Turn signals not working

[tsherry]

Working on a '71 F100 for a friend of mine. Here are the symptoms. Bear with me, I'm not quite sure how this switch is powered, despite having worked on Fords for 40 years.

1) Turn signals do not work at all. Flasher checked as good, wiring in column harness checked for continuity, wires test OK. No dash indictor lights.
2) Brake lights work.
3) Emergency flashers work.
4) head, parking, and tail lights work.
5) fuses all intact.

When brake lights are on, and turn signal switch is switched to right turn, right rear brake light goes out (as I would expect it to, if the TS switch would then be powering that filament). Ditto, when turning the switch to left.

[sargentrs]

First, make sure you have good, clean grounding points especially in the bulb sockets and housing mounting screws. You need to find the break/faulty circuit. Sounds like it's isolated specifically to the turn signal circuit. The power to the turn signals comes from the fuse panel where it is spliced into the harness to the back up light switch. Then it is spliced to another wire and goes to the turn signal flasher and wiper switch, then to the instrument cluster via a 2 prong connector (http://www.fordification.com/tech/wirin ... _quick.jpg) which then feeds the turn signal circuit at the column harness plug via a blue wire from that 2 prong connector. http://www.fordification.com/tech/image ... iring2.jpg You didn't mention, do your back up lights work? The same wire on the back up light switch that power your turn signals also powers your wipers/washer. Do they work? To summarize, the path is fuse-back up switch-flasher-instrument cluster-TSS-rear light harness-rear light bulbs.

Back up lights work = OK from fuse panel
Wipers work = OK from splice with wipers
Power at blue wire on column connector = OK from flasher and instrument cluster
Power at rear harness, OK from turn signal switch

So if your hazards, wipers and back up lights work, then the problem exists between the T/S flasher and the tail lights. If you have power to the blue wire on the steering column connector, your problem exists between the turn signal switch and the tail lights. If you have power to the green and yellow/black wires on 5 prong connector where all your rear lighting is joined, then your problem is in the harness/turn signal filament in the bulb. Follow me?

[tsherry]

Beautiful. Thanks!

[tsherry]

This morning's progress:

Back up lights work, wipers work, no power to blue terminal on column harness. Digging deeper this afternoon.

Thanks for the help.

[tsherry]

Also, no dash lights of any kind. Lamps are all tested and good. Hmmmm.

As with many of these old trucks, butchery writ large has happened under the dash, with aftermarket gauges added, a security system of some kind, etc, hacking into the original harness. This is gonna be a job.

[mac6150]

I had similar issues with instrument cluster lights. I finally broke down and bought a instrument cluster from Dakota digital. For me it made a world of difference. At first I wanted to keep everything original, but finally gave up and decided to look at reliability of new instrument cluster. Plus I liked the tach option the new instrument cluster brings with it. I added LED tail lights and they work great. No so with front parking lamps. The turn signal does not work when the main lights are on. I'll have time next week to finally take them apart and see what is going on. Its probably the bulb since I found some LED bulbs which "were supposed to work", but obviously don't. Anyway its always something with these old trucks.

[sargentrs]

Back up lights work, wipers work, no power to blue terminal on column harness.

That is progress! Sorry if I'm a little random here. I would run a jumper straight from the fuse to the blue wire connection on the steering column connector and operate the turn signals manually. If good then that narrows it down to between the flasher and the steering column. Don't you just love electrical gremlins?! I had a '74 Dodge Dart that drove me nuts with a turn signal problem. I tested every wire and connection from the fuse panel to the tail lights. Eventually found rust in the rear bulb socket dimples where the bulb twists in and locks. A little steel wool wrapped around the end of screwdriver and a good cleaning and everything was fine.

[tsherry]

"That is progress! Sorry if I'm a little random here. I would run a jumper straight from the fuse to the blue wire connection on the steering column connector and operate the turn signals manually. If good then that narrows it down to between the flasher and the steering column."

Yup, Gonna try that. As with most weekends, today was filled with replacing a clothes dryer (and two trips to the hardware store for the right pigtail), prepping garage doors for paint (and finding that they're probably not worth repainting!) and to deal with the warm weather, a couple hours in the above ground redneck pool and adult beverages.

[tsherry]

Tried direct power from the fuse panel to the blue harness wire on the column.

Nuthin.

Hmmm.

[sargentrs]

Before you have to go deep diving into the dashboard, run a jumper back to the individual tail lights and see if they light up. Then back up to the 5 prong rear wiring harness connector. Sounds like you might have a couple of issues.

[sparky72]

A small lead acid 12v battery (like you buy for garage doors or home security system backups) with a couple of alligator clip equipped wires has helped me sort out a lot of electrical gremlins. It’s easier than running a long jumper.

[tsherry]

Turn signals are alive again.

The power feed runs from the fuse box to the backup light switch, then to the wiper / washer switch, then to the flasher. There was intermittent power coming out of the washer feed, and I decided to abandon that feed, cut it, and then spliced it into a key-powered source.

That problem solved. If at some point the owner wants to replace the washer/wiper switch, we might be able to restore the original connection.

Now, onto the dash lights. Currently I have the high beam indicator and one turn signal indicator with all new lamps and cleaned connections on the printed circuit, but I haven't verified which tab on the connector is feeding the lamps. Thunderstorms outside right now, so no desire to continue work tonight!

[sargentrs]

Thanks for the clarification and posting your fix! Keep us updated on your findings with the TS indicator bulbs. This is a frequent issue and many people will be interested.

[tsherry]

Dash lights are now working. The fuse holder looked OK, but the printed circuit was a real mess. All of the exposed copper was green with corrosion. I pulled all the light holders, filed the brass contacts clean, and carefully scrubbed the copper with a fine brass parts cleaning brush (engine cleaning brush, truth be told) until they were nice and shiny. Put those back in, checked the voltage at the harness, zero.

Back to the fuse panel. Popped out the 2A fuse, contacts still looked fine. could not get any voltage out of it. Put the cleaning brush on a cordless drill (after disconnecting the battery!) and cleaned up the fuse contacts.

Success!

Don't judge the contacts just by sight. Clean them anyway.

[sargentrs]

Excellent! I've never read of anyone else doing that with the circuit panel overlay. Thanks for the update!