Melted wire on 1250.

[red56turbo]

Just picked up a nice, original 1250. PO said it had an electrical problem and he hadn't looked into it, otherwise it ran great. I believe him seeing he was a very honest 85 year old. Anyway, pulled off the tank and found my problem. Someone did some shade tree wiring and replaced half of the wire from the ignition switch to the coil with a butt connector. No big deal with the connection. The problem is the whole wire from ign. switch to coil is melted to the point the insulation is falling off and the wire broke. I did a temp wire together and got it to start and she runs great. Probably will replace the wire for now till I can get a different harness.

Anyone have any idea why the wire would get so hot to the point of melting and breaking. Only the coil wire was affected. Key left on, overcharged battery, bad coil, break in insulation allowing grounding?
TIA for any ideas. Hate to put her back together and fry something else or even worse, catch it on fire.

[save_old_iron]

that wire is specific to the ignition coil only and would have had to draw in excess of 30+ amps to melt the insulation off. Something as simple as a slip of the wrench tightening down the (+) coil terminal nut while leaving the ignition switch in the RUN position could cause a direct short to engine or chassis ground.

if you are concerned about another meltdown, a 10 amp fuse / holder could always be placed in the line leading to the ignition coil - yes - one more thing to go wrong in the future - but it would give peace of mind against another melt down

[R Bedell]

This is a good example of what will happen when one "over amps" a fuse. The wiring in the Cubs (IH built) should have a 10A rated fuse, NOTHING over 15 Amp fuse. The fuse would blow first before the wire melts.

Just think, that this wire sets right under the gas tank.

[save_old_iron]

Roland,
Check me out on this.

I looked at the 1250 wiring diagram in the resources section, I see a fuse for the lights and another for the PTO. It looks like a straight shot off the battery thru the ignition switch "I" terminal to the coil - no fuses. Is that correct? That's why I recc'd another fuse / holder to ease Josh's concerns about this ever happening again.

[R Bedell]

My comment was directed towards the threads I see where a larger fuse was installed in lieu of the correct size.

You are correct on the Q/L series, there is no fuse protection to the Ignition Circuit. It certainly wouldn't hurt to install a inline fuse (10A) to add protection.

[red56turbo]

Hey Guys,
Thanks for the comments.
Save old iron is correct in saying there's no fuse, straight shot from ign. switch to coil. This wire was spliced roughly halfway to the coil by newer wire with a butt connector. Is it possible the old wire under the dash lost some insulation and the bare wire touched the frame causing the overheating??

RBedell really brought my concerns to the forefront. Hot electrical wiring and gas equal .

Hopefully it was just a fluke with bare wire versus ground. Once I replace the wire with new, I'll be ok. Just wanna make sure I'm not missing anything.

Thanks all.

[save_old_iron]

Josh,

one possible cause of the wiring burning is just as you say - a short to ground somewhere along the length of the wire supplying power to the coil. If for example the short was present near the coil, the ENTIRE LENGTH of the wire would be fried.

If the short happened under the fuel tank, just the wire from the TANK BACK TO THE IGNITION SWITCH (and possibly back the battery) would be burned.The wire from the coil to the short would not be affected. So a little detective work on the burned wire could tell a little more about the story of the event that burned the wire.

Another scenario is possible. If the ignition wire contained a poorly made spliced connection, the connection would eventually corrode and develop a resistance to electrical flow. This resistance, in combination with current flow to the coil, would generate significant heat - think soldering iron. This heat would be localized to the connector and generally affect only the immediate area around the connector.

Josh, when you rewire, consider using MARINE GRADE wire. The insulation is thicker (increased resistance to vibration and abrasion) and the wire strands are pre tinned to prevent corrosion from oxidation due to exposure to oxygen and moisture in the air. I use wire sold at Greg's Marine, sold on Ebay.

http://www.ebay.com/itm/14-AWG-Marin...02fc8a&vxp=mtr

One of the great things this seller will do for the buyer is sell 100 feet of wire in any color combination he has. You can buy 20 feet of red, 30 feet of white, 10 feet green, etc until you total out to 100 feet. You do not need to buy 25 foot rolls of a single color. Any combination of 11 colors can be put together in a single shipment. The wire is also top shelf quality.

[teejk]

thanks for the link...at first I didn't think 16ga was enough but reviewing the wire diagram and considering that the switch is the "weak link" in the chain, I guess it works.

[R Bedell]

14GA wire is what was used by IH.

[teejk]

Originally Posted by R Bedell

14GA wire is what was used by IH.

I use 12ga on everything myself (don't really need much of it unless you are rebuilding several of these).