L2550 Charging Problem

I have owned this tractor for about 6 years. In the past month or so, the battery has gone from weak to dead. I replaced the battery less than two years ago, not knowing how old the one in it was.

I searched here for threads about charging problems, diagnosis, etc. I have cleaned the battery cable connections, belt is tight, fuses are all good, all the lights burn. I charged the battery with a charger up to 12 volts. What I don't have is the 14 +/- from the alternator, even when the engine at half throttle. I read it at 13 once, but it is not steady.

This has a voltage regulator, took the cover off and didn't see anything suspicious, perfectly clean inside. I installed a volt meter today just to monitor, wired it at the switch on the AG terminal, and it shows the same as my volt meter at the alternator, I'm under 12 volts, and even teaching up the engine it gets to 12, that's it.

These alternators aren't terribly expensive, and I don't mind getting a new one, but I sure would feel better about shelling out the cash if I KNEW that was the problem.

I've read that it's normal for the alternator not to kick in until 1300-1500 rpms. That seem odd to me. I use this around my house, always have. The only time it gets extended use is doing snow removal or hauling firewood, otherwise it is used occasionally, and never a problem until recently.

Any help would be appreciated.

Jim L. said:

I'm assuming that the alternator does not have an external voltage regulator.

If wanting to be absolutely sure, then could dismount the alternator and take it to a shop or auto parts place to have it bench tested. But this test is about the same as you have done, after 5 to 10 minutes should have around 14 volts output.

Having experience a fellow could fix the alternator if it were only the voltage regulator and knew how to look up parts and such and where to get them.

The easy way would be to look at the Denso number on the existing alternator, find a replacement with the same style connector, cross referencing the L2550. That is what I recommend, and you can post the Denso number on this forum and confirm against the available replacements.

Click to expand...

I posted I have an external regulator, or I said I took the cover off of the regulator.

The parts manual I have lists the alternator number is 15253-64010. Seems a popular piece used on many applications. Quite a few places sell them both new and reman.

As an update to my tractor. Dave did provide me with testing info for the alternator and regulator. The alternator tested faulty, plus I found a badly corroded wire to the regulator. So after a couple emails/conversations with Dave, I decided to replace the alternator with a one wire unit and abandon the regulator. I purchased this:

https://www.amazon.com/dp/B00KGIDF9Y/ref=psdc_15719751_t1_B072Z6WR3B

It arrived today, so I removed the old one to see if there were going to be issues mounting the new. I was pleasantly surprised the mounting lugs aligned so no real issues. The one thing I did have to adapt was the pivoting lug on the new unit had a bigger hole than the existing bolt. The old alternator had two pivoting lugs that fit between a casting on the engine. The new one has one lug. I turned a bushing to fit in the new lug that would fit the existing bolt and it tightened up nicely. The adjustment lug was even tapped to accept the old adjustment bolt, easy!

I will have to get a shorter belt, the old belt lets this alternator hang too far away from the engine and I would not be able to put the side cover on. I'll get that fixed tomorrow.

Connected the existing single red hot wire to the new unit and started the tractor. I brought the RPMs up to about 1000 or so and checked the output with my volt meter, it was 14.7!

The only downfall, with the old wiring disconnected (the 3 prong plug to the old alternator is the only thing) all the idiot lights on the dash are on. I had installed a volt meter to see what the actual voltage was doing, the temp gauge is a gauge, not a light. I may add an oil pressure gauge next to the volt meter, I don't need any other. The lights can stay on.