Wow, what long thread this is! I am inside with a cold today, so instead of working on my Jag roof latch problem I decided to read up on what others are saying. I am glad I did! And Gus, you have my utmost respect for the work you have done to address this issue. I am a retired electrical engineer so I understand a lot of what is involved. I would think the hydraulic bypass solution would be the "correct way" to solve this, but the resistor method might work too.
In any case I have a question. If a person was willing to just latch and unlatch the top manually, allowing the hydraulics to raise and lower the top, is there any reason that the BPM would not "be happy" and not show the "top not latched" message? Someone has disabled the hydraulic system to the roof latch in my car, there is no fluid being applied to that area. I can see that it must have leaked there because there is a residue of fluid still evident. Although I would like to have my top work as it was designed, I might be willing to do it manually for the time being. What I can't tolerate is the "top not latched" message that continually displays. I have checked out the operation of the three microswitches in the latch area and they all seem to be functioning. How does the BPM determine that it is me using the key wrench pushing the ram rather than hydraulic pressure?
Again, thank you so much for your work in this area. I am very impressed with your research.

 

BINGO--Give this man a cigar!! From almost the very first I thought this would have been the best and most foolproof solution and is probably the way the car should have been designed in the first place.


Doug

 

The more specific answer to your question is that there are micro switches associated with the hydraulic latch that report to the BPM the physical location of the latch. Consequently, Allen key operation of the latch will (should) extinguish your 'top not latched' message.

There have been numerous reports, mine included, that the micro switches and the BPM can get out of sync and just refuse to do anything. Manual operation of the top and latch seems to resolve the issue.

So, go manual until such time as you can get everything resolved.

Now what you need is a leather covered Allen Wrench with a big Jaguar medallion on it.

 

I am presently dealing with the damage to our condo in OC Md and I want to get back to it but your question is valid. I want to provide you with a link to a TSB that covers the entire open and close operation. The bottom line is that all must be satisfied when closing or the windows will not go up and in the case of the opening the roof will not retract until the switches in the header are satisfied. Please read the link it provides the position of the switches, open and close sequence and the control & security module operation.

Link http://www.jagrepair.com/images/TSB/XK8/501-11am.pdf

I hope this helps!

 

Lanny,

First a caution (apologies if you know this stuff): If you plan to experiment with manual operation of the top or the latch, the pump must be de-coupled from the hydraulic hoses first. This is done using a petcock on the pump body (back in the trunk). All the way counterclockwise for manual operation. DAMAGE can result if manual operation is attempted with this left undone

Some while back, I tried some experiments similar to what you have in mind, and with the same motivation ... aiming toward manual latch operation.

Example: I raised the top using the pump just to the point where the latch was ready to begin closing. Then I de-coupled the pump, manually closed the latch, pushed again on the "raise top" button and hoped the system would be fooled into thinking it had done the latch closing. No joy. Tried the same sequence but re-coupled the pump to the hoses just before the final push on the "raise-top" button. Again, no joy.

I let it go there, concluding that the system would not be so easily fooled. I'm not saying it can't be done, but it won't be as simple as I had hoped.

Logic circuits have always given me headaches anyway.

FWIW.

 

Dennis,
I'd guess that's a 'time-out' problem.
If the header latch was physically disconnected from the hydraulics then manual operation should send the correct sequence of events outlined in Gus's pdf to the BPM.

 

Steve,
It would seem so. BTW I also tried this test ... Raise the top with the pump just to the point of latch closure. Wait a while. Complete the closure. (all using the pump) This does not confuse the system.

Maybe if I had held down the raise-top button at the same time as manually closing the latch ... It doesn't seem the logic circuits could possibly tell the difference between doing that and normal operation, does it?

If that's all that's needed, we could maybe replace the latch hose circuit with some sort of shunt at the pump, maybe with an orifice to limit flow, and let the pump pump away while we manually operate the latch.

 

Dennis,
I think you've probably hit the old nail.
Presumably the BPM has to be tickled by the top switch before it looks for the correct sequences from the 3 top latch switches.
My Top Closed switch is not functioning reliably and I'm going to try heaving on the Allen key to see if that makes it kick in but I don't feel highly 'top motivated' in January.

 

Wouldn't it be wonderful if this entirely different "3rd solution" to the green shower problem could be implemented with some "kit" similar to what is offered by the pressure relief kit or the resistor kit.

Such a kit would include plugs or shunts to install at the pump where the hose to the latch attaches and some kind of handle that looks nicer than having an allen key hanging out the header.

Doug

 

Today I dove into the "top not latched" issue on my 2002 XK8. The first thing I am trying to do is figure out what was done to the car by the former owner. I have determined that they simply disconnected the two hoses that run to the latch. There was evidence of fluid that had leaked,so it is pretty obvious why they did that. They have also rewired the rear windows to operate on a toggle switch so that they can be opened or closed at will. The top still goes up and down with the switch on the console, and seems to work well.
The problem is, the BPM insists that the "top is not latched". I traced the signal from the switch on the right side lift ram, it grounds as it should when the top is up. Then I checked the three switches that live in the header. They all close as expected when the latch is operated with the allen wrench. It would seem that all the signals that should be there to satisfy the BPM are there, but not so. I wonder if it "knows" the windows have not been raised? I can't see anything in the schematic that would indicate that, but something is telling it that the top is unlatched. If I could figure out how to hardwire the necessary conditions to kill the darn warning I would do that. I will keep you informed if and when I can figure this out. If I can get this to work I just might make myself a fancy leather covered "JAG" tool to latch the top, as test point suggested.

 

There's more Witchcraft associated with this wretched top control than any other part of the car.
Following on from my conversation with Dennis - are you holding the close button down while operating the Allen key ?
Also, out of interest, what have they done to blank off the ports to the latch ?

 

This led me to a scary thought:

If, as Steve suggests, the previous owner just plugged off the pump's latch ports, rather than providing some sort of shunt allowing flow between them, then ...

For the full period when the system thinks its operating the latch (while we're holding down the raise-top button) there will be a dead-head (highest possible pressure) condition at the pump. In a "normal" car we see dead-head only for a fraction of a second. Maybe this is OK here since there are no hoses in play at that moment, but still ...

If the latch ports on Lanny's car really are just blanked off, rather than shunted, should we think more about this before holding down that raise-top button for an extended period, i.e. while we manually operate the latch? Call me paranoid, but with this system paranoia is the only sensible attitude.

(This is not like my tests where the pump had been manually decoupled and so was allowed to pump freely.)

 

Good point.
Being a double acting ram one of the solenoid valves on the pump body must switch the two ports going to the top catch between flow and return so shunting them should always be OK.
Plugging them will produce full pressure on one port in both 'directions' of attempted ram movement and I don't think unplugging the solenoid will help either.

 

I agree Steve, it would seem that plugging off the ports would be a terrible thing to do. However, as near as I can tell the lines to the latch have simply been disconnected at the pump. They are tucked back behind the pump. It would seem to me that the pump should gush fluid when activated, but it does not. The top moves up and down under it's own power, and seems to operate well. Is there a solenoid valve that perhaps has been made inactive? That would seem to be the logical explanation. I have not removed the pump for close examination. Maybe there is more to see if I did. I bet Gus would know.....
As for the closing sequence, I kept the pressure on the top as I tried to mimic what I thought the latch would do as it closed. Not too long, just until I heard the pump start to strain a little. That did not "fool" the BPM. I still get the "top not latched" message.
I will try again today.....

 

The light being on indicated to me a switch is out of alignment or just not working. The open and close operation of the pump is by reverse polarity on the motor and the lift and latch operation are dictated by the latch and main control valves along with other relays and switches.

 

Gus,
You've done a huge amount of work on this.
Does the pump power the latch ram when turning in one direction and the 'lift' rams in 'reverse' with the two solenoids on the pump deciding which is flow and return?

 

new problem with my convertible top. i replaced the hoses to the latch last summer. had the top working fine. last week i went to put the top down and it went down fine but the hydraulic latch came up. i raised the roof and the latch went down befor the top was fully open. now i cannot get the top to open, close or anything. i tried to manually operate the latch and it only comes up part way. tried to decouple the hydraulics with the petcock, removing both hydraulic lines to the latch and still cannot move the top. any ideas?

 

Have you checked the fluid level? Do you hear the pump motor at all? Also check the 40 amp fuse in the boot fuesebox if you do not hear the pump.

 

40 amp fuse is good. full of fluid. have both lines disconnected. cannot move top by hand. when i hit the switch all i hear is a click, presumably one of the solinoids.

 

tried jumping hot wire from battery to white wire from pump motor, nothing happened.