Battery cable issue

[Donald]

I am working on my old snowcat with Ford 300 cu inch engine. I am not sure what the issue is but it seems battery cable related.

If I turn the key to omON a fan comes on. Turn to START and I hear a little spark and then things go dead. Turn key from START to ON and no fan. Wiggle things and I can get the fan to work. Turn to START and same thing as before. (Have yet to see the spark.

Each cable is all one piece from the lug end to the battery clamp. The wire goes into the clamp with the insulation right up to the battery clamp. Cannot see any bare wire or corrosion. The battery clamp and battery post look clean. The lug end looks good.

I am thinking there is an issue under the insulation or within the battery clamp that I cannot see.

I am think I will just get some 2 gauge new battery cables.

I have wire brushed the ares where the ground wire connects to the engine.

While not 100% conclusive, it seem when I wiggle the red cable the fan comes back on.

 

[OVERKILL]

Easy enough to check with a jumper cable I'd suspect, do you have a set handy?

 

[mk378]

Yes it's fun to buy parts but there is a scientific way to diagnose this.

First consider a mechanical problem of the engine or one of the accessories being siezed. If the engine can't turn you will get a click and no crank, and a lot of voltage drop. Confirm that the engine can be turned with a breaker bar on the crank pulley bolt.

Then assuming it is an electrical problem, use a voltmeter to check where the voltage is being lost. You will need an assistant to turn the key while you check under the hood.

First measure on the battery posts (not the terminals) to confirm battery voltage stays up during a starting attempt. If the battery itself drops to near zero, it is bad.

Then measure across each connection while trying to start. From the battery - to engine ground, from battery + to the starter big wire. A good circuit stays near zero volts. A bad one has several volts. Narrow down the testing once you find a drop. For example go from the battery post to the terminal, from one end of a wire to the other, etc.

 

[Donald]

Yes it's fun to buy parts but there is a scientific way to diagnose this.

First consider a mechanical problem of the engine or one of the accessories being siezed. If the engine can't turn you will get a click and no crank, and a lot of voltage drop. Confirm that the engine can be turned with a breaker bar on the crank pulley bolt.

Then assuming it is an electrical problem, use a voltmeter to check where the voltage is being lost. You will need an assistant to turn the key while you check under the hood.

First measure on the battery posts (not the terminals) to confirm battery voltage stays up during a starting attempt. If the battery itself drops to near zero, it is bad.

Then measure across each connection while trying to start. From the battery - to engine ground, from battery + to the starter big wire. A good circuit stays near zero volts. A bad one has several volts. Narrow down the testing once you find a drop. For example go from the battery post to the terminal, from one end of a wire to the other, etc.

Yes I understand that if the engine was seized I would get a lot of voltage drop with the key turned to START. But after releasing the key from START back to ON, the voltage would go back to normal. In my case it does not. Its dead until I wiggle the battery cables.

If I have to order a nice 2 gauge battery cable, I minds well order both given I will probably be stuck paying for postage.