Bob Yeh

I have been reading all the soft top problems I coule find in the net. No good suggestions yet. I have a 1997 SL500. The top does not retract sometime. It fails maybe 50% of the time. The front locks unlatch but the top does not retract after after. The pump seems to work hard when that happens. If I give it a push, it seems to work better but still not 100%. I opened the trim on top of the windshield. No leak. Fluid level is correct and stable. What could the problem be? What else should I check? Is the pump too weak? Is the fluid pressure adjustable?

Thanks
Bob

sl500_dallas

I just had this identical problem about 1 month ago.

It turned out that one of the microswitches in the driver's side front pillar was out of alignment. My mechanic worked on it for a couple of hours and after several attempts got it adjusted. It has been working perfectly ever since.

Total repair bill was $255.00.

Bob Yeh

Thank you for your reply. I saw the two switches on top of the windshield next to the locks. Are they what you were refering to? Not sure if they can be adjusted though. The mounting positions seem fixed.

sl500_dallas

Those are probably them. I really would not try adjusting them yourself though. My mechanic was using diagnostic codes to guide him while he worked. Also, you may end up doing additional damage to expensive parts. Plus, you don't even know if the switch is out of alignment until you get the fault codes out of your computer.

As soft top problems go this is one of the cheapest repairs possible. A lot of the problems with soft tops cost thousands of dollars to fix.

nickg

check your battery before doing anything else. commonest cause of problems is a dying battery.

Bob Yeh

The battery is new and I open/close the top while the engine is running.
The pump seems to be working while the top stop moving. If the micro switch is bad then the pump should stop right? I am more convinced that one of the hydraulic cylinder (the one retract the roof) has an internal leak or the pump does not generate enough pressure.

MB Tech - USA

90% of the time it's the hydraulic cylinders on top of the windshield that leak internally, do you notice that your 50% failure rate is usually on hot days or after you have run the top a couple of times?

Also, are your windows going down? And even so, the switches in the doors that indicated the windows are down sometimes get misaligned over time.

Just some ideas for you.

Bob Yeh

I have checked the top cylinders and found no leaks externally. My guess is that the front cylinders are only used to lock and unlock only. Once the top is unlocked, there should not have any pressure passed to the front cylinders. If there is a leak it should not prevent the top to retract.

It could happen at any time at any temperature. Windows and roll bar always go down like it suppose to. Once the front locks are unlocked, the top stops to retract. I can hear the pump continues to work for another couple of seconds. After that, the top switch blinks and everything stops.

sl500_dallas

The motor kept running when I was having my problem with the microswitch.

The motor would make a sound like it was laboring hard, then it would let up, then it would try again until I released the red button.

Bob Yeh

haha, "laboring hard". That is exactly what happen to the pump. It makes a "laboring" sound every few seconds. Again, I did not see how the switch can be "adjusted". I might just replace it. Do you have a part number?

MB Tech - USA

Two quick things -

I stated the cylinders may leak INTERNALLY. You won't see any visible fluid leaking out, yet the system cannot build sufficient pressure to move the fabric top. Also, the cylinders are still pressurized until the pump stops, so internal leaks on any cylinder effect the entire systems pressure whenever the pump is running. By an internal leak, I mean that excessive amounts of fluid will return to the reservoir.

BUT, since you stated that the pump stops and the light blinks, this indicates that the system is setting a fault code, most likely a microswitch issue, either top locks or possibly windows. You need to see what code is set in order to continue diagnosing.

Bob Yeh

Made an appointment with a MB shop. They claim they have the scanner to read the soft top code.

Bob Yeh

Took the car to the shop. The scanner can't communicate with the OBD II port. Tried the round connector (X11/4 I think) from the engine bay worked.

I got 2 codes. 112 and 124. 112 is driver side top lock fault. 124 is some limited switch error. We decide to fix the top lock first. The owner ordered a "valve" (cylinder I think) from the dealer. I thought the microswitch can be ordered separately from the cylinder. Can someone confirm that? Hopefully it will fix the problem.

p.s. The scanner made by autologic is pretty neat. It talks to all the sub-systems, not just the generic OBD II code.

Bob Yeh

Hey I think I got my problem fixed. The shop ordered the lock mechanism, which costs around $450. It includes the lock, cylinder and the microswitch. I really did not want to pay that much for the part. I took the unit out myself. The switch IS adjustable. Can’t tell without taking it out. The switch was loose. The factory used some red paint to lock the screw. It was broken. I tightened the screw, apply new Threadlocker, put it back, works fine so far.

sl500_dallas

Woohoo! Way to go Bob Yeh.

Would you provide detailed instructions/pictures if available on how you accomplished the task?

This may come in handy for the rest of us at some point.

Bob Yeh

Sure, I will be gald to do it.

1. Remove the top trim. There are 4 screws on each side (see picture). One is hidden under the rubber. Once all the screws are out, pull the top trim towards the back of the car. A flat screw driver works pretty good. Disconnect the electric switch in the middle of the trim.

2. The lock mechanism is secured by 3 torx screws to the body. The hydraulic lines are secured to the cylinder by two clips. Inert a small flat screw between the clip and the cylinder to open it. The line can be pull out of the cylinder after the clips are released.

That is it. Pretty easy. Took me less than a hour.