Bulb Failure Warning

[simondmill504]

Suspect wasting my time asking but wonder if anyone has any ideas. Bulb warning came on now and again when braking, then behaved itself. Not now, on every time brake pedal activated, also comes on with rear fog lamps. Needless to say lamps working OK, obvious suspect is the Rear lamp Relay Module, but of course one each side. Anyone know how to test them?
Thanks

[davidr]

Hi. Please could you give us some more detail about your car? XJ40 or X300 and year would help us to help you

[BrianG]

Before you start down a possibly expensive route, take the rear stop/tail bulbs out and carefully examine the filaments or even possibly just change them out for new bulbs anyway as a test. I had the same occasional bulb failure warning on my then X308 XJ which after much hassle I eventually tracked down to one bulb, which appeared to be working normally. The filament, not immediately obviously as "blown", had become detached at one end from the supporting metalwork so that it was only just touching. The slightest bump, such as slamming the boot lid, would be enough to unseat the filament and cause the warning.

[simondmill504]

Hi
Thanks for both replies. Car is 1994 XJ40 4.0 Sport.
Appreciate comments about bulbs but given happens every time brake pedal pressed and with rear fog lamps still suspect relay module. Must be a way of testing them?