C100 ammeter doesn't work but its charging

[RED-Z06 2,221]

Its putting out 14.4vdc...but the meter never moves, its plugged in, in the back...is there a way to test it or is the 47 year old gauge likely pooched?

[Achto 27,601]

38 minutes ago, RED-Z06 said:

.is there a way to test it or is the 47 year old gauge likely pooched?

 

First check to see if it is wired correctly. If it is, then it may have just run its course.

[peter lena 8,634]

@RED-Z06 agree wit @Achto  on the possibilities , found related issues , cured by a total wiring check over , connections and corrosion , shorted hook ups . the thing that cured my problems , well horse related anyway , was increased / verified grounding up grades . battery cable ground point to , engine /frame corner , clutch pedal side , 4 ga battery cable , 10-12 ga wire from that to , volatge regulator mount bolts . total check over , pete

[squonk 41,150]

Ammeter has nothing to do with charging. It just reads the charging current. If the connections at the meter were bad, you wouldn't have any juice to the key switch to even start it. The meter windings are probably roached.

[gwest_ca-(File Mod) 11,046]

At 14.4 volts the voltage regulator should shut the charging off so no amperage flow which is what the meter reads.

It will likely still be charging but only 1/10ths of an amp which can not be read on the meter.

That is why the voltmeter has become the preferred charging system meter.

That same 1/10th of an amp will raise the battery voltage from 12 to 14.4 volts which is easily noticed.

If you decide to replace the ammeter with a voltmeter they are wired different.

 

The original ammeter is really a voltmeter. Between the posts is a resistor which all the current passes through. The meter reads the voltage drop across the resistor which is proportional to the current flow through the resistor. The ammeter is scaled to display the results in amps.

When an ammeter fails often the first noticeable condition is there is no battery power to the ignition switch. The resistor has failed.

In your case the meter has likely failed.

[RED-Z06 2,221]

6 hours ago, squonk said:

Ammeter has nothing to do with charging. It just reads the charging current. If the connections at the meter were bad, you wouldn't have any juice to the key switch to even start it. The meter windings are probably roached.

 

It does represent charging in the sense...charging vs discharging, normally you'll see it dip during cranking then recover once starting...then settle just to the right of center running.  Mine never moves.  Might take it off and poke around it

[RED-Z06 2,221]

Figured it out...the previous owner had the 2 wires tied to the same post...effectively bypassing the meter.  I put one of the spades back on the other post and assembled it back...now the meter works great...shows about 15 amps after startup 

[squonk 41,150]

1 hour ago, RED-Z06 said:

 

It does represent charging in the sense...charging vs discharging, normally you'll see it dip during cranking then recover once starting...then settle just to the right of center running.  Mine never moves.  Might take it off and poke around it

My point was you can throw the ammeter in the lake and the tractor will still charge of you get it running.

[RED-Z06 2,221]

40 minutes ago, squonk said:

My point was you can throw the ammeter in the lake and the tractor will still charge of you get it running.

Yes, as long as the 2 wires are together.  One fell off and everything went dark..I think I need to add a couple fuses...i havent seen anything yet for the main power or lift circuits 

[kpinnc 12,087]

I add the cheapo digital voltmeters on most of my tractors. When running, if I see 14+vdc, I know I'm good. 12.5+vdc or less, I'm on borrowed time. 

 

The pic below is battery voltage before cranking.

[peter lena 8,634]

@kpinnc thinking of changing over to that type of gauge , any downside?  pete

[kpinnc 12,087]

13 hours ago, peter lena said:

@kpinnc thinking of changing over to that type of gauge , any downside?  pete

 

Not that I know of. Just remember that most guages are not made for exterior use. You may not need marine grade stuff, but I do look for waterproof when I buy them.