After reading a few other threads and completing what they said to do, I am still stumped.

Issue:
Left low beam headlight is barely on, appears like it needs replacing. Left high beam doesn't work at all. (All other external lights operate as normal.)

Remedies tried:
1. Replaced all 4 headlights
2. Replaced all fuses behind the control panel
3. Cleaned and lubed all prongs/connections to headlights

Thoughts?

 

Is there a grounding point (or more than one) that needs attention? You've done just about everything else, try making a temporary new ground from the offending fixture to the engine block or even to the body panel.

Use a length of solid (not stranded) wire if you can find one and scratch through the paint on an unseen area.
(';')

 

A more few things to try...


1. Run a new and heavy ground strap from the engine block to the chassis.


2. Add an additional ground strap from the hood to the greater chassis.


3. Check your bullet connectors and fuses for corrosion and breaks a.


4. If your car is a series 1 or 2...find a Series 3 headlight harness complete in a recycling yard and replace the entire harness you have. It's mostly a plug in and bolt in operation. Series 2 especially, the wiring is internally inferior to series 3 wire. Not all copper is created equal.

 

Would that work for the tail light harness as well?

 

Going by the list of cars you have on your sig, the only one not sold is the '73 XJ6, so I assume we are dealing with a S2 car?.

If so, I always eliminate the 2 headlight fuse blocks on the radiator support top panel, and simply join the wires using crimp butt connectors and heatshrink for the weather. OK, the purists will flame me, life goes on.

Then I use a volt meter, and remove the outer headlamp unit, and unplug the beam unit. Insert the Black meter wire into the Black wire terminal of the socket. Probe the Red meter wire into any of the coloured wire terminals, and switch on the headlamps. Note the voltage reading. You should see battery voltage, or very close.

Now move the Red probe to the other coloured wire terminal, and change the beams with the flasher stalk inside the car. Note the voltage readings.

Battery voltage indicates a good supply AND a good earth path for that beam unit only. You will need to repeat this test on all 4 beam unit sockets.

Low voltage will be a bad earth, which can be proven by earthing the Black probe on a known good earth point.

S2 cars suffer more from bad/non-existant earths to headlamps than any other system failure, including fuses.

I know this sounds long winded, but getting the basics right at the beginning saves many hours down the track.

The fact you got some beams working and some not has me heading for earths. The power supply is simply Lo beam, and Hi beam, with splices off to the beam units, BUT, the earths are 4 seperate points, some alongside the radiator, and on the bonnet itself.

 

My car is 73' Series 1,apparently 19 body numbers from the first of the S2's. So it could be either,but that is irrelevant in this thread.
I had all sorts of headlight problems the day I got mine(first issue I sorted). It was the earth connections to the radiator support. Replaced them with new home made ones,all good 12 months down the track.

 

Tis interesting, this electrickery stuff. In an ideal auto electric world, complete circuits would exist that did not involve the chassis or engine block as a leg. Each load would be isolated electricly and have two leads. One from the battery and one back top the battery. Switching could be done on either leg.


But, car makers save coin. Copper wire is expensive. So, they eliminated the use of wire or actually merely lessened it by using the engine block and chassis as a part of the circuit. Oh, and by making grounds at several locations, we get 'floating". An EE would not be pleased.


So,a ground attack solves many an electrical issue. Starting with the large battery - cable to wherever attached. On Jaguars, it is the wing wall. Clean, lube and tighten.
Thence, down and under. A ground strap from engine/trans to chassis. Clean, lube and tighten.


Now, on Jaguar bonnets, doors and boot lids, we have electrics. In some way they are grounded back to the chassis. Those must be intact or things electrical will not work properly. And, not to forget the instruments mounted in wood. Wood is a poor conductor at best. so, aground strap is provided. if not clean tight and lubed, the instruments will do odd things, if they do anything at all.


Way back, when, not long after I got my 83, I noted the outboard head lamp was dark. Not anew thing to me. Bad seal beam, as in many critters before it. Swapped in a new unit. More fiddly than in domestics, but done. Ugh, still dark. Started probing. Ugh, poor a... ground. Cleaned, lubed sand tightened. Epiphany!!! Well, I jut left the new seal beam in place. it is a shade brighter than it's mates, but it is light.
The original is in the spares bins.


Ana adventure with the fuse box on the wing wall is a tale for another day.


Carl