1975 Ford 4100 Charging light On

pdstonge

New User
Charging Light is coming on after start. Have checked volts at battery while running is 13.4 at 1200 RPM. removed regulator and found trimmer on backside, increased setting and retried now volts are 14.5 at 1200 rpm however light is still on. Addition symptom is now all lights are off at ignition on.
 
(quoted from post at 12:45:28 10/24/22) Charging Light is coming on after start. Have checked volts at battery while running is 13.4 at 1200 RPM. removed regulator and found trimmer on backside, increased setting and retried now volts are 14.5 at 1200 rpm however light is still on. Addition symptom is now all lights are off at ignition on.
believe this is representative of your tractor. You will see the 3 amp fuse between ign sw and gen warning lamp, it is likely blown, thus your symptoms.
pKMRhz4.jpg
 
Depends on which '75 4100 you have. 1975 was the last year for the thousand series and the first year of the x600 series. There was a 4100 model in both series. The thousand series model called the 4100 was the regular 4000 ag chassis model. The x600 series 4100 model was a reduced hp version of the 4600 SU. If you have the earlier thousand series model, then the schematic that JMOR provided is the correct one for your tractor's original electrical system. If you have the later x600 series model, then it is different in that it should have an alternator with an external voltage regulator.
 
(quoted from post at 14:13:47 10/24/22) Depends on which '75 4100 you have. 1975 was the last year for the thousand series and the first year of the x600 series. There was a 4100 model in both series. The thousand series model called the 4100 was the regular 4000 ag chassis model. The x600 series 4100 model was a reduced hp version of the 4600 SU. If you have the earlier thousand series model, then the schematic that JMOR provided is the correct one for your tractor's original electrical system. If you have the later x600 series model, then it is different in that it should have an alternator with an external voltage regulator.
f the later with alternator, look for 4 amp fuse.
 
(quoted from post at 11:53:03 10/24/22)
(quoted from post at 14:13:47 10/24/22) Depends on which '75 4100 you have. 1975 was the last year for the thousand series and the first year of the x600 series. There was a 4100 model in both series. The thousand series model called the 4100 was the regular 4000 ag chassis model. The x600 series 4100 model was a reduced hp version of the 4600 SU. If you have the earlier thousand series model, then the schematic that JMOR provided is the correct one for your tractor's original electrical system. If you have the later x600 series model, then it is different in that it should have an alternator with an external voltage regulator.
f the later with alternator, look for 4 amp fuse.
Thank you Gentlemen, the problem was the fuse. Just for added info I do have the later series with alternator and external regulator. As mentioned the regulator after removal has a trimmer on the backside. I believe this updated before I purchased as it's not painted blue. Again thanks for your help.
 
(quoted from post at 04:39:07 10/25/22) By "trimmer", do you mean a variable resistor, sometimes called a potentiometer or a trimmer resistor?
Hi Sean, I would say variable resistor. It does control the voltage output back to the battery. Not sure of the recommended level but reading at the battery at 1200 RPM I m seeing 13.7 volts now.
 

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