PatS

Hi All. I've looked all over for an answer to this without asking, and couldn't find one. So... I recently obtained a 1998 R129, a long-time dream car of mine. It was 'rode hard and put away wet' over the years, so I've been putting money and work into it. I recently replaced the front left and right hydraulic cylinders (thanks, Top Hydraulics!) so I can now get the hard top on and off. Problem is with the soft top. It worked perfectly the first time, but from the second time and onwards it 'almost' works. Meaning, it goes down perfectly and everything moves, works, and locks like it should. When raising it, though, the compartment cover opens, the top comes up, the front locks, the compartment cover closes (I didn't notice which order the top front locking and the cover lowering happens, but it seems right), and then the rear part of the top starts lowering and "goes wrong". Instead of lowering and locking into place like it should, it cycles between starting to lower, stopping after about 2" of movement, reversing until it's fully up again, and doing this over and over for as long as I care to hold the switch. I checked the compartment cover switch A25S2 on the right side of the car and it's both working fine and adjusted correctly. The hydraulic system is full and none of the cylinders leak. The rear locks are in the right position to accept the soft top hold-down dealies, and like I said the rear locks function correctly with the hard top. Help! I really thought the cover-locked switch was going to be the problem. Any ideas?

bobterry99

I can't think of a likely scenario that would cause what you are witnessing. There is something I would try.

I would pause the operation at the point it fails and manually move the bow well beyond the point at which it reverses and resume. I suppose it would reverse as before, and if it did I would again move it manually and then check the state of all of the inputs to the soft top controller with a multimeter. If you wish to do that and need help, reply back.

PatS

I would certainly check the inputs with my DMM, if I only knew where the connector is and the pinout. I would appreciate any help I could get. And, you can be as technical in your answer as you like, because I was an electronics tech for 27 years before I finally went back to college and got my BS and MS degrees in electrical engineering... I actually wouldn't mind finding out the interface protocol of the controller so I could have a go at building a code reader for myself. But I imagine MB keeps that a closely guarded secret.

bobterry99

This thread explains how to test the functionality of all of the limit switches. With the fabric bow in the position described in my earlier post to this thread, these X2 inputs should short to ground: 4, 7, 8, 11, 29, 30; these should be open to ground: 26, 28, 44, 45, 46.

PatS

Today's update, maybe others can learn from this. I'll update over the next few days when I hope to get all the intermittent problems found and fixed...

So, they say that when you are up to your a** in alligators, movement in any direction is defined as forward progress. I made forward progress today! 8^)

The hard top is on because this is the Seattle area, and you just can't live with the top off more than a day or two unless the soft top works. Today, out of the blue the top open/close switch on the console started blinking, and the chime started ringing to be annoying. At first pushing the switch forward would make it stop for awhile, but then it finally stopped helping.

When I got home from work I investigated the switches at the X2 connector on the soft top module. I measured them all with the top locked on, then took the top off (there was only me, so I held the top up with 2x4s off the car to simulate it being removed), then measured the switches again, then re-locked it down and measured them another time. The symptoms of the control switch being lit / flashing and the chime sounding disappeared when the top was locked back down.

The results were that all the switches were in the correct positions in all cases, except for X2 pin 28 (A22S2, Bow Locked) and X2 pin 46 (S84/3, Soft Top Open). A22S2 was initially open with the hard top locked on, was still open with the hard top off, but was closed (as it should be) when the hard top was once again locked down. It's brother on the other side of the car X2 pin 45 (A23S2) was closed, then open, then closed. Therefore, this A22S2 is barely adjusted right, or else the switch contacts are intermittent. I'm thinking it's the adjustment since I had a similar problem on the front right switch when I replaced the front hydraulic cylinders.

S84/3 is a different matter. It read 33.8 ohms the whole time. I would expect it to remain the same since the soft top wasn't moved, but a closed switch should read less than 0.1 ohm and an open switch should read well over a million ohms. There's no way the controller is seeing 0-1 volts through almost 34 ohms (I should think), so the controller is probably seeing an 'intermediate' state when it's time to close the rear bow, and it malfunctions then... I'll check that switch when I have time and sun to play with the hard top off. Hopefully I can figure out exactly where it lives!

I'll update this over the three day weekend when the weather promises to be nice so I can leave the hard top off and look more closely at the switches and adjustment. Hope this can help others at some point! And thanks again for the info BobTerry99.

PatS

Okay, more update. I think it might be fixed (knock on wood). A22s2 has stopped misbehaving, and as many times as I found myself writing down a reading opposite of what I just saw today I think maybe it never was. The switch light and chime re-started with the hardtop on yesterday. Today's investigation showed S84/2 (passenger side above the windshield, X2 pin 11) was open with the hardtop on. Played with the hardtop and it started being closed with the top on and open with the top off (as it should). Tried the soft top, found that with the front locked, the tonneau cover down, and the rear bow not closing that S84/2 was open no matter what.

When I replaced the hydraulic cylinders above the windshield at the start of all this, that switch was not working at all - the metal part that pushes down on the switch when it's not locked was bent too far down, so the switch would never indicate that it was locked. I 'bent it straight' at the time and it seemed to work, but it seems the hard top and soft top front locking pins are slightly different (wear, I suppose). The adjustment I had made caused S84/2 to operate properly maybe 40% of the time with the hard top, but not at all with the soft top. So when I tried to put up the soft top, it got to the part where it checks for both front lock switches being in 'lock', saw only one like that, and aborted the rear-bow-down operation. I carefully checked how much lock movement was required for S84/1 to change state, and straightened out the switch actuator paddle on S84/2 to match. When I went to start taking all the switch measurements again at different points in the soft top and hard top cycles, it was all magically working!

Also, I notice that the magnetic switch in the front middle and the magnetic switch on the left rear soft top frame both read about 33 ohms when closed (the wires to both read 0 ohms with the switch replaced with a jumper wire, so it's definitely in the switches). Maybe that's just characteristic of the reed switches.

So hopefully, there will be no further problems or required updates. One takeaway from this is that the limit switches can be adjusted so that one top works and the other doesn't. Another takeaway is that a spreadsheet with all the switches and their purpose, printed out with spaces to write down the state, saved me quite a bit of time today and helped keep everything organized for troubleshooting.

Oh, here's a Top Tip - when you take off the connector X2, take a permanent marker and darken around pins 10, 20, 30, and 40. I makes taking measurements WAY easier and more accurate!