Alternator/battery light flashes upon startup..

[RayIN]

I have a 2003 MF 451. The first time I started the engine the battery light was flashing. I asked the MF dealer who was selling it and he said that is normal, rev-up the engine and the light will go out. That is true every time I start the tractor_why?
It's almost like the battery SOC turns on the alternator. One time I drove/used it for ½Hr before the light stopped flashing.

 

[dstig1]

Doesn't sound right to me, but I don't have experience with that brand. It might be worth getting a voltmeter out and checking voltage @ off, at idle and a couple points with higher revs. If it continues to run and start then at least the alternator must be charging.

 

[WranglerX]

Certain alternator makes (like the Bosch on my VW dune buggy engine) requires a rise in rpm to a point it actually initializes charge sequence and ALT light goes out and alternator is producing charge voltage..... IF once you "initalize" alternator sequence and if you put voltmeter across battery and you are getting something like 13.8 to 14.2 (+/-) volts life is good....

 

[34Willys]

Sounds like a bad diode in the voltage regulator. I'd be worried that the light is flashing. That usually means an over voltage, were as the steady light usually means low voltage.
An alternator produces AC that is rectified through diodes, and will produce full power at idle rpm, there should be no need to rev the engine. The old DC generators were different and did need some higher rpms to produce full power do to the old voltage regulars that used 3 sets of points.
Your battery and cable condition could also influence your charging warning light.
Have you checked voltage at the battery when the light is on/flashing? Is the alternator belt slipping? Those are the first things I would check.

Patrick
PS Your dealer is an idiot, or at least thinks you are

 

[Roadworthy]

You're getting some good suggestions. You might also check the condition of the brushes. They could be worn out.

 

[RayIN]

The alternator output is approx. 14V when the light is out. Since the AGCO business owner said that is normal I'll agree with WranglerX. Now I've gotta look to see the alternator brand.

I can run the tractor all day and the GP27 750CCA battery always spins the starter motor normally, and the Perkins engine starts almost instantly.

 

[Mike1955]

You're getting some good suggestions. You might also check the condition of the brushes. They could be worn out.

Roadworthy I am leaning to a loose wire. Hence the light going on and off

 

[RayIN]

Roadworthy I am leaning to a loose wire. Hence the light going on and off

The light goes off when engine RPM's reach approx,1,200-1,500. The AGCO dealer said that is normal operation. Since I created this thread the light has operated this way/normal.