XJS facelift electric aerial

[Sonic!!!!!]

Hi
My electric aerial has developed a fault. The vehicle is a 1995 celebration coupe

When the aerial goes up it seems that the motor does not cut out in time, and the aerial fully rises and then comes out of its holder.

I have removed and checked the aerial assembly, and cannot see anything obvious wrong with it. Anybody had this issue or can offer any help please

[ptjs1]

Moved to "Electrics" sub-forum

[PaulGover]

It may vary by model year, but my '91 facelift has a Hirschmann aerial. It's electronics is a bit naff - as far as I could tell, it was simply a timer and switch; when you switched the radio on (or the ignition switch with the radio already on), it ran the motor for so many seconds, and assumed that put the aerial up; similarly, when you switch off, it runs the motor in the opposite direction for the same length of time. When the aerial is fully up or down, the motor just stalls. And of course, if the aerial's stuck, it stalls anyway . The timer circuit is relatively high-tech - power transistors and integrated circuits, but that doesn't make it smart!

To add to the fun, for some reason I forget, Jaguar need to delay the aerial lifting, so there's a low-tech delay relay in series with the aerial circuit. That's a low-tech tweak to a high-tech way of solving the problem...

Whatever, mine broke, which is why I know this. I replaced the Hirschmann circuit board with my own, using a simple analogue delay circuit and a couple of relays. The problem with mine was, I guess, that repeated long-term stalls from a stuck aerial might cook the power transistors. Alternatively, maybe it got water in and shorted something.

None of that is much help, I suspect. I could dig out the circuit I used, but I doubt you'd want to go to all that effort, including sourcing components and of course soldering it up and squeezing it into the case. Alternatives include sourcing a replacement Hirschmann aerial, other self-raising aerials, some other fixed aerial, and of course the ubiquitous coat-hanger! I don't know if its possible to get a replacement circuit board for the original aerial, but it's likely the mechanical gubbins alongside is showing signs of age - in mine there was an aluminium tube that held various components in place, and water ingress had rotted the end - I was able to source some very thin-walled brass tube to replace it from the local model/toy shop, but that was pure luck. The rest of the mechanism was fine, all nylon gears and similar.

[ptjs1]

As Paul G says,

The XJS aerial operation and circuitry is interesting and not necessarily intuitive! I've never really understand exactly why the delay function was built-in. Anecdotal musings that I've read says it's a throwback to avoid aerial cycles when the ignition needs to be turned on and off, for example when the car is difficult to start, or when turning off ignition to open garage doors / gates etc at end of journey. Either way, I've just got used to seeing the aerial retract as I walk away from the car.

Paul has mentioned the motor timer but I don't believe it's the timer which limits the amount of mast travel. There is an internal limiter which dictates that the aerial has reached the top or bottom of its travel. I'm not sure what the limiter comprises (a notch on the toothed mast or similar perhaps?) The Jaguar maintenance TSB references that the aerial full travel is about 7 seconds and the timer will cut the motor out at about 12 seconds. See the TSB here which may help in you removing the mast and reinstalling it.

http://jagrepair.com/images/TSB/TSB2/XJ ... ration.pdf

The late Hirschmann aerials fitted from about 1993 came in 2 versions - the standard version with the delay, and an identically-looking version without the delay that was fitted to cars with rear spoilers. This was because the spoiler would snap the aerial if the boot was opened immediately after turning off the ignition. So a different non-delay circuitry was fitted along with a bridging wiring that keeps the boot latch locked until the aerial has retracted.

I've just fitted a spoiler to my 1994.75 model and the jaguar kit comes with the replacement aerial and bridging wiring. Having now fitted it all (see the magazine for a write-up soon) I can't decide whether to sell my original aerial or keep it. Seeing as used aerials LHD4120AA go for about $350 on ebay, I may sell it.

With the price of a used aerial, I would be minded to carefully remove the mast and toothed cable and see if I could find the limiter issue and fix it first. If the limiter is built into the mast mechanism, maybe just a replacement mast will cure the problem?

Good luck

Paul

[ptjs1]

Sonic,

I found this thread and video which may explain the issue and the sleeve that limits upward travel.

https://www.jaguarforums.com/forum/xjs- ... le-167645/

Cheers

Paul

[PaulGover]

...
Paul has mentioned the motor timer but I don't believe it's the timer which limits the amount of mast travel. There is an internal limiter which dictates that the aerial has reached the top or bottom of its travel. ...

You're right! AFAIR the limiter is a mechanical stop, and the timer just supplies power to the motor for longer than should be needed to reach the stop, so the motor turns and then stalls.

Such a crude design given the high tech components. A modern version ought to have Hall-effect sensors and the like to spot the stalling, together with "Plausibility" tests to check if you want to listen to the chosen radio station, a slew of OBD-II error codes and Radio Aerial Enablement Control Unit hidden under the front bumper .