Modifying stock flasher system

Allright, not heavily modifying, but I need to add a circuit breaker.

My '68 has the original solid state flasher and turn signal switch. It worked beautifully when I first got the truck running, but first I lost my directionals and then I lost my brake lights. Brake light switch has power in and out of it, so that's fine. I pulled the turn signal switch that mounts to the steering column apart and it is fried. The nylon was melted and there were black scorch marks, etc.

I have a replacement switch ordered. When it shows up I want to put a 20 or 30 amp circuit breaker somewhere in the system to prevent this from happening again. I was just thinking I'd splice the breaker into the power wire to the switch (A/460-461).

The question is: will 20-amp be okay or would I need 30? Will splicing into the A/460-461 help keep the flasher from frying in any way or just the switch? If there's one power wire I could put the breaker on to safeguard the system I'd rather just put the one in there.

Anyone know? I need to get this sucker ready for our OD trip and TDS and I'd hate to be using hand signals the whole time.

There is a circuit breaker in the 3 lever light switch...you didnt mention it so I wonder if either:

Someone rewired and got rid of it...

Its there, but malfunctioning.

The power into the whole lighting system is on the wire that runs to the F pin on the cannon plug that connects to the back of the 3 lever light switch. If you take the cannon plug off the back of the 3 lever switch, look real close at the inside of the plug and you will see the letters.

The primary power distribution wiring looks like this:

http://www.m715zone.com/jonmisc/primary.jpg

If you follow the big wire from the alternator toward the foot starter switch and find the block on that wire that is the factory splice...the smallest wire from that splice will go through the firewall and split at another splice. The middle wire on the opposite end of the splice from the wire that you followed to get to the splice is the one you want.

Short....you should already have the proper size circuit breaker in the 3 lever switch....but something is wrong to make the problem you have...I'd bet the 3 lever switch is bad.

it seems pretty common for the switches to go out as I think someof it has to do with construction quality and 24 volts but I might be wrong too. I had a brand new headlight switch go out in the deuce on me in texas shortly after putting it in then used the one out of my 725 to get me home without a problem. same with the turn lever in the 725. ????????????

Jon, that's perfect! Thanks, man. You saved me some time tracing wires and scratching my head. I hate electrical. I'd rather be welding or spinning wrenches.

Yes, my electrical system has been hacked by previous owners and no, there is currently no fuse or breaker anywhere to be found in the truck. So adding that breaker to the F pin on the cannon plug will safeguard the whole lighting system? Cool. That'll let me rest a little easier behind the wheel.

Now the only $64 question - should I run a 20- or 30-amp breaker?

Yep on pin F...that will safeguard the whole lighting system!

Dont know on the breaker size BUT....

Since the stock alternator is 60 amp, I would think the 20 amp would be enough...hate to be wrong though...

Maybe someone will chime in who knows better....lets see...at once, you can run:

High beams, brake lights, parking lights, 4 way flashers and dash lights....if no other lights have been added to the load....

Yeah, aside from my 350's HEI there's nothing electrical in the truck besides the lighting system. And even that's not all there.:)

I'll put the 20-amp in and throw a 30-amp in the glove box just in case. Thanks again.

You might also want to print out this diagram. I think it is the best description of the entire lighting system. I have one print out on my desk at work, one in the glove box of the truck, one under the seat of the truck and two more in my shop at home. The wires and switches are the same as M35's as well.

http://www.m715zone.com/vb/pages/man...g/lighting.pdf

These are schematic diagrams showing the current flow inside of the stock turn signal distribution box during each state of operation. They give a look at what is going on inside of the box.

Ironically I finished these one year ago today just before the zone crashed. Jon has a copy and is going to publish them on the zone someday, if he hasn't already.


The system at rest with no power applied.
http://landru.myhome.net/sivart/atrest.jpg

http://landru.myhome.net/sivart/brnt.jpg

http://landru.myhome.net/sivart/ltnb.jpg

http://landru.myhome.net/sivart/ltwb.jpg

http://landru.myhome.net/sivart/rtnb.jpg

http://landru.myhome.net/sivart/rtwb.jpg

Why not upgrade to the sold state flasher box and the modern turn indicator/switch. A much better design and will help get rid of some of the problems.

Quote:

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Originally Posted by k8icu

Why not upgrade to the sold state flasher box and the modern turn indicator/switch. A much better design and will help get rid of some of the problems.

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Uuuh. As I said, my truck was solid state from the factory.

New switch came today from Antelope Valley Equipment, http://www.avettruck.com/. I'd recommend these guys if you're in So.Cal. Part showed up just barely 24hrs after hanging up the phone with them and I didn't pay extra for next day shipping. They got it right out the door. It's the newer unit like the 2.5 and 5 tons use, but it works and that's all I care about.

Got brake lights, directionals, and hazards again. I'll install the breaker as Jon indicated and hopefully all should be good.

Thanks to all again for the help.

Your great illustations and info is ou there Amphi...its in with the early harness description on this page of the Manuals:

http://www.m715zone.com/vb/view.php?pg=early_harness


Thanks again Amphi for shedding light on this previously dark subject!!!

Brute4c,

Thanks for pointing to that page. I had not seen the addition to the end of the wiring page but of course I don't look every day.

I hope it helps somebody someday.

It already has...and will again!!!

I miss read your post I thought you were saying you had the old style switch. sorry.