alternator question

Ray IN

Member
The dash indicator light comes on when I turn the tractor headlights on. This is on a diesel 2510 that I just replaced
the alternator on. Speeding up the rpms does not help. Any ideas what is going on here? It is a 3-wire alternator.
 

Check the Voltage with Fast Idle both with no lights on and with lights on..Voltage should remain the same or Higher.

Sounds like your regulator is not working.. ( or your belt is slipping)..
 
Might check your connections on the large gauge wire going to the batteries, if it's been wounded and not carrying enough amps that might do it. Might even be warm where the damage or bad connection is at if there is a bad connection. Would be best to put a voltmeter on the system and watch what happens to the voltage when the headlights are off and then on as well. Please post those voltages for better help.

Really could be just a case of crusty wiring under the dash panel too.
And a Motorola alternator will do it because of the big red isolation diode heat sink on the back of it causes too much voltage drop when the current goes up.
 
What alternator? Deere never came with a Delco 10SI or 12SI if that is what you are calling a "three wire" alternator. If you DO have a Delco on there - just bypass the regulator and see if the light goes out. There is a regulator-bypass port in the back of the alternator. Just stick a sharp piece of metal in the hold like the end of a nail. If you have an OEM Motorola, does it have a piggy-back regulator?
 
Looking at PC957 a Motorola alternator is shown for ALL 2510 serial numbers and there's NO generator listed,that I see.

You have to remember the 2510 was NOT built in the 3010/4010 era (1960 - 1963), it was built in the 3020/4020 era (1965 - 1968).
 
I have a 2510 that is completely original and it has an alternator. The first model year for them was 1966. 2510 came out 2 years after the 3020 and 4020.
 
Ok I checked the voltages. When tractor is first started and the idiot light still on, battery voltage is 12.5. Rev it up a little and light goes off, voltage at battery is 14.5. When lights are turned on, voltage is still 14.5 both at battery and at alternator. Idiot light just barely glows and is only visible at night. So I think it is charging fine, but must be getting some stray voltage somehow. I did rework some of the wiring so I should take another look at that I guess.
 
Not so much "stray voltage" as "voltage drop" somewhere between the alternator and battery and key switch, which supplies power to the indicator lamp causing a difference in potential across and current flow though the indicator lamp.
 
Very good info there, and it helps a lot. Yeah, you've got the 'night glow' issue which does affect some but not all set ups. As assumed, it's a minor issue and mainly cosmetic and can be addressed if desired by placing additional resistor around the idiot light such as to shunt away the current allowing it to glow. But the downside to this approach is that one can bypass so much current that the key fails to turn off the engine. Automotive value used was 10 ohms, but was a wire made of iron such that the power rating was quite significant considering it's length which was from the ignition switch to the alternator wired in parallel with the idiot light circuit. So the power rating for that resistor as an add on device should be 10 watts or better if you want it to last under difficult situations such as dead battery in the winter needing a jump start, etc. that neither of us can fore see at this point. They can be pricey depending on source. eBay with china source will be cheapest, and you'll have to wait for the boat to get here. You could spend as much as $25 from USA sources with shipping and I never go there - the deal is for me, I happen to know it cost them $0.15 to make it in china. You don't always get what you pay for example if ever there was one. Not to go political but back in the day, it cost the same to make it here. If 10 ohm allows the tractor to keep running when you shut off the key then go with 15 ohm or higher. Other solution that may or may not work is to double up on the large gauge charging wire from the alternator to the batteries, but this is doubtful to work as well as the idiot light bypass method. And here I'm assuming your tractor was never set up with an idiot light bypass resistor in the first place which is the real cause of the night glow issue in the first place.
 
Lee, you don't like the diode idea, eh?

One or two diodes in series with the indicator lamp will drop enough voltage to put the light out, and still allow it to function normally in case of alternator failure, and allow the engine to shut off.
 
It has it's uses but installing can be an issue along with getting the right ones. More in favor of the traditional approach in use for decades is the real reason I didn't mention diodes. Resistor method will also give him instant charging at idle and he won't need to rev it up a bit. I personally use two parallel light bulbs in a clearance light and sometimes do have to turn on the heater or headlights in order to get the originally generator equipped chevy to die. So back when it was just one bulb and no resistor, I too would have to rev up the engine and the amp gauge would literally go twang as it pegged to the right with the surge of charging current. Three years of that and one day it stayed over there. Was faster for me to go with two lights than a proper resistor. After of course I replaced the burned out and stuck full on mode voltage regulator. Lesson learned. Your method is quite valid too, so now he has more cards to play with, thanks. If I broke down and got some of those resistors for my own use, I know I wouldn't be able to find them when I needed them.
 

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