M4900 Electrical Problem

[docmx]

I've replaced the battery two times in the last year. Found I had a bad alternator and replaced it at the time of the second battery. Now I find the battery is low again!!!??? Voltage reads at 11.98. Any ideas where I might be having a electrical bleed?

 

[BrierPatch]

Does the M4900 have a seperate voltage regulator or is it built into the alternator? Have you checked the the voltage at the battery when the tractor is running and all your lights on to see if it is charging good? You should see around 14-15 volts at the battery when the tractor is running and should be able to maintain that with all your lights on.

I had to replace the voltage regulator in my B7200 a couple of years ago.

Good Luck,

 

[docmx]

Yes, the voltage regulator is built onto the alternator. I am charging he battery now, but will check voltage when running. If low, got any ideas as to the problem?

 

[docmx]

Just checked the voltage while tractor was running and it was 12.25 at both the battery and the alternator.

 

[BrierPatch]

That sounds too low. It will not charge the battery very well at that voltage. If you turned on all your lights while it was running did the battery voltage slowly start to go down. Try increasing the tractor rpm's to see if the voltage would go up? Can you check the voltage at the alternator with the tractor running, but with the battery dissconnected (check the alternator output)? Can you tell if the belt on the alternator may be slipping?

 

[BrierPatch]

Assuming your alternator is good, since you just replaced it, I am wondering if you may have cruddy connector or lose or broken ground wire/connection comming off the alternator.

 

[BXpanded]

Can you check the voltage at the alternator with the tractor running, but with the battery dissconnected (check the alternator output)?

That's not recommended for alternators. Running without a battery can cause damage.

 

[BrierPatch]

That's not recommended for alternators. Running without a battery can cause damage.

Thanks for Pointing that out! Sorry I got carried away. Don't disconnect the battery or the alternator while the engine is running.

 

[number two]

A battery fully charged reads 12.6 volts(2.1 volts per cell)6 cells on a 12 volt battery.At 12.25 volts,you're not charging.Engine running should be around 14 volts.You've changed the battery twice this year-Either you're not using it much or you've been charging it.No dash indicator that you have charging system trouble?It doesn't sound like you have a current draw problem.To check for a draw,disconnect a battery cable and hook up your test light between the disconnected battery cable and the battery post you removed the cable from. If it lights,you have a draw-disconnect wires or remove fuses until light goes out,indicating the problem circuit.
When I diagnose a no charge situation,I use my grounded test light to check for power at the alternator output terminal-the big one.If it lights,I assume the wiring is OK.You must have a dash light or guage for no charge-if that's not showing anything wrong,it could indicate other problems,which could indicate bad wiring or bad voltage regulator.Maybe have the alternator checked. But it sure sounds like you're not charging.Got to fix it.Good luck and post back.

 

[docmx]

I am getting a low charging indicator light at the dash. I just can't figure out why since I removed the alternator, had it tested...it was bad, and replaced with a new alternator. The tractor ran for an hour or two with the warning light off, then it came on again. It appears as if this new alternator is not charging. I charged the battery last night to full charge 12.6+ and started it this morning...checked the voltage at the alternator and it was 12.6. I guess I will take this new alternator off and have it tested...maybe they sent me a bad one???