Negative battery cable gets HOT

[TNford]

I have a ?66 Ford 5000 diesel SOS. I am bleeding the fuel system after rebuild, but can?t crank the engine for very long or else the negative
battery cable gets smoking hot at the starter and the terminal. It has had a 12v conversion before I got it. None of the lights or instrument panel
has worked since I?ve had it, and was wanting to get it all up and going.

 

[Billy NY]

Sounds like a bad connection, are the terminals and or cable ends clean ?

 

[Fordfarmer]

All Fords were 12V from the factory ftom '65 on.
There is a small lever on the left side (as you're facing it) oc the fiel pump that allows you to manually pump fuel to bleed the filter and lines as far as the injection pump.
The cables will get hot with emough cranking. If they're getting hot quickly, either your starter is drawing too many amps, or there's a bad connection. You want all connections clean, bright, and tight.

 

[Texasmark1]

First is external appearance of all surfaces touching....nice and bright....clean. Second is adequate torque.....good and tight...not too tight as to strip the copper threads, but not loose.

Third is the crimp-cable connection in the connecting wire terminal....inside where you can't see it. Cables are cheap enough to not have to put up with bad crimp problems. I always use as large as I can get for the application. On my tractors, that's 00 gauge wire. TSC sells cables.

Any time you feel warmth, you have loss caused by resistance caused by too small a conductor for the amperage-time applied, corroded interfaces, or inadequate pressure (bolt loose).....that's it, the "smoking guns".

 

[Texasmark1]

Lots of batteries are attached to the tractor frame which is steel with a steel screw with rusted threads pressing up against rusted castings. First of all cast iron and steel screws aren't your best conductors like the copper wires. Rust just insulates the connection.

A good cleanup of that mating surface will work wonders for your available amperage. While you are at it, pop the cables at the battery and do a cleanout of that mating surface...with the little wire brush, readily available, made just for that purpose.

 

[TNford]

Could very well be a bad connection. I will be sure of that tonight after work. Thanks guys!

 

[Dean]

Bad connection, internally corroded cable or undersized cable.

Relatedly, starter motors are intended for intermittent duty only. Excessive cranking will overheat the starter motor and can cause failure. It is generally recommended to crank no more than 20 seconds without a significant cool down interval.

Dean

 

[Bern]

If it's getting hot at the starter terminal, it's most likely a corroded bolt inside the starter end cap. I've seen that many times - the bolt is steel and the end cap is aluminum. The fix is to either remove the cap and clean up the bolt, or else re-locate the cable to one of the starter mounting bolts.

 

[Sean in PA]

Good advice given by all. Another thing you could try to bleed the system and get it started is to pull start it if it has an 8 speed. If it has the Select-O-Speed then that's not an option.

 

[TNford]

I think I have seen that bolt corroded. Thanks Bern!

 

[El Hombre]

And once you clean up the connection, put some grease on them. Then they won't rust in the next month like bare metal. And then you won't have to do it again for a long while.

 

[Bern]

Where it matters is where the bolt seats up inside of the cover. You cannot see this area without taking it apart.

 

[Hobo,NC]

A voltage drop test will prove the health of the ground cable are any cables/connections EZ as pie and no guess work involved.

Google Voltage drop test

Another way to find a issue with internal voltage drop inside the starter/component.



https://www.youtube.com/watch?v=XhRPLgH6uZg&t=338s

 

[Bern]

Bogus. Go to 8:50 in the video and watch the voltages at both the battery and the starter - they are the same. I don't care how good the cables are, there's no way they will be exactly the same. Don't buy into this guy's BS!

 

[Hobo,NC]

Don't matter if you believe what you see are not what the test does is prove you have a good circuit if you did not then you would spend the time to isolate the culprit... Yes there is a spec I think .7V drop on the positive and .2V on the negative side... The flag goes up when you see 1V plus then its time to isolate the problem... Its hard to get a handle on it unless you take the time to do the test most just fudge with it and hope there luck does not run out on'em..

There would be no need to go on a witch hunt for a problem that does not exist..

The real problem is folks don't test a good operating system to build a knowledge base of known good... You are good enoufh to prove it and build a tester are more than likely have a couple of voltmeters that you could lean the power they have... You can fight it all you want the prof in the pudding is there you will have to find it..

 

[Bern]

I'm telling you man, that video is fraudulent! Go to 8:50 and tell me what you see. I see a meter than reads 11.60 volts BEFORE the engine
starts cranking, and 11.60 DURING cranking. How is that possible? It's not - it's smoke and mirrors. Try it on one of your own rigs if you
don't believe me.

In addition, the point of the test was to show a voltage drop in the cables during cranking. I do understand voltage drop testing sir - I
teach it for a living. And I'm here to tell you, there's no battery cable in existence that has zero volt drop under load.

 

[Hobo,NC]

I don't know why the voltmeter is locked in at 11.6 you would have to ask him....My guess they forgot to turn off min/max on his last test.... At 9:10 it explains what you should see....

The demonstration is a diagnostic process not a best guess...