[eeyankee]

I have a GT-235 garden tractor. When I run my tractor without the PTO engaged, it runs fine. As soon as I engage my PTO, my battery light comes on. I assume that either the voltage reg is bad or the PTO is drawing too much load. Any ideas? Thanks for the help.

dominick

 

[man4mopar]

If you have a DC amp clamp you can quickly test and see what it pulls for amperage both full circuit at battery and individual item PTO etc.

Or you can disconnect the PTO connection and ohm it out. Some times things change though when loaded vs a low voltage ohm test. Take your running voltage 13-14.5 and divide by the ohm reading and you have your amp draw. That said things change when loaded/heated etc, resistance increase due to heat/reactance/inductance or decrease from expansion and short out. Math for such things, amp clamps are quicker

 

[MichaelTJD60]

Do you have just a GT235 or a GT235 with the electrical generator/outlet on it?

Sent from the MTF Free App

 

[eeyankee]

Do you have just a GT235 or a GT235 with the electrical generator/outlet on it?

Sent from the MTF Free App

GT235 with no outlet. It is a 1999 model.

 

[eeyankee]

I did some tests from the service manual. Seems my alternator may be the issue, it is only putting out 33 volts vs the required 40 volts on my 9A regulated alternator. Its weird, the light went out yesterday...need to keep an eye on it.

 

[man4mopar]

When you found the 33 volts AC off the stator was that engine at operating/high rpm? 33 volts AC full wave rectified is enough to make 46.6 volts DC. Then the voltage regulator will adjust it down. As it is permanent magnet rotor that capable 46.6 volts DC will drop when load is applied. I don't know the efficiency of that regulator to tell you how many amps you can get before it no longer can make the 13-15 volts.
My guess if your stator ohms out good both cold, warm and you are shy on voltage 33 Vac when should be 40Vac you have weakened earth magnets on the rotor.
Have you measured voltage at battery with everything on pto engaged? Should be between 13-15 volts.

 

[CFoote]

This series tractor (LX,GT,GX) seem to have a rough time with this battery light. It plagued my LX for a couple of years as well. I would triple check all your ground connections -- even if it doesn't appear there is corrosion on the connectors, clean them up anyway. With the light flickering on and off, it would lead me to believe that its a ground issue. Just my $.02

Chris

 

[eeyankee]

When you found the 33 volts AC off the stator was that engine at operating/high rpm? 33 volts AC full wave rectified is enough to make 46.6 volts DC. Then the voltage regulator will adjust it down. As it is permanent magnet rotor that capable 46.6 volts DC will drop when load is applied. I don't know the efficiency of that regulator to tell you how many amps you can get before it no longer can make the 13-15 volts.
My guess if your stator ohms out good both cold, warm and you are shy on voltage 33 Vac when should be 40Vac you have weakened earth magnets on the rotor.
Have you measured voltage at battery with everything on pto engaged? Should be between 13-15 volts.

I had the engine running at high RPM's when 33 volts was measured, regulator at 7.12 amps. The battery was measuring 12.5 volts when running, no PTO engaged. Not sure if the light went out due to me running the engine and possibly charging the battery enough or if it was a loose connection. Since it only happens when I engage the PTO, I am going to see if it happens again this week...sure it will, nothing goes away. Are you saying the battery should be at 13-15 volts when running similar to a car?

One good thing I realized this weekend, I did replace the engine last year (purchased form small engine warehouse) and I have a 3 yr warranty from B&S. Looks like they will cover parts and labor...

Thanks for the feedback, good info.

 

[man4mopar]

I had the engine running at high RPM's when 33 volts was measured, regulator at 7.12 amps. The battery was measuring 12.5 volts when running, no PTO engaged. Not sure if the light went out due to me running the engine and possibly charging the battery enough or if it was a loose connection. Since it only happens when I engage the PTO, I am going to see if it happens again this week...sure it will, nothing goes away. Are you saying the battery should be at 13-15 volts when running similar to a car?

One good thing I realized this weekend, I did replace the engine last year (purchased form small engine warehouse) and I have a 3 yr warranty from B&S. Looks like they will cover parts and labor...

Thanks for the feedback, good info.

Yes I would be looking for 13-15 volts. 12.5 volts will charge and maintain if it keeps that with required loads but is near absolute minimum. I would suspect your charging the battery is what is keeping the light off and when you engage the PTO your 12.5 volts will drop.
Have you ohmed out the stator?
Making sure all connections are clean at connection surfaces is good advice by Cfoote.

 

[eeyankee]

Yes I would be looking for 13-15 volts. 12.5 volts will charge and maintain if it keeps that with required loads but is near absolute minimum. I would suspect your charging the battery is what is keeping the light off and when you engage the PTO your 12.5 volts will drop.
Have you ohmed out the stator?
Making sure all connections are clean at connection surfaces is good advice by Cfoote.

I have not ohmed out the stator...what value should it see?

 

[man4mopar]

I have not ohmed out the stator...what value should it see?

The ohm readings will depend on how the stator is wound, be it single phase, 3 phase then wye or delta. And if they supply a ground to the voltage regulator with the coil end wires.


If you have a tech manual the information should be in there. They would have coil resistance +/- it will be low resistance like 1 to 2 ohms , and the coil to ground resistance, if they ground the coil the coil tap will have slightly more resistance to ground then the grounded tap.
My guess is they do not ground the coil if single phase and if 3 phase is Delta wired meaning none should read to ground. If one reads to ground they all should read to ground, if only one ohms to ground that is likely a ground connection ran with stator coils to supply a ground for the regulator.
I don't have a schematic, tech manual or hands on experience with a GT235 to give more accurate information.

 

[Harryc]

To the best of my knowledge that warning light on the GTs measures stator output, but you really need to look in the tech manual for that machine. With that said I've seen it caused by a bad cell in a battery, the voltage regulator, and a bad ground. My opinion is that one of these other conditions throws off the circuit sensing the stator output. Get yourself a tech manual. You're into an area where you really need one. For example you say the stator output is 17% low, but do you know the actual tolerance for it? If it's 15% tolerance and that light is intermittent ... well you'd have a good clue then. Forgetting about the warning light for a moment, your main mission at this point should be to get your charging system working. As stated you want to see 13.5 to 15vDC across those battery terminals at WOT. I'm going to toss a guess out there and say you need a VR. We'll see ...

 

[man4mopar]

I would ohm that stator before replacing a voltage regulator. If the stator is shorted it could wreck the new voltage regulator.

My google search for gt235 stator I see two wires. That means it would be single phase if the internet is correct

What does your meter read in ohms lead to lead?

What ohm readings do you get each wire from stator to engine block?

What is the ohm reading from engine block to battery ground?

What ohm reading do you get between the two wires from stator?

Disconnect VR battery connection and start engine. What DC voltage do you get from the regulator at low rpm and high rpm?

Can also check for AC voltage from the regulator to see if the rectifier bridge is working. Do you see AC voltage ?

 

[eeyankee]

Thanks to all for the ideas, I am going to do some testing this weekend.

I used the tractor last night and no light after 2 hours of mowing...

The Battery voltage was 13.2 volts at full speed, not sure what changed except that I unplugged and plugged all the components back.

I will keep an eye on it and see if it changes or drops.

Thanks again.

 

[Craigers]

Need to revive an old thread.

I also have a GT235 and my battery light constantly stays on. I just replaced the battery (needed to as the old battery had square posts with a horrible connection).

I checked voltages on the voltage regulator and here is what I've found (I have a 3 wire reg, 2 yellow & 1 red).

With the regulator unplugged, the voltage from each yellow wire coming from the engine (I have to assume coming from the stator?) is about 11VAC.

With the regulator plugged in, the bottom yellow wire is showing about 27VAC consistently, the top yellow wire cycles from 0 to 27VAC.

With the regulator plugged in, the red wire voltage is less than 1V.

This leads me to believe the stator or alternator is bad, not the voltage regulator.

Anyone know what kind of ohm reading I should get across the two yellow wires? Is that likely my issue?

 

[man4mopar]

Need to revive an old thread.
I checked voltages on the voltage regulator and here is what I've found (I have a 3 wire reg, 2 yellow & 1 red).

And the 4th should be regulator case to chassis common/ground connection. This is important as if it gets corroded and the connection is bad the VR will not function correctly.

With the regulator unplugged, the voltage from each yellow wire coming from the engine (I have to assume coming from the stator?) is about 11VAC.

Sounds like you are taking a AC reading single yellow to chassis common is this correct? What voltage do you get yellow to yellow?

With the regulator plugged in, the bottom yellow wire is showing about 27VAC consistently, the top yellow wire cycles from 0 to 27VAC.

Sounds like you have a bad connection of the wire to stator.

With the regulator plugged in, the red wire voltage is less than 1V.

This leads me to believe the stator or alternator is bad, not the voltage regulator.

From your information I lean towards poor connection to the stator. Either break in the yellow wire you read 24v and 0v intermittently or in the coil of the stator.

Anyone know what kind of ohm reading I should get across the two yellow wires? Is that likely my issue?

It should be very low as it is just a connection to each end of a coil of wire. So depending on how accurate your ohm meter is it may read the same as your meter reads lead to lead.

If you have a break in the connection you would get a OL or high ohm reading.

 

[Craigers]

Sounds like you are taking a AC reading single yellow to chassis common is this correct? What voltage do you get yellow to yellow?

You are correct on the single yellow to common, each around 11VAC. I measured yellow to yellow and saw 27.5VAC. Does that clear the stator as the problem?

It should be very low as it is just a connection to each end of a coil of wire. So depending on how accurate your ohm meter is it may read the same as your meter reads lead to lead.

It was very low. The same as the meter lead to lead, about .5 ohms.

From your information I lean towards poor connection to the stator. Either break in the yellow wire you read 24v and 0v intermittently or in the coil of the stator.

Is it possible the regulator is causing the 0 to 27 VAC problem with the 27VAC reading from the stator?

Great info and thanks for your help!

 

[man4mopar]

You are correct on the single yellow to common, each around 11VAC. I measured yellow to yellow and saw 27.5VAC. Does that clear the stator as the problem?

No but is a good sign for the stator. What do you get for a ohm reading yellow to chassis ground? If it reads OL your stator should be good.

Is it possible the regulator is causing the 0 to 27 VAC problem with the 27VAC reading from the stator?

Great info and thanks for your help!

Yes it is possible the VR is causing the readings you see. Would be a short or transistor hanging closed too long inside the VR.

 

[Craigers]

No but is a good sign for the stator. What do you get for a ohm reading yellow to chassis ground? If it reads OL your stator should be good.




Yes it is possible the VR is causing the readings you see. Would be a short or transistor hanging closed too long inside the VR.

Checked the ohms from stator to ground, it read OL.

Anything else I should check before ordering a new VR?

 

[man4mopar]

Checked the ohms from stator to ground, it read OL.

Anything else I should check before ordering a new VR?[/QUOTE

The new VR should fix your issue. If you haven't yet load test the battery for good measure. The VR is bad per your testing but a poor battery can shorten the life of the new VR. Most places that sell batteries test for free.

Nice work!