520-h charging gauge reading wrong

[whtractors24 3,335]

My 97 520-H gauge seems to read right when you turn key on but when it’s running it full throttle the gauge reads 16 volts or so . I checked the battery at full throttle with my volt meter and read 14.3 . Do you believe this is a faulty gauge ?

Edited November 2, 2020 by whtractors24

[lynnmor 7,719]

The gauge may be reading too high, check the voltages with both meters with the engine at idle and with the engine off.  If the voltages match with the idle and off tests, the voltage regulator may be leaking some AC that only one meter picks up.

[953 nut 59,271]

If your R/R doesn't have a good ground the voltage output can be high.

[whtractors24 3,335]

It does Match up I tested that. Maybe try my other regulator . 

[whtractors24 3,335]

1 minute ago, 953 nut said:

If your R/R doesn't have a good ground the voltage output can be high.

What is r/r ? 

[whtractors24 3,335]

1 hour ago, lynnmor said:

The gauge may be reading too high, check the voltages with both meters with the engine at idle and with the engine off.  If the voltages match with the idle and off tests, the voltage regulator may be leaking some AC that only one meter picks up.

Thought if it’s putting out to much ac that would make high dc power. At full throttle on my Digital  amp meter I’m at 14.3 and tractor gauge is up near 16 . 

[lynnmor 7,719]

14 minutes ago, whtractors24 said:

Thought if it’s putting out to much ac that would make high dc power. At full throttle on my Digital  amp meter I’m at 14.3 and tractor gauge is up near 16 . 

No, you have a voltage regulator to do just that.  R/R mentioned above means regulator/rectifier.  Did you do the tests I mentioned?  I hope you are using a voltmeter not an ammeter.

[whtractors24 3,335]

50 minutes ago, lynnmor said:

No, you have a voltage regulator to do just that.  R/R mentioned above means regulator/rectifier.  Did you do the tests I mentioned?  I hope you are using a voltmeter not an ammeter.

Yes I did use a volt meter and on it was 14.3 at full throttle but the gauge on the tractor was higher than what volt meter tested at 

[stevebo-(Moderator) 8,495]

Someone mentioned check ground. 

[lynnmor 7,719]

Someone mentioned checking voltage at idle and with the engine off, that didn't happen.

[whtractors24 3,335]

11 minutes ago, lynnmor said:

Someone mentioned checking voltage at idle and with the engine off, that didn't happen.

I did engine off 12.6 

idle 13.2 -13.4

[lynnmor 7,719]

1 minute ago, whtractors24 said:

I did engine off 12.6 

idle 13.2 -13.4

Did that match the tractor gauge?

[whtractors24 3,335]

42 minutes ago, stevebo said:

Someone mentioned check ground. 

Steve I checked ground even ran a jumper ground to regulator still same . I checked voltage behind the gauge while off / running it’s same as battery . However when the machine is off if I’m at 12.6 on my volt meter the gauge on the tractor seems to be reading a tad higher . I’m starting to think it’s a faulty gauge . I will swap the one from my other 520 here today to determine if it’s the gauge . 

[whtractors24 3,335]

11 minutes ago, lynnmor said:

Did that match the tractor gauge?

Not 100% accurate no . I also compared it to my 91 520 that  the tractor gauge is working properly . The 97 seems to be bit high . 

[whtractors24 3,335]

9 hours ago, lynnmor said:

Did that match the tractor gauge?

Ok determined it is in fact a faulty tractor gauge !