IDIOT LIGHT QUESTION

[degerb]

Hi guys:
I have a 1991 M/F 253 Perkins that I am restoring. I have no history on the tractor, since it was purchased at an auction. None of the idiot lights, guages or tach were working. I have all of them working now except the Alternator light. It doesn't come on when the ignition s/w is turned on, or turned off while the engine is running per the maintainance manual. I do not have an Ohm meter. It is a 3 wire alternator, the Indicator terminal on the alternator I think is supposed to give a ground to the light before starting. When I check the terminal with a meter, with the engine stopped it shows a ground, still no light. When I ground the wire from the light, the idiot light comes on. I checked the voltage across the battery terminals and I get an indicated 12.51V regardless of engine RPM. Its driving me up a wall.. do I need the alternator checked at Napa? I would appreciate any input from you guys!! Thanks Don

 

[DaButcher]

Alt. idiot light connection should be a ground when not charging and have 12+ volts when charging. I don't know if the NAPA test will test that connection or not, but the battery voltage running should be around 14v. so a test is needed. If it passes double check all your ground wires from alt. to battery and to the engine block.

 

[degerb]

Thanks for the input. Undoubtly that is what I will have to do. It's just frustrating when I can't pin it down for certain!

 

[skyhook]

When you say "3 wire" you mean the plug has 2 and then there's a separate
one that goes to the battery! Like this....

if thats the case,,
take "pin 1 " wire and connect it directly to the battery, then start your machine,
you should have 14.5 volts at the battery now.
If you do, your alt is good, do not ground any of these wires,
the alt is at ground.
The pin 2 connection can also be tapped directly into the battery connection,
by a small wire and then (before starting) connect pin 1 to the battery.
Remove pin 1 when you shut your machine down, because pin 1 is only used to
"excite" the alt and get it charging as in when the ignition is turned on.

 

[The kid]

Hi guys:
I have a 1991 M/F 253 Perkins that I am restoring. I have no history on the tractor, since it was purchased at an auction. None of the idiot lights, guages or tach were working. I have all of them working now except the Alternator light. It doesn't come on when the ignition s/w is turned on, or turned off while the engine is running per the maintainance manual. I do not have an Ohm meter. It is a 3 wire alternator, the Indicator terminal on the alternator I think is supposed to give a ground to the light before starting. When I check the terminal with a meter, with the engine stopped it shows a ground, still no light. When I ground the wire from the light, the idiot light comes on. I checked the voltage across the battery terminals and I get an indicated 12.51V regardless of engine RPM. Its driving me up a wall.. do I need the alternator checked at Napa? I would appreciate any input from you guys!! Thanks Don

Don, you didn't say whether this was a diesel or gas tractor. Big difference in wiring, whether or not you actually need an idiot light. ~kid

 

[degerb]

Thanks all for the responses guys. I finally gave up and took the Marelli alt. to a repair shop. It needed a new rotor, a new regulator section and they replaced the bearings. Every thing works fine now idiot light included. So for a couple of hundred bucks I'm back in business. I checked online and with shipping, I might have saved a few bucks but with a local shop at least I can take it back if I have problems.Thanks again you guys are great! Don