Another 89 Cab issue - soft top latch does not always disengage....

[ajmarton]

Ok. It looks like all this summer use has taken its toll on my 89 Cab's soft top. When I try to lower the top one latch (driver's side) does not cleanly disengage from the bracket on the windshield. I stop it before it tweaks something (I can see it pull), reverse it and try again. I can usually baby it out by gently pushing the top up on the driver's side as the latch disengages. Any suggestions on what is going on here and how to adjust the system. Andrew

[ajmarton]

Ok. I stumbled across some prior threads on the "Top Latch Motor" issue so I suspect that is my problem. So now I am wondering if anyone has cleaned / lubed a motor to keep it healthy or working and can offer some advice on how to get to it and what to do.

[bgmilner]

Hi. I had a similar problem with my 88 cab. My mechanic did a 'lube job' on it and it was much better. I'm in Canada so tend to have the top up for most of the winter. I find that first thing in the spring, the one latch is still a little sluggish, but after one or two up/downs, it frees up nicely and works the remainder of the summer as it should. I had the 'lube job' several years ago.

Cheers, Brian
88 Marine Blue cab.

[lindemans]

I have the same issue with my 89 cabrio (one of the last 3.2-s) and have identified the problem elsewhere.

The latch-motors are controlled by a relay in the control unit.
One of the relais does not always properly engage and therefore one of the latch-motors 'remains stuck while the rest starts moving.

In the 3.2 the control unit is in the passenger footwell; I still need to replace the faulty relais. In the meantime my workaround is to heavily stamp with my right foot on the passenger floor while pushing the button with my left hand.....

If your car is a 964, I'm not sure where the control unit is but it may be a sticking relay too.
It is more likely to be a relais or faulty switch than the motor itself.

[ajmarton]

Thanks lindemans. Mine is a 3.2 as well. Do you have the part number handy by any chance.

[lindemans]

Originally Posted by ajmarton

Thanks lindemans. Mine is a 3.2 as well. Do you have the part number handy by any chance.

If you have a 3.2 as well, the control unit is behind the wooden panel in in the front of the footwell; under the carpet.
If you can get the latch motors running again by knocking on that box, it is definitely a relay that does not properly engage anymore due to age/wear.

I do not have a partnumber for the control unit, but these units tend to be expensive. In any case far more expensive than the part that causes the problem. So as opposed to replacing the box, I would find a handy electronics guy that can replace the relais for you.
That's what I plan on doing myself over the winter period. If I cannot find identical relais that I can swap, I will remove the existing relais; solder wires to the circuit board and connect these to a standard relais you can buy at any electronics / car acc shop....

But, make sure this is the actual cause before you proceed.

I took a ride with my 10-year old niece a couple of weeks ago; she wanted to open the top of course. When I noticed the top left latch would not release I asked her to stamp her feet, and there it went....hilarious (for little nieces).

[ajmarton]

Good point, I will lube and check contact points first and see if that helps. I will also make sure that I am on level ground as I typically put the top down in my driveway which has a slight incline. And that's a funny story about your niece.

[lindemans]

My faulty relais did not have an issue with the electrical contacts that need to get connected. It is of mechanical nature.

Somehow when the electromagnet pulls the metal plate that drives the electrical contacts, this metal plate encounters a little resistance when moving.
It gets stuck and doesn't mover enough to close the contacts.
A little touch with the finger (or a little shock) makes it move beyond that point that last bit to close the contacts.

In fact, the relais components are of identical mechanical build-up to the ones in the DME relais; who tend top havce a similar failure pattern.

While typing this: it may be good idea to cannibalise a new DME relais for the parts to fix the cabrio control unit !

[Lorenfb]

"While typing this: it may be good idea to cannibalise a new DME relais for the parts to fix the cabrio control unit !"

Those relays in the cab top control units NEVER fail!

Besides, most all relay failure modes are:

1. Open coils - relays fail to operate (aren't intermittent)
2. Oxidized contacts - open circuit (are intermittent)

and don't fail because of weak coil magnetism for the armature (contacts).

[ajmarton]

Thanks for all the input. I will post an update once I get a chance to play around with it. Probably in 2 weeks.

[lindemans]

Originally Posted by Lorenfb

"While typing this: it may be good idea to cannibalise a new DME relais for the parts to fix the cabrio control unit !"

Those relays in the cab top control units NEVER fail!

Besides, most all relay failure modes are:

1. Open coils - relays fail to operate (aren't intermittent)
2. Oxidized contacts - open circuit (are intermittent)

and don't fail because of weak coil magnetism for the armature (contacts).

The fact that relais in general have "most common causes of failure", does not rule out other means of failure. Having a MSc in E Engineering I know how relais work.

With one of the relais in my control unit, the metal part that is pulled towards the magnet to move the contacts, gets stuck half way. Only the slightest touch of that part makes it move the last bit to activate the contacts.
This metal part rotates along 2 small pins and I suspect the movement gets stuck at this spot. That might well be due to many years of vibrations (unit is solidly mount ro metal in the footwel) causing wear. There may be another explanation why it won't move that last little bit, but fact of the matter is that this just happens to happen.

I have found exactly the same issue with one of the 2 relais units in a DME relais that failed after 16 years of service (the DME relais actually contains 2 separate relais of identical mechanical construction as in the cabrio control unit).

My only objective sharing my experience on the forum, is to help finding the root cause of the problem. A latch-motor that does not work, is not by definition a failure of that motor. Some may be tempted to just replace this expensive part only to find out the problem is still there.

I am nog saying there is a relais issue here, but it is well worth checking because identical problems here were (in my case) related to such issue.

Keep us posted !

[Lorenfb]

"I am nog saying there is a relais issue here, but it is well worth checking because identical problems here were (in my case) related to such issue."

Read here under Vibration;

www.systemsc.com/problems.htm

The answer to this common problem is there.

[lindemans]

Great site !

Are the originally mounted relay units still available for repair ?

[Lorenfb]

"Are the originally mounted relay units still available for repair ?"

Never had to replace one in 10 years.