HELP with 755 alternator and battery overcharging?

[Jaymien]

Could someone tell me what i can do to troubleshoot battery leaking problem. Here's where I'm at. Bought a new battery from JD dealer about 2 months ago. almost immediately the battery started to leak from under the 2 covers on top of the battery...not very much at first. Last couple of weekends more leaks appeared, so i called dealer and asked if i could get new battery. they instructed to check alternator for overcharging first. So, battery has 12.5 volts with engine off, running the battery has 14.6 volts. Not sure how to check the regulator since i believe it's inside the alternator. Could it be a grounding issue? Could it be a battery issue? what's the next step here? photo of alternator attached, i believe it's 35amp original to the machine.

TIA damien.

 

[Coyote machine]

Why did you replace the battery in the first place?
14.25 Volts is about the highest one would want to see at the battery while running. 14.6, V, though not off the charts is a little high. Could be the internal voltage regulator is starting to fail. Do you have any specks on what the alternator is supposed to put out and the range the V-reg is supposed to run at? What does the battery say when you put a load on it like headlight high beams? It should drop down some from the load.
Is the battery you put in the tractor specked for the tractor in terms of CCA, etc?
Post back results.

 

[Jaymien]

the previous battery wasn't holding charge well and had trouble starting motor. the new battery is TY6192 from JD which is the correct battery for the 755. There are no marks on the alternator (it has been painted several time though), but from the pictures in the manual it looks to be the nippondenso 35A part # AM100808. I'll check tonight on what the battery does when under load from lights when running, but through the rpm range battery would drop to about 11V and then always leveled off at 14.6V regardless of rpm (high or low, or idle which is about 1400rpm). With engine off and all lights on, voltage drops to 12.1V quickly and then leveled off around 12V and seemed like it was going down slowly, but i didn't watch it for too long, maybe 5 minutes.

from JDparts they say specs are:

Specification

Weight 6.55 LBS 2.97 Kg
Voltage 12.000
Amperes 40.000
Brush_Style
Vendor Code Y
Mounting Style 5
Length 4.406 IN
Radius Mounting 2.913 IN
Thread Size 0.00 IN
Regulator Setting 14.5
Frame Style OPEN
Fan Type INTERNAL
Load Dump Protected NOT_DEFINED
Finish
Note C

 

[Coyote machine]

Most alternators for 12 Volt systems level off below 12.6V. The expected high volt range would be around 12.25. The extra is possibly not so much over, but may be showing signs of age of the bridge rectifier and or worn diodes in the alternator/voltage regulator. You may not be far off replacing the alternator with a newer one- but before doing that I'd have it tested on a bench at a local reliable auto store or alternator *rebuilder. (Don't know if people are still doing *that on a regular basis anymore?)
I'd also check the new battery outside the tractor for hairline cracks or anything that could be allowing acid to escape from under the caps. Are the cells filled just to the top of the split ring in each cell? If the battery is overfilled it could also cause some overflow from under the caps.
If there is any case damage get a new battery under the warranty that came with it. There is a dealer's secret code that tells when it was made too....

 

[bgk]

Why did you replace the battery in the first place?
14.25 Volts is about the highest one would want to see at the battery while running. 14.6, V, though not off the charts is a little high. Could be the internal voltage regulator is starting to fail. Do you have any specks on what the alternator is supposed to put out and the range the V-reg is supposed to run at? What does the battery say when you put a load on it like headlight high beams? It should drop down some from the load.
Is the battery you put in the tractor specked for the tractor in terms of CCA, etc?
Post back results.

I had a similar problem with a JD 755. battery acid overflowed. Voltages were almost identical. I installed a new battery... from JD dealer. I cleaned out battery compartment, used battery mats to soak up acid... no luck. Dealer indicated I needed new alternator (expensive). Same thing happened with new alternator and new battery. Same voltages as before. Spent time cleaning up acid and repainted everything. I ordered a gel battery and the problem went away. About 6 months later I traded the tractor in for 2720. Dealer did not want "old alternator" since it was used.

 

[Jaymien]

i got a hold of shop that rebuilds alternators and starters. they suggested check the battery including specific gravity of acid. i checked and it's 1.225 which apparently is slightly low but okay. battery has no cracks and looks okay, cells are filled to just above rings in each cell. not sure if that is overfilled or not. I'll bring the alternator in and have them look at it.

i might go this route if the alternator checks out good. what else could it be?

 

[Coyote machine]

Seems like a gel battery might solve the problem, though it seems strange that the battery you have can't seem to handle what the alternator is putting out. As I said before, 12.6 is a little high for output to the battery- I'd say close to or slightly above the 'normal' voltage range, thus the problem of acid overflow you're experiencing. I would ask the shop if there is any way to tweak the upper limit of the Vreg down to around 12.25V max output. It's probably not adjustable, but it might be able to be tweaked.
I wouldn't go buy a new alternator yet, it might not change anything, as stated by bgk. And it's an expensive chance to take to solve this problem.
The split rings, slightly above is not a problem , but you could try very carefully to lower the amount of acid with a turkey baseter to just at or slightly below the split rings. WEAR SAFETY GLASSES to do this and dispose of the acid carefully down the drain.
I'd also do preventative maintenance on the battery posts and cable ends too. Clean each till it shines and check your ground cable where it attaches to the frame. Coat the posts with the cables attached with a spray battery sealant after adding the felt rings under each post clamp. Seal the frame ground cable the same way without using the felt washer. Make sure all connections to the battery are snug enough to not be able to twist on the post. While at it clean the battery box area too with baking soda powder and wash till clean.
Let's see what the alternator tests out to show where we're at.

 

[Jaymien]

thanks for the tips! i'll take the alternator in on monday and see what the guys say. i really don't want to spend the $250 on a new one. the battery had leaked so much that the tray was pretty much covered and had leaked out the sides on got onto some of the painted body panels. i pulled all of them off, cleaned them with battery cleaner spray (paint wrecked in some spots), cleaned the tray and everywhere i saw spillage. The battery is almost new, so the posts are new and when the new battery went in i put on a couple of new cable end clamps. i'll post back with alternator results next week. thanks for your help.

 

[Barry 1]

Sounds like an over-filled battery to me,too.

 

[Coyote machine]

I looked back at the specks you posted and it shows the voltage regulator set at 14.5 Volts as the upper limit. As stated, 14.6 V is not going to make any difference over 14.5 nominal rating. What strikes me as strange is the fact someone else seems to have experienced the same problem on the same model tractor and found a new alternator did nothing to resolve the issue. Therefore it would seem that is not the problem, but you are nonetheless experiencing boiling off of the acid water mix which is damaging your tractor's metalwork. Not a good thing. And not going to solve itself.
Please make sure the replacement cable ends are solidly tightened to clean metal from the cable to insure the best flow of current through the entire charging circuit. You could coat the ends of the cables in anti-seize and then clamp them down to increase the amount of wire that passes current through it.

The only other thing I can think of at the moment is the actual cable(s) are weak and worn out, thus high resistance to current flow through the circuit, resulting in the alternator sensing a need to crank out more voltage to make up for the shortage.
What year is your tractor and how many hours are on it?