the Output Test function.
[Done, Go Back]
[Close Controller, Go Back - 06]
Expected Fault Codes -
After completing the adaption, run an Auto-Scan to verify if any errors still remain.You may have some errors listed in the VCDS scan, for example:
Address 26: Auto Roof
3 Faults Found:
- 02000 Switch Position
008 - Implausible Signal
- 00830 Convertible Top Control Module (J256)
004 - No Signal/Communication - Intermittent
- 03246 - Sensor for Canopy Flap; Left (G596)
008 - Implausible Signal
- 03247 Sensor for Canopy Flap; Right (G597)
008 - Implausible Signal
Clear the errors and cycle the roof normally. Run a final Auto Scan to verify that the faults have been cleared and everything is okay.
Trouble Shooting -
After you have everything back together and the top still doesn't function properly, check the next thread for additional help -
One of the most common problems with the roof not working is due problems with the convertible top Roof Flap Servos (RFS). If your top suddenly stops working, or doesn't open or close all the way, or if the windows stop working correctly odds are good one or both of the RFS is to blame. At this point you will need to run a fault scan with either an OBDeleven or Ross Tech VCDS to identify the fault code. (More on VAG software friendly OBDII devices here).
I have tested the OBDeleven and while it can be used to find and display a roof-related fault codes, it does not have the ability to run the Adaptation (Output test) to clear the faults for this problem. You can read more about OBDII diagnostic devices here.
If the top is still working as it should and there are no faults in Address/Control Unit 26 Auto Roof, then you can still go ahead and perform the servo cleaning as described below. However, if a fault has been registered, it will require a VCDS to run the Adaptation (Output test) in order to clear the fault and get the top working again.
Note - The term "Adaptation" comes from the Workshop Manuals, when in fact, the VCDS requirement is to run the Roof Flap Initialization which is listed under the Output Tests. This performs a cycle test to make sure the component is within operating parameters and then clears the faults.
NOTE - A downloadable PDF file for these instructions are available here.
Overview -
The RFS has two primary components; the left and right motors (V381 & V383) and the corresponding potentiometers (G596 & G597). When energized, the motor drives the potentiometer main gear which moves the servo arm and ball link to raise and lower the flap. At the same time, the potentiometer sends a real-time position signal to the J256 Convertible Top Operational Control Unit (CTOCU) so it knows if the flap is open or closed. In the event the servo gives a false or out-of-tolerance reading (implausible signal), the CTOCU will lock out the E137 switch (center console roof switch) which will prevent the top from moving to avoid a collision between the top mechanism and the flaps.
Think of the potentiometer like a dimmer switch; turn it one way the light gets brighter, the other way, the light gets dimmer. This is because the voltage changes as the dial is rotated. In the same way, the roof flap potentiometer provides the CTOCU with a high or low value so it "knows" if the flap is up or down.
For a more detailed explanation on how the convertible top works including Measurement Blocks, Fault Codes and Adaptation, click here. Also it's worth reading through Self Study Program 391 linked here.
The Cause of the Fault -
Over time, the grease inside the servo housing can migrate from the gears onto the potentiometer and gunk-up the electrical contact between the circuit board the little copper "fingers" on the contact gear. When this happens, a false signal or "implausible signal" can be generated which will result in intermittent operation of the top or no operation at all. While some service centers recommend replacing the flap servo, this doesn't always solve the problem since even new servos can eventually end up with grease in the potentiometer too.
Purpose of the Adaptation -
When a fault has been registered, the Adaptation has to be performed to allow the CANBUS to establish the new max and min values of the potentiometer. Unlike a normal on-off switch which only has two positions, the potentiometer has a range of positions. The Adaptation allows the CANBUS to "learn" the new expected values for Group 001, Blocks 3 and 4 which should be between ~42 and ~184 as it moves the RFS potentiometer. This is why simply clearing the fault won't make the problem go away even if you've clean up the servos since the out of range values are stored until the Adaptation has been performed.
Fault Scan for Soft Top Diagnosis -
After running an Auto Scan, look under Address 26 Auto Roof. Reported roof flap faults might look something like this:
Address 26: Auto Roof Labels: 8J7-959-255.lbl
Control Module Part Number: 8J7 959 255 B
Component and/or Version: 256 VSG TT H14 0110
Software Coding:
Work Shop Code: WSC 00000 000 00000
VCID: 3E73D87369826EEEA6F-806B
4 Faults Found
- 02000 Switch Position*
008 - Implausible Signal
- 00830 Convertible Top Control Module (J256)
004 - No Signal/Communication - Intermittent
- 03246 - Sensor for Canopy Flap; Left (G596)
008 - Implausible Signal
- 03247 Sensor for Canopy Flap; Right (G597)
008 - Implausible Signal
*This refers to E137 Convertible Top Operating Switch located in the center console.
In this case, the J256 Controller (P/N 8J7-959-255, located in the trunk) received an unexpected signal from the flap servos G596 and G597 and doesn't know if the flaps are up or down or somewhere in between. To avoid a possible collision between the top mechanism and the flap, it deactivates the E137 switch in the center console. When this happens, you can expect to see "Soft top cannot be used" displayed in the DIS.
Getting Started on Repairing the Servos -
CAUTION - Before removing the RFS from the vehicle, It's a good idea to place a towel down inside and around the area under the RFS. This will help prevent anything from falling into the "abyss" as recovering a dropped screw or bolt will be not be fun!
NOTE - These instructions are for both the left and right RFS. However it's recommended you only remove and repair one at a time to avoid mixing up the left one with the right one. If you remove both RFS at the same time, it's a good idea to mark the case and the arms "L" and "R" so you know which goes where. The left and right servos are exactly the same part, it's just flipped for left or right operation. However if you look carefully, the arms are different so don't mix them up.
GETTING HELP - Since this topic has been coming up more frequently as the Mk2s continue to age, rather than addressing each and every Forum members post, I have created a Q&A post just for this topic. If you have any problems or questions about how to do the RFS R&R, please post them in the link below -
Roadster Roof Flap Servo (RFS) Repair Questions and Answers
This post is provided as an open Q&A post for anyone doing the How to: Audi TT Mk2 (8J) Convertible Roof Flap Servo R&R post linked below. https://www.ttforum.co.uk/threads/how-to-audi-tt-mk2-8j-convertible-roof-flap-servo-r-r.1786641/#post-8851001 I have copied and pasted a number of old posts...
www.ttforum.co.uk
Tools You Will Need -
• 10-mm socket
• T-20 Torx driver
• Business card, old credit card, stiff paper stock or an old aluminum soda can
• Isopropyl alcohol and/or electrical contact cleaner
• Paper towel, cotton swabs and/or soft brush
• Ross Tech VCDS for clearing error codes and performing the adaption of the flap motors. As noted, no other OBDII device, including OBDeleven, has the capability to perform the necessary Adaptation and fault clearing.
1 - Accessing the Roof Flap Servo
1.1 - Open the convertible top so it's in the stowed position. The procedure for manually opening or closing the top can be found here.
1.2 - Disconnect the ball-link from the flap and secure it to the clip on the underside of the flap so prevent it from getting damaged.
1.3 - Use a pencil or marker and draw a circle around of each of the four bolts. This will help you realign the bracket when you reinstall it later.
1.4 - Unscrew and remove the four 10-mm bolts holding the Flap Assembly.
2 - Removing the Roof Flap Servos -
2.1 - Unscrew and remove the three T-20 Torx screws and remove the RFS.
2.2 - Disconnect the RFS plug.
2.3 - Remove the RFS from the vehicle.
3 - Opening the Roof Flap Servo Case -
NOTE - Before opening the RFS case, use a white hobby marker and make a line on the arm and case so you can be sure the arm is re-installed in the correct orientation when you put them back together. See the photo in the Trouble Shooting section below for reference.
3.1 - If present, remove the Audi product sticker.
3.2 - Making shims: Shims will be used to keep each of the clips released during this step. You can use a business card, an old plastic hotel key or even strips from an aluminum can. Cut seven strips 1/4" wide x 1/2" long
3.3 - Wedge the shims into each of the seven clips to disengage them. Use care as you don't want to break them!
3.4 - Once all the clips have been shimmed, release the two small retaining clips on either side of the connector. Use a small flat screwdriver and starting at the plug socket gently pry the two halves apart. Then work around the two halves to separate them.
4 - Remove Servo Arm and Disassemble Potentiometer
4.1 - Once the RFS is open, you will see the three major components; the Motor, the Contact Gear and the Circuit Board. The Contact Gear and Circuit board are the two halves of the potentiometer. There are two traces on the circuit board and three copper "fingers" on the Contact Gear.
4.2 - To remove the Contact Gear, press the corner of the Servo Arm Axle inwards (arrow) and push the entire axle down and out of the Contact Gear. NOTE - Use caution not to put pressure on the Contact Gear as there are three very small contacts on the other side of the Contact Gear.
4.3 - Once the Servo Arm has been removed, remove the Contact Gear.
4.4 - Turn the Contact Gear over to reveal the contact "fingers. The circuit board and fingers are now ready for cleaning.
5 - Cleaning -
5.1 - After removing the Contact Gear, carefully remove excess grease from the three Contact Fingers. Be very careful not to bend or damage the fingers!
5.2 - Remove all excess grease and clean the circuit board traces (black concentric circles).
5.3 - Remove any excess grease from the back-half of the Servo Case.
6 - Reassembly -
6.1 - Verify the Servo Arm orientation to the RFS case using the white lines you marked previously, and ensure the position of the arm is aligned correctly.
6.2 - With the Servo Arm in the correct position the Contact Gear is ready to be installed with "fingers" down against the circuit board.
6.3 - Press the Contact Gear fully onto the Servo Arm Axle. You should hear a "click".
6.4 - Align the front and rear cases and press them together. Ensure all clips are fully engaged.
6.5 - The RFS is now ready to be reinstalled in the vehicle.
7 - Installation of the Servo to the Flap Assembly -
7.1 - Connect the Servo Motor plug.
7.2 - Align the Servo Motor with the three screw holes. NOTE - Be sure to align the Servo Arm External Axle with the hole in the frame.
7.3 - Insert and tighten the three T20 Torx screws.
7.4 - Re-install the Flap Assembly with the four 10-mm bolts. (Tighten to 5-Nm).
7.5 - Connect the ball-link to the flap.
VCDS Adaption of the Flap Motors -
If there was a fault registered, an Adaptation must be performed or to the roof will not function. When performing repairs/replacement of the Flap Servos, it's necessary to use a VCDS to run an Adaption. If you just clear the faults and you don't run the Adaptation, the roof won't work.
For more information on the Adaptation and VCDS Measurement Blocks, take a look at the link below -
FAQ - Mk2 Roadster Convertible Measurement Blocks, Fault...
Section 1 - Convertible Top Fault Codes When the roof fails to operate properly, it will require a VAG software compatible OBDII diagnostic device in order to identify the DTC (Diagnostic Trouble Code) and affected components. Since fault scans and drill-downs can often take a while, it's a...
www.ttforum.co.uk
[Select]
[26 - Auto Roof]
[Output Tests - 03]
[Select] Selective Output Tests
[Choose]Convertible Top Flap Initialization
[Start]
Note - At this point, the top is fully open and in the stowed position. When you hold the convertible top switch, the top will NOT fully cycle as you might expect. Instead, it will start to move the flaps, and then stop. At which point you release the switch and then hold it on again. The flaps will move again and stop. This will have to be repeated anywhere from 20-40 times until the flaps are all the way down so the top is in the fully closed position.
Now you can run through the full close cycle. As you did to lower the flaps, you will have to do this over and over (on-release-on-release) for the entire cycle to close and then open the top. This will take about 5-7 minutes. It's a good idea to have the engine running to keep the voltage up during this process.
Be sure to operate the Convertible Top throughout a complete Close/Open sequence BEFORE exiting the Output Test function.
[Done, Go Back]
[Close Controller, Go Back - 06]
Expected Fault Codes -
After completing the adaption, run an Auto-Scan to verify if any errors still remain.You may have some errors listed in the VCDS scan, for example:
Address 26: Auto Roof
3 Faults Found:
- 02000 Switch Position
008 - Implausible Signal
- 00830 Convertible Top Control Module (J256)
004 - No Signal/Communication - Intermittent
- 03246 - Sensor for Canopy Flap; Left (G596)
008 - Implausible Signal
- 03247 Sensor for Canopy Flap; Right (G597)
008 - Implausible Signal
Clear the errors and cycle the roof normally. Run a final Auto Scan to verify that the faults have been cleared and everything is okay.
Trouble Shooting -
After you have everything back together and the top still doesn't function properly, check the next thread for additional help -
