The Stovebolt Site Forums The Shop Area The Electrical Bay Stop Lights Flash Off and On

I have a 66 c10 3 speed on the column. I replaced the turn signal switch in the column about 6 months ago as it was broken. I replaced the entire switch assembly and my turn signals, brake lights, parking lights all worked fine until today. The problem is that when I have the truck running or just the key on my brake lights in the back flash on and off just like the truck has 4 way flashers. However nothing is on. This truck does not have 4 ways. The turn signal lights in the front do not flash until I put the turn signal on and then the correct bulb will flash in the front but both stop lights will flash. Brake lights still work normal. What the heck happened????? I am stumped. Every thing functioned normal until today. Thanks for the help on this one.

Chris0151,

It sounds like your new turn signal switch may have broken internally. Could this be one of those poor reproduction horror stories that show up here occasionally.

Stuart

Stuart, Thanks for the info. When I replaced the switch I ordered it thru Classic Parts. I looked at the old switch and the only thing broken on it was the plastic part that the turn signal level connects to. I ordered the whole switch because I did not know exactly what would be broken when I got the column apart. I changed the whole switch even though I probably didn't need to just so I wouldnt have problems. I suppose now if it is the switch I probably will have to pay for another one. I hate to think that I am going to have to pay for a switch and go thru this every six months or so. I kinda figured it might be in that switch but I wasnt certain. I have been very careful not to pull down or push up on that new switch for fear of it breaking. The other switch was already broken and the level was laying on the dash when I bought the truck. Thanks for the information. Does any one out there have a better quality switch than the one I bought??

Some questions: Does anything change if you push on the brake pedal? Does anything change if you separately turn on park and head lights? Do the tail lamps seem alright- bright, dim? Do the tail lamps change brightness when the brake lights flash? What changes if you remove the flasher- lights go out, lights remain on, brake lights work normally with the brake light switch? My first thought is that something in the rear light ground circuit is involved with your trouble. If the rear lights are dim, even though they are flashing, I would start checking ground connections. I don't have a wiring diagram to look at, but if the rear lamp circuit is getting grounded through the flasher/front end ground, you could get that kind of operation. This is speculation at this point. If you have a voltmeter, rig up some long leads so you can measure voltage between the battery ground and the rear lamp ground. You should see only a tenth or two voltage on the meter with the lamps on. Connect the voltemter with the negative probe at the battery ground, positive probe at the lamp ground, so the meter will read up-scale. If the reading goes negative, switch the connections.

As a shortcut test, connect a jumper wire from the tail lamp housing or lamp socket to the battery ground. If the lights work normally, you have a body ground matter to resolve.

The switch is a possibility, but I would first look at the circuits.

Harvester

Check the adjustment of the switch on the brake pedal. Maybe its just a little to close.

Chris0151,

If you can turn the key ON and recreate this flashing brake light scenario, would it be possible to wrap your hand around the flasher and see if it is indeed cycling the lights. This would mean the turn signal switch is telling the flasher to do its thing. The flashing of the rear lights would be at a consistent rate, not random.

Stuart