Voltage ??

[Kawookie]

I am currently working on a gas farmall 400.. I had to have the starter rebuilt and the guy that did it told me to check the tractor, something not right... I have had tractor for 10 years or so.. I put starter on and it fired right up good... But when I put a voltage meter on anything when it's running I can't get a reading, (test light shows power) but as soon as I turn the key off I get a 12.5 reading just fine... Any ideas where I should start to look?? Thinking key switch?? Thanks

 

[Non-farmer]

Digital or analog meter? Are you seeing 0 volts, or numbers jumping all around? Most digital meters don't like the electrical "noise" old tractors produce when running and show erratic readings. Analog meters don't have that problem.

PS: 12.5 is a bit low. Ideally, you should see 12.7 volts.

 

[560Dennis]

More details please ?
This guy said to check what ?
How long after you stopped tractor did you check voltage ?

 

[da.bees]

Maybe as guy that did it said,"something not right".

 

[used red MN]

Most digital meters don't like the electrical "noise" old tractors produce when running and show erratic readings. Analog meters don't have that problem.

Times 2, this is likely the cause of what you are seeing. Does it have an alternator or a generator?

 

[M-MAN]

You have an open circuit somewhere possibly. Could be from the vr or the switch. Had it happen to my International last year. A new switch and all was good.

 

[Geo-TH,In]

Digital or analog meter? Are you seeing 0 volts, or numbers jumping all around? Most digital meters don't like the electrical "noise" old tractors produce when running and show erratic readings. Analog meters don't have that problem.

PS: 12.5 is a bit low. Ideally, you should see 12.7 volts.

This is my go to meter to measure the batteries amps and charging voltage and charging voltage.
The meter is showing the new battery has 1035 cranking amps at room temp.
Most of the time charging volts is around 13.4 v give or take a little.
If the battery sits overnight a fully charged battery will show 12.7 to 12.6 v.
I have 2, One meter in each pole barn. I wouldn't be without one.