A4 convertible top not working - hydraulic issue?

[dtamack]

I have been frustrated for months now with a used 2008 A4 that was a basket case. Long story short, I solved everything but the convertible top and the bluetooth phone module not working right. I checked everything with the Ross-tech tool, and the phone module simply does not respond. That I can leave alone for the moment. The convertible top module shows only an improbable signal fault, which I erased. The issue is that the top begins to open by unlatching at the windshield, but then you can hear the hydraulic pump running, but nothing happens. What does happen is that it seems like the hydraulic flow is trying to close the top, even though it is already at the limit before the latching system takes over. The pressure in the system remains for a bit, then you can manually lower the top once the pressure abates.

I am sure that the pump is working properly and I checked all the solenoids for function. Is it possible that one of the position sensors is not closing or opening when it should? Is it possible that the solenoids are moving the wrong direction and causing the flow to go to the wrong hydraulic cylinder? When I say I checked the solenoids, I made sure that they clicked when I applied 12V to them. I can't be sure that they open fully, etc.

I installed a used roof ECU module from another A4 cabriolet but there was no difference in the roof function. Does anyone have any ideas on the next steps to attempt. Luckily it is not my daily driver, so I can take my time. The interior is mostly torn out at this point.

Any help?

[Gowking]

Do you have the top tool? Have you tried manually opening the top completely then manually closing it completely? That seems to be required to reset these convertible tops.

[Plxa4q7]

Pump and motor could be running but not providing enough flow to build up pressure to actuate the top. The top will separate from the front window frame without flow or minimal flow from the pump, but will not fully actuate. The motors for these tops suck. I currently have two 2007 convertibles and have had troubles with motors on both. Replaced just the motor earlier this year on one of the cars and no problems since. No faults logged when top didn’t operate (checked with vag-com).

Also check this out from Ross Tech forum: https://forums.ross-tech.com/index.php?threads/6165/. There is some good information in there about top operation

[dtamack]

I did try manually opening the top and manually closing it. I might try it again. I did it some months ago, with the key on.

[dtamack]

Thanks for the link, I will check it out. The top separates from the windshield header by a motor, not the hydraulics. The reason I think that it has the flow going the wrong way is that some people have suggested 'helping' the top open while someone else holds the switch to make the pump try to open it. When I did that, the top was really unable to move rearward at all. Once I turned off the switch and waited, the pressure would subside and the top could be moved rearward. i remember a training flow diagram out there somewhere on the internet, but I cannot find it again. I should have printed it.

[Plxa4q7]

You referring to this? http://www.volkspage.net/technik/ssp/ssp/SSP_278.pdf

[dtamack]

Omg that’s better than the one I saw! Thanks a million. I’m going to kill a tree printing it and solve this problem once and for all!


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[zeroskater88]

Hey damask, I have the exact same issue with a car I own. All sensors and everything check out in vcds per the measuring blocks. Pump runs and I have resistance when trying to manually push (to assist pump) in opening.

Have you gotten any further? I've spent a few hours digging into it today and this is where I am with it. Thinking pump.

[zeroskater88]

Dtamack, after reading that pdf it looks like the hydraulic system is working as intended due to the non return valve. The hydraulic system is pressurized but unable to be manually moved until it depressurizes.

Feel like we have pumps making noise but not doing any of the legwork needed to put the top down.

[dtamack]

Dtamack, after reading that pdf it looks like the hydraulic system is working as intended due to the non return valve. The hydraulic system is pressurized but unable to be manually moved until it depressurizes.

Feel like we have pumps making noise but not doing any of the legwork needed to put the top down.

I actually think after digging into it that I have a short in the wiring. I checked each of valves and number three had no voltage to open it when the pdf says it should. I will try again but it is actually encouraging to know that you have this too, because I thought the dealer screwed it up.


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[zeroskater88]

Currently working on this issue with vagpro.co.uk

They told me prior to having a pump rebuild completed that I should pull the motor assembly and bench test. Report back to them if motor spins clockwise or counterclockwise.

I'll have to do this later on today after work.

[dtamack]

I won’t have a chance to work on mine until this weekend. Good luck!


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[zeroskater88]

I won’t have a chance to work on mine until this weekend. Good luck!


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Thanks man, just a note for the path you're on at the moment. Don't you think you'd be throwing a code of some sort if you had an inoperable solenoid? I don't have any flashing indicator light when starting the car or anything and no codes.

[dtamack]

Zeroskater88, I guess if it were truly shorted from 12V to gnd, it would throw a code, but I think it might be shorted 12V to 12V on the output after the top controller. I need to recheck my work with the volt-meter though. Could also be a bad ground.

[zeroskater88]

Zeroskater88, I guess if it were truly shorted from 12V to gnd, it would throw a code, but I think it might be shorted 12V to 12V on the output after the top controller. I need to recheck my work with the volt-meter though. Could also be a bad ground.

Have you by any chance removed the electric motor cover at any point in time and reinstalled it 180 out? Try rotating it 180 degrees

[dtamack]

Have you by any chance removed the electric motor cover at any point in time and reinstalled it 180 out? Try rotating it 180 degrees

Ugh! That was it! I now need to put the entire car back together. What an idiot I am. I spent hours over the course of 8 months to try and figure this out. Thanks a million for the suggestion!


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[dtamack]

Incidentally, I had taken the cover off for the second time because the brushes had become stuck again (back in 2020). This time I was able to spread the holders, WD-40 them and then verify that the brushes were free with a small pointy pick. They slid easily in and out, and when I rotated the motor they moved ever so slightly side to side. I don't see how the pump could lose power unless the brushes were only partially touching or the fluid level was low.

[zeroskater88]

You're welcome!

[zeroskater88]

I had my motor/pump/valve body Rebuilt by top hydraulics and it is 100 percent better than oem. The top operators quicker and more smoothly!