Can I test the amps from my alternator like this?

[rsmith02184]

Hi

I have been having charging issues with my JD4100. I have replaced regulator and battery. What worries me is the wires that go to the regulator from the alternator are getting really hot. The regulator is getting real hot too. Also, the red wire that goes from the regulator to the battery to charge it, is also getting hot.

So, I am suspecting that the alternator might be putting out too many amps. I don't have an inductive meter so I was wondering if I could test the amps by disconnecting the positive cable to the battery and then connecting my multimeter to the positive post and positive cable and take an amp reading.

This is supposedly not a good thing to do on cars because today's cars are full of computers...but this tractor doesn't have a lot of computer parts.

Can I do this?

Do you suspect another problem other than the alternator?

thanks

 

[tbenn7362]

dont put your amp meter inline unless it is rated for the current (60 amps?). Check the voltage at the battery with it running and minimal electrical load(everything off) and then check the voltage with everything on. acceptable voltage range should be 13.8--14.8. if it is in range then i would believe the alternator/ regulator are working correctly.

 

[jinman]

dont put your amp meter inline unless it is rated for the current (60 amps?).

I quoted you, tbenn7362, because what you said needs to be said loudly. Some VOMs have a 10 amp current probe, but the "M" in VOM is "milli-ammeter." That means less than one amp, actually thousandths of an amp. If you put one of these inline with your alternator, you will pop an internal fuse or blow the meter sky high. I used to know several engineers and techs who would build meter shunts to measure high current. Today, I'd suggest a cheap clamp-on gage. They are available at Harbor Freight, Northern Tools, and even Radio Shack. If you want to troubleshoot a problem like this a clamp-on meter is very handy and worth the money.

 

[rsmith02184]

I have one of those small dynamo type alternators....not the heavy duty ones. I think it is a 20 amp alternator. I have a new Ideal multimeter. Does any of this make a difference as to whether or not I can do the test in series?

 

[jinman]

I have a new Ideal multimeter.

What is its maximum current rating? My guess is it is less than 1 amp. Do you have the model of the Ideal multmeter? The image below clearly shows the maximum scale is 10 Amps using the special jack that has a meter shunt built-in.

 

[OrangeJbird]

DO NOT use a multi meter to measure amperage in charging circuit. Use a meter that measures inductance in the wire. ie. clamp on amp meter.

 

[OrangeJbird]

Hi


Do you suspect another problem other than the alternator?

thanks

Bad ground somewhere . . . or regulator problem.

 

[brandoro]

If your voltage is in the correct range and your current from the alternator is still high then the battery could be the problem. See if you can get it checked or swap it with a known good battery and see how it works then.

 

[rsmith02184]

i have a brand new regulator and a brand new battery.

the charging system is working.

it just is getting real hot.

is that normal?

by the way, i have the Ideal multimeter you posted in the picture.

 

[jinman]

i have a brand new regulator and a brand new battery.

the charging system is working.

it just is getting real hot.

is that normal?

by the way, i have the Ideal multimeter you posted in the picture.

When did you first notice the wires getting hot? Did this happen after replacing the battery and regulator? You really need to check battery voltage while the tractor is running and when it is not running. I would measure the voltage at the battery before starting and then again after starting. Then, I would start the tractor and pull the positive lead from the battery while the tractor is running. If the tractor dies or the wires cool off, then you have to suspect the battery. You should be able to turn on the lights and any other electrical loads with the battery disconnected and have them operate normally.

How about glowplugs? Have you checked to see if the glowplugs are operating all the time?

I don't think your wires should be getting hot, but your meter is not sufficient to put inline and measure current. You need to make some voltage measurements as several of us have suggested and maybe get a clamp-on inductive meter if you can't find anything wrong by making voltage readings. You really need to check what voltage is coming from your alternator and then what is going from the regulator to the battery. You might also check for AC voltage that would indicate a rectifier has gone bad.