Brake Switch Problem -
Is there a way to clean the brake/stop light switch on a TD? Mine is
installed on a four way brake line junction just aft of the master cylinder.
If I remove it to inspect, will brake fluid pour out and I will have to
purge the system? It seems apparent that this is a pneumatic system, that it
works off of the brake fluid pressure, i.e. not mechanical off the pedal.
Having never removed one, I don't know what to expect. Would appreciate a
clue.
Although a replacement switch is relatively inexpensive, it's the time
factor I am concerned about, as I would like to get the car back on the road
for this weekend. Thus, if the switch can be cleaned, then I will do that as
a temporary measure.
I discovered (was told) last night that I did not have brake lights. Regular
tail lights worked fine. Spent half today trying to diagnosis the problem.
Using an ohmmeter across the brake switch, it reads a dead short when the
brake pedal is depressed, as expected (ignition OFF). If I disconnect the
stop light wires (purple/white and brown/white) at rear, thus no load, I
read my expected 12 volts at the brake switch or at the rear when pedal is
depressed. However, when the bulbs are reconnected, thus presenting a load,
it is a different story. The voltage at the switch, when pedal is depressed,
is then zero or near zero. The switch just will not pass more than a few
milliamps (like my ohmmeter) across it. Contacts must be oxidized, worn,
dirty etc. Thank you Lucas!
Brakes are fine, MC reservoir is full. Installed new bulbs, but this did
not correct the problem. Disconnected tail light and license plate wires,
but still no voltage at switch. Sequentially disconnected stop light wires,
no improvement. Has to be the brake switch (unless someone has another
idea).
So in conclusion, can I remove the switch for inspection without all the
brake fluid pouring out? The workshop manual and pass TSOs do not address
this issue.
Thanks for any help or suggestions.
Stu Keen
1951 MGTD MkII
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