Branson 4520c voltage rises to 20V!

[richied2003]

Hi folks,

I have a 2015 Branson 4520c that had the battery die recently. I jump started it and finished my mowing. I put the battery on a trickle charger and next time it started right up..but interestingly, the charge light was still on on the charger before I disconnected. I assumed due to the 5+ year old battery.
Anyways, yesterday I decided to check the voltage, with engine off and sitting for over a week witout the trickle charger and the battery read 13.5v! I started the tractor that turned right over and watched the voltage start around 16v and steadily rise over 10 minutes or so to over 20v. I varied engine rpms and even turned on all lights and AC and reduced to idle and voltage stayed over 20v.
So pretty sure the regulator is gone, but after a call to a parts place, they couldn't find a regulator. Anyone know if its part of the alternator?
$442 for that!

thanks

rich

 

[richied2003]

Looks like it’s answered in another thread. Not a cheap fix, looks like I’ll need an alternator...$442 Anyone ever get one repaired?

 

[K5lwq]

Take it to a alternator/starter rebuild shop. They will make it better than a new one.

 

[richied2003]

So an update and request for advice. I finally got the alternator to a repair shop that fixes them. The owner is very good and knowledgeable. He's tested the alternator every which way he could, and it works just fine putting out 14.2 volts. Under a heavy load it drops a bit he said as expected. He said there is a 2 prong sense line connector, he even disconnected it and the alternator still put out a solid 14.2 volts.
Soooo, anyone have an idea on what the heck can be happening while on tractor that causes the voltage to rise to over 20v? After 15 min or so its literally out of the 20v range on my multi-meter...I need to switch to the 200 v range to get a reading. Note, other than the meter reading, there is no indication of a problem anywhere on tractor, all lights , AC, engine etc run just fine no blown bulbs etc. I found the high voltage when the old battery go dead needing to jump the machine a few times, even after running/mowing,and replaced it. Before doing so I measured voltage at battery terminals and discovered the high voltage condition(and because it mysteriously stopped needing a jump start).
The alternator guy suggests checking the battery ground connections which I will do, this makes the most sense. I was gonna have him just replace the regulator anyway for $75, but after checking numbers, he couldn't find a replacement.
I pulled the manual down, found linked in this forum(thanks for posting whoever that was) for the 20 series tier 3, cab model, (4520C). Not terribly helpful though, the alternator section just mentions the two bolts for removal(even says wrong size, both are 12mm, it said bottom one is 14 mm) and the schematic shows a generator not an alternator...so basically its useless to help debug. It just said to replace alternator if over 15.5v, and doesn't even discuss the 3 electrical connections on the back.
Any help is appreciated. I'll be reinstalling this weekend and probably calling a tractor repair place if I can't find a bad ground or something else causing this.

thanks folks!

 

[crashz]

Did you say that you replaced the battery or just charged the old one? I wonder if it could hold a charge, but under load /charge its failing. I'd try that next if your grounds are good.

Tractors are brutal to batteries. They get tossed and jostled all they time they are running.

 

[CH4Ohio]

I know it's a dumb question, but you do have your meter set on DC Volts, right?

Have you tried another multi-meter just to verify your readings since the guy at the shop is getting a different output from the alternator. There's no way that your battery or anything else on your tractor can add to the total voltage, so it is indeed curious that his readings are normal and yours are not.

Just a thought.

EDIT -- Just realized . . . Actually, My Kubota 2002 B model has a separate voltage regulator. It has a dynamo, instead of an alternator though and the regulator is behind the dash. Had the original and a cheap Amazon replacement both go up in smoke last summer. Now has a genuine Kubota OEM replacement in it and, so far so good.

Unless you have a separate voltage regulator I still don't see how mounting the alternator on your tractor could result in different readings than what was seen at the repair shop.

 

[richied2003]

Yep, DC volts... it reads about 14.2 or so initially. After 15 min or so it’s at 19v. So I did replace the battery since it was 6 years old, no difference. Funny thing that got me down this path is that the old battery needed a jump even after mowing for 2 hours. I did and parked it and put trickle charger on. I don’t live where tractor is, came back in a week the charger indicator was still on. Not concerned, 6 year old battery. Tractor starts I mow and no jumping needed. I park the tractor, forgot to connect trickle charger this time, come back in a week and said **** battery probably dead, I measured it and the 6 year old battery is at 13.5v! More expletives, how can that be and the tractor starts right up now. That’s when I first got concerned and found the rising voltage while running. Kept measuring every few and it goes over 20. Alternator guy says the regulator needs to sense battery so I’m gonna go thru the wiring as best I can. Let me I said I don’t trus the schematics because they show a generator, no regulator. Could just be a nomenclature issue due to Korean translation.

 

[ptsg]

I think I would run just a jumper cable straight from the Negative post of the battery to the body of the alternator and measure the voltage again to see it if still creeps. This would figure out if it's a grounding issue.

 

[richied2003]

Great idea! Thanks... I should have thought of that.

 

[Slowpoke Slim]

A long shot, but are you sure it's not the meter?

Sitting there "on" for over 15 minutes straight, measuring your battery?

As a tradesman that works with multimeters almost every day, I learned a long time ago of the value of having a high quality meter when working on and troubleshooting electrical circuits.