Alternator

[Becharpa]

I just replaced my battery but as soon as I start the Mahindra 2015Hst tractor the battery gauge still shows very low voltage. I'm wondering if my alternator is bad and not recharging my battery. A few days ago I made a mistake and tried to jump my old battery but switched the polar cables on a battery booster, pos to neg and neg to pos and may have screwed something up. I've checked all fuses and all looks ok. Maybe I broke the alternator? tractor does start, but if feels like I have low voltage in the battery as it is sluggish to start like battery is almost dead. it is a new battery. temps have been below zero lately and the tractor is not in a warm barn? I've treated diesel with K1 kerosene and some 911 service stuff but I'm just not sure?

 

[k0ua]

I just replaced my battery but as soon as I start the Mahindra 2015Hst tractor the battery gauge still shows very low voltage. I'm wondering if my alternator is bad and not recharging my battery. A few days ago I made a mistake and tried to jump my old battery but switched the polar cables on a battery booster, pos to neg and neg to pos and may have screwed something up. I've checked all fuses and all looks ok. Maybe I broke the alternator? tractor does start, but if feels like I have low voltage in the battery as it is sluggish to start like battery is almost dead. it is a new battery. temps have been below zero lately and the tractor is not in a warm barn? I've treated diesel with K1 kerosene and some 911 service stuff but I'm just not sure?

Measure the charging voltage with a good digital voltmeter. it should be in the range of abut 13.8 to 14.4 anything lower than 13.8 or so would be a possible problem unless you are at idle.. rev it up to 2000 rpm and see if it is nearer to 14.4 or so. If it is 12.6 or lower. alternator is not working at all.. possible you blew out the diode trio. in the the alternator with the reverse voltage. Alternators can be easily rebuilt.

James K0UA

 

[Becharpa]

Thanks I have a voltmeter and will try that tomorrow. I appreciate the advise.

 

[skipmarcy]

As KOua said, you need to run the engine up in RPMs to excite the altenator before it will charge. Then after it has excited you can let it idle again and it will show a charge if operating correctly. On my 4110 I have to get mine up to at least 1800 RPMs for a second before it will charge - if I just started it and let it idle it would not charge at all no matter how long it runs. Different altenators excite at different RPMs for several different reasons but it only takes a second at that speed and you're good to go. As far as your tractor "dragging" when starting at that low of a temp - this could simply be the cold. You say your tractor starts so this is good considering the temps and no block heater or such. You also need to make sure the cold cranking amps of your new battery are what your tractor requires too.

 

[Dogman125]

I'll have to try that with my 2002 E350 DI. Replaced alternator once, with no result. Dealer here didn't know any answers. But, while cutting the other day, noticed that it was charging. Thanks for the info.