My Willys 3A and 3B Community

3A, 3B, DJ Technical Knowledge Base => "Original"-- Technical Questions, Answers, Observations => Topic started by: 1955CJ-5 on January 07, 2015, 09:40:58 PM

Title: Fuse?
Post by: 1955CJ-5 on January 07, 2015, 09:40:58 PM
So the other day I'm bouncing along, heater on "HI"..everything is great and the l-134 is humming along...and then I thought I'd try the "LO" heater setting...it's a three position switch....

So before long I'm getting that sickening odor of hot electrical ...

I realize at that point that there is nothing I can do..as the heater is wired to the amp gauge which is wired directly to the hot side of the starter switch and thus directly to the battery....

The only thing that will break the circuit is a melted wire...

Well as it turned out it was only the resistor in the switch..selecting "HI" again eliminated the odor...but it got me thinking...

If I were to add a fuse(or a switch)...probably in the feed wire from the starter to the rest of the loom...what size would it be and how would I go about it...

Anyone done this?

Ideas?
Title: Re: Fuse?
Post by: garage gnome on January 08, 2015, 05:33:03 AM
That smell may have been the resistor heating up and burning off something. What kind of switch is it? I had a cheesy one burn up and short out. I put a 10 amp fuse in after that.
Title: Re: Fuse?
Post by: 1955CJ-5 on January 08, 2015, 10:05:56 AM
Hi Nate,

It's an original switch...and I'm sure it was just the resistor burning off some crud....

but if it had been more serious, then the only way to break the circuit is to jump out, open the hood, and disconnect the battery..I never did get that battery disconnect switch installed, i couldn't find an under-dash location that didn't require lots of extra battery cable or cutting holes....

Title: Re: Fuse?
Post by: garage gnome on January 08, 2015, 08:53:40 PM
I had one of those in my red jeep, but it burned up. Only worked in high and off. Ted still has one and that one is on its way out too.
Title: Re: Fuse?
Post by: 1955CJ-5 on January 08, 2015, 09:48:32 PM
The resistor will eventually give out....then "HI" and "OFF" will be the only options...but it looks the part!

Title: Re: Fuse?
Post by: CJPilot on January 09, 2015, 08:04:23 AM
How about adding the fuse and swapping the old resistor for a new one with a higher wattage rating?
Title: Re: Fuse?
Post by: 1955CJ-5 on January 09, 2015, 10:41:26 AM
The resistor is an odd one that it tapped in the middle for the medium setting and tapped at the end for low...if I remember right it's ceramic with a wire coiled around it...


But, the heater is not my main concern, I'd like to fuse the entire harness with a single in-line fuse in the feed wire from the starter lug, so that any behind the dash short circuit would be protected....
Title: Re: Fuse?
Post by: johnrb3b on January 09, 2015, 11:15:35 AM
I fused my 3B wiring that way and discovered that the horn is a big current hog. If I'm driving down the road with the headlights on and blow the horn long and loud (like in a parade) the engine stops. The horn will blow the fuse and that kills the ignition.
I'm going to fuse the horn separately with a 10 Amp fuse and the headlights and heater each with its own 10 Amp.
Title: Re: Fuse?
Post by: 1955CJ-5 on January 09, 2015, 11:45:50 AM
Thanks John,

That was another question and now you've answered it...how many amps?

Have you tried a slo-blow fuse?

Having the engine quit when/if the single fuse blows kinda complicates things....

How about one of those circuit breaker units similar to the one on the light switch? Is that just a thermal switch?
Title: Re: Fuse?
Post by: 1955CJ-5 on January 09, 2015, 08:59:44 PM
Interesting info on slo-blow fuses here.....John, one of these maybe all you need...

http://www.littelfuse.com/~/media/files/littelfuse/technical%20resources/documents/application%20notes/littelfuse_application%20note%20slow%20vs%20fast%20auto%20fuses.pdf
Title: Re: Fuse?
Post by: Bob W on January 09, 2015, 09:48:31 PM
Typically a fuseable link would be used there. It's just a short length of smaller diameter wire with flameproof insulation. In case of a major short the link.will burn out before the heavy main wire. Then all the branches from there get their own fuse.
Title: Re: Fuse?
Post by: Mike S on January 10, 2015, 03:37:53 PM
Fusible links are available in various amperage values in most auto parts store. They are common on Toyotas, for instance.

It would pretty easy to put a small blade fuse panel on the front DS fender for the headlight loom.
Title: Re: Fuse?
Post by: johnrb3b on January 13, 2015, 01:26:44 PM
I haven't normally used slo-blo fuses in automotive applications, mostly because you're not dealing with huge inrush current. Big motors have an inrush rating of many times their running amperage. Headlights, the horn, etc don't have that problem.
Title: Re: Fuse?
Post by: Gunslinger on January 18, 2015, 09:26:52 AM
I was worried about the same thing, so I added a small fuse block that I got at NAPA.  Primary comes off the Battery main, and it has 4 fuse locations, I use on for the heater with a 10 amp fuse, I know its not period correct, but it is safe and isolates the high draw circuits from the engine.  It also mounts nicely on the fire wall right next to the on-board trickle charger I use to keep the battery topped off in the low use months.
Title: Re: Fuse?
Post by: 1955CJ-5 on April 28, 2015, 02:04:56 PM
Elsewhere on this site(non-jeep projects) i mentioned being the new owner of a 29 Model A.

In searching for parts I ran across this little item, as Model A's are not fused either....


http://www.snydersantiqueauto.com/3575

I ordered one...I'll see how it adapts to the 3a.....
Title: Re: Fuse?
Post by: johnrb3b on April 29, 2015, 11:47:23 AM
Pretty fair price for what you get -
fuse holder, 2 fuses, wire pigtail, custom mounting bracket with screws.

Some guy is doing the old Model A people a kind favor. That's easily a $20 part on the normal market at today's markup rates. Of course you could make your own from parts in your scrap drawer, but it wouldn't be as neat.

I have a drawer full of fuse holders of various kinds. I've been using them on my 3B. I'm fusing separately the horn, lights, wipers and ignition. I'm using the fuseholders to fill some of the many, many holes in the dash drilled by POs. Definitely not original, but functional.
Title: Re: Fuse?
Post by: dat on April 30, 2015, 01:49:04 PM
Quote
Hi Nate,

It's an original switch...and I'm sure it was just the resistor burning off some crud....

but if it had been more serious, then the only way to break the circuit is to jump out, open the hood, and disconnect the battery..I never did get that battery disconnect switch installed, i couldn't find an under-dash location that didn't require lots of extra battery cable or cutting holes....


looks like a fuse on the back of that switch,   I don't have a heater on mine so I don't know, but from the picture it looks like a fuse
Title: Re: Fuse?
Post by: 1955CJ-5 on April 30, 2015, 06:19:55 PM
There is a fuse and there is also a resistor.

I guess it just sort of reminded me when it got hot, that if it had been any other powered circuit there is no immediate disconnect or fuse......
Title: Re: Fuse?
Post by: 1955CJ-5 on May 03, 2015, 06:23:28 PM
The fuse holder arrived, well made and it fit the Model A to perfection....

Next order I'll get one for the 3A..


Title: Re: Fuse?
Post by: 1955CJ-5 on June 19, 2015, 11:32:37 PM
Well I finally did it. Everything fit just fine with only one hole drilled in the fuse bracket and a longer screw used to fasten it through the starter switch and into the starter...

Parts were from www.Brattons.com, a model A ford parts
supplier..

switch # 20190
cable  #  20180
Bracket# 20170

Now for a supply of spare 30 Amp fuses!

Title: Re: Fuse?
Post by: Julian on June 30, 2015, 11:36:26 PM
Fusible links were commonly fitted to later Jeeps such as the Cj5 and Cj7, they were positioned in two locations:

1. From the solenoid going to the fuse box and instrument panel and hence most of the harness
3. From the solenoid to the alternator feed.

The headlights and starter did not have fusible links, for safety reasons on the headlights (they have a momentary circuit breaker) and the starter would have knocked one out fairly regularly.

The purpose is to protect the harness from melt down, not individual items from blowing fuses. They are a little more than just a piece of wire in a flameproof sleeve but still fairly cheap.

A good investment in an old Willys.