Alternator Light

b8200hst4wd · Jun 20, 2001

On my B8200 HST. When I start it the Alternator Light comes on sometimes if I rev it up it goes off other times it goes off by itself. After a hour or so of mowing the light also goes off sometimes it doesn't come on at all. I checked the battery and the fan belt tention. Help!!!

Alex (B8200/HST/4WD/FEL/MidM/Tiller

GlueGuy · Jun 20, 2001

May have blown a diode in the alternator, but could be the voltage regulator. Check the output at the battery. Should be about 15 volts when the tractor is running.

The GlueGuy

Bird · Jun 20, 2001

<font color=blue>Should be about 15 volts when the tractor is running</font color=blue>

I thought it should be about 14.4./w3tcompact/icons/wink.gif

Bird

b8200hst4wd · Jun 20, 2001

I'll do that

Alex (B8200/HST/4WD/FEL/MidM/Tiller

GlueGuy · Jun 20, 2001

Bird,

You're probably right, but I've seen it vary by more than 1/2 a volt on a "properly" running system. As long as it's over 14 volts, I call it good (and as long as it's not over 15 volts)....

In fact, I would check it before and after starting the engine. Off should be close to the rated 12 volts of the battery (a little more), then 14.5 +/- when running. It gets a little more involved to isolate it between the regulator and alternator.

The GlueGuy

Von · Jun 20, 2001

Alex,
The same thing happened to my B8200. Its the Voltage reg. Cost is about $80. Its a real pain to change, you have to take the gas tank out to get to it. Have fun doing it!

Bird · Jun 20, 2001

GlueGuy, I was just ribbing you a bit. It can vary, but I always hope for 14.4 to 14.6 with the motor running and 12.6 with it off, plus or minus a tiny bit.

Bird

patrickg · Jun 20, 2001

12 volt battery is nominally 12.6 volts (lead acid battery has about 2.2 volts/cell). If the battery was run way down cranking a cold engine or running lights with engine off or ... then it might charge as high as 15 volts or a bit more for a while but tapers off as the voltage of the battery rises (assuming a good battery and charging system). You might expect something like 13.8 - 14.2 volts if everything is OK and tractor has run long enough to replace energy removed to start it. Volt meters are NOT the last word in batt monitoring. An amp meter is a good tool and easy to install. An amp meter will show rate of charge and discharge (except starting current) if wired correctly. An "E" meter (see solar or alternative energy sites/suppliers) tracks energy in and out and R E A L L Y keeps track of the batt and charging system but is beyond the level of interest of most tractor folk.

If you have access to an osciloscope, a look at the alternator output waveform will immediately reveal a bad diode. Output should be symetrical, with one bad diode (out of 6?) there will be a missing contribution from the one diode. A forward and reverse conductivity check with a ohm eater uh err ah ohm meter may also show a bad diode. Sometimes the failure is temperature related and heating or cooling the suspect diodes one at a time will reveal the culprit. Similarly a can of "Freeze Mist" or equivalent could be used to cool the regulator assembly. Cooling or heating the defective part may cause it to work if not working or quit working if it was working, making finding an intermittent much simpler. A can of "Cool Mist" is cheaper than the smallest billable time increment at the repair shop.

Hope some of this helps you or someone else lurking in the woodwork. If in need of further detail, just ask.

Patrick

Von · Jun 20, 2001

Patrick,
There are only a few things that need to be mentioned. First there is not an alternator on the B8200, it has a dynamo which puts out 24v AC. The second thing is the voltage reg. is a sealed unit and is non-serviceable. I went thru the vary same thing and just had to change the voltage reg.

StoneHeartFarm · Jun 20, 2001

<font color=blue> I checked the battery and the fan belt tension </font color=blue>

Have you checked all grounds and connections between the battery and the light?

SHF