[xj40] Aerial Wiring Woes

XJ40
1

While washing the car today the pedant in me finally had enough of the aerial going up and down on the ignition switch instead of up and down when the radio is turned on and off.

Roger is a 1993 car (July 1993 actually) and has a factory CD changer and appropriate head. Haynes tells me that my car should have a single Light Green/Black wire going from the head to the aerial, which I believe should be hot when the radio is on.

The PO replaced the aerial and as usual it’s not an OEM unit. However, its function is per the wiring scheme that should apply to my car - i.e. it has a one wire input which when hot means the aerial is up, and vice versa. The PO had wired this into an ignition-controlled circuit so I thought it would be but a moment’s work to find the Light Green/Black wire and connect it to that instead.

An hour later I concluded that my 93 does not have the wiring Haynes describes as ‘Typical 1993 and 1994 audio system’ with respect to the aerial, it appears to have the ‘Typical 1988 to 1992’ wiring - even though it has the '93-onwards CD changer and eight speakers.

With apologies for the long preamble (I’m famous for them), here’s the meat of my question: The older scheme still has that Light Green/Black wire, going to something Haynes ambitiously calls a ‘Microprocessor (Antenna Logic)’ so if I can find that wire I can simply re-route it direct to the aerial.

Where’s this ‘Microprocessor’, then? I must have one because I’ve found the original connector for the ‘Antenna Up’ and ‘Antenna Down’ relays, and their outputs are functioning (i.e. they go hot for about 30 seconds when the radio is switched on or off). However, I can’t find the light green/black wire in the boot harness so I’m wondering if the space-age technology antenna logic computer is in the cabin somewhere.

The only other things I can do are (1) live with it - not likely (2) find a pre-93 spec OEM aerial - too pricey or (3) invent a way to convert the momentary outputs from the so-called microprocessor into a go/no-go output that suits the aerial - too silly.

Justin–
Justin Hill, Surrey UK
Jaguar XJR 07/1993 “Roger”
Volvo 850 20-valve 1995 “Victor” the freebie
jhill@cka-net .com

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

2

In reply to a message from Justin Hill sent Sun 9 Jan 2011:

Justin,

What you really need is a copy of the wiring diagram in JDHT
CD-ROM JHM1130 so that you can sort out the wiring.

The Light green/black wire to which you refer, on your '93
model, runs from the radio (14-way white connector pin 4) to
the CPU (48-way black connector pin 13). It does not go to
the aerial.
The output from the CPU is from the 48-way yellow connector

  • pin 22 on the White/purple wire for the ‘UP’ relay K2 and
    pin 60 on the White/black wire for the ‘DOWN’ relay K3 in
    Relay Module ‘K’ which is above the right rear wheel arch in
    the boot forward of the aerial.

The wiring to the aerial itself from the Relay Module ‘K’ is
on a Green/red wire for ‘UP’ and a Green/blue wire for ‘DOWN’.

Does that make any better sense?–
The original message included these comments:

Roger is a 1993 car (July 1993 actually) and has a factory CD changer and appropriate head. Haynes tells me that my car should have a single Light Green/Black wire going from the head to the aerial, which I believe should be hot when the radio is on.
The PO replaced the aerial and as usual it’s not an OEM unit. However, its function is per the wiring scheme that should apply to my car - i.e. it has a one wire input which when hot means the aerial is up, and vice versa. The PO had wired this into an ignition-controlled circuit so I thought it would be but a moment’s work to find the Light Green/Black wire and connect it to that instead.

–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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3

Thanks Bryan but (showing my ignorance) what CPU are you referring to? I thought there were about eight of the things in the car - where is this one? Is this the thing in the boot high up on the offside wing?

And is the device that Haynes calls the ‘Microprocessor (Antenna Logic)’ just a function of the CPU you’re talking about, rather than a specific piece of hardware? And is Haynes just wrong?

JustinOn 9 Jan 2011, at 18:47, Bryan N wrote:

The Light green/black wire to which you refer, on your '93
model, runs from the radio (14-way white connector pin 4) to
the CPU (48-way black connector pin 13). It does not go to
the aerial.

–
Justin Hill, Surrey UK
Jaguar XJR 07/1993 “Roger”
Volvo 850 20-valve 1995 “Victor” the freebie
jhill@cka-net .com

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

4

In reply to a message from Justin Hill sent Sun 9 Jan 2011:

Justin,

CPU = Central Processing Unit (a.k.a ‘Microprocessor’) and
there is only one of those. It is under the passenger side
dash behind the knee bolster / glove-box and has one black
6-way connector, one black 48-way connector and one yellow
48-way connector, so you cannot miss it.
It has various elements built in to it, one of which is the
aerial logic circuit.–
The original message included these comments:

Thanks Bryan but (showing my ignorance) what CPU are you referring to? I thought there were about eight of the things in the car - where is this one? Is this the thing in the boot high up on the offside wing?
And is the device that Haynes calls the ‘Microprocessor (Antenna Logic)’ just a function of the CPU you’re talking about, rather than a specific piece of hardware? And is Haynes just wrong?
Justin
On 9 Jan 2011, at 18:47, Bryan N wrote:

The Light green/black wire to which you refer, on your '93
model, runs from the radio (14-way white connector pin 4) to
the CPU (48-way black connector pin 13). It does not go to
the aerial.

–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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5

CPU = Central Processing Unit (a.k.a ‘Microprocessor’) and
there is only one of those.

Thanks. Having spent my whole career working with computers was just confusing me. So the thing that runs the gearbox and the thing that runs the ABS and the thing that runs the fuel injection and the thing that runs the ignition and the thing that runs the immobiliser/alarm and the thing that runs the aircon and…

Anyway, it sounds like what I can do is disconnect the existing aerial outputs from the CPU and hard-wire the light-green/black to one of them, which will get that signal into the boot where I can connect it to the aerial, yes?

JustinOn 9 Jan 2011, at 20:27, Bryan N wrote:

–
Justin Hill, Surrey UK
Jaguar XJR 07/1993 “Roger”
Volvo 850 20-valve 1995 “Victor” the freebie
jhill@cka-net .com

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

6

In reply to a message from Justin Hill sent Sun 9 Jan 2011:

Justin,

Depends if the after-market aerial you have installed is
compatible with the '93 model wiring. On the '94 models post
VIN 687218 they fitted an Harada aerial which dispensed with
the CPU aerial logic circuit because it has its own in-built
logic circuit.

If the aerial fitted to your car is of that or similar type,
the wiring is much simpler. The Light green/black wire from
the radio (pin 4 of the 14-way white connector at the radio)
goes directly to the aerial, completely by-passing the CPU
and the Relay Module ‘K’.

Can’t help you beyond that.–
The original message included these comments:

Anyway, it sounds like what I can do is disconnect the existing aerial outputs from the CPU and hard-wire the light-green/black to one of them, which will get that signal into the boot where I can connect it to the aerial, yes?

–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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1 Like
7

Just to clarify - I didn’t install it, the PO did. And it’s of the later type (like a Harada). My problems all started because Haynes told me my 93 was wired for that type of aerial. Clearly, it isn’t so I’m going to have to bodge something.

JustinOn 9 Jan 2011, at 20:47, Bryan N wrote:

Depends if the after-market aerial you have installed is
compatible with the '93 model wiring.

–
Justin Hill, Surrey UK
Jaguar XJR 07/1993 “Roger”
Volvo 850 20-valve 1995 “Victor” the freebie
jhill@cka-net .com

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

8

…and I did. I made a little two-relay setup that ‘converted’ the older style momentary-up, momentary-down behaviour to the later type. Now my aerial goes up and down when it should, including that childishly-delightful short pause between when you turn the car off and when the aerial starts to retract. Little things please little minds, my mother used to tell me.

JustinOn 9 Jan 2011, at 21:04, Justin Hill wrote:

so I’m going to have to bodge something.

–
Justin Hill, Surrey UK
Jaguar XJR 07/1993 “Roger”
Volvo 850 20-valve 1995 “Victor” the freebie
jhill@cka-net .com

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

9

In reply to a message from Justin Hill sent Sat 22 Jan 2011:

I know what you mean , is it going to retract ? , or is this
the time it gets stuck ?

Derek…–
The original message included these comments:

…and I did. I made a little two-relay setup that ‘converted’ the older style momentary-up, momentary-down behaviour to the later type. Now my aerial goes up and down when it should, including that childishly-delightful short pause between when you turn the car off and when the aerial starts to retract. Little things please little minds, my mother used to tell me.
Justin Hill, Surrey UK
Jaguar XJR 07/1993 ‘‘Roger’’
Volvo 850 20-valve 1995 ‘‘Victor’’ the freebie
jhill@cka-net .com

–
Derek, kent '93 Daimler 4.0L solent ,'93 4.0L,westminster .
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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10

I know this is an old topic but it may help someone trying to fix a 1991 XJ40 with a Hirschmann aerial.

The relays just forward of the aerial in the R/H side of the boot are :- Green relay plugged into the black socket with white/black wire connected to pin 85 on the socket is the UP wire. The green relay plugged into the green socket with a white/green wire plugged into pin 85 on the socket is the DOWN wire.

Pin 86 on both the sockets is 12v live even with everything off on the car. Earthing the white/black wire the aerial goes up and earthing the white/green wire the aerial goes down. This is not a momentary earth for up and down as you have to keep the connection till the aerial extends fully or retracts fully.

How the microprocessor controls this I must still work out but if it is damaged I will fit a spring loaded center off 3 way switch and earth the center terminal with white/green and white/black connected to the other two terminals. This will be the easiest way to do it giving you a fully functional aerial with manual operation. No big problem.

11

I pulled the radio out to sort out the wiring and found that a blue wire in the harness to the radio was not connected. I plugged in into the antenna slot next to the 4 pin power plug and the antenna was working. No need to fit a switch after all.

12

Always good to hear about a simple fix that worked. Thanks for the report.

1 Like