[Mgs] Electrical system questions

[Paul Hunt]

1.  Correct, single-circuit cars had a small 4-way brake pipe union with a 
hydraulic brake light switch screwed in to that.  Early dual circuit systems 
had a larger union with the failure switch, the brake light switch was 
screwed into the pedal box.  The mechanical switch is a 'normally closed' 
type, i.e. when the brake pedal is pressed it releases the switch to close 
the circuit and light the lights, and vice-versa.  You have to be careful 
with these switches - if they aren't screwed in far enough the lights will 
stay on all the time.  But if they are screwed in too far it stops the pedal 
coming back as far as it should, and hence the piston in the master doesn't 
clear the bypass port in the cylinder, so when the hydraulic fluid gets hot 
and expands it can't escape up into the reservoir, but locks the brakes on 
instead.

PaulH.

----- Original Message ----- 
> 1) ...  In
> the same vicinity are two wires not connected to anything, one green with
> one of the female bullet receptacles on it and the other green/purple with 
> a
> bullet connector on it.  According to my schematic, those are the two 
> wires
> that should go into the stoplamp switch.