Self retracting aerial

[barold]

My electric aerial has developed an annoying habit of disappearing back down the wing after initial successful erection After some 5 minutes it simply lowers itself. This is so bloody annoying. Usually if I stop, turn off, restart and drive off it'll behave itself. Doesn't make any difference if I turn the radio off and then on again, it just sulks down there in the boot.

Any ideas ?

Thanks.

[robv12]

no idea why, but used aerials are cheap and plentiful, I would get one off ebay and do simple swap over, a 10 minute job

[barold]

Thanks Rob, Though I can't think how the aerial motor itself would decide to retract. If it remains up for after 5 minutes or so, then on a long run it remains so for hours.

I'm in the process of trying to eliminate what I sometimes do after start up, Lights on, footbrake on prior to changing into Drive, etc, etc.

I guess, looking at other posts that if this is my biggest problem, then I should probably simply accept it as one of those indefinable Jaguar idiosyncrisies (where's the spell checker here?)

Maybe it's connected to the non functioning CD changer which I keep meaning to obtain a replacement for from you.

Slainthe.

[thejpster]

Well the radios can be pretty flaky, but if the aerial's cheap to replace I'd start there. As far as I know they just receive a 12v signal from the radio which means 'radio is now on' so it's up to the aerial unit itself to raise the aerial with the signal appears and stop the motor when the aerial is fully extended. Conversely when the voltage goes away, the motor retracts the aerial and stops when it's fully in. This means if the connection to the radio comes loose at any point, the aerial will retract. It could also be a failure of whatever mechanism the aerial uses to detect whether it's full up or down.

JP

[oldtimer]

Hi Barold,
Just been looking at the wiring diagram for my 73'XJ which might give us a hint.
The Aerial is powered via a relay, which in the case of the XJ is mounted next to the Aerial motor in the boot. When the radio is switched on a live feed goes to the the relay.

As we know a relay is an electric switch. The switch is operated by passing a current through a coil, the coil is wrapped around an iron core. When the coil is energised we have an electro magnet. The connections on the relay are marked W1 supply in and W2 supply to earth. Now we have a working movement controlled by the radio on off switch.

There are three further connections on the relay Marked as C1 C2 C3 A seperate live fused feed (nothing to do with the radio) connects to C2 . When the radio is switched on the coil is energised and moves a contact to close the the points of CI and C2 that then runs the aerial motor up. When the radio is switched off the coil is de energised and contacts C2 and C3 close
giving a supply to retract the aerial

Before any repair can be carried out the problem needs to be identified. You have already said the Aerial works. I'll put money on the Aerial motor being operated via a relay! This needs to be found

[oldtimer]

Barold,
Please totally disregard my previous entry. I ment to press the delete button

I've just found an appropriate Workshop manual complete with wiring diagrams.

Having had a quick look I would suggest the Aerial should not be the first port of call.
I did notice an up timer and a down timer in the diagram

Getting late for me

Oldtimer

[thejpster]

There is no timer in the diagrams I have. It's all integral to the aerial motor assembly.

[oldtimer]

Hi Barold /Thejpster

I have a Jaguar manual, Title XJ6 2.9 & 3.6 Part No JJM 10 04 05 This comprises of 5 Manuals containing 88 sections
I have in front of me Part 5 Section 80-88 Electrical Harnesses, Components & circuits.

So I am faily confident I have the correct Manual for the appropriate model.

The great shame is that I do not know how to scan in the wiring diagram.
Would you believe that six A4 sheets are devoted to just the radio and aerial.

As numbered on the wiring diagram:-
No 1 Radio Relay Location Passenger side - towards left of dashboard
No 2 Radio " Centre of dashboard
No 3 4 5 and 7 8 9 Speakers

Now the interesting bit

No 6 CPU Location Passenger side - toward right of dashboard
Note 6.1 Aerial up timer contained inside No 6 CPU
Note 6.2 Aerial down timer contained inside No 6 CPU

Now to the boot 2 relays, One aerial motor , one aerial

No 10 Aerial up relay - operated by CPU up timer - when this relay closes up goes aerial
No 11 Aerial down relay - operated by CPU down timer - when this relay closes down goes aerial

Well now you have it.
First Question, what on earth is a CPU, perhaps one of our learned friends can tell us, no guessing please.

Where to start. We know the Aerial actually works, so leave that for the moment. I see that relay 10&11 are identical and both have individual earths. Perhaps swap the relays over and thourghly clean each earth connection. Switch on and test

I've been sitting gazing at the wiring diagram. Don't get mislead, if you set aside all the other trivia it comes down to 3 bits. These being the CPU up in the dashboard and two relays in the boot. We know the aerial is doing exactly what it is told to do

Of course being a mature vehicle there is always the chance of a bad earth or connection

Just thought, when the Aerial goes down of its own accord does the radio remain on?
Should do. If the radio does go off then look at Relay No1

I have no idea where the CPU or No 1 relay is located except they are buried in the dash above front passenger knees

Finally, I studied the diagram sent in by thejpster - it appears incomplete to me where did it come from?

I hope that helps, let us know your progress

Regards Oldtimer

[thejpster]

A CPU will simply be a control module.

I see the confusion has arisen because I assumed the original poster had an X300 like me. I forget this is also an XJ40 forum! My picture is from the X300 workshop CD, while you are looking at an XJ40 manual. Clearly the aerials on the two differ.

[robv12]

and , don't forget 40 ones also differ as production went on

early XJ40, does not have CD capability, this only came in late 1990 (I would need to check vins), but no 3.6 had CD capability, most 2.9's did not (if any at all) and some early 4.0 did not either

we need a model and a vin number of the car in question to move forward

[barold]

Wow! Thanks again for all the help. Yes, the radio remains on when the aerial does it's disappearing act.

1996 X300 XJ Sport Vin : SSAJPALG3BJ770270 hope that helps. I used the car on 3 separate
trips today, and the aerial behaved itself each time. I must say, that as a problem, it's not much of one! The only time that it really is a bloody irritant is leaving a Motorway Services and 5 minutes later ......Musico departo. Thankfully, I only use Motorways 2 or 3 times a year.

Being an auto too, means the old way of trying get something back on again by knocking the gearbox in neutral at around 70 or so and switching off the ignition for a couple of seconds then restarting would do the trick. ( By the way, don't try this unless your'e going in a straight line and relatively light traffic )

[robv12]

got to be an aerial fault OR a head unit begining to fail, 300 units are failing now on a regular basis

aerial swap is easy, 308 is the same unit, just find one off ebay, 35 quid buys one, or try Neville at NE Jag Spares 0191 586 7770, top man mention me

[oldtimer]

Hi Rob v12,
Am I missing something!
We are told that the Aerial rises and lowers when the radio is switched on and off as it is supposed to do, but occasionaly the Aerial retracts of its own accord.

From where I am, "sitting on my Bar stool" it seems the Aerial/motor are doing exactly what it is supposed to do, so I cannot understand your suggestion that it should be replaced.

However, in my earlier post I identified three items from the wiring diagram that need some investigation, these being the CPU and two relays. These being the very items that control the Aerial/motor.

So far there has been no response or comment to that element

I await your comment , meanwhile , time for another Gin & Tonic

Regards Oldtimer

[thejpster]

Unfortunately oldtimer, the documents to which you referred are for an earlier model of XJ. The OP (original poster) above states he has an X300 - that is, Model Year 1994 to 1996 or VIN 720125 to 812255. This means the aerial is a fully integrated system which simply takes a 12v on/off signal from the head unit.

The fault lies with the aerial, the head unit or the cable between the two and the aerial is the cheapest place to start.

If you carry a pocket voltmeter with you (I do, but then I spent six months worried I had a dicky fuel pump relay), you might be able to pull over and probe the signal pin on the aerial module next time the fault occurs. If the signal is still good, it's definitely the aerial. If not, it's likely to be the head unit. If it is the head unit, one workaround would be to remove the signal wire from the head unit and route it to a switch fitted somewhere or simply to the ignition. It depends if you mainly listen to radio or mainly to tapes/CDs I guess.

[oldtimer]

Hi TheJpster,
Well there you go and I thought I was on a winner, it helps if one uses the correct road map!

It all makes sense now and your recomendation should to be acted upon.

The interesting thing is that 115 people have been watching the progress of this thread and hopefully have learned something as I have.

In due course it would be nice to here what the fix was and that every thing is working well

Regards Oldtimer