Jaguar XJS
1978-1996Faults written up for this generation: likely causes and the order to check them in.
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10
Air Conditioning Problems
On the XJS the usual story is a slow leak: once the charge is low, the pressure switch stops the compressor clutch engaging, and it looks like a dead compressor.
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8
Alarm Keeps Going Off
An XJS alarm that goes off when you get in is most often just the disarm sequence: opened with the key, the car gives you about 15 seconds to switch the ignition on.
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4
Alternator Not Charging, Battery Light
The original Lucas alternator is the usual culprit. But a slipping crank damper, the warning-lamp wire and loose connections mimic it with a healthy alternator — I'd…
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5
Battery Drain
On the XJS it's usually the power aerial: its motor sits on a permanent feed and keeps running when its board corrodes or its cord breaks.
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8
Blower Motor Not Working
On the XJS a blower that won't blow is usually the small speed-control board inside the blower itself — its power transistor fails and leaves high speed only, or shorts…
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4
Brake Light Switch, Turn Signals Not Working
On the XJS, lower brake lamps that die while the high-level lamp still works usually come down to the bulb-failure unit in the boot or its plug.
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9
Brakes and ABS Problems
On 1989–1995 Teves III cars, start by listening for the ABS pump at key-on: one that won't run is usually its relay, one that won't stop is a blocked feed or the…
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3
Cassette Player Not Working or Ejecting
On these radios it's almost always the rubber drive belts inside: heat from the heater core behind the radio stretches, snaps or melts them.
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6
CD Changer Not Working
On the facelift XJS the boot changer is an Alpine unit, and an E-01 or E-02 almost always means a disc or the magazine is jammed inside, not that the radio has lost the…
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8
Central Locking Not Working, Door Won't Open
On the XJS a door that won't unlock is far more often a binding rod, a rod off its clip or a lock out of step than a failed motor.
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3
Climate Control Problems
On the XJS the climate control usually goes wrong at the flaps rather than in the electronics: a blend-flap servo stuck on hot, or lost vacuum that leaves the doors…
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4
Convertible Top Not Working, Pump and Relays
On the XJS convertible a dead top is usually electrical: the console top switch, the top motor relays, or the interlock that wants Park and the handbrake on.
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6
Electrical Problems, Bad Earths
On the XJS most electrical faults are bad connections rather than failed parts: a missing or loose engine-to-body earth, tired glass-fuse contacts and the blue relays…
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5
Headlights Not Working
On the XJS dead or dim headlamps are nearly always a relay at the front left of the engine bay: the latching dip relay, or the headlight relay with corroded contacts.
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6
Heater Not Working
On the XJS no heat is usually the vacuum heater valve on the bulkhead or a blocked matrix. I'd feel both heater hoses first: if the outlet stays cool, it's coolant flow.
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7
Instrument Cluster, Gauges Not Working
When several gauges misbehave at once, the cluster's own earth or its plugs are the usual culprit — I'd add a second earth wire and check the pins first.
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9
Misfire, Rough Idle
On the 4.0 six, a misfire or rough idle is usually a failing coil, aftermarket ones above all, or water in the ECU connector, and the two often turn up together.
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9
Overheating, Cooling Fan Problems
On the XJS, running hot is almost always too little air at idle: a seized auxiliary electric fan, a fan that gets no power, or a worn viscous clutch on the belt fan.
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6
Power Antenna Stuck
Before buying a new aerial, feed its motor straight from 12 V. If it runs, the fault is upstream: the board inside the aerial, a hidden in-line fuse, the delay relay…
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7
Radio Code
When a known code is refused, the radio has usually locked itself out, or the digits went in too fast.
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10
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…
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9
Radio Replacement and Stereo Upgrade
Almost any single-DIN radio fits an XJS, but nothing plugs straight into the car's wiring, and the colours don't mean what an aftermarket radio expects.
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10
3.6 and 4.0 Won't Start
On the six-cylinder XJS a crank-but-no-start is usually one of three cheap parts: the crank position sensor, the EMS relay beside the ECU, or the yellow-base fuel pump…
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3
Speakers Not Working or Crackling
Prove which end is bad before spending: move a good radio channel onto the silent speaker's wires.
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10
Transmission Problems, GM400 and ZF Gearbox
On the V12's GM400 I'd start with the vacuum modulator hose, the kickdown switch and the fluid level before anyone quotes a rebuild: no change up, or no drive after…
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15
V12 Won't Start or Starts and Dies
A V12 that cranks but won't fire usually has one break in a short chain: pump prime, main relay, spark, then the firing signal to the injectors.
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6
Window Motor, Windows Slow or Not Working
On the XJS, when both door windows die together it's usually the feed — the window relay or the thermal breaker, since on 1988–94 cars the circuit has no fuse.
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8
Won't Crank, Starter Relay
On the XJS the relay and the starter both fail often, and one jumper wire tells them apart: key at II, 12 V on the white/red wire from the relay to the solenoid.