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cruise control switch on the console (underneath the driver-side console ashtray). It will require that you remove the
console veneer entirely.
“I found the fuse wiretied closely to a bundle, as well as electric taped over the fuse housing to another line (dunno why
- I eliminated the tape when I was in there). I found a 2A fuse in there, but the manual calls for a 1A - both of which
are odd, given that the stock Jaguar stereo had a 10A fuse on it -- fused to that same power input as the inline fuse is on
(as versus the ignition/accessory input which tells the stereo to wake up). I checked with the local Jaguar dealership
and he said there shouldn't be a problem for that line to carry 10A, so I switched the inline fuse to a 10A and the stereo
works fine.”
Actually, the situation could use a little more explanation. The Haynes manual and the ROM seem to talk only of a
“radio” and otherwise provide little info on wiring of the stereo system, but with almost any system there are actually
two separate power supplies: a switched and an unswitched. The unswitched is connected to the battery at all times
while the switched turns on and off with the ignition key. In the old days when things were simple, the unswitched line
drew only a tiny amount of power, since all it did was maintain the settings on the tuner presets and the like; the
switched line, which powered the amplifier itself, the tape drive mechanism, and anything else you didn’t want on when
the car was off, drew the relatively heavy current. Hence, the switched line would be fitted with a 10A fuse or some
such, while the unswitched line would get only a 1A.
Then the serious autosound buffs came up with the idea of installing huge capacitors in the power supply to a stereo
system. These “stiffener capacitors” can range from 0.25 farad (already larger than most any other capacitor used
anywhere by several orders of magnitude) up to 1.5 farad; the rule of thumb is 0.001 farad for each watt of amplifier
power. These capacitors are typically about the size and shape of a 12-oz. beer can, and some stereo buffs connect up
entire banks of them! Their purpose is to maintain a rock-steady voltage supply to the stereo when the stereo itself calls
for a sudden surge of power, such as when a heavy bass note is hit.
The problem is that such capacitors cannot be on a switched line. In fact, installing them in a car requires some care in
pre-charging through a resistor before connecting, or something will get fried. Once installed, they must remain in
continuous connection with the battery at all times, and disconnecting the battery for servicing the car requires
discharging and recharging through the same resistor when reconnecting. If installed on the switched circuit, the first
time you hit the ignition key the contacts within the ignition switch would weld themselves into a handsome little glob.
As a result of these developments, the modern stereo systems have changed the standards. They still require a switched
and an unswitched power supply, but in order to take advantage of stiffener capacitors and other power supply
upgrades, the heavy current is taken from the unswitched line. The switched power supply now becomes merely a
“signal” that the ignition is on, and therefore draws almost no power.
Obviously, if you remove an original deck that drew its amplifier power through the switched line and install a newer
deck that draws its amplifier power through the unswitched line, the first thing that’s gonna happen is you’re gonna
blow the tiny fuse that was originally intended only to maintain station presets. Straw’s dealer is correct, almost any
circuit in the car will handle a 10A fuse without trouble, so you can merely replace the 1A inline fuse with a 10A to
make your new deck work. On the other hand, you might opt to run a new heavy-duty power supply wire from one of
the two main terminals on the firewall directly to your new deck to make sure it’s not starved for amps when you’re
rockin’ out.
CD CHANGER ADDITION: David Brown sends this info on installation of a CD changer in the boot: “I believe all
post-’88 cars are pre-wired. Depending on what year you have, a 7-pin DIN socket (that’s what we call it in the UK
anyhow) will be found in different places in the boot (trunk).
“... a Clarion changer unit will plug straight in and you’re all set.
“For a Philips or Alpine unit, you have to disassemble the plug on your CD changer and rewire a couple of pins around.
Basically you can control the unit as it is currently wired, but you would hear nothing. The head unit expects the
sound signals to be traveling down some otherwise unused pins. Simple experimentation shows what they are.