Jaguar XJS Radio Not Working, Radio Fuse
When an XJS radio goes dark, measure before you buy anything. On these cars it's usually a feed: the small in-line memory fuse under the console, a main-panel fuse nobody links to the radio, a fuse that looks fine but doesn't grip, or a missing earth strap. I'd only condemn the radio once both feeds and the earth are proven at its plug.
How bad is it · Safe to drive
Safe to drive
But a radio that died together with other electrics after a jump or a starter fault is worth tracing properly: a chafed battery cable behind it is possible.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
The small in-line fuse on the memory feed
Pre-facelift radios take their permanent feed on a red wire through a small in-line fuse under the console — usually 2 A, easy to miss and easy to replace with the wrong value. Loud aftermarket radios blow it again and again.
Main fuses fine, console lighting works, radio dark. Or it plays but loses its presets after the car has stood a couple of hours.
Look under the console: through the driver's-side ashtray opening, under the selector, or by the vent under the left tunnel cover. Early cars may have two, red and yellow. Pre-1987 cars also carry a 20 A in-line fuse near the radio for the radio relay. Test both sides of each with a test lamp.
Fit the original value. UK ratings run about half of US ratings for the same holder — a 2 A Lucas fuse is roughly a 5 A US one.
A main-panel fuse the handbook does not tie to the radio
Later cars have no console fuse: both radio feeds come from the main fuse panels, one of them behind the driver's knee bolster, and not always under a radio label. After a flat battery or a jump start one can blow while the listed fuses are fine.
Dead after a flat battery or jump start, or only the small red security light is lit — the memory feed is there, the main feed isn't.
Drop the knee bolster and test every accessory fuse with a test lamp; designations are often printed on the back of the panel cover. On a 1994 car, for example, the thin purple wire at the radio plug is memory and the thicker White/Blue is the main feed.
Replace the blown one, whatever the handbook calls it.
A fuse that looks good but doesn't make contact
Thirty-year-old fuse clips corrode, loosen or get pushed back out of the block, so a perfect fuse passes nothing. An in-line holder can have a cracked solder joint that works on the bench and opens once tucked back under the console.
Radio and heater fans die together, or it comes back when the fuses are touched.
Wiggle each fuse and the whole fuse box with the radio on; check both clips grip the fuse ends, and that no spade terminal has slid backwards out of the block. Measure across the in-line holder in place, not on the bench.
Clean the fuses and clips, click loose terminals back in from behind, resolder the holder.
A loose feed or a missing earth strap behind the radio
Some factory radios need their own earth strap from a lug on the back of the case to the transmission tunnel, besides the earth pin in the plug. Without it the radio can refuse to start, or trip as if shorted. A radio that moves in its opening also loosens its rear connections.
It cuts out over bumps or when the engine is started, comes back when pressed, or won't power up although the feeds are live.
Measure both feeds at the moment it drops out, and make sure neither is shorted to earth. Pull the radio, check the plugs and the earth strap, and clean any corrosion.
Refit or renew the earth strap to a clean chassis point and tighten the plugs; contact cleaner on the connectors is worth trying.
The radio itself has died
The units are thirty years old: capacitors leak and eat the board, regulators and output chips fail, solder joints crack. Many general repairers no longer take them, though car-audio specialists still do.
Both feeds live and the earth good, yet dark — or only the security light flashing and never a CODE prompt, or gibberish on the display.
Measure the feeds at the plug before condemning it. On the bench, look for bulging or leaking capacitors and dry joints.
A used original repaired by a specialist — for example about $150 — or a modern unit, which won't run the factory boot CD changer. Pin any adapter harness by function; colours and positions don't always match.
A break in the memory wire
The permanent feed runs as one wire from the in-line fuse to the plug. When both fuses test good but nothing arrives, the wire itself is open.
Fuses live on both sides, switched feed present, no permanent 12 V at the radio plug.
Follow the diagram for your year from the in-line fuse to the plug and look for a break or a bad old splice.
Run a new permanent feed through its own 2 A in-line fuse straight to the plug. Join wires with solder and heat-shrink, not wire nuts or tape.
The fuse inside the radio case
Some factory radios carry their own blade fuse inside the case — the one drawn inside the radio on the diagram is internal. A short while working on the aerial or the dash with the battery connected can blow it.
Dead straight after electrical work behind the dash or on the aerial, with every fuse in the car good and both feeds live.
Pull the radio and look on the top of the chassis or inside the housing — on a 1988 car, for example, a 10 A ATC fuse.
Replace it, and next time disconnect the battery negative lead first.
Wires swapped at the radio plug
The plug carries the switched supply, the permanent feed and the aerial trigger. After a few radio swaps they're sometimes crossed.
Fuses good, but the radio dead or the aerial odd — even aerials that keep failing.
Measure each wire, key off and on, against the diagram for your year.
Reconnect by function, not colour.
Dead right after a new battery
A late radio can stay unresponsive after its power has been cut until the car has been started once.
The battery has just been changed or disconnected, and the radio does nothing at all.
Start the engine and try it again before taking anything apart.
Starting the engine brought it back.
A shorted aerial relay
The radio drives the power aerial relay, and a shorted relay can stop the radio working even with every feed in order.
12 V on both feeds and a good earth, yet the radio won't run properly.
Disconnect the aerial relay and try the radio again.
Replace the relay.
Water in the radio
The radio sits under the heater and air-con outlets, and water through old window seals or a spilt drink corrodes it inside.
Dead or erratic after rain, a leak or a spill; the tape or CD slot looks stained.
Pull it, open it and look for corrosion; check every hot lead at the plug.
Worth trying: clean the contacts and the corrosion inside. A badly corroded board is usually beyond repair — a used unit is cheaper.
Crackle, or volume and fade that stop working
The volume and fade controls are potentiometers on a small board inside, and their tracks wear and gum up.
Snap, crackle and pop as the knob turns, sound dropping in and out, or a control that does nothing.
Work the control with tuner cleaner in it; then pull and refit the harness plugs, check the speaker leads and the speakers.
Worth trying: cleaner first. Once it stops helping, take the pot board from a donor of the same model — the AJ8700 was also fitted to XJ6 saloons of the period, and the CM5905 is a likely match. A donor with its code can go straight in.
Buttons, lights or display dead while it plays
On the 1995–96 face-off Alpine the contacts between the face and the body wear. Elsewhere it's the switch board, the bulbs soldered to it, or the rubber strip joining the display to the board. Radio lighting also has its own feed and fuses.
Sound fine but buttons ignore you, the display loses segments, or the face stays dark — pressing on the face may bring it back.
Check the lighting feed at the fuse panel; then clean the face contacts, look for a failed capacitor on the switch board, and reseat the display strip.
Worth trying: clean and reseat, resolder new bulbs, replace the capacitor.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Is it the code?
If the display lights or shows CODE, it has power — see the code page. Nothing lit means power.
freeNew battery just fitted?
Start the engine once and try again.
freeDisconnect the battery before working
Negative lead first. A slip behind the dash can blow the fuse inside the radio.
freeTest all accessory fuses
Every one, with a test lamp — not only those listed for the radio. Wiggle each and check the clips grip.
freeFind the console in-line fuse
Pre-1993 cars: on the red wire, through the driver's-side ashtray or under the selector. Fit the original value, often 2 A.
a fuseMeasure at the radio plug
Switched feed, permanent feed and earth; check they aren't swapped. Fuse good but no voltage at the plug means a broken wire.
freeCheck the earth strap and the internal fuse
Radio out: strap from the back of the case to the tunnel, and the fuse on or inside the case.
freeOnly then replace the radio
A repaired original keeps the boot changer; a modern radio loses it.
used or new unitWhat it usually isn't
Don't spend money here first:
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- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.