I just inherited a 2001 AC 300.
Had a dead battery that wouldn't start.
Recharged battery, sat overnight, started up fine.
After running about 45 minutes, the machine died while driving it (moving in 3rd gear). After it died, the battery was drained and wouldn't restart.
This is my first ATV, but if this were a car, I'd say it was the alternator, not the battery.
How can I verify whether the system is producing enough to recharge the battery when running? I know that idling will discharge the battery, but it wasn't idling when it died so there should have been enough power to be recharging the battery.
I could put a new battery in, but I'd have to run it for a quite a while to see if the battery is draining and not getting recharged.
Any suggestions?

 

Recharge the battery with no more than a 2amp trickle charge overnight or for about 12hrs. It should also be disconnected from the machine. Test the battery voltage with a meter and youshould have something around 12.5 volts DC or maybe a little more. Let the battery sit for a few hours (4-6) then recheck it with the voltmeter again. If the battery discharges just sitting there then it is not taking a charge and is tatered. Needs to be replaced.

But, you machine should have a pull start and should run even if the battery is totally dead or bad. That means is could be the magneto not putting out juice or the voltage regulator not letting it get to the battery.

If you can get it running again and put a volt meter across the battery terminals you should have around 14volts. If your battery has already checked out good and you have less than 14volts here it is the regulator or the magneto. IF I was going to check the magneto I would start by checking the wire where it comes out of the crank case as they can ground out there. I think the best way to check a voltage regulator is to trade it out with a known good one. But don't just go buy one as it is about a $200 part and usually cannot be returned if its not what you need.

I would test the battery, then test the magneto to see how much volts it is putting out at the battery while it was running, and then look at the voltage regulator.

Hope that helps and welcome to the forum.

SJ

 

Thanks for the suggestions--I'll give them a try over the weekend. Here's a bit more information too:
At first when the battery was dead, I tried pull starting. It would run for a second or so and shut off.
Then I hooked up a battery charger. With the charger connected, it started. As soon as I unhooked the battery charger, it'd die.
So I charged the battery for a few hours, then let it sit over night. Started the next morning with the electronic start without problems. So we ran it down the road for 30-40 minutes. That's when it died again, with the battery dead and couldn't start it.
Since my post I charged the battery overnight and it started up just fine to load it onto the trailer.
Then someone noticed that there was a disconnected wire in the back, someone said it was the starter solenoid? I haven't had a chance to check the battery charge since then or see if this single wire could have caused the problem.
I'll post again next week after checking things out more.

 

I finally got back to this, here's the deal:
Found a disconnected wire to the starter solenoid.
Charged the battery. After sitting one week, still showed 14-15 volts before starting, so it looks like the battery is holding a charge.
I then noticed that the voltage regulator was completely disconnected. there are two wiring harnesses, one with two wires and one with three that weren't connected. don't know why so I plugged them back in.
After doing that and starting it, I'm reading 19 volts out of the voltage regulator with the two wires, and 19 volts at the battery as well. I'm assuming that the two-wire connector feeds from the voltage regulator to the battery? Seems a little high to me, maybe someone knew it was too high and disconnected it? I've ordered a service manual, but don't know right now what this should be reading.
My dad passed away this summer and that's how I got this ATV, we keep joking that he took some secrets with him--maybe he had disconnected it on purpose?

 

I think you could have a problem with your battery. Since it is showing 14-15volts just sitting there not hooked up to the bike? Should be between 12-13volts. Once it starts you should have between 14-15 volts with the headlights on and the engine revved up to 5000rpm.

I usually start the machine, put the probes onto the battery, then mash the throttle. I usually see about 13.2V then it spikes to like 14.9 or 15.2 and then goes back down to around 13V when the rpms dies off. You are not supposed to keep the throttle revved up for a long period of time.

It also says in the service manual to use an AC multi-meter to get these results so if you are using a different one (especially one with a needle in it and not a digital meter) you may get different results.

SJ

 

The battery in my meter went dead, so I decided not to trust the earlier readings.
After replacing the battery, I only had about 11.6 volts at the ATV battery, but it has also been run a bit without getting recharged, so I think it's losing the charge it originally had.
Then I started the ATV and connected the voltage regulator, still only getting 11+ volts while running.
So now I'm waiting for a battery charger to arrive to restart the process as well as the service manual. I'm betting it's the voltage regulator, but I won't know for sure until I get everything I need to do the testing right.
Perhaps if the voltage regulator is going bad, it might have put out too much voltage at one time, that's why someone had disconnected it. I suppose if it's bad it might also give inconsistent performance--sometimes putting out too much, sometimes not putting out anything at all. Hopefully this week I'll be able to do some better testing.

 

I ordered a good battery charger, changed the battery in my voltmeter, purchased a voltmeter capable of reading A/C, and got the service manual in. Here's where I'm at:
[*]Battery charger indicates the battery is very good and holds a charge.[*]Voltage regulator failed all tests (resistance, voltage). When taking the voltage regulator off, I could see it was definitely blown on the back. [*]Ordered a new voltage regulator and connected it. [*]With the new voltage regulator, I'm getting 14.4 volts while running, so it looks like I'm getting the right voltage back to the battery to charge it.[*]The stator passes all resistance tests.[*]HOWEVER, I'm getting over 100 volts at high RPM from the stator. I don't have a tachometer so I can't tell if I'm at 5000 RPM, but it's very quick to exceed the 60 volts. I'm betting that under 5000 RPM I'm getting 80 volts or so. Either that or my voltmeter isn't giving me the right numbers, but it should...

The manual doesn't say anything about too much voltage out of the stator, but I'm wondering if this led to the original regulator failure.

The wires coming out the stator seem good, so I guess I could run it a while and see if the regulator blows again, or tear into the stator???

 

My service manual says for a 2001 AC 300 the magneto Coil Peak voltage while charging is 30-45volts (yellow to yellow) and the magneto max output is 220W at 5000rpm.

It also says the voltage between the 3 yellow wires coming from the magneto with the engine running at a constant 5000rpm's should be 60Volts. It also says to use ONLY the Fluke 73 meter or the readings may vary due to the internal wiring of the meter. My numbers always seem to be a little higher than the book numbers as well. so the 60 to 80V sounds good to me but the 100V?? makes me think either the meter is reading it incorrectly, it is getting a spike or it the engine's rpm's are too high.

So I agree with you that you should ride it but you may want to check the numbers again and check the rpm's. If you get the same numbers ride it.

The service manual has tests for the magneto testing its trigger and charging resistance and and voltage and making sure its close to the specifications in the manual.

If it passes, then ride on.

SJ

 

good thread, thanks!

 

This may sound to simple to solve your problem, but this is what happened with my brothers ac 500. He replaced the battery but the posts were opposite of the original battery, when he rode the machine hard his weight on the seat shorted across the top of the battery.