check the tail lights first.
The taillights ground with the mounting bolts.
If you had a bad ground on the flasher it would result in erractic operation of the turn signals but the stop lights and taillights would remain unaffected.
Since your stop lights are not working properly, I would repeat what I said in an earlier post that I strongly suspect a problem in your taillights themselves.
I had a similiar problem with my deuce where the turn/Stop bulb center connector had shorted out intermitently and would cause the turns to not work or the stops to not work, and then the light switch circuit breaker would trip and I would have no lights at all. The fix was a new set of tailights.
Before going to far into this, I would take a few minutes to check the bulb sockets in your taillights. It would not hurt to check the wires from the tail lights to the main harness to make sure they have not rubbed bare on the frame.
To have your stop lights cease working cannot be a resullt of a bad ground in anything but the tail lights. The only other suspect could be a turn signal switch, but that is highly unlikely. The stop lights only ground occurs at the frame in the rear and the connection to the battery. You can check the quality of the ground by measuring the resistance of the socket shell of the light to the negative post on the battery. It should be 1 ohm or less. You can also check for the presence of power at the light by doing a voltage test in the socket. That would verify that the power of the signal or brake switch is getting to the light. There really should be no need to check much more than this to determine what is wrong.
In respect to the idea that a set of tailights can cause this problem, I cannot believe my truck and the problem I had with my tailights is an isolated event. Take out the bulbs and look for a burnt center conductor. All you need is one bad socket and you will get the symptoms you are getting now.
You can check grounds on the truck, but if it starts it has a good enough grond to operate a light.
Just my two cents.
RL
