My hand brake indicator lamp has a 100 ohm resistor from the battery indicator lamp that gets very hot. Brake indicator not working. Don't have multimeter at home to test. Anyone know why it's so hot and should it be there. Can't see it in the wiring diagram.1981 xj6 series 3

 

There is supposed to be a resistor across the battery warning lamp, yes. But not from the battery warning lamp to the handbrake warning lamp.

The alternator won't begin charging unless it sees some resistance here. Normally the warning bulb provides the resistance the 'excite' the circuit. I presume Jaguar added the resistor so the alternator would still work if the bulb burned out.

Cheers
DD

 

As I understand it, and that is barely, resistors get hot. when voltage is reduced, it is converted to heat. It can't just disappear!!

Way back when, Old Fords used a resistor to reduce 6v to just under four. For junk racing, we bypassed them in hopes of getting more fire to the plugs at a higher RPM. WE raced wound out in second gear. Some cars had a hook on the dash to keep the trans in second. Worn ones were won't to jump out, not good.
But, hard on points. Might take two distributors to complete a meet.

So, somewhere I read that one could use a lamp in lieu of the resistor and reduce the voltage less than the stock unit. Pre meter days, so, I dunno. it did seem to extend point life and was quite neat to have that bulb lit as the engine "roared".

Get a meter or two. Very inexpensive at HF!! I've about three. One reads by inductance, slick.

And, I made a patch cord to plug the meter in via the cigar lighter outlet. Real volts at real time under various conditions. Way ahead of the Jaguar meter in the fascia that is slow to react and only an indicator rather than a true measurement device. I used the meter to determine which lead was + and thusly which was -.

A slick quick way to check batteries of all kinds to see it they are OK or ready to toss. I use a ot of AA rechargables, but, eventually they are done for.

Carl