cpu for convertible top 1988 cab

rekstein1 · 04-13-2021, 09:13 AM

Having issues with 2 cpu's that I had repaired, one by ECU in Florida and the other repaired in Germany. Still no go with the top operating properly.
It simply won't signal the motors to open. Close yes,open no.

Does anybody have a loaner known working cpu for the 911 that I can borrow to see if its the repairs or the car that's the issue.?

Every part of the convertible top has been gone over. replaced 2 limit switches in the top. replaced the gears in the front motors. Frankly I,and the mechanics are out of ideas as to why it won't open

Help!!!!!!!!!!!!! Somebody!!!!!!!!!!!!!!!

porschyard · 04-13-2021, 10:38 AM

If your mechanics can’t figure it out your best chance is either find someone who ACTUALLY understands the top systems or failing that see if you can find one of these Test programs. It will walk you through the testing and diagnosis and if you have some electrical skills you should be able to pinpoint the problem your self. As to the rebuilt control units, I know the guys at Specialized ECU personally and would be highly surprised if the problem is the control unit. Richard.

pavegeno · pavegeno's Garage

I've sent just about every module to these folks with 100% success including my auto top ECU. Even honored a DME ECU warranty claim years later.

https://www.ecudoctors.com/pages/about-us

Is your parking brake set? Later modules incorporated an emergency brake interlock. Check the sensor switches that strike the A Pillar to signal when the top is closed. Check your switch under the dash. Another place to check are the two motors and transmission.

Good luck.

rekstein1 · 04-14-2021, 10:19 AM

I gave them the test plan you have mentioned in your post. Before I sent it out to a mechanic I personally ran the test plan and could find nothing wrong other than it had to do with the cpu. The gears in both motors have been replaced, all limit switches have been checked. ECU also gave me a rebuilt new one that passed on there equipment. I even have a video of it. My previous unit was repaired by ECU and it worked for years. This time the unit was returned to them them honored the warranty and we plugged the repaired one and got nothing, the opening of the motors would not happen. So this issue is, the signal to open the motors does not happen. Once the top is up it will move forward and back as well as the motors rotate in one direction. The other direction the motors will not work. If you apply power to the circuit from an outside source the motor will move. so its not the wiring. So with that information is seems that the cpu fails to send the reversing voltage to the motors to open. WE are open to anything we might have missed, but know one at ECU will spend the time to go point by point as to the voltage read outs.

The 1988 does not have the emergency brake switch that you mentioned. That was the 1989. 2 different mechanics with over 50 years experience looked at this and it comes back to the CPU

When they called ECU to go over things they were told to go jump in a lake, not great customer service. that's when they or I could get a hold of someone, or someone actually returned a call,or a different person the problem was dump into their lap responded Its a said commentary when a successful business looses its way

If you know someone there I would like there number. Please PM me

thanks

megerian · megerian's Garage

This may not be helpful but I have a 1988 cab and there is for sure a parking brake switch. Without the brake engaged the top doesn’t move. I am also wondering about your statement that it moves forward and back but then you said in one direction the motors will not move. Can you clarify?

Also when you talk about the switches are you talking about the switches at the front of the cab top or the white switches behind the right side speaker cover?

pavegeno · pavegeno's Garage

Quote:

Originally Posted by megerian

This may not be helpful but I have a 1988 cab and there is for sure a parking brake switch. Without the brake engaged the top doesn’t move. I am also wondering about your statement that it moves forward and back but then you said in one direction the motors will not move. Can you clarify?

Also when you talk about the switches are you talking about the switches at the front of the cab top or the white switches behind the right side speaker cover?

Yes, 88s did not originally come with an emergency brake switch, but they were updated at some point and if the module has a 964 part number, which I remember mine does, you have to have the emergency brake on. This likely isn't your problem, but it may be worth checking the emergency brake sensor. If I recall correctly, there is a handoff that takes place from one motor to another in the sequence as the top nears vertical so it could be an issue there as well. Travel switch senses the open but the next switch not sensing the fully extended position as the top fully opens. Just shooting in the dark trying to help. Good luck!

mysocal911 · 04-15-2021, 08:22 AM

Quote:

Originally Posted by rekstein1

When they called ECU to go over things they were told to go jump in a lake, not great customer service.

You did get a full refund, right?

There're other sources that provide cab top control unit repairs.
This may help you diagnose your problem, check under Porsche, Cab Top here;
https://www.systemsc.com/problems.htm

megerian · megerian's Garage

Here is a theory - happy to be proven wrong :-)

The CPU is fine - no problem there. When you close the top, a slightly incorrect adjustment of the right hand side transmission assembly is triggering the white switch, rendering the top completely stuck. When you open the top, this switch is no longer triggered, and everything is fine.

The fix ? Remove the rear speaker cover on the passenger side, and adjust that assembly so that when fully closed, the white switch is NOT triggered. I had incorrectly thought this white switch was the limit to stop the top from moving forward during normal operation, but its not - during normal operation, that white switch should never be triggered - its essentially a fail safe to shut everything down for a misaligned top.

rekstein1 · 04-15-2021, 12:44 PM

To clarify, the cpu that controls the top is a 991 unit not a 993. The 993 unit has special connection for the just for the parking brake.

to clarify the open and close position question. if the top is partially open it will move forward and backwards. With the top switches taped closed , as ECU recommends,the motors should function by opening and closing. The motors will only rotate one way, and that is closed.

The motors will work in both directions by bypassing the cpu and applying 12v as directed in the test plan. the motors open and close fine

with the tape removed and the top in the fully locked position the motors will not unlock.

a dilemma isn't it? something is telling the motors via the cpu not to unlock

rekstein1 · 04-15-2021, 12:45 PM

will try the white switch theory and get back to you

mysocal911 · 04-15-2021, 12:47 PM

Quote:

Originally Posted by megerian

Here is a theory - happy to be proven wrong :-)

The CPU is fine - no problem there. When you close the top, a slightly incorrect adjustment of the right hand side transmission assembly is triggering the white switch, rendering the top completely stuck. When you open the top, this switch is no longer triggered, and everything is fine.

The fix ? Remove the rear speaker cover on the passenger side, and adjust that assembly so that when fully closed, the white switch is NOT triggered. I had incorrectly thought this white switch was the limit to stop the top from moving forward during normal operation, but its not - during normal operation, that white switch should never be triggered - its essentially a fail safe to shut everything down for a misaligned top.

That limit switch, only affects the up movement of the top. His problem is that the top doesn't open when closed.

mysocal911 · 04-15-2021, 12:52 PM

Quote:

Originally Posted by rekstein1

will try the white switch theory and get back to you

Did you read the link provided for troubleshooting?
https://www.systemsc.com/problems.htm

Once the top is in the middle, it should move up or down independent of the SL/SR and ZL/ZR switches.
In this position, the UP & Down limit switches and the SL/SR & ZL/ZR switches can be easily tested with an ohmmeter,
and the complete functionality of the cab top simulated/tested.

It's an extremely simple process to troubleshoot that system!

megerian · megerian's Garage

Dave - I respectfully disagree - from personal experience, I can verify that when the white switch is triggered the top will not open.

mysocal911 · 04-15-2021, 01:47 PM

Quote:

Originally Posted by megerian

Dave - I respectfully disagree - from personal experience, I can verify that when the white switch is triggered the top will not open.

If that were the case, then one could only open/move the top manually, using a tool, once the switch closed at any position, right?

megerian · megerian's Garage

Yes - that is exactly what happened, and here is how I fixed it. On my 88 cab (same year, same car as this one) for some reason, one time the cab top sort of dropped harder than usual onto the windshield. Maybe it was the slope of where I was parked, and while I normally like to support the top as its closing, this one time I didn't. At this point it was dead. Switch did nothing. Since I know exactly how this works, as I have taken the whole thing apart several times, I removed the right rear speaker and saw that the main arm had travelled just a bit farther than normal and closed the white limit switch. Without moving the top at all , I just loosened up the white switch, which is connected by 2 small phillips screws, just enough to move it away from the arm and open the switch. Presto, top works perfectly again.

I adjusted the little metal piece that triggers the switch, reattached everything ( and of course I never close the top anymore without supporting it for its last few seconds and lower it gently ) and everything works.

rekstein1 · 04-17-2021, 07:47 AM

Update_ in regards to Megarians theory the top dead center limit switch which you refer to was indeed put in the open position(non triggered closed position) as well it was tried to be bypassed, as well as tried to be totally disconnected, this was all tried and the motors would not begin the sequence to unlock.

Some background details to the 438 people that view the forum on a daily basis. The car after i tried fixing it was taking to a 26 year certified Porsche Mechanic. Whom when he left the local Porsche dealership to go private ,lost its certification because no else had the full certifications at the dealership at the time he left. The son who also looked at this situation also has over 20 years of high end car service.

Regarding ECU. I like many of you have had a positive experience with them prior to this time. Good, prompt, service. I along with the mechanics are willing to admit if we missed something. However, something has changed at that company. This was related to me by the mechanic who also felt he was treated poorly and has had extensive dealing with them over 20 years
When the mechanic called ECS and asked to speak to a technician and even offered to pay for the technician's time to go through the cpu readings he was told no. Its not like we are asking for anything we are not will ing to pay for. what kind of customer service is that?

What can one conclude from that attitude except some of the following assumptions?

1) they pay their technicians on pieces of completed work and they don't care about anything else
2) this is a known problem to them and they just want to keep repairing units and charging $95 for a test or $450 for a unit and don't care about their customers regarding this unit
3)their testing equipment has a flaw in it
4)the company has lost their way
5) the mechanics are missing something and I and they are wrong and we don't understand what we are doing wrong.

I again ask the members of this forum if anyone has a known working 911 version CPU for a convertible top. that i will gladly rent, buy and have overnighted to my home. I would like to drive my car this summer and put an end to this

I have attempted to PM John Walker as I see he is well respected mechanic and member of this Forum but have recieved no reply. Does anybody have his number.

I am posting my cell if anyone wants to discuss this repair with me. (201-874-6040)
The shops number (973-726-7222) please ask for John Sr.

I will be posting to the forum a negative experience with ECS ahead of this post and hopefully someone at ecu will give a damn and help.

I can only truthfully relate my experiences and disappointment with them. I deal with people all day long and try to do my best. I always go the extra mile because of reputation and pride. I would hopefully expect the same of someone at ECS
that is all I am asking

Dr Richard Ekstein

timmy2 · timmy2's Garage

John Walker posts his phone number in every reply he makes. Visible if you are viewing in anything but the mobile theme mode. (That sucks)
It is here at the bottom of his post:
Question on drilling the floorpan for sub and amp mounts

megerian · megerian's Garage

Richard - It seems like it may indeed by the cpu after all, but just for clarity, can you actually post the exact behavior? Since you said that when in the completely closed position, the top doesnt not respond at all to the rocker switch pushed. You also said that once open, the switch moves the top forward and back?

So - some questions:

When the top is completely stuck how are you opening it, are you using the screwdriver in the manual hole technique?
Once its open and you said it correctly starts moving, does the closing sequence complete normally? By closing sequence, I mean that the front edge of the top drops onto the windshield, which in turns activates the closing motors.
If thats all true, then once the top drops onto the windshield, you should still be able to use the rocker switch forward or backward, and it should still work, to either activate the closing motors, or start the top moving backward again.

I am just trying to determine where in the sequence everything stops working.

rekstein1 · 04-17-2021, 11:11 AM

Ok, lets start with the top in the fully closed position pressing the open switch will not cause the motors to unlock. yes the key is in the #1 position and the light comes on to say the top opening process has been initiated.

as the top will not open we then go to the cpu apply 12v to the wires to open the motors. the motors open. reattaching everything ,pressing the button the top will now fully go back.

returning the top to a midway position, pushing the switch in either direction the top will move forward and back. Now with the top still open, covering the anterior 2 switches with tape by the motors hitting the switch the the motors will close. now trying to "open " the top the motor will not open.
the grounds have been checked we are at our wits end. Hence the plea for John Walker!
Please call!!!!!!
The mechanic explained it to me the the cpu is not changing the polarity from positive to negative and negative to positive which would of course open and close the motors. something in the cpu
is not happening. i forget which 2 pins he said was involved , but in essence that is the problem

it is a polarity issue within the cpu.

hope this helps

please i want to drive my car this summer help!!!!!!!!!!!!!!!!!!!

mysocal911 · 04-17-2021, 06:39 PM

Quote:

Originally Posted by rekstein1

Ok, lets start with the top in the fully closed position pressing the open switch will not cause the motors to unlock. yes the key is in the #1 position and the light comes on to say the top opening process has been initiated.

as the top will not open we then go to the cpu apply 12v to the wires to open the motors. the motors open. reattaching everything ,pressing the button the top will now fully go back.

returning the top to a midway position, pushing the switch in either direction the top will move forward and back. Now with the top still open, covering the anterior 2 switches with tape by the motors hitting the switch the the motors will close. now trying to "open " the top the motor will not open.
the grounds have been checked we are at our wits end. Hence the plea for John Walker!
Please call!!!!!!
The mechanic explained it to me the the cpu is not changing the polarity from positive to negative and negative to positive which would of course open and close the motors. something in the cpu
is not happening. i forget which 2 pins he said was involved , but in essence that is the problem

it is a polarity issue within the cpu.

hope this helps

please i want to drive my car this summer help!!!!!!!!!!!!!!!!!!!

This test provides key information. Possibilities:

1. The locking motors' timing may be incorrect, i.e. the phase of brass gears relative to locking motor switches.
2. The cab top ECU has a problem related to the unlocking mode when the locking motors are locked.

If you would like to discuss your technical problem, you can call the website mentioned in post #7.