Jaguar XJ40 Turn Signals Not Working
On these cars there's no flasher relay: the central processor behind the glovebox pulses the indicator relays inside the four corner modules. A fast flash on one side is a lamp or holder on that side; one dead corner is its module or its wire; everything dead at once is the battery or the processor. I'd check the battery first, then the bulbs and wing repeaters, then swap the modules side to side.
How bad is it · Garage, carefully
Drive only if you can signal by hand
The car runs normally, but other drivers can't see what you're about to do. Dead indicators are also an inspection failure.
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.
A broken switching wire between the processor and a corner module
The processor earths a yellow/slate wire for the left side and another for the right, once or twice a second, and the relays in the corner modules follow it. If that wire breaks on its way to one module, that corner goes dark while the rest flash.
One front corner and its wing repeater dead on both the stalk and the hazards; the fault stays put when the front modules are swapped; the sidelight on the same fuse works.
With the plug off, check continuity of the switching wire from the processor's 36-way yellow connector, through the 36-way black connector at the A-post, to pin 4 of the module's 9-way yellow plug. Earthing that wire with the ignition on should light the lamps.
Run a new wire alongside the old one. Check the harness before buying a new stalk, processor or module.
The bulb-failure module at that corner
Each corner module holds the indicator relay and the relays for that corner's other lamps. A cracked joint or a blown component inside stops one corner switching, and it can make a front indicator stay lit instead of flashing once the sidelights are on.
One corner misbehaves and the fault moves to the other side when you swap that pair of modules.
Swap the modules left to right, front pair or rear pair. If the fault moves, open the module and look for cracked joints or burnt parts on the board.
Fit a used module with the same part number. Resoldering can clear the warning without bringing the lamps back if a component has failed.
Everything dead after the car has stood: a flat battery
The indicators run through the processor, and it misbehaves on low voltage. A battery that has drained can leave indicators and hazards dead and a high-pitched whine from behind the glovebox.
Indicators and hazards both dead, bulb-out symbol on, a whine from the passenger footwell, after the car has stood for a while.
Measure the battery at rest and while cranking; charge it and try again before chasing wiring.
Charge or replace the battery.
Indicators flash but don't tick: the audible module or its speaker
The tick is a sound played through the audible-warning speaker in the steering column, not a relay. A loose pin on the audible module's connector, or a broken joint at the speaker, silences it while the lamps still flash.
Lamps flash at the right speed, but the tick, and often the lights-on warning, has gone.
Remove the panel under the glovebox and wiggle the audible module's large connector with the indicators on. Then find the speaker above the ignition switch and play sound through it from a phone.
Reseat the loose pin, check the module's earth screw, or resolder or replace the speaker — about 64 ohms, roughly 50 mm across.
A corroded holder, wing repeater or lamp earth
The indicator lamps share holders and earths with the side lamps, and the UK wing repeaters let water in at the connector. Resistance in a holder or earth makes the module call the lamp failed, and the tell-tale flashes at double speed.
Fast flash on one side with all lamps lit, a repeater that comes and goes, or a lamp that misbehaves after bodywork.
Pull each bulb on the fast side and inspect the holder. Earth a bulb directly and feed it 12 V: if it lights, the fault is in the earth path through the harness or the lamp body.
Worth trying: clean the holders and earths; close up slack plug terminals; fit a new repeater if the holder has rotted.
The central processor behind the glovebox
The processor is the only part shared by all four corners: each corner has its own fuse and earth. Its board develops cracked joints like the corner modules do.
All indicators on one side, or on both, dead together, with the battery good and the modules swapped.
At the 6-way blue connector on the column switch, earth pin 6 (yellow/blue) with the ignition on: the right indicators should flash. If they don't, and the switch makes contact in the right-turn position, suspect the processor.
Worth trying: take the box out from behind the glove pocket and resolder every joint you can reach.
Won't self-cancel after steering work: shaft or wheel refitted off-centre
The cancelling cam is set by the steering wheel's position on the column. If the shaft or the wheel was refitted half a turn out, the cam sits offset and the stalk needs far more wheel movement to cancel.
Cancelling went wrong straight after a rack, column or alignment job; the steering lock may only engage with the wheel half a turn round.
With the road wheels straight, see whether the steering wheel is centred and the lock engages normally.
Worth trying: correct the shaft position at the joint, then refit the wheel centred; alignment itself is set on the track rods.
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.
Watch which lamps flash and how fast
Everything dead including the hazards points at the battery or the processor; one side fast at that side's lamps; one dead corner at its module or wire.
freeCheck the battery
Especially if the car has stood. Charge it before anything else.
freeCheck fuses with a test lamp
On 1993 cars the processor is on C3 (10 A) in the left box; front indicators share C7 (10 A) and rear ones B8 (15 A) in the box on that side. On 1988–89 cars the front indicators are on F5 (5 A) and the rear on F7.
a test lampClean the bulbs, holders and wing repeaters on the bad side
Look at the earths too, including the bolt in the boot floor beside the rear module.
contact cleanerSwap the modules side to side
If the fault moves, replace the module; if it stays, test the switching wire to that corner.
freeTest the processor from the stalk
Earth the stalk's turn wire with the ignition on. No flash with good wiring — resolder or replace the processor.
freeWhat it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar XJ40 Bulb Failure WarningIf the bulb-failure warning comes on with the fast flash.
- Jaguar XJ40 Headlights Not WorkingIf a headlamp is out too — the front modules switch both.
- Jaguar XJ40 Battery Drain, Flat After a Few DaysIf the battery keeps going flat after the car stands.
- XJ6 (XJ40) fuse boxesWhich fuse feeds each indicator on your year — other years from the same page.
- Jaguar XJ40 Wipers Not Working, Wiper MotorIf the wipers died at the same time as the indicators.
- 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.