1994 VDP has been parked since purchase of '97 XJR in January. Needed to drive, so hooked up battery and started right up (been starting every month or so). After driving 2 days, parked and shut off and went in house. Noticed front parking lights were on, so thought I failed to turn off, went out but could not turn off. Brake lights, not tail lights, were also on. Lights go off as soon as ignition key on. Help! Have to connect/disconnect battery to use.... Ideas?

 

Hi Shelby,

That's a strange one. Check the electrical schematics for any common points that can provide power to those lights. You can download the 1993/94 XJ Electrical Guide here:

http://www.jagrepair.com/images/Auto...ec%20Guide.pdf

There are four Bulb Failure Modules, one at each corner of the car. The exterior lamps are powered via relays in their own BFM. Since the symptoms you describe involve all four BFMs, the problem must be upstream. I would think that maybe a switch was not disconnecting, but the parking lamps and brake lamps are controlled by different switches. A relay sticking in the ON position could also be the culprit, but I can't think of a single relay that is involved in both of those lighting circuits.

I can't recall whether the Central Microprocessor (CPU) is involved in all those lights, but corrosion on the CPU connector pins due to water ingress is a common problem that can cause weird symptoms.

Study the schematics and hopefully some common point in the circuit will be apparent where a malfunction could cause your symptoms.

Cheers,

Don

 

Could a malfunction in the hazard switch on the console be a point of cross over? I can't think of any other cross over point.

 

The hazard switch connects to the CPU, and the CPU then controls whatever lights are illuminated when the switch is closed. I can't remember if the brake lamps come on when the hazard switch is closed, but if so, that does sound like a possible culprit.