YM 2000 Electrical Problems

[Gary2]

Hello All:

I replaced my alternator and regulator about a year ago or so with the 1972 Datsun 510 parts from NAPA as recommended in this forum. The NAPA part numbers are 13-8002 for the alternator and VR521 for the regulator. After finding a short circuit in the fuse block and replacing it with a fuse holder that holds the modern type automotive fuses, the charging system has worked well. That is until several weeks ago when I noticed the voltmeter (aftermarket Sunpro) pegged out to the right. I placed a multimeter across the battery and it was reading 15 to 16 volts so I shut it down. Continuing to look for problems with the motor off I noticed that the factory instrument light bulbs were burned out. I replaced them and they burned out again when turning off the ignition switch (engine not running). They will light up as normal with the engine not running but as soon as I turn off the ignition switch, the bulbs burn out. Then, using the multimeter to check for a voltage spike when turning off the ignition, I was shocked with a voltage that felt like something I use to get from my old lawn mower. The voltage does not register on my old analog voltmeter.

After talking with several people, some think that the increased voltage could only be generated by a coil and that there may be a diode that is not functioning. A local alternator remanufacture checked the alternator and said it was ok. I installed a new regulator and still have the same conditions, high voltage during the engine operation and instrument lights burning out when the ignition switch is turned off when the engine is not running.

Checking for short circuits I have stripped the wiring harness down to single wires and looked over all the wiring. The only way I can get the instrument lights not to blow during ignition shut off is to turn on the head lights or disconnect the two prong plug going to the alternator with poles labeled N & F or disconnect the regulator.

Has anyone experienced this sort of problem? Am I using the right alternator or regulator? This is a great forum and I have learned a lot of good information from all the experience out there. I am considering adapting a Delco one wire alternator to the tractor if I cannot figure it out.

Any help would be greatly appreciated, thanks Gary

 

[California]

I've used the 70's Datsun alt/VR set since early 2004 without problems, so I don't think mis-application is an issue.

Could that spike be AC getting past a bad diode?

 

[normde2001]

If all you are doing to blow out the bulbs is to turn the ignition switch on/off, I would start by replacing the ignition switch, and get a digital meter.

 

[Jagmandave]

I doubt it's a bad ign switch, and if the alt is not turning because he didn't start the motor, then where would he get a burst of a/c voltage? It's a diesel so there's no ign coil or condesor to feed back.............seems like the only place it could be coming from is the alternator somehow, but the alt checks OK.........
It's a puzzler for sure................

 

[Fredex]

Kinda sounds as if the alternator is running full blast all the time. That would mean regulator unable to control alternator - even the new regulator. Possibly a short or ground between regulator and alternator field terminal or same possibilities inside the alternator. If the alternator field is regulated on the hot side then full battery voltage will send it to max output. If it regulates the ground end of the field then a full ground at the field terminal will send it to max output. Might try measuring the voltage at the field terminal of the alternator with it running or maybe disconnecting the field terminal to see if the voltage comes down. If disconnecting the field clears the high voltage then the alternator is OK otherwise not. It is possible that the service guy just tested to see if the alternator would produce full output w/o checking to see if it could be regulated.

 

[FL_Jerry]

I think this is how it goes. The external regulator feeds some voltage back to the Field winding for regulation, the F terminal you see. I think the N is neutral for the windings. The external regulators take care of the voltage sense, IG connections etc.

I don't know if this charging system uses a grounded field input or if it regulates B+ input to the F input, but either way, if it isn't right, the voltage will be too high.

The regulator picks up the sense voltage from some point and gets an ignition sense line too. The IG line is provided by the Fuse box you ran
into...I think.

If both check good out of the tractor, then I would say your A connection or the IG sense line isn't making a good connection and trying to adjust the Field coil and Alternator up.

So, I would start checking continuity of these inputs to the regulator with a meter. When the ignition switch is "on", there should be voltage at the IG input to the regulator. The A input to the regulator is tied to the Batt B+ and I would assume this is the sense line by which the regulator makes adjustments.

I'm pretty sure this is close to how it goes,,,

FL_Jerry

 

[California]

I think this is how it goes. ...

If it might help clarify anything here, I recently put a YM2000 wiring diagram in oldgrizzlybear's 'thermostat' (thermostart) thread.

 

[Gary2]

Fredex:

I checked the voltage at the alternator F terminal with the engine running and it was between 5 and 8 V. The running voltage across the battery was 15. Disconnecting F the voltage at the battery went down to 12 to 13 V and did not seem to be charging. Also, with everything connected and running, I turned the ignition switch off and on and the engine seemed to be laboring more than you would expect from a charging alternator with the switch on.

FL_Jerry:

The following conditions were tested with the engine not running.

1. The F terminal (white/black wire) has 12 V with the ignition switch on. There is continuity to ground with the ignition switch off.
2. The N terminal is grounded.
3. The new fuse block is wired the same as the original with the IG line (yellow wire) taken off a 10A fuse. There is 12 V at the back of the regulator with the ignition switch on. There is continuity to ground with the ignition switch off. In just checking this line I was shocked when I turned off the ignition switch.
4. The white/red wire has 12 V at the A terminal of the alternator, the starter solenoid, the B terminal of the ignition switch and the regulator.

Fredex and FL_Jerry, I am not the sharpest when comes to dealing with electricity; I hope I have checked what you were looking for, if not I can easily check something else. Any idea what is going on?

Could the alternator shop have missed a bad diode? After they checked it the first time I checked the A terminal at the alternator and found it had continuity to the housing so I took it back and they said that was ok.

California, thanks for the wiring diagram.

 

[FL_Jerry]

"There is continuity to ground with the ignition switch off. In just checking this line I was shocked"

So the engine wasn't running and you turned the switch off and it shocked you?

FL_Jerry

 

[FL_Jerry]

Also, make sure there isn't any AC coming out of Alt. Just flip your Meter over to AC and measure from frame to Alt post, or B+.

Jerry

 

[normde2001]

I would be checking the diodes in that alternator about now.

 

[Mahindra35]

If you received a noticeble shock when shutting down you have received
a secondary voltage from some kind of coil or solenoid or relay when the magnetic field collapses
when the power is shut down to the devices coil.

Maybe check the fuel shut off solenoid and circuit on your injection pump or any solenoids that operate any hydraulics that are normally activated with the key ON.

I am not not familiar with your particular tractors entire wiring or hydraulics but your tractor may also have a battery load solenoid that cuts power to your electrical bus when the key is turned off.

Look for what is called blocking diodes that connect to the relay or solenoid and are wired from the positive terminal of the solenoid or relay and then connect to ground.

These diodes are designed to direct the collapsing secondary voltage from the windings of the coils to ground to prevent what you have described.

If one of these diodes has failed there is no path to ground for the solenoid or relay coil and
a momentary high voltage is directed back to circuits of the electrical system.

Blocking diodes are normally installed across the field windings of solenoids and relays,some are internal to the solenoid and wont be found in your circuit.

The diodes look like small resistors.


Denny
//Mahindra35
PC-SYSTEMS

 

[California]

There aren't any solenoids, coils, etc on the YM2000 in stock configuration so far as I know. It's a very simple tractor.

Does this tractor have some option controlled by a solenoid? Front pto clutch, for example?

 

[Mahindra35]

There should be a fuel cutoff solonoid in your diesel injection pump

A Pto Clutch could be a source of high voltage reverse current as you have said.

Essentially "ANY" electrical device on the tractor that uses a coil
even a horn relay.

Any DC coil will "Induce" a much larger secondary voltage when the primary voltage to the coil
is shut off. This is how your lawn mower coil works when a magnetic field passes
over it

It induces a secondary High Voltage when the primary field collapses.

This is why it felt the same to you when you shut the key off as your lawn mower felt.

The horn relay if it even has one would not be suspect in this case because it would only be activated when the horn button was activated.

Do a thorough search for any possible source. A load relay for your battery bus will look almost identical to the starter relay you use to find on Ford Motor vehicles.

I am sorry I am not familiar withn your particular tractor but all vehicles use
these type of devices in some capacity and can be a source for your described problem.

You could disconnect the alternator from the circuit temporarally and
see if you can duplicate the condition.

Denny

 

[Fredex]

Fredex:

I checked the voltage at the alternator F terminal with the engine running and it was between 5 and 8 V. The running voltage across the battery was 15. Disconnecting F the voltage at the battery went down to 12 to 13 V and did not seem to be charging. Also, with everything connected and running, I turned the ignition switch off and on and the engine seemed to be laboring more than you would expect from a charging alternator with the switch on.

FL_Jerry:

The following conditions were tested with the engine not running.

1. The F terminal (white/black wire) has 12 V with the ignition switch on. There is continuity to ground with the ignition switch off.
2. The N terminal is grounded.
3. The new fuse block is wired the same as the original with the IG line (yellow wire) taken off a 10A fuse. There is 12 V at the back of the regulator with the ignition switch on. There is continuity to ground with the ignition switch off. In just checking this line I was shocked when I turned off the ignition switch.
4. The white/red wire has 12 V at the A terminal of the alternator, the starter solenoid, the B terminal of the ignition switch and the regulator.

Fredex and FL_Jerry, I am not the sharpest when comes to dealing with electricity; I hope I have checked what you were looking for, if not I can easily check something else. Any idea what is going on?

Could the alternator shop have missed a bad diode? After they checked it the first time I checked the A terminal at the alternator and found it had continuity to the housing so I took it back and they said that was ok.

California, thanks for the wiring diagram.

Well, 5-8 volts at the F terminal is probably a bit high. That voltage regulates the alt. output which, at 15 volts is high. Disconnecting the F terminal brings system voltage to 12-13. That is a good thing - should cause alternator to stop charging. The shock you received when turning of IGN Sw is probably from collapsing magnetic field in a coil somewhere - in the regulator or alternator field, maybe somewhere else. You didn't say what that regulator terminal connects to.
A puzzler. Shop sez alternator is OK. Regulator is new. One of them isn't right. Either there is a phhhht diode in the alternator or the regulator is doing something funky or the regulator is getting bad data about battery voltage. Checking/adjusting regulators can be done but you have to take the can off and sometimes they are riveted on. One easy check is the wirewound resistors. They are usually under the base. See if one or more is burnt. Also check that on the old reg you took off
On EDIT: Just re-read your original post with more care. You burned out indicator/idiot bulbs and were shocked while turning off IGN SW with egnine not running. I'm going to walk the plank here and put my money on a bad diode in the alternator. The alternator diodes should keep those inductive-kick transients out of the rest of the electrical system. I don't think there is anything else on the tractor that can develop a strong enough kick to burn out the bulbs.

 

[California]

Checking/adjusting regulators can be done but you have to take the can off and sometimes they are riveted on. One easy check is the wirewound resistors. They are usually under the base. See if one or more is burnt.

I think he did as I did, and replaced the original mechanical regulator with a modern potted one. If so, there's nothing to adjust and no resistors visible. Since the problem continued unchanged after replacing the regulator, I would turn my attention to the alternator.

On EDIT: Just re-read your original post with more care. You burned out indicator/idiot bulbs and were shocked while turning off IGN SW with egnine not running. I'm going to walk the plank here and put my money on a bad diode in the alternator. The alternator diodes should keep those inductive-kick transients out of the rest of the electrical system. I don't think there is anything else on the tractor that can develop a strong enough kick to burn out the bulbs.

If he doesn't have any optional equipment then it has to be the alternator, no matter how improbable. There's nowhere else to look. I think at this point I would swap in a rebuilt alternator. I think I paid $29 (72 Datsun no A/C) and that's cheaper than tearing your hair out chasing mysteries.


Gary, can you clarify - no optional front pto, no electric remote hydraulics control, no electric anything aside from headlights and horn?

There should be a fuel cutoff solonoid in your diesel injection pump
...You could disconnect the alternator from the circuit temporarally and see if you can duplicate the condition.

These early Yanmars are about as simple as a shovel. You want to stop the engine, you close the throttle all the way to the end. It stops. There's no electric fuel cutoff, it's apparently mechanical within the injection pump. See the wiring diagram I referenced above. I like your idea to unplug the alternator and see if the problem continues. There isn't a bus relay or horn relay, and the starter solenoid is the only other coil on the machine so far as I know.

 

[normde2001]

"I like your idea to unplug the alternator and see if the problem continues."

He said he did that, and the problem goes away. I agree, buy a $29 alternator. I would still check those diodes.

 

[Soundguy]

Could a key-off solenoid have been added by a prev owner..?? or a low psi charge-fuel pump? Either would benefit from a reverse shunting diode setup that was mentioned earlier..

Soundguy

These early Yanmars are about as simple as a shovel. You want to stop the engine, you close the throttle all the way to the end. It stops. There's no electric fuel cutoff, it's apparently mechanical within the injection pump. See the wiring diagram I referenced above. I like your idea to unplug the alternator and see if the problem continues. There isn't a bus relay or horn relay, and the starter solenoid is the only other coil on the machine so far as I know.

 

[Mahindra35]

I think everybody has a pretty good handle on this one.

If the alternator is out of the circuit and the problem goes away,and it sounds
like everyone that is familiar with these tractors on this thread are pretty sure there are no other "Coils" of any kind then that is your source.

If I understand that you took the alternator to be tested and they simply
put it on a test stand to verify output they would not detect a "leaky diode"
in that manner. A leaky diode could still produce rated output.

Dissassembly and physical testing of the diodes would be the better way
of knowing the condition of the componets.

If he is using a mechanical Voltage regulator remember it uses a coil to
vibrate the contacts and might be a source but that is probably unlikely.

Normally these transiate reverse voltages dont burn out filiments in light bulbs. We are usually more worried about protecting electronic componets
from these spikes such as Ignition modules and Onboard computer componets.

good Luck

 

[Gary2]

Thanks for all the replies:

Measuring the AC voltage out of the alternator is around 90 volts running with the ignition switch on and around 75 volts with the switch off.

To my knowledge there are no other solenoids on the tractor other than the starter. The electrical equipment consists of factory head lights, rear turn signals, NAPA horn wired into the existing horn circuit and a rear halogen work light that I just installed on the pre-wired red/black wire circuit that terminated at the rear axel.

If I disconnect the two prong plug going to the alternator terminals F & N the voltage spike / bulb blowing condition goes away when turning off the ignition switch.

The new regulator is similar to the original with points but the new version does not have adjustment screws like the original Hitachi.

I believe the ignition switch is original because I replaced the key with the JD part number CH12206.

I will return the alternator to the shop and ask them if they will disassemble and check the individual diodes. Thanks for all the responses; this is truly a great forum because of you. Will keep you posted, Gary