As the weather turns colder, one thing I will be interested in whether anyone has issues with either the pressure limiting or the voltage reduction solutions.

I am wondering if Jaguar engineered in some extra pressure margin to deal with issues such as increased viscosity, increased system friction and lower battery voltage (without the engine running) at colder temperatures.

I do recall the manual specifies the factory system not be run at very low temps (I think below around 40 degrees F if memory serves me).

 

I believe the low temp issue has more to do with the fabric and the rubber membrane under it than the hydraulic system.

 

As part of me investigation into the cause and fix for the roof operation problem I did see the recommendation on the temp and I am convinced that it was raised with the old fluid and not the synthetic Pentosin CHF 11s that is used in the system today. If this were the case several cars would be dead on the road because this fluid is used in brakes and power steering on many other cars. I dropped the roof on a ride in early December to see the holiday lights at night with the wife and it was cold. Use good judgment and you will be fine.

 

Well, I finally got my resistor installed. I followed much the same process as documented with terminals to reverse connections if I choose. Initial reaction is no difference in the feel of the operation and no noticeable difference in travel time. I'll now be doing more extensive tests of my own and reporting same here.

Best,

 

Steve,

Great. So are you planning on doing actual pressure measurements? This would be a very good thing, seeing as how my own are pretty primitive. Anyway, you've reminded me that I wanted to post something about ...


Temperature effects: the one thing about this project that keeps me up at night.

During testing, as voltage (and so peak pressure) was lowered more and more, the latch was the first thing that started acting up. Below about 800-850 PSI it consistently failed to capture the top. Since both the Voltage Reduction and Relief Valve systems are designed for 950+ PSI max, there should be at least 100 PSI of headroom. But (seems like there's always a "but") as things get colder one or more of these could happen:

- The convertible top could shrink or stiffen a little, requiring more force to close the latch,
- The latch rams or hook mechanism might themselves require more force to operate (thickened lubricants maybe),
- If using Voltage Reduction and operating "engine off", source voltage (the battery) will go down very slightly with temperature,
- If using Voltage Reduction, peak torque from the pump motor for a given voltage might go down a bit (again, lubricants).

If one or more of these effects gets big enough, the latch could fail to close. So maybe it's worth reviewing the available remedies in such a case:
- With either Voltage Reduction or Relief Valve we can manually pull down on the top at latch-closure time to help the latch capture the top.
- With Voltage Reduction, if operating "engine off" we can try "engine on" or (should that fail) remove the resistors from the circuit.

This may be tempting fate, but if anyone using Voltage Reduction encounters what seems like a temperature-related problem, please post it here or send me a message.


Thanks,

 

While I have no problems to report the weather has been so nice out I just decided to leave it out. Haven't put the top up in 2 weeks.

 

Me either...other than to cycle it one time to try the resistor. I've had mine down for two weeks too.

 

I put my resistor in a couple of weeks ago. It seems to be working fine, but I did notice the other day that when I tried to close the top with the car NOT running that the top did not latch. I started the car and that gave me the "ummph" it needed to finish closing the top. Obviously, the resistor is lowering the pressure. It could be my battery, but I just thought I'd let everyone know what happened.

 

Kevin,

I was going to ask about temperature, then I noticed where you live. OK, that ain't it ...

What is the value of your resistor(s) please?
Is the fluid level OK?

Do you have a feel yet for whether this was a one-time thing, or will repeat each time you raise the top?

(This may be a duplicate post ... I lost internet connection on first attempt)

Thanks,

 

Hi Dennis,

Right, it wasn't the temperature. It was probably 85 degrees at the time. I used the "No Cut" installation method in your newest write up and a a single 0.20 ohm, 100 watt
resistor from http://stores.ebay.com/abillionstore. The fluid in the resivoir is just above the min line.

I failed to mention in my previous post that at the same time I installed the resistor I was putting in a new stereo system at my son's shop (isn't that handy). We noticed that the strut on the passenger side was leaking and we installed a new one while we had everything apart. The previous owner had experienced the green shower and it looks like I narrowly avoided a green flood in the back seat! I wonder if we introduced some air in the system when we changed the strut? Is there a way to "bleed" the system other than opening and closing several times?

 

Quick update. After the last post, I decided to cycle the roof a few times to see if I could remove any air bubbles. The top went down once and didn't come back up. Upon inspection, the reservoir is now almost empty. Looks like the new strut has a problem and I didn't avoid the green flood after all. Back to the shop!

 

Aw, jeez. Sorry to hear that. Hope it sorts out quickly.

On your original report, two possibilities stand out:
- If the battery were depleted from its time in the shop, that could maybe explain what you saw (unlike the relief valve, this system is slightly sensitive to battery voltage when operating "engine off").
-The trouble with the strut, or air in the system, might have somehow contributed to lower pressure (to be honest, though, I don't really see how that would happen).

Anyway, if you have a chance please let us know if running "engine off" works OK when you get things back together.

Thanks,

 

Well, we have taken the car apart again and it looks like the previous owner had the green flood in the back and did a DIY repair on the hose.



My son knows place that will repair the hose. I'll take a pic of the repair and post it as well.

 

A successful repair of the hose would be a most welcome addition but many have tried, including Jaguar, and none have succeeded.

 

You are correct, test point. They couldn't repair the hose, but instead they remade it. It's the steel braided hose on the left.

 

That is one good looking hose! Just a note be sure to insulate the braded hose from electrical conductors.

 

Thanks everyone. I got the car back tonight and wanted to confirm that the top is closing now in the "engine not running" mode, but it's acting a little quirky. The top opens fine, but when I close it, it "stalls" right before it's going to latch and raise the rear windows. If I let off the switch and press it again, the latch closes and everything is fine. The first time it happened, I thought it was just me slipping off the button or something, so I did it again. Same "stall" at the top, releasing and repressing the button and it latches and the rear windows come up. Strange.

 

Kevin,
At times the roof will operate sluggish for many reasons. If you are game I am going to suggest that you use WD40 on the rams in the back and the latch piston at the latch. Along with it spray around the moving parts at the latch and operate it a few times and let’s see what happens. WD40 will provide you with a temporary relief of friction but do not over do it. Give that a try and we can go from there.

 

I am quite sure I will get flamed for this but just cannot resist. You can try solving the problem by removing the resistor, installing the pressure relief kit, and from then on operate the top up and down with the engine running as Jaguar recommends. Side benefit is that you will not wear the hell out of your battery and operation of the top will be consistent every time.

Duck Doug--here come the bricks!

Doug

 

Well, since your insightful reply was aimed at me, let me cast the first brick.

Obviously, there is some sort of friction between the "relief valve" camp and the "resistor" camp. It started a long time before I joined this forum and I really don't know all the details. Personally, I really couldn't care less. They both seem to be viable alternatives to solve the same problem. I'm the first person on this forum that has reported any problems with the resistor, and it turns out it was a problem with a previous fix on the hydraulics that was done poorly.

Doug, my current problem could be that my battery is low, it could be poor lubrication, as Gus is trying to point out, it could be something completely different. But, I know for a fact you aren't trying to help. You just want to take a dig at Dennis through me. I really thought this forum was above that.