Steering Column Repair: Brake, turn signal, and tail lights not working, turn signal switch, turn signals

Question
QUESTION: I have a 1990 Chevrolet Silverado , 350 cu.in. ext. cab pickup. Last year, I did some extensive work on the steering column due to excessive looseness in the tilt mechanism. I tightened the 4 bolts and in the process replaced the turn signal switch,ignition switch, key lock cylinder and windsheild washer switch. Since then, ocassionally the turn signals stopped working and I fixed them by sqeezing the multi wire connector/harness located near the bottom of the column. Recently, I had no turn signals, no brake lights and no tail lights during the evening with headlights on. Yesterday, I pulled the multi-wire connector apart and reconnected it. I then turned the ignition to "On" and the turn signals, and brake lights worked, but no tail lights. When I turned the parking lights on, I suddenly had no brake lights, turn signals and still no tail lights. Any idea what the problem might be? Thanks!

ANSWER: Hi Art:
Sorry about your truck troubles.  Everything you did makes sense for the turn signals, brakes and 4 ways, but as soon as you start talking about parking or tail lights, you have add a variable that takes the problem out of the column and puts it elsewhere in the truck.  The taillights do not go through anything in the column, nor do the parking lights.  But they all run in the same harness from the cab to the rear of the truck.
My best guess would be that the problem is near the bulk connector to the rear of the truck.  This connector and harness begins right next to the fusebox and runs along the floorboard under the driver sill plate.  
It is a flat connector with about a dozen wires in it.  the wires should be aluminum rather than copper and that often is part of the problem.
I hope that gives you a place to start.  I would suggest working with t a test light to determine where the current stops.
Lastly, you may want to double check the ground connection form the battery to the body of the truck.  If you are losing a good ground, then you will get erratic things happening with all the lights (as in your case)

Good luck
Doug

---------- FOLLOW-UP ----------

QUESTION: Hello Doug,

Since your reply, I've traced the wiring harness you spoke of from the fuse block to both of the rear bulb circuit boards and found no evidence of broken wires, wires with worn insulation, or poor grounds. I replaced the right and left bulb circuit boards. I still get non-functioning turn signals, tail lights and brake lights (with functioning headlights) when the headlight/parking light switch is turned on and functioning brake lights and turn signals when the headlight/parking light switch is in the off position. I have also put ammeter between the positive battery post and the positive battery cable and got zero. However, when I put a voltmeter between the negative battery post and the negative battery cable or the vehicle's frame, I get just under 12 volts. Is that normal and do you have any other ideas?

Answer
Hi Art:
The only other thing I can think of is a bad ground.  Make sure the wire form the battery to the side of the fender is intact and make sure the cab and bed of the truck have a good ground connection.  If you can't find one, then make one from the frame to the bed near the back of the truck.
Other than that, I think we're about at the end of repairing your wiring problem on-line and it needs to be done in person

I hope that works
Doug