Can I test the amps from my alternator like this?

[Treemonkey1000]

Make a poor mans clamp on: If you wrap several turns of insulated wire around your alternator output line. Then connect that to your DMM in the AC mode. It will give you a reading. Now getting that reading to correlate to a specific value is where the trickery (and math) is involved. If you have a light or motor drawing a known amount of current you wrap the same number of turns around a single wire say the Hot wire on the AC lead. You can't wrap around the neutral and hot lead. That will give you a AC value for that current.. It would be cumbersome but cheap. I used a similar method to read AC current using a low resistance high wattage resistor to calculate current..
Cheap AC current reading. I don't blame the guy for not wanting to go out and spend more money if he can get it fixed with the resources or tools he has.

 

[Transit]

Tree, That will only give you half the information needed, AC amps. DC amps will be very tricky if not imposable to read. A 50 amp shunt resistor would be ideal, but alas they are not easily available.

 

[Transit]

That's what has been requested more than once. They are having a problem getting a schematic posted. However, the VR is a "black box" and can't be serviced. With a diagram, they could check wire colors, connections and pin-outs.

Can you have "them" E-mail the prints to you and than work on posting them?

 

[John47]

depends.. and not just the adult diaper..

if it is a permanent field type charger....

soundguy

True, but I'm thinking "real" alternator as we have in road vehicles.
We used alternators with built in diode/regulator packs in underground vehicles many years back.
One main problem was dust getting into the main battery isolators, one good jar over a rough patch of road, and the dust became an insulator under the isolator contacts. One dead alternator and four burnt out light bulbs.
I came up with a solution tested it and saved my employer a lot of money over the years with less down time on the scooptrams.
Just part of an electricians job, to save himself work!!

Essentially what happens when you disconnect an alternator from the battery, is the reference voltage is lost, the regulator is screwed!! It doesn't know how to regulate anymore in laymans terms. So the output voltage goes up to many hundreds of volts, smoking the diode pack and regulator.
Yes even a low battery voltage presents some sort of reference!! Albiet it below 12 when a battery is discharged, but it's better than nothing!!!!
Forget linear power supplies where the reference is a zener diode!!! The battery replaces the zener in a charging circuit.

When you have a bad back and the batteries weigh in at around 90 plus pounds, you soon start to THINK!!!

 

[Transit]

So my diagram is not all that far off the mark after all.

 

[Mace Canute]

I don't know if this will help or muddy the waters...I lifted it from CHARGING SYSTEM MAINTENANCE | smallengineinformation.com

"TROUBLESHOOTING GUIDE TO 15/25 AMP CHARGING SYSTEMS

NOTE: zero ohmmeters on each scale to ensure accurate readings. Voltage tests should be made with engine running at 3,600 rpm without load. Battery must be fully charged.

PROBLEM 1: NO CHARGE TO BATTERY

TEST 1: trace B+ lead from rectifier-regulator to key switch, or other accessible connection. Disconnect it from switch or connection. Connect an ammeter from loose end of B+ lead to positive terminal of battery. Connect DC voltmeter from loose end of B+ lead to negative terminal of battery. With engine running at 3,600 rpm, read voltage on voltmeter.

If voltage is 13.8 volts or more, place a minimum load of 5 amps* on battery to reduce voltage. Observe ammeter.

*NOTE: turn on lights, if 60 watts or more. Or place a 2.5 ohm, 100 watt resistor across battery terminals.

CONCLUSION 1: if voltage is 13.8 to 14.7 and charge rate increases when load is applied, the charging system is okay and battery was fully charged.

If voltage is less than 13.8 or charge rate does not increase when load is applied, test stator (test 2, 3, and 4 below).

TEST 2:Remove connector from rectifier-regulator. With engine running at 3,600 rpm, measure AC voltage across stator leads using an AC voltmeter.

CONCLUSION 2: if voltage is 28 volts or more, stator is okay. Rectifier-regulator is faulty. Replace the rectifier-regulator.

If voltage is less than 28 volts, stator is probably faulty and should be replaced. Test stator further using an ohmmeter (tests 3 & 4 below).

TEST 3: with engine stopped, measure the resistance across stator leads using an ohmmeter.

CONCLUSION 3: if resistance is .064/0.2 ohms, stator is okay.

If resistance is infinite ohms, stator is open. Replace stator.

TEST 4: with engine stopped, measure the resistance from each stator lead to ground using an ohmmeter.

CONCLUSION 4: if resistance is infinite ohms (meaning that there is no continuity), the stator is okay (not shorted to ground).

If resistance (or continuity) is measured, the stator leads are shorted to ground. Replace stator.

PROBLEM 2: BATTERY CONTINUOUSLY CHARGES AT HIGH RATE

TEST 1: trace B+ lead from rectifier-regulator to key switch, or other accessible connection. Disconnect it from switch or connection. Connect an ammeter from loose end of B+ lead to positive terminal of battery. Connect DC voltmeter from loose end of B+ lead to negative terminal of battery. With engine running at 3,600 rpm, read voltage on voltmeter.

If voltage is 13.8 volts or more, place a minimum load of 5 amps* on battery to reduce voltage. Observe ammeter.

*NOTE: turn on lights, if 60 watts or more. Or place a 2.5 ohm, 100 watt resistor across battery terminals.

CONCLUSION 1: if voltage is 14.7 volts or less, the charging system is okay. The battery is unable to hold charge. Service battery or replace as necessary.

If voltage is more than 14.7 volts, the rectifier-regulator is faulty. Replace rectifier-regulator."


Did you check the glow plug relay? It's located up in front of the radiator.

 

[RobertN]

I was thinking a sense resister. We use them all the time at work, to measure milliamps on computer memory. But, that's it, milliamps. To get a high power one is not hard, it is just $$$.

Tree, That will only give you half the information needed, AC amps. DC amps will be very tricky if not imposable to read. A 50 amp shunt resistor would be ideal, but alas they are not easily available.

 

[jinman]

Smitty, I think I'd look at Tractor Supply (TSC) in their old Ford section for an ammeter. You can buy them online too, + - 30 or 60 amp. This will give you a calibrated meter with a built-in shunt that you can put inline with your regulator output, if only temporarily, to measure current as you first posted. I think we'll be in the same "boat" as now because we still won't know what is drawing that excess current, but at least you'll have some idea of how much current is being drawn. Of course, if there is AC on the line, it won't tell you how much AC current is being drawn and you might find that the needle fluctuates wildly due to the AC.

EDIT: Do not put this type meter inline with your battery cable between the battery and the starter. When you start the tractor, you will fry the meter due to the excessive starting current.

 

[rsmith02184]

here is the schematic. i hope it is legible.

 

[rsmith02184]

I can't believe the schematic is blurry. I can't win on this thing. I will try it again this afternoon. I am a high school teacher and I can't get to the scanner until 2pm today.

sorry everyone and thanks for your patience.