Bulb Failure Unit for Sidelamps

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penfold
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Joined: Sat Dec 29, 2007 4:27 pm

Bulb Failure Unit for Sidelamps

Postby penfold » Sat May 18, 2019 11:17 am

I am tracing various electrical problems on my 1979 XJ6 Series 3 (RHD). The car is in Thailand but I was told it came here from Hong Kong. It might have been a UK market car originally as it has the speedometer in MPH.

Neither of the front sidelights were working. According to the Haynes manual the bulb failure units for the sidelamps are in the boot on the rear bulkhead. This is true of the two units for the tail lamps, but I found that the front LHS failure unit is mounted next to the small fusebox on the passenger side footwell area below the dash. This unit had failed and having bypassed it, I now have the front left sidelamp working. However, I cannot find the bulb failue unit for the front right sidelamp. I think the supply is separate from the LHS lamp because on the RH inner wing where the wiring connectors come through, the red wire to the side lamp is connected via a bullet connector to a red wire that joins the loom headig towards the dash area. The wiring diagram shows four individual bulb failure units for sidelamps (one for each corner of the car)

Does anyone know the location of the bulb failure unit please? I cannot locate it.

mike020150
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Joined: Wed Feb 08, 2006 6:26 pm

Re: Bulb Failure Unit for Sidelamps

Postby mike020150 » Sun May 19, 2019 10:46 am

According to an early parts book I have, there can be three bulb failure units plus one bulb check unit which looks like it's located above the main fuse box on the driver's side of the car. The bulb check unit is cube shaped unlike the bulb failure units. Hence, perhaps it's an issue with the check unit? Mike.
2014 XK Dynamic R convertible; 1977 Daimler Double Six Coupe; XE S

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penfold
Posts: 5
Joined: Sat Dec 29, 2007 4:27 pm

Re: Bulb Failure Unit for Sidelamps

Postby penfold » Tue May 21, 2019 11:04 am

Many thanks for the input.

The bulb check unit seems to be the device to which the signals from all the various bulb failure units are fed and connects to the warning lamp on the dashboard.

It seems to me now that UK market cars had a single bulb failure unit for the two front sidelamps. Having bypassed that and got the LH sidelamp working, I have since found a separate fault on the RH sidelamp (poor ground) and have now resolved that problem. So I am pleased to report that all my lights are working properly now.


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