Bulb Module Locations
Joined: Feb 2014
Posts: 20,477
Likes: 15,251
From: Crossroads of America
Hi Jagbro,
As 95Leaper says, the rear Bulb Failure Modules are just ahead of the tail lamps behind the side carpeted trim panels, which can just be carefully pulled away from the body.
The front BFMs are mounted in the engine bay behind the headlamp assemblies.
The BFMs contain a "Turn Signal Fail Logic" circuit, but the actual flashing of the turn signal lamps is handled by the Central Processing Unit or Central Microprocessor (CPU) behind the dash to the right of the transmission tunnel (on LHD cars).
You can download the 1991 XJ40 Electrical Guide at the link below, courtesy of Gus and his jagrepair.com website. The guide shows the wiring schematics and gives the locations of all the electrical components:
1991 XJ40 Electrical Guide
Cheers,
Don
As 95Leaper says, the rear Bulb Failure Modules are just ahead of the tail lamps behind the side carpeted trim panels, which can just be carefully pulled away from the body.
The front BFMs are mounted in the engine bay behind the headlamp assemblies.
The BFMs contain a "Turn Signal Fail Logic" circuit, but the actual flashing of the turn signal lamps is handled by the Central Processing Unit or Central Microprocessor (CPU) behind the dash to the right of the transmission tunnel (on LHD cars).
You can download the 1991 XJ40 Electrical Guide at the link below, courtesy of Gus and his jagrepair.com website. The guide shows the wiring schematics and gives the locations of all the electrical components:
1991 XJ40 Electrical Guide
Cheers,
Don
Thread Starter
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Senior Member
Joined: Jan 2017
Posts: 111
Likes: 12
From: Los Angeles
Ok, Don thanks for your quick response. The right turn signal flashes fast, and the bulb failure indicator is lit on the dash. But there are no bulbs out. The bulbs flash at normal speed from the outside. The bulb indicator only comes on during right signal WHEN HEADLAMPS ARE ON.
I've installed new Jaguar Dealer issued bulbs in all right turn socket applying circuit grease (no change).
So is this likely to be the BFM OR CPU units?
I've installed new Jaguar Dealer issued bulbs in all right turn socket applying circuit grease (no change).
So is this likely to be the BFM OR CPU units?
Joined: Feb 2014
Posts: 20,477
Likes: 15,251
From: Crossroads of America
Ok, Don thanks for your quick response. The right turn signal flashes fast, and the bulb failure indicator is lit on the dash. But there are no bulbs out. The bulbs flash at normal speed from the outside. The bulb indicator only comes on during right signal WHEN HEADLAMPS ARE ON.
I've installed new Jaguar Dealer issued bulbs in all right turn socket applying circuit grease (no change).
So is this likely to be the BFM OR CPU units?
I've installed new Jaguar Dealer issued bulbs in all right turn socket applying circuit grease (no change).
So is this likely to be the BFM OR CPU units?
I can't recall whether the circuit for the main light switch (to the left of the steering wheel) is interconnected with the column turn signal lever switch. It might be worth checking the schematics to see if a short between those switches could cause your symptoms. Otherwise I'd lean toward a BFM acting up. Not sure whether it would be the front or rear.
I know a lot of owners have dealt with BFM problems and I think there may be some instructions for repairing them. If you don't find anything with the Advance Search function in this forum, check the archives at the Jag-Lovers forum.
Cheers,
Don