1975 chevy c20.

[tdcfroggy2004]

I have a 1975 chevy c20 and have problems with the drivers side turn signals not wanting to work with the head lights on . The passages sides work ok . Replaced head light switch , turn signal cam
And now just the driver side rear won't blink and I have no horn ?
Any ideas ?   On the horn button cup the plastic three screw thing broke to pieces 

[roundhouse]

Does the rear light up when you step on the brakes ??

Do the rear lights and front lights blink when you activate the hazard light switch ??
It's the same bulb and the same wire
So if the brake lights work you know it's not the bulb or most of the wire

The brake light wire goes from the brake pedal switch up thru the turn signal cam under the steering wheel
Then back down the Column thru the firewall  and to the lights.  That's how it is able to flash the brake light only on one side and transform the brake light into a turn signal


Check the wires where they pass thru the firewall just above the fusebox

Locate the wire on the inside that is the left turn
I cant remember if It passes thru the firewall and then splits front and rear or splits under the dash
Anyhoo track the wires from the rear up to the engine side of the firewall

I used a sharp probe and a test light to Pierce the wires and see where the problem was

My test light would blink on the inside of the firewall but not on the outside
Turns out the large connector plug where all the wires pass thru the firewall was bad
Some wires had no continuity thru it
And no amount of taking the connector apart and tweaking the prongs would fix it

I did the easy way and drilled a small hole thru the firewall next to the big connector installed a grommet and then cut the wire on the inside.  Spliced on a short section ran it thru the grommet and cut the wire under the hood and connected it together to bypass the large plug

Turn signal switch was bad on mine too
 And that combined with the bad connection thru the firewall drive me nuts

Sounds like you have a problem with a ground wire somewhere
Check the side marker lights
They are tied together with the parking lights and the turn signals
 They light up with the parking and head lights but blink with the turn signals  by being grounded not to the body but to the other parking lights somehow

Unplug them both and see if that changes anything

[zieg85]

Welcome from NW Indiana