For reasons I don't understand, I have three wires going to the brake reservoir cap. I assume it's for the fluid level switch.

I didn't think anything about it until one day I noticed one of the wires was off, and of course, the other two are each attached to the two terminals--so there's no quick way to determine which terminal my broken wire goes to.

I've attached a photo. The two wires that are currently hooked up both go into a single tube of black insulation, which disappears underneath the vacuum booster. One is black, one is black with a white(ish) stripe.

The other wire is black with a white(ish) stripe, and it has its own piece of black insulation which also snakes under the vacuum booster and disappears.

I looked at the Electrical Guide and I see the reservoir booster only has two connections. So this third wire is a mystery to me.

Can anyone tell me which terminal the third wire goes to? Or is it a vestigal part from an earlier rewiring job?

Also, FWIW: I've never seen the dash brake light ever come on under any circumstance.



Jaguar XJ6 S3 brake reservoir. Cap has two terminals, three wires--one broken.

 

That's my guess; it has the general appearance of such.


Worth investigating, of course.

It's a simple circuit. The bulb has 12v "+" whenever the key is "on". The switch inside the cap provides a ground.

I'd begin simply giving the switch plunger a few jiggles to see if the warning lamp comes on. The switch and wiring take a lot of abuse over the years from removing the cap and from being leaned against when working on the engine. And, if not correctly positioned, the cap can foul the hood when the hood is closed.

Cheers
dd







Jaguar XJ6 S3 brake reservoir. Cap has two terminals, three wires--one broken.[/QUOTE]

 

Thanks, I'll look into that.

 

Greeting James . . . and you will be pleased to know that your excellent pic provides the answer you seek, but I have added confirmation. Whenever 2 wires of identical colour are involved, that which has become unjoined, is most likely to be re-attached to its identical "twin". Jaguar generally attempts not to assign same colour codes to wires in circuits of different purpose. The 2 wires are "black with a white(ish) stripe" OK? Now James, my eyes are pretty ancient but, from where I sit, I would have described them as "black with a yellow stripe". Yes?

Now turn to your copy of the S57 Wiring Diagram. Got it? If not, go to the Stickys and download it. Why? Because it has a diagram for your warning lights (Fig 9.1) and Brake Fluid Level Switch and associated Warning Light are impossible to miss. Yes, it has only 2 contacts -

• one has black (B) wire connecting to ground;
• second connector has 2 wires, both "black with yellow stripe" (BY);
• one (BY) wire goes to Bulb Check Unit;
• one (BY) wire goes to Warning Light;
• confirmation like that is priceless.

Hope this helps,

Ken

 

Doncha just Love it when some Wire Butcher gets their little nippers and crimp connectors out and CHANGES WIRE COLORS?!

At least you have a good idea what color the wire should be.

In college, students could bring in their own cars to the shop and we would repair them. Student was only out the cost of parts and we got valuable experience.

Auto Electrical class; some guy had "customized" his engine compartment. When he opened the hood, it was my second favorite color, RED! Everything was RED except the chrome head pans, carburetor and headers. Even the intake manifold was RED. All perfectly matched with engine bay color. It looked like a dragon's mouth (car was dark green)!

He had bought several hundred feet of RED wire of various gauges, and completely rewired his engine bay! Now he had electrical trouble and wanted us to fix it. Instructor took one look, asked class if anyone wanted to give it a try (for massive extra credit no less), but as we were near the end of the year and pretty sure of our grades anyway, No Takers.

I never saw that car again.
(';')

 

Yeah, I've messed with mine a few times with varying luck. One of ther tabs on the cap on my car is busted. At one time, I bodged in a connection that seemed to work. No longer, the "shim" fell out and is lost. I've a spare. But the plunger shaft is badly corroded. I've sanded and wiped, but not slick enough for the float to operate it. Deferred further efforts. I just relay on a semi regular under the bonnet check on fluids and other stuff. No more leaking rear calipers, so the BF level remains up to level.


Yup, I do have a couple of the brown vinyl or plastic sheaths that protect the electrics. Each aged and stiff and barely go in place.
But, an issue for another day, mebbe. Other stuff precedes.


Carl.

 

Ditto on the S57. The best electric schematic I've ever used. Mine came courtesy Bob Loftus. Each page sheathed in plastic. It has resolved many an issue for me and others that I've shared pages with.


Carl

 

Biggest problem with all old cars like this is Charlie Allthumbs always seems to have got to the car before you !

 

I'm not color blind, but I am color weak. If the color is murky or in a small area, I struggle. I was looking at it and figured it was white that was dingy from age or engine-compartment gasses, etc. But I'll accept that it could be yellow.

I have the hard copy and the scan. I had looked at them both (just in case they were different editions) and missed the "BY" and "B" labels altogether. Thanks for pointing that out, that makes sense.

I'll likely marry the two black/yellow wires together. I don't like having wires just laying around going nowhere, even if they appear to be doing nothing.

 

I like to work on old radios, and if you want to watch anyone who repairs old radios go pale, let them look at a radio that's obviously been worked on and things have been changed, and no documentation on how it was changed. These usually end up being parts donors.

 

The good thing about a used car is that you can blame any problem on the previous owner.