Hello all,
I have a question about the switch panel on the XJ6
I was tracing out the wiring on the back of the switches and some of the wires go this to "block" shaped thing circled in BLUE
Can anyone tell me what this block is used for?


Looking at the front facing side of the panel, the location is marked by the X
(note this isn't my pic, I didn't have one handy, I just used a generic pic I found online)



Thanks
Ken

 

Might be wrong but it looks like a voltage stabilizer to me. These were used to reduce and dampen voltage to the instruments (fuel and temp gauges specifically, as I recall) to prevent the gauge from giving erratic readings

Cheers
DD

 

Be aware Ken, that the "printed circuit" board used to wire up the instruments is prone to cracking and failure in cars of this age. Mine did, and it is a well kept car. Symptoms are just one or two gauges working, or sometimes working, then not working. Solutions is to either fine solder repair it (difficult) or wire each gauge separately.

 

I agree with Doug, but how it works I don't know !

 

I've recently been spending alot more time with my '74 Triumph TR6. The Jag is in pretty good shape and since buying it 3 1/2 years ago I had neglected the TR6. The Triumphs use Smiths gauges also. I learned from reading the Triumph forums that this vintage Voltage stabilizer is not electronic but electro-mechanical.

The correct output, which you would see on a digital miltimeter, is 12V(or whatever the supply is) - 0v - 12V - 0V - 12V - etc etc. An analogue meter might show that but it can change quite quickly, so you might get wide swinging needle.

The idea was that this intermittent supply would average 10V, in the face of changeabale supply from the battery/dynamo/alternator, to 'stabilise' the fuel and temp readings. The gauges are heavily damped, so you see no swinging needle.

This was done with a delightfully 19th century design, a bimetallic strip that, heated by the current, bent and broke the circuit, then cooled and made the ciruit again. No electronics at all! But people have devised electronic equivalents with transistors that do provide a constant 10v, and the gauges see no difference!

 

Thanks Doug, Mekon, Fraser, Indy-Jag
very informative

 

INDYJAG-84
Thanks so much for that informative description. But our cars were NOT built in the 19th century. That solution is SO incredibly '60's -'70's Bri'ish electrical genius/quirky, I couldn't have been
the ONLY reader overcome with the desire to have some marmalade toast & mug of strong tea...

 

on a side note. The back of Jag switches look a bit confusing. (previous owner's work)
This mess circled in BLUE is for the wiper.
By chance can someone point me to a diagram to figure out which pins are for what?
I was expecting something simple, like 4 wires, one +/- pair for high speed and one for low speed
But the wiper switch has 6 tabs
Also the metal tab above the one with the green/brown doesn't have anything plugged into it. I suspect something was accidentally pulled out. As I have 3 loose wires not plugged in anywhere


I'm going to replace all the switches with something new (but still classic looking, maybe those switches with the lever throw)
But need to sort out this rats nest first so I can plan for which wires will be going to which switch.

Thanks all