hot alternator wires

[elkman]

My Yanmar 1401d 18hp had the alternator connector melt/burn until it didn't connect anymore. When I put in a new connector the wires started to get hot so I disconnected them. From someone who only has rudimentary understanding of electricity I'm at a loss for the analysis of the problem. I hooked a voltmeter to the alternator wires and nothing registered but when I touch the two wires they spark. I also thought that perhaps I got the wires reversed when I hooked them up so I tried them reversed with the same results. What's the next step?

 

[ByronBob]

Sounds like a ground issue. You have a positive touching a negative somewhere.

 

[BB_TX]

Did you have your meter in the AC or DC mode? Don't know if the diode bridge is internal to the alternator or external. Reading directly out of the alternator and before the diode bridge, you need to be on AC. Downstream of the diode bridge you need to be on DC.
Something is obviously causing your alternator to put out too much current. Could be a failed diode bridge, bad voltage regulator, short in the wiring. etc. I don't know anything about the Yanmar 1401d charging circuit. You will probably need a schematic of the tractor to troubleshoot it. Maybe someone on TBN will have a shop manual for one and be able to help.

 

[slowrev]

Hows the battery doing ? Is it charged up ? Gor water/acid in it ? Could be a bad alternator or Battery or short somewhere.
Ben

 

[elkman]

I had the meter on DC current. I'll try on AC. Is the voltage regulator an aluminum rectangle with fins like on an air cooled engine? Can I deduce anything if it gets hot only when the key is turned on, not that I've checked yet? /forums/images/graemlins/confused.gif

 

[mopacman]

if it gets hot with engine not running it probley has shorted diodes. It will not put out any power if it is not hooked up or if the battery is completely dead. Larry

 

[boustany]

The only reason a wire would fry on an alternator is over current (a short circuit) whereby the wire is acting like a heating element/fuse.

Turn off the tractor. Disconnect the fried wire from the alternator. Disconnect the positive side of the battery. Put the meter on Ohms. Check the intact side of the wire (away from the alternator). With the ignition off, is there a low resistance (the same sort of reading you get if you connect the meter leads together) or is it open circuit? Chances are there is a low resistance or short between the wire and the chassis, probably because of insulation failure. Basically if you have a shorted wire, you should fix it yourself.

If this isn't it, I'd suggest you bring it to a dealer, because you could cause some grief or damage fiddling around with the alternator or charging circuit. Some alternators will put out a very high voltage and fry the electrics if something goes wrong. I would do it myself and check the alternator.

It could be the alternator or regulator is bad and the wire is frying because the battery is pushing power through that circuit to ground. I doubt that would be the case because the alternator probably would have burnt up with the wire.

You have to check the alternator with the battery disconnected. If a diode has failed or if the alternator has a short, there will be a low resistance when the positive lead of the meter is one the positive lead of the alternator and the negative lead is on ground.

A lot of alternators have built in voltage regulators these days (its just a $0.10 chip anyhow).

 

[elkman]

Thanks for the help boustany. I've checked the alternator on AC and it puts out 36v at 2000rpm. The circuit is closed when the fried wire is disconnected and the positive battery terminal is disconnectedand the key is off. I looked all over for a wire shorted/insulation worn and could not find one. I disconnected another plug going to the regulator (4 wire) and found the cuircuit (for the two alternater wires) to be closed. Does this mean that all I have to do is replace the regulator? Does it have to be the one for the tractor or will an aftermarket auto regulator work?

 

[boustany]

Hmm.

I think you need the regulator connected to the battery/alternator for the output of the alternator to be regulated.

Obviously 36 volts is the wrong answer: it should be 14 ish DC, but if it measures on AC, then I'd say the diodes are likely fried, but I can't be sure. The thing is, a short circuit on the output (the big wire) could have caused the diodes to fry.

My guess is a bad diode (or two) in the alternator.

While the function of regulators is very similar, I suspect you want to replace a regulator with the same one. I guess if I were on a desert island, I'd try whatever regulator I found,. but I wouldn't do this on my tractor. Unregulated alternators can put out very high voltages which will promptly fry the electronics, lights, etc., on a tractor or car.

Honestly, I'm flying blind here, and I'm worried you are going to damage your tractor. If at all possible, I'd bring it to a dealer or a mechanic.

Failing that, most cities have places which will rebuild alternators for a reasonable cost. I would get a regulator 'just in case'

You might feel better if you check out this site:
http://members.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm . It explains some stuff pretty well.

Good luck

 

[normde2001]

Sounds like you need a regulator/rectifier, (it has the diodes). The 36vac is a normal reading for your alternator without the regulator hooked up. It is the item you mentioned with the heatsink, but, unfortunately, I don't believe there is an aftermarket unit available and oem's are quite pricey.

 

[Harrygoodwrench]

Just a thought,
I'm sure you could retrofit the alternator to something more readily available. I stepped up to a GM 10si alternator off a chevy so I could run more acessories. My alt on my Jinma only put out 29 amps and not enough for spot lights and a electro/hydraulic pump I added. I found that GM alt and it bolted up pretty easy. Had to fabricate a bracket and wire up but the wiring was the easy part. Now I got output up to 80 amps. More than enough amperage and over the counter parts available to rebuild if needed.
You could go the single wire type but they usually require a high RPM to self excite the circuit so you have output. Diesels usually are low RPM and depending on pulley sizes/ratio's may or may not be enough RPM.

 

[Soundguy]

a 10-si 3 wire job would work out great.. just add a diode to p1 from ignition switch to make it automagically excite.. and then no problems..

Soundguy

 

[elkman]

Thanks to Norm and Boustany, I found a new regulator (OEM) for $58 I think it's worth it to not try adapting something else. My question is to Norm; The meter was on AC showing 36V, should it have shown 36V DC and have a diode fried like boustany says might be the case. In that case is the alternater bad too?
Vernon (ELKMAN) Reynolds

 

[Volfandt]

36v AC would be a normal output on the alternator before rectification. Some voltage is lost when it's rectified to DC and more is dropped due to the charging load.

Since you have a separate alternator and regulator charging system, all the electronics, i.e. diodes, SCR's, resistors, transistors etc., are in the regulator. Theres generally 4 diodes that make up the bridge rectifier and one or two more that are the blocking diodes, that is they keep the battery from discharging back though the regulator, wireing and alternator to ground when the engine's off. Sounds like one of these diodes in the regulator may be problem. Unfortunately theres no adj and no repair of it, it's an R&R repair.

As for the alternator, in your charging system all it does is to provide a voltage output dependant upon control from the regulator. Remove the regulator's control and the alternator will put out all it can make as the regulator controls the alternators output. 36vAC is normal for an unregulated alternator.

Switching and controlling all that current produces beaucoup heat, hense the cooling fins on the regulator.

Sounds like you got a pretty good deal on an OEM. Make sure it's properly mounted as it also uses frame ground.

Good luck
Volfandt

Volfandt

 

[boustany]

I mostly have experience with cars not tractors, but I would suspect the dides are in, or very close to your alternator. I could be wrong here, but you can tell probably if there is a heavy wire (6 guage or 8 guage or so) going from the alternatore to the regulator. If it goes from the alternator or something close to the alternator (like a heavy metal box) then thats where the diodes are at.

Every alternator I've seen as long as I can remember the diodes are bolted directly onto the alternator. It would be my guess thats where yours are. Since diodes make AC into DC, and AC should measure 0 volts DC, if you measure AC then chances are the problem is with the dioes.

 

[slowrev]

I agree with Boustany, All alternators I have seen have the diodes built into the alternator. The only exceptions are those that have the alternator built in under the flywheel like small Briggs and other lawnmower type engines and smaller outboard engines.
All External Automotive type of alternators seem to have the diodes built in and an either an internal or external regulator.
Not familiar with your situation though.....
Ben

 

[normde2001]

Some Yanmars, (YM2000/240), have the rectifier in the alternator and will show unregulated, (20-40), DC voltage with the regulator unplugged. Others, (YM1610), have it in the regulator and will show unregulated AC, (20-40vac), with regulator unplugged. 'According to Hoye', there are 5 different regulators. Hope you got the correct one. A parts book or YM1401 owner could tell you for sure or you might check here for reference.

 

[Harrygoodwrench]

Looking at the parts pics I see some most likely have the rectifier remotely mounted in the regulator due to the heat sinks on the case.
Some are obviously just regulators. Most rectifiers I've seen are installed inside the alternator to be cooled by the alt fan. Rectifiers do get hot. Thats why they tell you when using or done using a welder let the machine run for a few minutes to let them cool down
So I would guess his is a external type.

 

[sparkcrazy]

Have any of you guys given thought to a permanent magnetic alternator with no diodes or rectifiers. How fast can these things churn and how much output can they provide before they get too hot? Can they be used to weld steel or to boil water and can they be rewound with thicker wire in the rotor? Has anybody experimented with this? Cheers and hope to hear from you soon. Very important.

crazy

 

[mitch becton]

from what i know about alternators and the burning of wires this is almost always the regulator whether it be internal or external it is called going to full field which means the alternator is putting out every bit of enegry possible . this will burn wires and possibly cause fire to happen also. most of the time a bad rectifier/diode will cause a whining noise when they start going bad also a bad battery will cause the same effect because the alternator is trying to power some thing that is dead and will burn itself up trying to keep up also if this is done for a long period it will burn up the stator and at this point you will need to get a rebuild job. if you found a regulator for $58. and its o/e that was a good deal.