Electrical short on JD855?

[DaveNay]

Last weekend I was using my JD 855. After I shut it down to take a break, it wouldn't start again. The battery wasn't supplying enough juice to turn it over if I put my 250A battery charger/starter on it it would only crank about 1/8 turn then nothing. I noticed a crack near the positive battery post in the plastic, so I figured I had an internal battery short and I disconnected everything and left it alone.

This weekend I bought a new battery (OEM spec, nothing fancy) and when I hooked it up, it would barely activate the gauges and still wouldn't crank the engine at all. I've been messing around with it for a couple hours now, and it has drained the batter to the point where when I turn the key, I get nothing at all. Again if I put the 250A charger/starter on it, it cranks about 1/8 turn then stops (I am thinking it can't get past the compression stroke).

I have disconnected the lighting circuit (plug behind the selector switch) as well as unplugged the pre-heat controller and the PTO controller in an attempt to isolate where the short might be, but with no luck.

Edit: I have also checked all the fuses with an ohm meter and they are all good. I have power at the appropriate places so I know the fusible links are good too.

I am asking if anyone has any suggestions for hunting down this type of short or symptom? I have turned over the engine by hand (screw driver on the fly wheel) so I know it is not locked up.

 

[Willl]

Do you have access to a digital volt meter ?

Edit; Oops, missed the ohm reading so of course you've got a volt meter.

What is your exact battery voltage with key off and with key in crank position ?
(probe the posts of the battery only)

What is the voltage at starter positive terminal with key off and with key in crank position ?
(probe the starters metal case and the very tip of the positive terminal)

 

[DaveNay]

Do you have access to a digital volt meter ?

Analog. I can borrow a digital from work tomorrow. Do you have something in mind?

 

[Willl]

You might be able to see a fault with the analog, you could try.

 

[burnieman]

I had almost the same thing on my 955. It was the positive battery cable. It was corroded inside. Put the new one on and no problems for months now. Good luck

 

[DaveNay]

I had almost the same thing on my 955. It was the positive battery cable. It was corroded inside. Put the new one on and no problems for months now. Good luck

I can test that by bypassing with jumper cables.

 

[Zebrafive]

I had almost the same thing on my 955. It was the positive battery cable. It was corroded inside. Put the new one on and no problems for months now. Good luck

Bad cable or cables is my guess too.

 

[burnieman]

I can test that by bypassing with jumper cables.

I think I tried bypassing with cables too but it didn't work. I don't think the cable had a good enough contact or something. I turned the key and shook the cable. It tried to start so I went from there.

 

[DaveNay]

I had almost the same thing on my 955. It was the positive battery cable. It was corroded inside. Put the new one on and no problems for months now. Good luck

Bad cable or cables is my guess too.

This definitely appears to be the issue. I removed both the positive and negative cables from the battery and connected the battery to the starter post and the starter frame using jumper cables. When I turned the key to the on position the dash lights turned on and when I tried to start it it cranked (weakly though, the battery is a little drained from working with it yesterday). I will need to figure out if it is the positive or negative cable (or both) that needs replacing.

 

[DaveNay]

This definitely appears to be the issue.

Definitely the positive battery cable. I reconnected the negative and removed the positive completely. Jumper cable from battery post to starter battery terminal. Turn the key and it fired right up. Old cable is in the truck so I can match the length tomorrow at Farm & Fleet (I don't trust them to look it up.)