Brake lights flashing

[tattooboy37]

Brake lights started flashing recently after no changes or recent work. I had installed a new turn signal mechanism some months back and had everything working nicely. I don't drive her that often and the last time I hooked up the battery and turned on key the brake lights started flashing. The funny thing is, I normally never had any flashers or switch for them either. They blink when the turn lever is in straight position. They both blink when I put on right signal and everything is normal for the left signal. front signals both work normal and do not flash. I did replace the battery lately too, don't see how that could affect things but I'm no electrical expert.
1963 C20

[forestb]

Check your grounds. I just thought I would say it before anyone else does.

[tattooboy37]

checked all the grounds and they seem to be clean and all still connected. did more tests w/ the lights and here are the results. maybe someone will see a pattern I'm missing. all bulbs mentioned are in the rear, front still working fine.

Key in Off position
No brake: nothing
Apply brake: Left bulb (top filament, weak) Right bulb (lower filament, strong)
(flashing sound in truck and temp gauge is pulsing, lights stay on but have a
pulse to them)

Key in On position
No signal/ no brake: Left bulb(top filament, weak) Right bulb(lower filament,strong)
Both blink
R signal/ no brake: Left bulb(top filament,weak) Right bulb(lower filament,strong)
Both blink, a little faster than other examples
L signal/ no brake: Left bulb(top filament,weak) Right bulb (nothing)
Left Blinks, nothing on right

No signal/ w/ brake: Left bulb (top, weak) Right bulb (lower, strong)
Both bulbs stay on w/ no flashing or pulsing no noise in truck

R Signal/ w/ brake: Left bulb (top, weak) Right bulb (lower, strong)
Both bulbs stay on no blinking, inside cab turn indicator stays
on and doesn't blink either

L Signal/ w/ brake: Left bulb (top, weak) Right bulb (lower, strong)
Left bulb blinks, right bulb stays on and inside indicator blinks


I tried switching bulbs w/ each other and have same results. why does left side bulbs top filament work and only the lower filament on the right. I thought both filaments should work w/ brake and only one of the filaments during signal. Is this correct? could I have crossed wires when hooking up the tail light sockets or does it matter(both sides have two wires, do each have to match a specific side in socket) I know the right and left sides of the truck have their own 2 wires for the signals I'm just referring to connection to socket

[jtrichard]

looks like a bad ground on the left tail light ... and you may have cross connecting in the turn switch there was just a post not long ago (and i cant find it) that shows the contacts in the switch and how they were just touching enough to do things like your having

[tattooboy37]

I just regrounded tail lights to bed. bed to frame and put a 4ga ground from engine to frame. no change what so ever. maybe got the left side brighter but same pattern as before. I will try to test turn signal switch per
http://67-72chevytrucks.com/vboard/s...d.php?t=573215

do I need a test light or can I use a multimeter?

[tattooboy37]

I tried testing things like I mentioned in the last post per the other thread. I made sure to check schematics for 63 compared to 66 like he was referring to and made the changes for different colored wires.
Testing the brake switch
(no pedal): orange wire had full 12v
(w/pedal engaged): white wire bounced from 10.8-11.35 and
caused signal flasher to click, no signal indicator light, tail lights worked w/ no flashing or pulsing.
Tested signal switch
(w/pedal engaged)
: white wire bounced from 10.6-11.2 w/ same clicking
: pink wire had same results as white wire
: violet wire has same results

Same test but w/ turn signal activated
:violet wire (left turn) holds at 11.3, no clicking no signal indicator light
:violet wire (right trn) 9.8-10.4, slow click and signal light indicator lights up solid w/ slight pulse
:pink wire (left turn) meter reads 0, no noises, nada
:pink wire (right trn) holds at 10.5 , slow click and signal indicator lights up solid w/ slight pulse

Key on
Yellow wire on signal switch: jumps from 1.5 - 9.5 w/ various in between. if I hit the brake pedal it sits at 10.95
(left turn signal) numbers dance all over the place
(right turn) # dances
Pink wire: (left turn) # dances
Light Blueleft turn) # dances
Violetright turn) # dances
Dark Blueright turn)# dances

I'm wondering if its the signal flasher that is bad but it does make clicking sounds while lights are flashing.
Also wondering why things are flashing w/ just the key turned on and nothing engaged.

[tattooboy37]

bump

[jtrichard]

unplug the wiring going to the rear and see what is going on at that plug also unplug the hood .... i bet the contacts are bent in the turn switch i wish i could find that post that was up not that long ago he had same kind of problems

[tattooboy37]

We'll do. I was hoping to not have to tear into the new turn signal switch. but that does make sense. it did seem a bit stiff while operating the signals but I thought it was due to the plastic inside. my last one had gotten so sloppy due to the condition of the plastic inside that the lever would just hang giving me a left turn all day. I'll also check the plugs on the firewall and in the rear as well.

[tattooboy37]

jtrichard was correct. bent prong in the turn signal switch causing the left signal actuator to stay in contact the whole time. only a 1/16 of an inch but that's all it was. i'll post a pic soon so people in the future can avoid my headaches. never trust a new part even if it works for awhile. lesson learned.