Porschec4

'90-C4-Cab Top Disaster!
Had an issue with the Cabriolet Top Controller-Was not letting the top latching motors over the windshield engage or disengage all the time...pulled the controller from under the dash-() and dis-assembled it to find several cold solder joints on the printed circuit board in the location of the connector pins. Having been in the P.C. manufacturing business for well over 50 years, I am very familiar with this issue. I reflowed/re-soldered all the cold solder joints that were evident, re-assembled the unit, re-installed it(),turned the key and depressed the switch...Voila, instant gratification-works Every time now!

That's the Good News-Here's the Bad News-() While the top was being lowered,I heard a sort of "groaning noise" then a straining of the passenger side drive motor-The driver's side of the top seemed to retract normally while the passenger side was not.
At this point, I heard a loud "Snap" and I immediately shut the ignition key for fear that the dreaded "B-Pillar " break had occurred. I could not find any breaks in any of the linkage or bow parts but upon further examination, I found that the Cabriolet top drive arm on the raise/lower transmission-passenger side had snapped in half at the large 19 MM bolt hole. I believe there was a previous crack at that joint but I can't be sure.

I found a parts dealer not too far from me that has one at a fair price, so I am not totally "up the creek." I loosened the 19 MM bolt on the driver's side transmission so that We can operate the top in the "manual" mode with electric latching. My only concern is -What caused this?

Note: After this happened, I pulled both transmissions to find that the passenger side quadrant gear had frozen in place. I soaked the center bearing with "Blaster" penetrant
and was able to free up the gear so that it operated freely. Tested the whole assembly on the bench with the drive cable in my drill to operate it...went from one end of the travel to the other to be certain there was no binding. Temporarily joined the broken drive arm to test everything (Drive motors both worked and cables were operating-drive cable ends were extended proportionately.) Synchronized both transmissions to their respective indicator marks, made sure the micro-switches were in their proper position and got everything back together as was before this happened.

Gave it another try only to find the same scenario with the arm breaking again.

I dunno where to go from here-Any thoughts on this or has any one here had this happen? Any help with this issue would be Greatly appreciated!

Thank You!

Best Regards,

Tony
__________________
90-964-cab
Old Today, 05:10 AM

Rocket Rob

Sorry that your cab has had difficulties. While this is not a common problem with 964's, I have read a few threads over the years about it happening. See below.

Good luck with the repair.

https://rennlist.com/forums/964-foru...olet-roof.html
https://rennlist.com/forums/993-foru...p-snapped.html
https://rennlist.com/forums/964-foru...964-owner.html

Porschec4

RocketRob-

Thanks much for your reply!

Will be ordering the "operator arm " this morning.

How, what and where else can I inspect to look for additional damages pertaining to linkages, etc. while I'm wating for my parts to come in?

Thanks much again for your help...Greatly Appreciated!

Best Regards,

Tony

Rocket Rob

Tony - Note, I haven't had to do this myself. This is a thread that someone posted to fixing the problem. From what I understand, you need to open the two cab top transmissions and make sure they are in good shape and that they are securely bolted. Then you need to go through the synchronization procedure to make sure that both sides are moving the top at the same time. Its when they get out of sync that the top can break.

Adrian Streather's Enthusiast's Companion manual available from Bentley Publishers has some coverage of the conv. top system operation on Page 307.

https://rennlist.com/forums/964-foru...fun-begin.html
http://forums.pelicanparts.com/porsc...tible-fix.html

Porschec4

Rob...I have Adrian's Book that I purchased when I bought the C4...

I will look up your reference on page 307...


Thank You Brother!

Best Regards,

Tony

Harry Apps

You've been quite lucky (!), more often than not, it's a "B" pillar that breaks.

Have look here for further set-up procedures.
Although the TSBs relate to the earlier model (>89), the principles are very much the same.

Porschec4

Thank You Harry!

World of information on those Pages!

Gonna see if I can investigate further to try and align the top properly according to
the tech bulletin.

Thanks much again!

Best Regards,

Tony