<VV> re: light gremlins

[djtcz at comcast.net]

as others said, mysterious light behaviour is often a bad ground, forcing the electricicals to  flow "backwards" thru other bulbs to use their grounds.

It may be considered good practice to clean and tighten ground straps every now and then, using somewhat of a shotgun approach. http://www.silverbulletcomicbooks.com/busted/images/060502/henry3.jpg

I prefer to fix the ones that aren't working, or aren't working well.  It can even be argued that unless I check (measure voltage drop) my repair work (connection cleaning) , I can not be sure it is "perfect."

A "bad" ground, fuse, connection, or even wire can be identified by measuring the voltage  across it with device current flowing.  Perfect wires and connections have zero voltage "drop" when part of an energized circuit.  All real wires and connections have some resistance, but it should be no more than a few % when handling full power.  Something like 0.3 volts for a 12 v circuit.
http://www.aa1car.com/library/voltage_drop_test.gif
http://www.prestolite.com/images_training/fig23-neg-cable-test.gif

http://www.prestolite.com/images_training/fig24-solenoid-voltage-drop.gif
http://www.excelauto.com/online/Tech.d/Image.d/StrVdt-2.gif
http://www.excelauto.com/online/Tech.d/Image.d/StrVdt-2.gif
http://www.tpub.com/content/neets/14188/img/14188_118_1.jpg

--
Dan Timberlake

-------------- Original message -------------- 
From: Grant Young <gyoungwolf at earthlink.net>
Subject: <VV> Brakes fixed, now light gremlins

Thanks to those who suggested I needed to back up and stop some more to fix my 
spongy brakes. All is well there now, BUT, I discovered another problem when road 
testing - no tail lights, almost. I have a left rear taillight that is on any 
time the key is on, except when the lights are turned on - then it goes out! The 
headlights (high and low) and brake lights work fine. The tail lights will come 
on one side when the turn signal is activated, but don't flash. Any 
trouble-shooting starting tips??? I am thinking it might be the main switch as 
the rear harness is new, and I have already gone through the brake light switch 
adjustment. Thanks again for all the great advise.
Grant