daveburke6

I am at my wits end with this problem, when lowering soft top, everything works fine, rear window lifts, cover opens, top goes into trunk, cover closes and ding indicates all is well. When I try to close soft top, cover opens, top goes up over windshield but rear bow does not lift. Eventually, system times out and I have to close top manually. There is a small leak in bow lift cylinders but since the bow lifts when putting top down, I don't believe this is the problem. The limit switch on the drivers side bow seems to be working since the bow lifts when putting the top down. Any ideas what might be happening?

Serndipity

Problems with the soft top bow not lowering can be caused by number of reasons, such as a malfunctioning hydraulic pump valve block and/or one of its solenoids, the compartment cover position switch not telling the controller it's closed and locked, the soft top bow limit switch not properly triggering in the down/up position etc..

However, a leaking bow cylinder(s), that both raise and lower the soft top bow, is a significant clue.

The hydraulic cylinders in our A208s are differential acting (e.g. can move in 2 directions). When the cylinder is pressurized on one side, the cylinder rod extends or retracts. The direction of motion depends on whether the pressure is applied to the piston or rod side. When pressurized on both sides, the cylinder rod extends, because the force acting on the piston side is greater, due to the larger active area. When the cylinder rod extends soft top bow moves in the direction of the soft top compartment.

Note: In addition to visible end seal leakage, the differential action also depends on the condition of internal seals, as well. This is why, when Top Hydraulics re-manufacturers the cylinders, all of the seals are replaced.

daveburke6

[QUOTE=Serndipity;7124333]Problems with the soft top bow not lowering can be caused by number of reasons, such as a malfunctioning hydraulic pump valve block and/or one of its solenoids, the compartment cover position switch not telling the controller it's closed and locked, the soft top bow limit switch not properly triggering in the down/up position etc..

However, a leaking bow cylinder(s), that both raise and lower the soft top bow, is a significant clue.

The hydraulic cylinders in our A208s are differential acting (e.g. can move in 2 directions). When the cylinder is pressurized on one side, the cylinder rod extends or retracts. The direction of motion depends on whether the pressure is applied to the piston or rod side. When pressurized on both sides, the cylinder rod extends, because the force acting on the piston side is greater, due to the larger active area. When the cylinder rod extends soft top bow moves in the direction of the soft top compartment.

Note: In addition to visible end seal leakage, the differential action also depends on the condition of internal seals, as well. This is why, when Top Hydraulics re-manufacturers the cylinders, all of the seals are replaced.



Thanks for the response Serndipity, I understand what you are saying, but the bow does lift when putting the top down so that the rear cover can open. Everything works fine when putting the top down. The issue is when I try to put the top back up again. The cover opens and the top comes out of the well and goes over the top of the windshield, The problem then is that the rear bow will not lift so the cover can close. It seems that if the bow lifted when putting the top down, it should also lift when putting it back up since the cylinder worked to lift it when putting it down and I think the limit switch on the bow is good because it worked when storing the top in the well. I did order new switches just in case and am going to order cylinders from top hydraulics because of the leaks. I am just trying to wrap my head around why the bow lifts when storing the top but not when putting it back up. Again, thank you for the response.

Serndipity

I always understood that your rear bow raised, when closing the the roof, but would not lower, when closing the roof.

Hopefully, all that will be necessary to restore your power roof operation, will be having the bow lift cylinder(s) rebuilt by Top Hydraulics, which will provide the necessary cylinder range of movement, to actuate the rear bow, up/down position switch (S84/15).

Additionally, the leak would worsen over time, which could avoid additional issues, due to seal fragments entering the hydraulic system, such as the pump's valve block.

I presume that when the bow would not lower, you dialed back the hydraulic pressure and manually lowered and locked the rear bow.

As the roof's controller, opens or closes the roof, at each stage, the position/limit switches are evaluated, prior to continuing.

I've enclosed some thumbnails, that show the necessary status of the switches and valve solenoids, when closing the roof. Since your stated problem is at stage 6, note the required conditions, before, during and after.

The good news, is that every position/limit switch can be checked, with just a simple multi-meter, which saves time and money (e.g. avoids guessing, unnecessarily replacing parts and labor).

This is possible because all of the controller input switch conditions, during each stage of operation, will be either open (e.g. seen as an open circuit, measured by high resistance) or closed (e.g. seen as a short circuit to ground, measured by low resistance). This test confirms that switch is properly actuating, as well as that the wiring, is not defective.

This can be easily be done, by disconnecting the connector from the roof's controller, noting the stage of operation and then measuring/verifying the appropriate resistance condition.

Lastly, FWIW, when power to the controller is lost, or components replaced, it's usually necessary to re-synchronize the roof (e.g. open/close manually). Have also read, that problems with the rear bow position switch were sometimes due to it fastenings becoming detached.

daveburke6

Hi Serndipity, It's the other way around, when lowering the top (opening) the rear bow will lift and the top opens as it should. When the cycle is complete, there is a ding from the top switch (s84) I believe and all is fine. When I go to close the top (raise it) The top comes out of the trunk and goes over the windshield but the bow never lifts and of course, the rear lid cannot close since the rear bow is in the way. I did order new limit switches (rear bow position) and top limit switch. I will replace these when I receive the rebuilt cylinders from top hydraulics and hopefully that will take care of the problem. One other piece of info is that after I put the top up manually, the light is the top switch flashes at about 1 hz. It does not flash when the top is in the trunk and all is locked.

Serndipity

daveburke6.......It's very difficult to diagnose and troubleshoot a power roof problem over the internet. That said, there have been far more successes, than not.

In your above post, as well as your first, you stated that your issue occurred, "when closing the roof" !!!!

That's exactly the stages of roof operation, that you seem to have,

At this time, given leaking cylinder(s), you have on order, replacements from Top Hydraulics.

However, because your issue could also possibly be due to a faulty or misaligned position/limit switch, to further diagnose/troubleshoot this possibility, in my last thumbnails, the methodology to check each switch (e.g. including all the prerequisites and actualization), using just a multi-meter to further troubleshoot the possibilities.

The thumbnails I provided, would enable you to sort this out.

Rather than continuing to comment further, please use forum search, where you'll find additional / detailed info regarding your latest observations concerning both, your power roof switch lamp flashing at 1 Hz and associated sounds (i.e. chimes).

GatorMB

Also what can happen inside the cylinder is a bypass syndrome where closing pressure is forcing fluid into the opposing side of the cylinder and valve controller.
I see it often in industry but not Benz.
Serendipity is on track.

However, a leaking bow cylinder(s), that both raise and lower the soft top bow, is a significant clue.

Cheers

To verify would require a transmission gauge set with adapters and a good working knowledge of hydraulics. (safety Glasses Please)

daveburke6

Hi Gator, thanks for the reply. What is really driving me nuts about this problem is that when I put the top down. the rear bow lifts like it is supposed to so the rear cover can open. However, when I try to close the top, everything is fine until except the bow does not lift so the cover can close, The hydraulics should be the same in both cases as should the operation of the limit switches. What I am thinking at this point is that because the rear bow is a littler lower (in the trunk) when it has to lift, that just maybe the limit switch on the cylinder is sending the wrong signal when trying to as compared to opening when the bow is locked to the rear cover. Again just a thought and I did order a new switch just in case and am sending the cylinders in for a rebuild.