94 bayou 300 failing stator? AC volts are 31,15 and 15 at idle

[Machias_Mike]

Hi all, 

Just looking for a second opinion before I start ordering parts.  It looks like from the below tests it must be a failing stator. 

Background - quad runs fine but when I use winch it will drain battery, I can then pull start but even after running for 20 mins if I turn it off, battery still dead and does not seem to get charged at all.  Voltage at battery after charging using trickle charger is 12.5.  Start up and voltage shows 13.1 at idle, if I rev it up voltage drops to 12.5.  LED lights also flicker at night even with fully charged battery.   Really more annoying than anything and if it is stator I prob will not change until it becomes more of an issue or maybe during next oil change.

Thanks for looking, appreciate any replies!

 

Stator plug and letters show how I tested.

[ ]  A  [ ]

B      C

   [ ]

 

Checked resistance on stator (manual says .1 to .7) 

A = .7

B = OL

C= OL

Voltage   idle and 3/4 throttle

A = 31/55

B = 15/33

C = 15/32

[Gwbarm]

From you voltage specs it seems your stator is putting out, how is your battery, is it fairly new, sometimes as they age they can corrode on the plates internally, the plates can actually bridge together which will cause charging problems, you might try using a higher amperage charger, maybe a 6 amp, the higher amperage will sometimes break the internal bridge and then it will charge normally. You might also check your voltage regulator for correct operation.

[Mech]

It might have a bad diode in the regulator. I'd check for any Ac on the battery with the engine running.

[Machias_Mike]

battery is less than a year old but is an amazon weize brand.  Seems to work ok.  I can use the winch quite a bit with the atv off before the battery is too dead to crank.  The only symptom seems to be that the charging system only puts out enough to just keep battery at whatever charge it is already at but never seems to have a net gain even after running for a while if that makes sense.  Maybe my expectations are too high and im just used to my yami 9.9 outboard that seems to be able to run two downriggers pretty much constantly as well as electronics while charging battery trolling around at 850 rpms.

I did try keeping the machine running while using winch and it seemed to help a little but hate to have the atv idling for so long.

Checking AC on battery shows .06 volts.  

[Mech]

The headlights are only 30 watts each, so with a tail-light and intermittent loads like neutral lights they only require about 70 watts, and the battery is a 15 Ah and we generally charge batteries at about ten to twenty percent of their Ah rating, so the charging might only be about 1.4 to 2.8 amps.. So the 5 amps for lights and the charging will only be requiring about 7 amps, and that is very likely all the charging puts out.

I'd expect the battery to be going flat even with the engine going and revving while you are using the winch.

Those resistance figures though, which I presume were with the stator unplugged, are all wrong so it looks like the stator is crook. If the regulator was plugged in while you were doing the tests it may be the regulator malfunctioning still.

[Machias_Mike]

Readings are stator unplugged near near pull starter.  The ohm readings say two of the three legs of stator are bad based on the manual  (.1 - .7 ohms is good).  Does the combination of the OL on the two legs and lower voltage the same two mean its going bad?  It still has voltage but shouldnt they all be the same?  

[Mech]

The ohm readings are suggesting there is a break in one of the three windings.  The three windings are arranged as in the attached diagram, and the one good reading is across/through the two windings that aren't broken. Going from the end of either of the two good windings, to the third winding which is broken, gives the OL ohms reading. 

The one good voltage is coming out of/through the two good windings, and the two bad voltages are when it's trying to get through the break in the third winding, which must have it's ends touching, or close enough, to let a tiny amount of voltage jump through when it gets a high enough voltage. The ohm gauge doesn't have enough voltage to jump the gap where the break is.

I'd check the wires at their ends where they attach to the terminals because that's a common place for wires to break, but apart from that I'd say the stator is bad.

 

1990-Bigbear-350.pdf

Edited October 1, 2023 by Mech

[Gwbarm]

I also bought one of the Weize batterys from Amazon, so far i have been fairly impressed with it, but i havent put it through what you have done with your, but so far its been better than the last one i bought, Mighty Max, had trouble with it from the beginning.

[Machias_Mike]

Thanks for the replies.  It seems the stator is failing.  Its really more of an annoyance than anything but hoping to have the time in the next week or two to replace stator.  Thinking of going with one from amazon.  Reviews look pretty good and $45 for a stator and gasket with 4.5 star reviews.  Seems like a no brainer, am I wrong to try it?

[Gwbarm]

Fairly easy job ,getting all the bolts out without breaking one is important. Once you get the cover off just unbolt the old  and bolt on the new and make sure wires are routed correctly 

[Machias_Mike]

Amazon stator and gasket came today.  Gasket was in a weird perforated vaccum sealed thing.  Ripped it trying to get it out but it luckily was on the top so used a bit of gasket seal.   No oil in pull starter casing, 20-30 drops in the part of the case with stator.  

hardest part was scraping old gasket off of bottom part, required lots of patience (red circle)

The new amazon stator didnt line up.  The  'wire keeper' screw was in wrong hole (see pic before i moved to the hole to the right), moved it to open hole to the right.  It fit but still didnt sit flush (theres a 'slot' for it on the cover).  Removed screw and it fit.  Prob not the best solution but with 3 screws in stator and the 2 pickup screws holding the stator wires im not sure there is way for the wires to come loose.   didnt use the included pickup and wire, kept original.  

Other than that it lined right up.  Wires were correct length and grommets fit tight in case,  3 wire electric plug fit (came with female end so you could replace that too but didnt use).

Now showing

13.5v - 13.2v when reved up (was 13.1v - 12.5v)

Ac 35v - 60v across all 3 wires (low was 15v on 2 of them before)

.8 across all 3 wires (2 showed OL before)

Time will tell if it fixes the issue but at least i still got the original 30 yo stator to throw back in.  

[Mech]

Good stuff.

[Gwbarm]

Glad you got it fixed I had the Same problem with replacement didn’t line up exactly like the old one but it was close enough wires came out in wrong place