I've got a 1971 Ford f100 short bed, equipped with a FMX transmission and a 1979 Ford 351 Windsor. I bought the truck last Thanksgiving and have been going through the truck all winter to get it safe/ legal for the roadways. Now that I'm getting close to putting it on the road, I have a blinker issue I can't fix.
[B]Problem:[B] The blinkers do not work when the truck is running and/ or when the lights are one. I tried to replace the ground to the blinkers and now the blinkers do not work at all. I assume I did not properly ground the blinkers when I redid the ground. Assuming I fix the ground, I'm likely back to square 1 with the blinkers only working when the truck is in the on position. The four way flashers have never worked on the truck either.
What I've tried so far Redid all of the grounds for the front and rear lights on the truck; installed a new headlight switch; installed a new blinker switch assembly; changed all the bulbs; cleaned front turn signal sockets; installed new flasher relay. And yes, I've checked/ replaced the fuse.
Even More Strange When the key is in the on position but not running, the fuse for the blinkers/ wipers/ hazards. shows 12 volts. When the truck is running, the fuse no longer shows any volts. It is worth noting that I had installed a an RPM and volt gauge that fed off of the blinkers/ wipers/ hazards.

Any suggestion on how to resolve my blinker/ fuse issue? Thanks.

 

Spit balling...
I think I had a similar problem 100 years ago and turned out to be the brake light switch. My problem was not the same as yours. It almost sounds like the iggy switch isn't releasing the start position. Solenoid?
I'm sure someone will come along shortly...

 

Thanks, TeachNlive4ever. I did forget to mention, I also installed a new brake light switch. As for the solenoid, it was replaced by the previous owner just a day or two before I bought the truck. Also, not sure if it connected, but I also have the neutral saftey switch Jerry rigged with a zip tie to keep it in the correct position.

 

You might want to check to make sure you have the correct bulbs installed. And that they are not installed 180 deg off.

 

The #1157 double filament bulbs have their nubs offset, ditto the sockets, so they can fit one way.

 

Nothing is impossible. Sometimes things happen.

 

Follow-Up Questions: Does a '71 F100 use two flasher signal relays (one for blinker, one for hazard)? If so, where are they located? I found one left of center under the dash but have not located a second one.

 

Directional flasher on or near fuse panel, 4 ways behind glove box I think.

 

1970/72 F100/350: T/S flasher plugs into the back of the instrument cluster (drivers side-upper).

4 way flasher located in a bracket that attaches to the dash w/one screw adjacent to the instrument cluster.

 

Do your ambers light up when the truck is running? (Headlight switch on)

 

By amber lights, I assume you mean the running/ parking lights that are illuminated when the headlights are on? If so, yes, they light up when the truck is running and the lights are on.

 

Update 1:- I've put much of the dash back together and now the blinkers will work when the truck is running but not when the head lights are on.

Update 2: I checked for the two flasher relays but could only find one. I found one left of center of the steering wheel under the dash. I did not fine one on the back of the instrument cluster or behind the glove box, as previously suggested.

 

Where is your 4 way flasher switch located?

 

FWIW, I am cleaning up and fixing the hacked wiring on my neighbors '70 F250. AFAIK the 70-72 have the same wiring system.
Do you have the wiring schematic/diagram for your truck?
*Not sure if posting a link to another site is allowed.*
http://www.fordification.com/tech/wi...t-lights01.jpg

Download it, print it out in 4 sheets, tape it together and bust out the coloring pencils. Trace the circuits for easy diagnostics.

This is important
If someone has installed a 73-76 or 77-79 column the wiring could be all kinds of goofed up. The later columns have the 'Hazard' switch on the column where as the 70-72s had the 'Emergency' switch to the right of the column in the dash next to the cigarette lighter. If wired correctly the column switch will not affect
It is also possible to partially bust the later Hazard switch so it only makes intermittent contact. This will cause diagnostic headaches as you attempt to trace down the ghost fault. Switch itself is held together by two small rivets, knocking your hand on the switch can pop one of the rivets which will then place the switch in a constant open position no matter if the switch is in the on or off position.

Emergency/Hazard blinker should be in a bracket mounted to the firewall left of the column/pedal box support brackets. It is a larger blinker about 1.5" long.

Signal/Indicator blinker is a bit stubbier, it is not located on the back of the instrument cluster, it will be to the left of the 'Emergency' switch on a bracket. It is well hidden and a stubbier cylinder ~1" long. Even with the dash gauge assembly removed the curvature of the dash will hide it.

Emergency blinker is designed to take a heavier load of all four lamps going off at once, where the signal one is only designed to do half the lights at once. This is done for that purpose and to keep the left/right divorce for signal purposes. Also if the blinker has been damaged or burned out, it will not work.

If it has been removed from its holder it may be floating in space above the column(behind the column/pedal box bracket) or tucked behind the windshield vent tubing.

Lights, signal, brake and emergency/hazard lights will still function with the dash cluster/gauges removed. This will make trouble shooting much easier. Just make sure not to ground out the gauge cluster connector.

If you can take pictures of the dash wiring and post them or a link to them, that would help out greatly.

If the truck has had trailer/camper/exterior lighting wiring added it may be this that is causing your current problem.

 

The four way flasher switcher is located to the right of the steering wheel, to the left of the cigarette lighter.