Fuse?

[1955CJ-5]

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?

[garage gnome]

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.

[1955CJ-5]

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....

[garage gnome]

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.

[1955CJ-5]

The resistor will eventually give out....then "HI" and "OFF" will be the only options...but it looks the part!

[CJPilot]

How about adding the fuse and swapping the old resistor for a new one with a higher wattage rating?

[1955CJ-5]

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....

[johnrb3b]

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.

[1955CJ-5]

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?

[1955CJ-5]

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

[Bob W]

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.

[Mike S]

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.

[johnrb3b]

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.

[Gunslinger]

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.

[1955CJ-5]

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.....