Alternator 100 series MF

keepalive213

Charge light has not worked for some time, battery dying even though its only 18months old.

Tested battery with meter while tractor running, read 12.7 v

Tried testing the alternator (guessing mode at this stage) pulled off both cables and tested alternator spades with multimeter and got no reading.

How can i conclusively check alternator?

Repair or replace?

https://ibb.co/k6L7Rv

Farmer

Start by earthing the small wire (with ignition on) to see if the charge light bulb is ok. If not, check bulb and wiring to ignition switch. This circuit needs to be in place to get alternator output

Edit: I'm assuming when you say that the charge light isn't working, that it doesn't light at all, even when you just turn the key. If it is working when you turn the key, forget the above and focus on the alternator

emaherx

keepalive213 wrote: »

Charge light has not worked for some time, battery dying even though its only 18months old.

Tested battery with meter while tractor running, read 12.7 v

Tried testing the alternator (guessing mode at this stage) pulled off both cables and tested alternator spades with multimeter and got no reading.

How can i conclusively check alternator?

Repair or replace?

https://ibb.co/k6L7Rv

If your trying to get a reading between the 2 spades it should be zero that's why the light goes out. Your chassis is Earth. You need to measure between chassis (or negative pole on battery) and the spade.

Also the alternator won't work properly open circuit so readings might not be useful without battery connected.

If battery light not working it could be just that line from switch to bulb to small spade on alternator.

With engine running and ignition on there should be 0 volts between large and small spades. But with tractor engine stopped and ignition on there should be a voltage difference.

Also simple check, if ignition light is blown (or a fuse?) tractor will not charge. Cheaper than an alternator.

orm0nd

emaherx wrote: »

If your trying to get a reading between the 2 spades it should be zero that's why the light goes out. Your chassis is Earth. You need to measure between chassis (or negative pole on battery) and the spade.

Also the alternator won't work properly open circuit so readings might not be useful without battery connected.

If battery light not working it could be just that line from switch to bulb to small spade on alternator.

With engine running and ignition on there should be 0 volts between large and small spades. But with tractor engine stopped and ignition on there should be a voltage difference.

Also simple check, if ignition light is blown (or a fuse?) tractor will not charge. Cheaper than an alternator.

+1 check the bulb and fuses etc,

30 to 70 euro should recond your own alternator if it's faulty


might be no harm to get the wiring tidied up a little as well

emaherx

orm0nd wrote: »

+1 check the bulb and fuses etc,

30 to 70 euro should recond your own alternator if it's faulty


might be no harm to get the wiring tidied up a little as well

And +1 on the wiring.
Nice pre made looms here:
http://www.tractorelectrics.ie/index.php?option=com_content&view=article&id=6&Itemid=10

satstheway

emaherx wrote: »

And +1 on the wiring.
Nice pre made looms here:
http://www.tractorelectrics.ie/index.php?option=com_content&view=article&id=6&Itemid=10

Off topic but where would you get an indicator switch for a 398?

orm0nd

satstheway wrote: »

Off topic but where would you get an indicator switch for a 398?

anything like this

https://www.dhfarmmachinery.com/products/indicator_switch_1682977.html?filter_set

emaherx

satstheway wrote: »

Off topic but where would you get an indicator switch for a 398?

https://www.johnconaty.com/MASSEY-FERGUSON-INDICATOR-ROCKER-SWITCH-1696497M1-p/15642.htm

satstheway

orm0nd wrote: »

anything like this

https://www.dhfarmmachinery.com/products/indicator_switch_1682977.html?filter_set

No it's a rocker switch with centre position off.

keepalive213

Op here, its looking like the alternator and battery are fine.
I disconnected the charging light and temporarily replaced it with a fuse until i get a new bulb tomorrow.
Now the battery is reading 14.6 v when running.
I wouldnt have thought a bulb could make such a difference.
I checked old bulb with multi meter and it seems to be blown.

emaherx

keepalive213 wrote: »

Op here, its looking like the alternator and battery are fine.
I disconnected the charging light and temporarily replaced it with a fuse until i get a new bulb tomorrow.
Now the battery is reading 14.6 v when running.
I wouldnt have thought a bulb could make such a difference.
I checked old bulb with multi meter and it seems to be blown.

You essentially need to turn on the alternator for it to work. With the bulb blown the circuit is incomplete. Glad you got sorted.

keepalive213

Multimeter best tenner ive ever spent

orm0nd

emaherx wrote: »

You essentially need to turn on the alternator for it to work. With the bulb blown the circuit is incomplete. Glad you got sorted.

found that out the hard way years ago, :rolleyes:

keepalive213

Op here, replaced charging light complete with new bulb, charging away 14.5v at the battery, cheap fix!