I see. So if I open up the latch motors, I may be able to adjust it. I'll take a look, thanks!

Will it be obvious from looking inside how they should be aligned?

The switch must open at the end of the latch rotation.

I've unmounted opened and tested both latch motors. Neither motor's gear has a broken tooth in the range of rotation (I know that both gears have suffered broken tooths during previous ownership, and those gears were rotated during a previous repair such that the broken tooth is away from the relevant rotational area during all regimes of operation). The cams that push the microswitches seem to be positioned appropriately. Both microswitches seem to work, and both seem to open at the same point near the end point of the latch rotation.

From a signals standpoint, it seems like these microswitches are sending the correct signals at the right time in the rotation of the latch...

Is there a precision adjustment to be made here? I would figure that if both switches open at the same point in rotation, and at that specific point the latches are positioned such that the top can safely be lifted up and away from the latch point, then everything seems to be good? Do both SL/SR have to open at *exactly* the same time?

I'm not sure that it's completely relevant to my problem, but here's what I think I'm currently confused about.. what I think I understand about the ECU's logic is the following:

1. If ZL/ZR switches are pushed down *AND* SL/SR indicate latches open *AND* close top button is being pushed *THEN* run latch motors to close latches.

2. If ZL/ZR switches are pushed down *AND* SL/SR indicate latches closed *AND* open top button is being pushed *THEN* run latch motors to open latches.

Let's think about when the ECU knows to *stop* operating the latch motors in either situation.

I understand that in situation 2, the way that the ECU knows to stop opening the latches and start retracting the top is that the SL/SR signals will change once the latches reach to the fully open position. This is because the open/close point of the microswitches inside the latch motors is actuated when the latches are reaching/leaving the *open* position.

But what about situation 1? Once the latches start closing, the SL/SR signals change immediately (as the latches almost immediately come out of the *open* position as the latches rotate), but there's still a long way to go before the latches are fully closed. How does the ECU know how to stop closing the latches at the right time? There is no additional microswitch being actuated or signal being sent once the latches get to the *fully closed* position. Is there? Why doesn't the motor keep closing the latches past the correct stopping point and cause damage? What am I missing?

Okay, after finding and reading these directions for how to replace the gears in the latch motors, I've learned that the cams need to be positioned such that the SL/SR is tripped at open *AND* at close. What I'd read had made me think just open (which is why I got confused above). Indeed, as one would expect, the way that the ECU knows to stop closing is that the same microswitch that tells it to stop opening gets tripped.

I opened up the latch motors again and adjusted the cams so that now the cam trips the switch when the latches are completely open *and* when the latches are completely closed. After reassembly I re-mounted the latch motors to test. I unplugged and re-plugged in the cab ECU to reset it, and got it to latch (as usual after freshly resetting the ECU). I tested both SL and SR microswitches at the "mid latch" position and found circuit continuity for both. Then I brought the latches to the completely closed position, and tested the microswitches again and found no continuity. Then I brought the latches to the completely open position and tested again, and found no continuity.

I am now confident that the latch motors are correctly timed, and that all my microswitches are operational and send the correct signals.

AND YET: once I got the latches completely open.... they refused to close again, as always (and yes I made sure that ZL/ZR were pushed down and neither passenger side microswitch was tripped).

So, I've ruled many things out, and have even made a repair to one of the latch mechanisms, but still have not found the root of my problem.

Next up: testing the microswitch signals at the ECU -- either the wiring between the switches and the ECU isn't delivering the signals, or the ECU is bad.

The ECU was replaced in the last 10 years by the previous owner (and has been used very little since), and is a 993 unit. Because it's seen so little use I have hope that it's not broken, and it's a wire continuity issue.

One slightly suspicious thing, though, is that the rightmost connector at the bottom of the ECU (that has MVL/MEL/SL/Hd/P) is not a normal connection like the other three: all 5 wires are soldered directly to the pins. I'm guessing there was a reason that the tech that put the 993 unit in felt he had to do this. Hopefully further testing can reveal if it's done right.

ALSO: I've noticed that at no point in trying to operate the top and either the latch motors or the main raising/lowering motor is the dash light that indicates top opening/closing turned on. Hopefully this is a real clue rather than the bulb just being burnt out.

Would be happy to hear further suggestions :)

Total Mickey Mouse! The installation is totally "butchered". Post an image of the ECU PCB bottom.

Did you miss this from post #34:

As with the Porsche cruise
controls, the mounting of this ECU resulted in vibrational stresses being applied to its circuit board.
The intermittent unit generally caused the cab top not to lock/unlock properly, e.g. requiring multiple
depressions of the open/close switch.

No, I didn't miss that, I'm just trying to troubleshoot everything I can before getting into a circuit board repair, especially on one that was somewhat recently replaced. And hey I did find and repair a different problem. Also, multiple depressions of the open/close switch does not solve this problem (which isn't to say it's not related, but caused me to look elsewhere first).

That said, this circuit board has definitely been repaired before -- hopefully it doesn't mean it's not repairable again?

http://forums.pelicanparts.com/uploa...1752218309.jpg
http://forums.pelicanparts.com/uploa...1752218309.jpg
http://forums.pelicanparts.com/uploa...1752218309.jpg

I've been testing the cab top ECU using this guide, and things seem to be mostly as expected except for the following:

1. Running a jumper wire between ground (terminal 31) and L, it says that the cab top opening/closing light on the dash should light up. In my case it does not. As mentioned earlier, it also doesn't go on at any point while I'm operating the top.

2. When testing Hd with the 12V test light, I found that regardless of whether the hand brake was up or down, I was getting 12V (test light goes on) between Hd and + (pin 30).

3. All the tests for the right locking motor passed. But for the left locking motor (and this is the one whose wires are soldered to the pin on the ECU instead of having a normal connector like the others) had slightly different behaviour under testing. For the right locking motor, connecting the 12V test light between + and SR, it lights up and shows 12V when the latch is between end points, and no light/voltage reading at all when it hits the end points. This is the expected behavior. For the left locking motor, connecting the 12V test light between + and SL, it lights up with 12V when the latch is between end points. But at the extremities I don't get 0V! At both latch end positions, the test light shows ~6V between + and SL instead of no reading. I'm wondering if this has to do with the wires I'm trying to test being soldered to the ECU?

4. Finally, testing the ZL and ZR switches. I found that testing ZR at the ECU terminals (continuity tester between ground (pin 31) and ZR) I get the expected results: continuity beep when ZR switch is depressed. But for the ZL switch (cont tester between ground (pin 31) and ZL), I see nothing when the ZL switch is depressed. I went and tested at the switch itself, and it works. So this might be saying that one of the wires carrying the ZL signal to the ECU is broken?

Number 4 seems like it's definitely a problem regardless of whether 1-3 are real issues.

I unplugged the microswitch from the connector and tested for continuity between the connector ends of the wires and the ZL pin on the ECU connector: no continuity. Just to sanity check, performed the same test on ZR and got continuity.

So this seems pretty conclusive -- the wire carrying ZL from the latch area to the ECU is damaged. This also makes sense as to why the latching stopped working very suddenly -- I guess at some point the connection just severed.

Unfortunately, figuring out where seems pretty challenging.... do I need to rip the carpet out? At this point I really wish it was the ECU :/

Following up: by shorting the ZL pin on the ECU to ground (to simulate ZL being depressed), I have confirmed that latch functionality is completely restored.

So I guess my choice now is to cut up the long harness that goes from the latch motors, down the length of the cab top, down behind the backseat then along the floor up to the passenger footwell in order to find where that wire is broken and repair it... or just short that ZL pin to ground permanently. The ZR switch still functions, so, as long as I'm careful and attentive when opening/closing it shouldn't matter? I guess this won't work if ZL being depressed will affect the raising/lowering function. I guess the question is: do *both* ZL and ZR need to depress to stop the main motor from continuing to raise the top? If so great. But if only one stops it, then this won't work.

Thanks everyone who helped me troubleshoot :)

Future people with similar problems, I highly recommend this cab top ECU electrical troubleshooting DIY guide here

So you never correctly checked the ZL connection at the ECU, just at the switch itself.
Not good troubleshooting!

Lol that's pretty uncalled for. I'm politely asking for help and doing my best. I think it's pretty inappropriate to post just to tell me you think I did bad job. ¯\_(ツ)_/¯

Great thread and glad I found it. I have been having intermittent issues with the driver's side latch not closing the top. Yesterday, for the first time, it did not allow the top to open until later in the day, after I drove the car with the top up. I will dig into this further, looking through this thread.

Question on the ECU: Can they be rebuilt at a place such as Specialized in Fl, which rebuilt the ignition ECU in my old 930?

Check here; https://www.systemsc.com/products.htm

Typically the repair is less than $300.

Thanks. I will probably first look at the ECU and go from there.

Thanks. I will first look the ECU and go from there.