Hello.

I am a new owner of a Jaguar XJ6 1994. Replaced the alternator the other day and that was a lot of fun!

I am having problems with the headlights on the care now. When I turn the dial switch to on, nothing happens. I can turn the toggle switch for the high beams and they come on, but no headlights. I did replace both bulbs with no change. Any thoughts or ideas what to look at?

I appreciate any help

 

Welcome to the forum whbonny,

I've moved your question from General Tech Help to XJ40 forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Hi whbonny,

Welcome to the Jaguar Forums. It's great to have you with us!

First of all, can you tell us why the alternator had to be replaced? What were the symptoms?

Secondly, were the headlamps working properly prior to the replacement of the alternator?

You can download the '93-'94 XJ6 Electrical Guide at the link below, courtesy of our forum member Gus. The schematics will show you how to trace the power and ground from the head lamp bulbs back to the

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

The right and left headlamps receive power via separate Bulb Failure Modules (BFMs) that receive battery power on separate wires and are grounded at separate points. The left headlamp is grounded at the stud on the left inner fender near the air filter housing and the right headlamp is grounded at the stud on the right inner fender near the windshield washer fluid reservoir. The high beams use the same ground points as the low beams, so since your high beams work the grounds would appear to be fine.

BFM failure is well-known, but it seems unlikely that both the right and left BFMs would fail simultaneously, so I would look upstream. The rotary light switch pack includes a small circuit board that contains the Lighting Logic Unit. Problems with the switch or circuit board have been reported.

However, in reviewing the schematic, I see that the rotary switch pack receives battery power on a Brown wire with a Black tracer line that comes from Fuse A5 in the Left Fuse Box, which is at the base of the A-pillar on the left side (driver's side on LHD cars). It would be worth checking that fuse. Problems with solder joints inside the fuse boxes are also well-known.

The high beam flash relays (left and right) which bypass the normal headlamp circuits to illuminate the high beams when the turn signal stalk is pulled (I think?) receive their battery power from entirely different fuses. So all that to say my first suspect would be that A5 fuse in the left fuse box. Please check that and let us know.

Hopefully others will have additional thoughts.

Cheers,

Don

 

Don,

Thank you for giving me some direction and things to check on, definitely will look at the fuse and fingers crossed. The alternator was bad when we bought it, the seller told us up front about it. The battery would not charge is what they told us. Did not know about the light problem until went to drive at night. The battery was out of the vehicle getting charged while I changed the alternator. Is there something that I could have done while changing the alternator? Did not pull or bump any wires that I know of.

Thanks again for the help, much appreciated.

Todd (whbonny)

 

Don,

I looked at the fuses. The headlamp fuse was blown, changed it but still no lights. I did change the bulbs the other day too so I don't think its them. Could they have done something to the electrical when jumping it as much as they did?

Thanks,

Todd Niles

 

Hi Todd,

The fact that the headlamp fuse was blown is good in the sense that it tells us something happened to draw too much current somewhere in that circuit. A short to ground is probably the most common cause of a blown fuse. Without looking at the schematics I can't think of the most likely places this might occur, but it might have even happened when the alternator was replaced. I suppose it's possible it could have happened one of the times the car was jumped, especially if the jumper cables were inadvertently reversed.

Normally you would start at the harness electrical connector for the headlamp bulbs and work your way backward to find the point at which you have 12 volts. However, since the headlamps receive their power via separate Bulb Failure Modules and are grounded at separate points, and both of your headlamps are dark, the problem must be upstream of the BFMs. You can use a test lamp, or better yet, a voltmeter/ohmmeter to test for 12 volts at various points in the circuit.

I think I would personally start at the rotary switch/lighting logic unit on the steering column. The steering column cowl is attached with a few Phillips screws on the underside of the lower cowl. With the engine running and the switch in the Headlight ON position, there should be 12 volts on the two Blue wires with Pink tracer lines. If not, test for 12 volts on the Brown wire with Black tracer line, which comes from the fuse you just replaced.

Also check for continuity to ground from the Black wire with Pink tracer line, which is the Logic Ground path for the switch. All the logic ground circuits terminate on the bulkhead in the trunk at the logic ground stud behind the battery.

Please keep us informed.

Don

 

Thanks for the help. We tried the brights and they worked intermittently now. Have read that the control module board that the lights are on may be bad. Ordered one and it came yesterday. Waiting for my son to get home and we will put it in and cross our fingers! He's anxious to start driving it and haven't been able to because of the lights. We did get the valve cover gasket and spark plugs changed, made a big difference in how it runs. Ran good before but idles much smoother and acceleration is far better.