Hi everybody, Dan Arizona here. My Son just finished HS in Tombstone and has begun College and just got his first truck. He picked a 72 F250 FE360 bone stock local AZ truck in nice shape with a couple hundred k dusty miles on her just last week. Great truck. EngGasket set is on the way, shop manual CD arrived, and I threw a fuel pump on her is all I've done. Up and running fine. Blinkers and emergency seem to work fine at first. Acting up, I threw bulbs and a new flasher in and no luck. DOuble checked part numbers which had no effect. Problems are intermittent. Flashers come on once in a while, seems after it sits a bit. Blinker immediately kills that same side brake light with no blink. Running lights work fine. When emergency flashers are inop the blinkers are too. Changing bulbs over seems to do the trick, then right back to the same issues. I've noticed a pulse/surge in the cab/instrument lights that first clear up with a little RPM then begin flashing again at about 3000 RPM. I wonder if voltage regulation is playing havoc on my flasher circuit? Acts up with or without ignition on. Any ideas? Please help me get this kid to class on time. Much Obliged.

 

Hi Dan, Welcome to FTE. Electrical problems are problematic sometimes. From what I read, I'm thinking you have a grounding issue. I always start at the rear of the truck. You need to do a super inspection of the wires. Sounds like one is chafed and is touching metal and shorting out.

Changing bulbs may have moved the wire enough to relieve the itch until it gets back to the trouble position.

Look very carefully at any splices where trailer lights may have been added, bends, pass throughs etc.



guluk



John

 

Check where the tail light harnesses make the turn under the tail lights from the body to the frame. They tend to chaff there and short or ground out.

 

Welcome to FTE

There are two flashers behind the dash, one for the turn signals-located on the back of the instrument cluster.

The 4 way emergency flasher is located on a bracket adjacent to the radio.

Both flashers have two prongs and look the exactly the same, but the 4 way flasher is a H/D (heavy duty) unit...and is usually so marked.

The H/D flasher can be substituted for the turn signal flasher. But, the turn signal flasher should not be used with the 4 way emergency flashers as it's a L/D (light duty) unit.

 

Do get that regulator checked out if the lights are flickering but another item to keep in mind is the turn signal switch. A bad one can create some bizarre symptoms.


mike

 

I would bet on the grounding issue. My project was a complete electrical nightmare, I replaced the entire wire harness for various reasons and still had sporadic function on blinkers and flashers. I took a tooth brush size wire brush to the light bulb sockets and where the light housings make contact to the body. I also replaced the light bulbs and everything is working fine now.

 

Turns out I was having brake light problems with flasher issue. I found that one of the clips on the flasher/brake fuse was spread open just far enough that sometimes it would arc enough to work and has been doing that long enough to wear a hole through the clip. I've secured the loose side to fasten tightly on the fuse and my flashers and brake lights work fine. I haven't diagnosed the blinkers yet. Thanks everybody.