battery terminals switched...damage?

ScottOkla · Jul 13, 2005

I recently replaced a dead battery on a L275 with a new battery after dark using the headlights on the truck as the only light. I had no tools with me and just needed to get the tractor on my trailer to move it.

I positioned the new battery so that the terminals were on the same side as the old ones but did not verify that the neg and pos were in the same places as the old ones. I pushed (no tools with me) the connectors onto the incorrect terminals, and they slipped on well enough to stay put. It started (how?) and I drove it onto the trailer.

After moving it (1 hr) to my place, I left it on the trailer overnight. The next day it was dead and I saw that the battery cables were connected to the wrong terminals.

I have used it a couple of times since, but the battery is totally dead and I have jumped it to start it. I replaced the battery, and it started fine with a new battery, but after a little use, that battery is almost totally dead also. I can still start it by jumping it.

My questions are: (1) how stupid am I? (2) what is the likely damage that I have caused? and (3) am I doing any more damage by jumping it and continuing to use it?

A relative passed away and that is how I now have the tractor. I am waiting for an owners manual to come in at my nearest dealer.

kully · Jul 13, 2005

more than likely you shorted out the diode in the alternator and the battery is not charging . check out the charging system . anyway sh/////t happens to all of us kully

EastTexFrank · Jul 13, 2005

The battery on our old JD 820 has been connected the wrong way round for the past 2 years, ever since my S-I-L installed it. I only found out about it because it hadn't been used for a while and the battery was flat. It was pretty dusty in there so I connected the battery charger up using the red and black battery terminal wires for reference. I connected it up, let it charge for a while, tried to start the tractor and fried the battery charger. I couldn't understand it so I cleaned off the top of the battery and there it was .... red wire to negative and black to positive. Strange thing is that it has run like that for over 2 years without any ill effects that I can see. In fact I used it about 4 months ago to cut a 40 acre pasture. Now I don't know if I should change it back over or what. What I don't want to do is to fry another battery charger.

TonyV · Jul 14, 2005

Hi Scott. I teach electronics at a college over here in Michigan, ( I say this only to lend some credance to what I'm about to post)....so heres my two cents worth. You probably have not damage anything beyond what was originally wrong with the tractor, and that is that you've a short, or a partial short which is drawing current from your battery even with the tractor turned off. This is likely what took out the original battery, the second battery and is now sapping the third. To confirm this suspician, just hook an ampmeter between the positive (or negative) terminal of the battery and the cable. Naturally you'll have to disconnect the cable from the battery to do this. Make sure the key is off when you perform the check. Perform this simple test first and let us know the result and we can go from there. If you find that you are drawing current, then the fun begins...finding the circuit thats drawing the current.

...Tony

Mike_C · Jul 14, 2005

It does not make sense that it started, because the starter motor is a DC motor, and if the battery was hooked up backwards a DC motor will spin in the opposite direction. Engines that are cranked backwards typically don't start, and further starters running backwards are not likely to engage the flywheel properly because they only engage when the gear is spinning in one direction (to allow it to be kicked out once the engine does start). Is there any chance that after you moved the tractor someone else flipped the battery cables on you?

TonyV · Jul 14, 2005

Hi Scott...after a good nights sleep after a late evening post, I thought I'd add another 2 cents to the pot. If it turns out that there is no current draw from the battery with the key turned off, then as Kully had suggested, have the alternator checked out. Most automotive stores, and maybe even some tractor dealers can bench test that for you.

On another note, I also wondered what kept the starter from running backwards with the battery terminals reversed. I didn't address that in my original post because, as you and another poster stated, the tractor still started....its still curious though. I'm no expert on tractor wiring, but I wonder if a rectifier circuit is employed somewhere in order to straighten out the polarity at the starter. Anyone know?

....Tony

Mike_C · Jul 14, 2005

I've never seen anyone put a rectifier circuit on a starter, and I'm sure it's because starters can draw hundreds of amps with a cold engine, so the cost of diodes that can handle hundreds of amps would not make it cost effective.

EastTexFrank · Jul 14, 2005

Now I'm totally confused. What you are telling me is that if the wires are connected the wrong way round, the tractor starter will turn backwards but not engage so the engine won't start.

That JD 820 (about 45 years old), has been in the family since new and starts and runs just fine although the battery will run down if it's left for a few months without the tractor being used. Maybe it's because it's an older tractor. Now I don't know what to do. Do I leave it alone since it's working or do I swap the wires around and put red to positive and black to negative?????? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

Maybe I need to go talk to ol' Pete, my guru. He worked at the dealership when my F-I-L bought it and has been the only one who has ever worked on it for the last 45 years. It might be that at some time in the past the battery leads were replaced and installed the wrong way round although I can't see Pete doing that. He's in his late 70's, has worked on tractors for 50 years and still puts in an 8 hour day doing what he's always done.

The mystery deepens?????????

TonyV · Jul 14, 2005

I agree, it couldn't be done directly on the starter. It could easily be done though through a relay/solenoid circuit. Seems like a lot of trouble to go through though just to insure against the battery not be connected correctly, but how else can you explain the fact that these tractors started at all? I'd be interested in hearing other viewpoints on this...I love a good electrical mystery. /forums/images/graemlins/smile.gif

...Tony

EastTexFrank · Jul 14, 2005

I've been thinking. When starting the JD 820, you have to turn on the ignition and press a starter button. Maybe there's a solenoid there???? If the starter motor runs backwards but does start the engine, would that mean the engine was running backwards. That's not happening because the forward gears are still forward gears.

Also, if the battery was connected the wrong way round, wouldn't the gauges fail to read properly??????

Maybe it is the terminal cables that are connected the wrong way round. /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

TonyV · Jul 14, 2005

Another possibilty Frank is that that tractor was originally a positive ground system. Somewhere along the line, someone may have changed it to a negative ground system (perhaps when converting from 6V to 12V??) but left the cables where they were, with the red cable grounded. Just another thought...the plot thickens. /forums/images/graemlins/confused.gif /forums/images/graemlins/smile.gif

...Tony

Volfandt · Jul 14, 2005

How's about another curve... /forums/images/graemlins/grin.gif

When one upgrades the old TO/TE series Ferguson tractors from 6v positive ground to 12v negative ground, the same old starter still works and turns in the correct direction.

Other than adding the alternator, the only other modification needed is to add one of those old style GM or Plymouth ignition resistors in series w/the stock coil to keep from burning it and the std points & condensor up. A newer style coil with the integral resistor negates the need for the resistor.
No mod is needed for the std starter.....

Volfandt

KennyV · Jul 14, 2005

Are those the thundering hoof beats of zebras???, here is a thought… Actually 3 thoughts.
First, never use the color of the conductor alone to determine the polarity, LOOK to verify that the cable you are about to hook to negative is attached to ground. (This assumes you know you are dealing with a negative ground engine.)
Second, you can not reverse the cables on a battery without tools… batteries have different size terminals, for this vary reason. Take a close look, you could not have connected the cables without resizing them, for that you would have to open one wider and close the other a lot to get contact good enough to support the current draw.
Third, you have some non related electrical problem, Either the charging system is not working properly OR you have an electrical drain you are not yet aware of…
KennyV.

ScottOkla · Jul 14, 2005

I don't recall for sure since it was a while back, but I think the cables had already been loosened up before I removed the original battery, maybe even taken off altogether. I managed to get them on the new battery with finger tightening and a few taps with a block of wood.

My only thinking was to make sure the terminals of the new battery faced the front like the old ones did. After that, I just stopped thinking I guess.

I don't know how, but it DID start once like that, and I remember seeing a little smoke coming from near the alternator. That should have been a clue, but it was a wet evening, and without much light I thought it was likely steam.

Lastly, When I put jumper cables on it, the light on the dash comes on even without the key being in. As soon as I put the key in and turn it to the start position, the light goes off and does not come back on while it is running.

I will study these responsed a bit. Any more suggestions are appreciated.

Highbeam · Jul 15, 2005

The starter doesn't care which side is negative or positive. Don't know why but in a pos-ground to neg-ground conversion you leave the starter alone.

I replaced my dozer's battery cables. I used two new red cables and they both went right onto the battery posts without any odd resizing. This is not a dependable method to determine which cable is which.

Gauges, those run by electrical senders would need to be wired differently to work right if you flipped the battery.

Isn't the battery just a big capacitor? Does it really matter?

ZackaryMac · Jul 15, 2005

Have seen it in the past where completely dead batteries have been hooked up to a charger backwards by mistake and come back pretty good, but with the posts reversed; the positive post was negative and vise-versa. Certainly threw me for a loop.

penokee · Jul 17, 2005

Scott - I may be missing something here, but I've had 4 old tractors - still have 2, and they are positive ground. Sounds to me that it may have been hooked up properly for the 2 years you mentioned. You can find out fairly easy by asking the question on the thread attached.
penokee /forums/images/graemlins/smile.gif

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