bad alternator?

moojamboo · Jun 7, 2012

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?

stevem5215 · Jun 7, 2012

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.

DieselMonk · Jun 7, 2012

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.

Soundguy · Jun 7, 2012

ditto that. check alt or reg, if external... a bad cell will just make the alt work harder to get volts up...

moojamboo · Jun 7, 2012

is there a way to check if its the regulator vs the alternator? can a belt being too tight cause a problem with charging?

Soundguy · Jun 7, 2012

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...

moojamboo · Jun 7, 2012

If i take the alternator off is that something a local autoparts store could test for me and tell me if its bad?

rasimmo · Jun 7, 2012

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.

BenQ · Jun 7, 2012

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.

moojamboo · Jun 7, 2012

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?

Soundguy · Jun 7, 2012

a multimeter would likely tell you whats wrong... but yeah.. store should be able to test it..

ps.. oem alternator # is SBA185046180

reg is SBA185516030

moojamboo · Jun 7, 2012

so i say we have an external regulator...but i can't seem to locate it. in the manual it shows a regulator separate from the alternator any ideas where i would look for it?

moojamboo · Jun 7, 2012

Thanks Soundguy....if the alternator is factory 1986 is it worth rebuilding? are there specialty places where they rebuild alternators? is there a good place to get ford parts online?

Soundguy · Jun 8, 2012

most towns have mom n pop stores that do gen/alternator and starters. IF it even needs a rebuild.. might be just a 40$ reg.

look behind the instrument cluster for that reg...

moojamboo · Jun 8, 2012

is there a way to test if the regulator is bad with a mulitmeter?

Soundguy · Jun 8, 2012

you can OBSERVE if the reg is bad, using hte meter and the alternator..etc

moojamboo · Jun 8, 2012

i'm fairly new at electrics...is there a way to isolate and test just the regulator? i took the alternator around today and couldn't find anywhere which would bench test the alternator (autozone said they couldn't cause they wouldn't have a part number). so at this point i don't know how to separate the regulator from the alternator in the circuit while trying to diagnose the problem.

how do i tell a regulator issue from an alternator issue with a mulitmeter?

Soundguy · Jun 8, 2012

if you can't test the alt.. it may be pointless.. if the alt was tested good, then you could infer regualtor issues if it did not charge.

find a REAL alternator/starter/generator rebuilder.. they will be able to test it..

deerseeker001 · Jun 8, 2012

i went through this took my alternator to a good electric repair shop tested the out put said it was good.this alternator was a 3 wire i went to a 1 wire alternator and now it works fantastic.