M817 Blinkers not Flashing

[Dahli6909]

So I plugged a new trailer into my 817 (had working blinkers) without knowing that the trailer had a shorted left turn signal. Troubleshot this down, found and repaired the short in trailer. Unfortunately, only after having wrecked something in the truck….

With trailer disconnected from truck. No trailer connected. Just truck for all the following testing. Blinker lights turn on but do not flash. Stay steady on. Troubleshot it to power going in to flasher module, steady output coming out. Bought and installed new module. Same results. Steady lights, no blinking. Talked to vendor, bought a 2nd unit. Installed same results. Steady lights, no blinking.

what the heck am I missing guys. I’ve tested everything I can possibly think of. Vendor is not giving me refunds because he says I ruined them. Says they test everything before selling and it’s impossible I got two bad units. I have reviewed the electrical, tested everything I can think of, all the lights work, all the switches work, can’t find any shorts, turn signals turn on/off properly just are steady instead of blinking.

I spent 15+ years as an automation engineer troubleshooting complex automation circuits, yet here I am beat by a simple flasher circuit .

Any ideas are greatly appreciated.

 

[M35a2duece]

check the flasher fuse

 

[Dahli6909]

check the flasher fuse

Any idea where that physically is? As far as I can tell the wires go straight from switch on column to flasher module. Also, wouldn’t that make the lights not be on at all vs on steady in turning positions?

 

[M35a2duece]

Any idea where that physically is? As far as I can tell the wires go straight from switch on column to flasher module. Also, wouldn’t that make the lights not be on at all vs on steady in turning positions?

It’s a special military only flasher fuse I think. Woven into the wires.

 

[Dahli6909]

It’s a special military only flasher fuse I think. Woven into the wires.

Ah, I will have trace though the wires a little harder to see if I can find that. Was trying to avoid cutting into the factory wire loom if I could avoid it. If it is the fuse wouldn’t I be not getting power at my switch or flasher module though?

 

[M35a2duece]

just randomly cut wires until it works. Kinda like they do in the movies defusing a bomb. If the wire doesn’t help just wire nut it back together. Sometimes I find it helpful to scotch lock pieces of old speaker wires to other wires like a sort of visual fuse…. You can see the glowing when your working in the night

 

[G744]

A little off for April fools jokes.

You might try doing a full continuity test on the turn signal switch.

The contacts may have fused with the trailer short.

DG

 

[Dahli6909]

A little off for April fools jokes.

You might try doing a full continuity test on the turn signal switch.

The contacts may have fused with the trailer short.

DG

I did full continuity test on all contacts, all switch positions. I tested all the wires from switch to flasher module for shorts to ground. Tested the ground at the module. Tested the wires for shorts to ground on every pin on the turn signal switch to ground (with bulbs removed) and found no shorts anywhere in the truck.
I appreciate the ideas, I am stumped.

 

[G744]

Dahli, I wasn't referring to you, rather the guy putting you on to the hidden fuse and cutting wires.

DG