bad alternator?

   / bad alternator? #1  
moojamboo

moojamboo

Bronze Member
Joined
Mar 12, 2011
Messages
92
Location
Nothern Vermont
Tractor
Ford 1710
our Ford 1710 wouldn't start the other day. jumped it and it ran fine. next day dead again. replaced the fan belt because it was loose and had needed to be tightened before with this problem. Still tractor won't start. volt meter on the battery says 11.93 volts jump the tractor on and the batery still reads a steady 11.93 volts even when reved to 2000rpms.

does this mean i have a bad alternator? is there a test i can do which will tell me if the alternator is bad for sure? could it be a bad battery? is there a way to tell a bad battery vs bad alernator?
 
   / bad alternator? #2  
Charge the battery with a charger fully, Then just turn all the lights and accessories on with it turned off and watch the battery voltage. If it goes quickly below 12v after turning everything on then the battery is suspect. If you have a bad cell it will probably drop to 10v and stay there. Each cell is good for 2v of power.
If the Alternator is bad it won't charge like yours. But, the alternator on these also has a voltage regulator you have to worry about. That makes diagnosis more difficult and usually you end up just guessing and trying one or the other, or end up with both of them replaced !

Steve

Ps. I had this problem on my FarmPro Jinma chinese tractor and I bought a delco 3 wire alternator to replace the chinese one. It's worked well ever since. The alternator was $29 for 63amp unit. Out of a 1975 GM product. Bolted right on. Had to rewire a little around the regulator and put a new plug on the alternator end for the field winding.
 
   / bad alternator? #3  
When your alternator is working, you should see at least 13.8V up to 14.7V with a good or dead battery. Doesn't matter. Your case tells me you need either a alternator rebuild, or a new one. Make sure that the alternator isn't slipping in the belt before you run out to replace or fix it.
 
   / bad alternator? #4  
ditto that. check alt or reg, if external... a bad cell will just make the alt work harder to get volts up...
 
   / bad alternator?
  • Thread Starter
#5  
is there a way to check if its the regulator vs the alternator? can a belt being too tight cause a problem with charging?
 
   / bad alternator? #6  
too tight a belt will reduce the bearing life of the alt.. which won't directly, immediatly effect charge..

might be time to take it to the auto store for a checkup...
 
   / bad alternator?
  • Thread Starter
#7  
If i take the alternator off is that something a local autoparts store could test for me and tell me if its bad?
 
   / bad alternator? #8  
every Autozone I have ever been in can do that and the battery while you are at it. I'm sure most others do as well.
 
   / bad alternator? #9  
Not sure about yours but most alternator i've worked with have internal regulators so you'd be looking at rebuild/replace.
some alternators have a wire from the ignition switch to exite the field and get the charging started. again i'm don't know how yours is cofigured.
Your battery voltage is low. it should be about 12.5v after charging. and not be much below 9.5v while the starter is cranking.
 
   / bad alternator?
  • Thread Starter
#10  
our ford has an external regulator. if i take both to the atuoparts store and the batery i shoudl be able to figure out which piece is bad?
 
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