[Edit, 06/25/13. This thread ended up being a long one, over 170 posts. For anyone wanting to skip all the history and just get to the answer, the final results of the manual-latch project can be found here. The same link is contained in my signature line below.]

OK, I think we're very close. I'll describe here a successful simulation of converting the latch from automatic, hydraulic to manual operation ... without triggering any "not latched" messages. But this is still a simulation, one step removed from a true conversion to manual, about which more below.

Simulating manual latch conversion: I ran tests, both raise and lower top operations, where the transit of the top was done under normal conditions (by pressing the raise/lower top switch) but the latch operations that precede and follow the transit were done manually, i.e. by opening the petcock at the pump and using the hex key to open and close the latch. So, for example, to raise the top ...
- open petcock, raise latch with hex key
- close petcock, press "raise top" button until top is raised and ready to latch
- open petcock, close latch with hex key (see note below).
No electrical changes of any kind were made.

On my car at least, both raise and lower top operations can be done this way without any error messages.


Now, a true conversion to manual operation would not involve opening and closing the petcock but rather removing the latch hydraulic hoses completely, and so being free to operate the latch with the hex key without messing with anything at the pump. But I think the above tests represent a pretty bullet-proof simulation of that since ....

I can't see any way that the car's electronics could tell the difference between the tests done and the real thing. (Comments on that?)


Some loose ends which I'll just mention for now, otherwise this post may surpass everyone's attention span (my own included).

- REALLY important! For reasons I do not yet understand, when it's time to close the latch, it is necessary to turn the ignition key to off as well as open the petcock, or else the latch won't move. I would have thought just opening the petcock would be all that was needed, but not so. If anyone pokes around with this, please be aware of this point and do not try to force the latch with the ignition on. More noodling required here.

- A true conversion would involve disconnecting the latch hoses at the pump. The ports could be capped, but I think it would be better for the pump to provide some sort of shunt instead, since there may be times when the system will try to pump through the (missing) latch hoses.

- I could swear these same test failed (i.e. gave "not latched" errors) a few months back, but I didn't write anything down at the time and just walked away from it. Not this time.

More to report on, and more to do, but I'm pretty optimistic now that this can be made to work without any major surgery; just some sort of shunt or caps in place of the latch hoses.

 

Hi dennis07, may I ask why you are converting to manual operation?

I find these tops, when working correctly, to be adaquate...

 

Hi, Rob.

It's just that there have been more than a few discussions of whether this idea could be made to work, and so it was one of those "because it's there ... " things.

The main motivation is people not wanting to replace failed latch hoses (of which there are many). But now that I think about it, maybe I would convert mine so as to save the hoses for when it's time to sell the car.

 

Fair comment dennis, but these hydraulic systems really need to be used regulary as the fluid tends to turn to treacle (as you will know!) if left idle.

Ive lost count how many ive bled with new fluid over the past several years, Some people seem to forget they have a convertible!!

 

I think this was mostly a thought experiment as to the way the system should have been designed in the first place. But it could also be a workable "fix" for someone experiencing the shower but not wanting to go through the hassle of replacing the latch hose. At that time, they could perhaps choose to block off the pump fittings that run fluid to the latch and just use the hydraulics to lift the top while manually opening/closing the latch.

I have to admit that I was originally a frequent convertible user when I originally bought the car (this being my first convertible and being in sunny SoCal) but then got the leak within a month of ownership. The dealer replaced the hoses under warranty and I bought the check valve and was again happily using the top. Then the pump died which the dealer replaced (again under warranty). These incidents with the workings of the convertible have sort of freaked me out to the extent I don't use the top nearly as much as I should for fear of something else going wrong.

Doug

 

Yes they do. Though I think the latest Pentosin fluid (11S ?) is pretty much resistant to gumming up.

Several guys here have said that if their latch hoses were to fail, they would want a way to avoid replacing them, switching to manual latch operation if possible. Me too. In such a case we would not have to worry about non-use of the (abandoned) hydraulic latch circuit.

So that was the reason for seeing if this could be made to work without throwing error messages. That, and "because it's there".

 

I think it's an invaluable exercise and I'm definitely paying attention.

If the system had manual latches at the windshield header (as virtually every system did before engineers got too clever) it would be vastly more dependable. Actually, my parenthetical remark about engineers may be inappropriate: it was probably marketers who promoted the change to 'fully automatic' operation.

 

I am glad to see that someone is still looking at this. Some of you may have followed my efforts on another (very long!) thread. My car came to me with the latch disabled. I determined that someone had converted the quarter windows to manual using a DPDT switch. They work very well. The hoses to the latch are disconnected at the pump, the outlets stand open. It looks like they disabled the soleniod valve that would normally send the fluid to the latch. I am sure they did this because I found evidence of the "green shower" in the header. They then disconnected the wires from the top up/down switch on the console and ran two new wires directly to the relays that operate the pump. The top goes up and down just fine. But I can not get the "top unlatched" message to go away. I tried many different solutions that I won't repeat here, but none worked. I finally decided that for the time being I will just push the clear button when I can't stand to look at the message anymore. But I would LOVE to be able to solve this problem. So I will be watching this thread very closely. If anyone wants me to enlarge on what I tried, so as not to unnecessarily repeat my efforts,please fell free to ask.

 

Lanny,

I had your efforts and results in my head as I was posting. I fear the prior owner of your car has hacked it so completely that we may not be able to predict its behavior. But there may also be a simple fix available. Consider:

I did not include this result above as things were getting pretty wordy. But one result I found is that with the latch closed, top up or down, petcock open, I can turn on/off at will the "convertible top not latched" message just by using the hex key to tweak slightly the latch position ... I must be moving it just enough to trip or untrip the "convertible top latch closed" switch.

Point being that the BPM seems here to care not at all about history or sequence of events, but is just reacting to the instant position of that switch.

As I recall, your car still has the latch-closed switch talking to the BPM. Is it possible you've got a bad latch-closed switch?

 

Thanks for your research here. I do like the idea of 'resting' the hoses until selling the car.
I've got a pressure relief valve in-situ but waiting for the shower does spoil the pleasure of taking the top down.
I'm convinced too that the BPM is relatively thick.
I've got a problem with the latch microswitch that kicks off the 'top lower' sequence and will be doing some fiddling once Spring springs.
I still don't understand Larry's 'Not Latched' problem - he actually jumpered the BPM inputs but I wonder if he managed to get the sequence of events (particularly keeping inputs open/closed) exactly as 'per the book'.

Re
REALLY important! For reasons I do not yet understand, when it's time to close the latch, it is necessary to turn the ignition key to off as well as open the petcock, or else the latch won't move. I would have thought just opening the petcock would be all that was needed, but not so. If anyone pokes around with this, please be aware of this point and do not try to force the latch with the ignition on. More noodling required here.
I think the solenoid on the pump allowing oil to flow from the latch to the pump reservoir is in the 'wrong' position with ignition on - to hold the top locked I'd guess - so you can't move the latch because the piston can't push oil out.
Do you even need to undo the petcock?

 

Many thanks to all involved here. I believe a simple manual top operation is indeed the ultimate answer, but don't know how possible that may eventually be. I will be following this thread closely....

 

Steve,

Glad you asked. I think I must misunderstand what the petcock actually does. For example:

Imagine starting with the top down, then raising it partially and releasing the raise top switch. The top hovers where you left it. Now open the petcock. I thought the top hydraulics would be uncoupled from the pump and it would fall back to where it started. But it still hovers. Now turn the ignition off. The top now does fall back to where it started.

I can't picture what's happening. Can you 'splain to me what the petcock is doing here ??

And ... nice cow!

 

Dennis,
I'm as much in the dark as you. Obviously the petcock bleeds the pump output back into the reservoir.
Both the lift and latch rams are double acting (I'm sure you know all this but bear with me)
So, there's a piston and hydraulic pressure can be applied either side of it to power the ram in or out.
The ram can't move, though, unless the fluid on the OTHER side of the piston can get away.
So, the control valve has to connect one side of the ram to pressure and the other to the reservoir (the two paths are 'Flow' and 'Return' technically).
If the top latch ram is fully extended when the top is locked closed then it would make sense to prevent it retracting when the ignition is on.
The top is passively maintained up by the lift rams toggling over centre but by blocking the return from the top latch you'd also have the security of the top latch not being able to move.
If turning the ignition off opens the top latch return you may not need to open the petcock since the return will already be 'vented' to the reservoir.
At least that's my guess.

The cow was a 'present' from someone - I've used a Purple Cow picture for testing various image posting techniques and now I've got one of my very own!!!

 

This thread is at the least very interesting. Just when you thought there was nothing more to learn about our overly complex and convoluted convertible top system you find out something new. I may have been one of the first to suggest that problems would have been greatly reduced had the original design been based on manual latching and I still believe that. The only objectionable thing I can see with converting an existing system to manual latching is the rather tacky futzing around with the allen wrench. A classy alternative would have been some classy looking handle finished in burl wood or brushed aluminum.

Still, if it were possible to get the system working manually without having to go through a strange system of intermediate steps (e.g., turn key on, turn key off, open petcock, close petcock, spin around five times and touch you toes, say Jaguar six times, etc.) might be preferable to the chore and expense of running new hoses.

Doug

 

Agreed. I wouldn't want to have to go through 15 different steps in order to raise and latch (or unlatch and lower) our top. My wife would pitch a fit if she had to find and crank an Allen wrench and open/close petcocks every time she wanted to drop or raise the top....

My 1986 Alfa Romeo Spyder convertible had two top latch handles, one on the driver side and one on the passenger side. Raise the top by hand, latch the two handles, and you're done. Or unlatch the two handles, lower the top by hand, and you're done. That's what I would ideally want our XK8 to do....

 

Yes, it's starting to click. I don't see all the cases clearly yet, but the ignition must be turned off in some cases to open a valve even if the petcock is open. Not so in others.

Jon ... having to use the petcock is required only during a simulation of manual latch operation. In the real deal, we just open the latch by turning the hex key, raise or lower the top in the normal way, close the latch with the key.

I may not have said this clearly, but it seems to me we now have enough info to actually convert a guinea-pig car (gulp). Maybe somebody whose hoses have failed and they want an alternative to replaceing them. All we need is:
- some sort of hose assembly to shunt between the pump's latch ports,
- a written procedure for raise/lower top with manual latch ops (about two lines long).

Edit: oops, not so fast, Dennis. From further testing, looks like the operation of the windows is not yet sorted out with manual latch operation. Stay tuned please.


I can supply the second. Ideas on a hose?

 

Just a bit of flexible off-the-shelf hose to connect the top latch ports together.
Probably look at pulling the top latch solenoid connector as well.
A bit of wiggling of the latch would empty the hoses to the latch, then the pump ends of the latch hoses could just be wrapped up.

 

Steve,

Would you have a spec' for the hose fittings by any chance?

[edit] Still A little fuzzy on this point, but capping the ports instead of shunting may still be better. Need to think a little more.

 

Off the top of my head I would use a fitting to join the 2 latch hoses (drained) together and make the 2 ports dump into the tank return. A nice handle could be made that stays in place provided you don't have to turn more than say 180. I wouldn't cap the ports as you would deadhead the pump (create max pressure) at the port.

 

The roof operation is dependent on 4 things the hydraulic system, electrical switches and two control modules BPM & SLCM and all are dependent on each other. The BPM & SLCM monitors the windows and doors and controls the operation of the roof from beginning to end on an open and close operation and it does this by monitoring the micro switches strategically places in the rams and in the header. The way I see it the CM’s should be satisfied when the micro switches are in the proper position and if they are not the CM’s will post an error. So the only way the CM’s would send a message is if one of the switches is malfunctioning or the system has been confused (out of sequence). The fix is to find the bad micro switch Open or close the roof manually or do a hard reset whatever applies.

Now the sequence of operation to open is this;

1. When the convertible top opening sequence begins the relays and solenoids will be in the
off position, ‘Convertible top down switch’ will be the only switch in the ‘open circuit’
condition.
2. Pressing the convertible top switch will signal the Body Processor Module (BPM) to send a
‘Open Convertible top’ signal to the Security and Locking Module (SLCM). The SLCM
will open both rear quarter windows, and sound the chime alarm to warn that the
convertible top is about to open. (Note: the rear quarter windows will be powered for a
maximum of 3 seconds).
3. If the front windows are closed they will be opened slightly. The SLCM will switch on relay
‘Top up relay’ and the ‘latch control valve’, the latch claw will start to raise.
4. As the latch raises ‘Convertible latch closed switch’ followed by the ‘convertible top closed
switch’ will switch to ‘open circuit’.
5. When ‘Convertible top closed switch’ switches to ‘open circuit’ the SLCM will switch off
relay ‘Top up relay’ and switch on relay ‘Top down relay’. This will change the hydraulic
pump from push to pull mode to start the opening of the convertible top. When the
convertible top leaves the latch claw ‘Convertible top ready-to-latch switch’ and
‘Convertible top raised switch’ will be switched to ‘open circuit’.
6. When the convertible top has fully opened ‘Convertible top down switch’ will switch to
‘closed circuit’. The SLCM will sound the chime alarm, raise any windows which it had
lowered except the rear quarter windows, and switch off the ‘latch control valve’ causing
the latch mechanism to close.
7. When ‘Convertible top latch closed switch’ is switched to ‘closed circuit’ in response to the
latch closing, the SLCM will switch off the hydraulic pump.

The trick is to operate it manually in sequence but not trying it I am not sure how necessary it is.
What I would do first is remove the plug on the pump to the roof latch operation I think it is the plug wire code “GW” I should note if you remove that plug improperly you are in for a big surprise that pump cost $460 on E-Bay used.

Remove the two hoses to the latch and leave them open but put the ends into a container to capture the fluid that will drain and cap both fittings on the pump. This will take the hyd pressure off the lines to enable a manually operation of the latch.

If all goes well you should be able to push the open switch and see the ¼ windows go down and your door windows to drop a little and you will get a tone. With the tone you open the latch manually and the roof will go down shortly after and when it does then you close the latch manually. The question now is when you let up on the roof open button will the system see it as a fault? I do not think it will if it is done in sequence.

The problem I see is if you are in a rush and you want to open and close the roof and or you are not familiar with the new operation YOU could confuse the system.

I have not tested this but it should work.

The roof motor operates in both directions to give you the open and close operation on the hydraulic system and the other plug on the pump is to operate the lifts open and close operation.

Forgot - Just my $.02