Overheating wiring harness

[DAG1]

Hi
When driving my recently restored 1959 FE35 23c yesterday, there was a sudden cloud of smoke from underneath the battery compartment with a few flames coming off the top of the block. These flames quickly died out (my rush to get a fire extinguisher was unnecessary!) but the end result is a badly burned wiring harness.
The harness was purchased at the time of the restoration from Agriline who have told me that they are not aware of any similar problems with their product. Therefore, has anyone any ideas as to what may have caused the overheating? Cheers.

 

[Gordon Gould]

If everything has been fine for a while with all you electrics working then suddenly this then maybe the insulation got chafed or cut on a sharp edge and shorted out. Just a guess.

 

[Dave M7040]

Do you have an alternator with a voltage regulator?
I have had some bad experiences with the regulators when they failed as they have a connection to full battery voltage and
are connected to the battery with thick wire(s) which can carry a lot of current.
Dave M7040

 

[DAG1]

Hi Gents. Thanks for your replies. No sharp edges for the wiring to chaf on. On further inspection, the loom has melted in at least four places and rather interestingly, the positive lead connected to the ammeter is also slightly burned. The flames appear to have come from some burning leaked diesel fuel which had run back along the tachometer cable! Hence why the fire died so quickly.
I have a dynamo rather than an alternator, but take the point about the voltage regulator. The engineer who restored the tractor has stripped out the burnt harness and we have compared it with the original 'tired' one which we took out. The wiring on the original does seem a bit more substantial.
As a result I have investigated buying an exact (as is possible) copy of the original lucas harness as I understand this is more substantial than the various replacements available. Once installed, we will be checking all cable and instruments etc. for shorts.

 

[Gordon Gould]

Sounds like the smart thing to do and BTW welcome to TBN, sorry we weren't able to be more help.

 

[BleedingOrange]

Is any of the wiring harness fused ? And are the fuses the correct size, for the size of wire they are suppose to protect ?

 

[john_bud]

Is any of the wiring harness fused ? And are the fuses the correct size, for the size of wire they are suppose to protect ?

Fuses fuses fuses. A properly constructed wire harness includes fuses to stop this sort of thing from happening. enough current to melt it in 4 places, should have popped the fuse! Even the wire to the starter should have a fusable link. It may be wise to hand construct a harness with larger wires, fuses and use a spiral plastic wire loom to protect the wires from chaffing shorts. These old machines have little electrical so the wire harnesses are simple enough to by hand one wire at a time.

Good luck and maybe you should think about mounting that fire extinguisher on the tractor?

 

[jenkinsph]

I am in agreement with john bud, got to be a simple harness easily built and add fuses where needed.

 

[DAG1]

Ahead of you on the fire extinguisher recommendation! Asking around locally and speaking to parts suppliers, consensus of opinion seems to be replace the voltage regulator regardless of the condition of the existing one and then as suggested by various TBN contributors, to make up own wiring harness. Including fuses sounds like a sensible idea, as none on there at the moment. Will see what can be done. Thanks again for all your suggestions, great to know there is a wealth of advice on the end of a computer!

 

[expedoman55]

Remember when comparing the harnesses it is about the gauge of the wire not the thickness of the wire and insulation together.. the new wire often has a clear sheathing over the colored teflon wire.. keeping that in mind it will also be thinner overall as the teflon coating is a higher heat rating etc.