JD 4100 voltage regulator/rectifier is smoking

[rsmith02184]

I have a JD 4100. Has operated fine for many years. Yesterday I was driving it and I noticed the discharge light (battery) was on. Then I smelled a really strong burning smell and I saw smoke coming from the shroud underneath the control panel.

Today I took it apart today and found that the voltage regulator/rectifier was all burned up. A new one costs $125. The guy at the shop says he would prefer to look at it to see if there is any other problem. I can't afford that right now. So I ordered the new regulator and I am hoping that is the problem.

In the meantime, can you give me an idea of what could be wrong other than the regulator. A real dumb-downed version will work best for me...I am not super mechanical.

The only recent change(2 years ago) was I bought a new 12 volt battery from an autoparts store. Like I said, it was 2 years ago but is there a possibility that I got the wrong volt/amps battery and it is running too hot????

any other ideas are welcome. I just don't know if I should bring it in to have it looked at.

thanks

 

[Egon]

Maybe charge and check the battery along with all the battery cables and connections. Also try and look at all the wires leading to the regulator for any damage.

 

[CharlieS]

If you'd put the wrong voltage battery in 2 years ago, i'd say you would have had problems before now. For example putting a 12 volt battery in a 6 volt system, a 6 volt alternater or generator would not have provided sufficient charge to the battery, you would have seen a difference in lights if you work at night, and the biggest thing, doubleing the voltage, a starter motor would have gone south pretty quickly, besides spinning at twice the speed. (more or less)
Assuming correct voltage, a battery with a larger than spec amp rating wont generally do any harm. Loads applied to the electrical system only take what they need, thus a larger amp hour rated battery just takes longer to drain (in a no charge condition) but they will take longer to charge up. Think filling a 1 gallon vs a 5 gallon bucket with water.
Not the best example but it gets the point across.
Egon mentions checking out the wiring so check for cracks in wiring insulation and any dead shorts between wires. be sure nothing has rubbed a bare spot that could create issues. If it were a bad battery, you'd have a low/no voltage issue but you could see it in the lights, and starting attempts also. Ditto low voltage from a bad battery connection. (think low battery in an auto)
Its quite possible a winding in the alternator has shorted sending a high voltage spike to the regulator or its possible it was just time for the regulator to go up in smoke.
My suggestion is as mentioned inspect the wiring, and pull the alternator, take it in and have it tested. Many places will test them free, or at most for a minimal charge. If the alternator tests ok, and wiring checks out, then more than likely it was just the regulators time to quit working.

 

[jinman]

I think you need to go over your wiring with a "fine-tooth comb." It is likely that you have a short/partial short somewhere and your alternator/regulator was working overtime thinking that the battery needed charging. Look for rubbed wires that may have shorted out. That man at the shop wanting to check for other problems is your friend. That's terrific advice. If you can't afford the labor charge, most likely you can't afford to burn up a $125 regulator either. By all means, check the alternator and check that the battery will take a good charge on a stand-alone battery charger. Check all electrical wiring and loads for shorts and when you hook things back up, pull all your fuses and put them in one at a time to make sure a problem doesn't pop up. Have everything where you can disconnect quickly if the new regulator shows any signs of overheating. Good luck! I hope you have a successful outcome.

 

[zzvyb6]

I had the same type of problem 5 years ago or so. The cause was a terminal on the female side of the VR that was too light to carry the charge and sense curent. It melted the VR terminal and that was my problem: TWICE.

The second time I saw the melted terminal plastic and the smoked metal clip. I replaced that with a much heavier terminal and things have been just fine since.

I had bought ANOTHER VR as a spare at that time since I was concerned about discontinued parts and this one is out there on the shelf.

 

[Soundguy]

, and the biggest thing, doubleing the voltage, a starter motor would have gone south pretty quickly, besides spinning at twice the speed..

I'd bet you'd be surprised to find out that most 6v starters do just fine on 12v batteries. Many antique tractors get converted to 12v and leave the 6v solenoids and starters in place.

6v windings are heavier copper. wattage ( heat output ) will go up.. but as long as you don't grind on it relentlessly.. it won't 'throw solder'. That was a big reason for the move to 12v.. copper conservation...

to the OP, I agree with Jinman check the wireing out.. look for shorts to ground especially in the larger bat cable and the charge line... anything that could withstand enough current long enough to smoke something in the middle.

alternator/dynamo could have gone south as well.. or.. the reg itself may have just become marginal..

soundguy

 

[rsmith02184]

well i have checked the wiring visually as well as tracing the voltage from the battery to the different connections and all seems well. There are some areas where the wires are not visible but it is doubtful that something rubbed bare there.

i also checked the voltage output on the alternator and it is in-line with what the technical manual says for my tractor.

more and more i think it was just a faulty rectifier.

but one last question: what is the stator and could that be involved with the burned out VR?

thanks

 

[Egon]

Alternator Fundamentals - Alternator and Voltage Regulator Operation

Page 13 should show the stator.

If your generator checks out good the stator should also be OK.

 

[rsmith02184]

ok..here is the update:

I replaced the voltage regulator and everything worked well for a week or so and then the discharge light came on again. This time though, the voltage regulator did not smoke or otherwise burn up.

Using the technical manual, I tried to test all the components to find out what is wrong. I even had a guy who is much more knowledgeable than me come take a look and this is what we found:

I tested what I think is the K7 safety relay doing a continuity test on the terminals. The manual says I should get continuity between terminals A and B. When I tested them, there was NO continuity. So I figure that relay is bad and needs to be replaced. However, a couple of the other terminals that should show continuity DID show it...so part of the relay seems to be good. Is that possible that part of the relay is good?

I also found one of the diodes but I don't know if it is V1 or V2. Either way I tested for continuity and it also showed NONE either way. So I assume it is bad also. I couldn't find the other DIODE that is listed as either V1 or V2. Any ideas where it would be? I know V3 is under the seat.

I am hoping that by replacing the safety relay and the diode, my charging system will return to normal. But I don't know if the new voltage regulator was damaged too. I took it out and it shows no signs of any internal burning.

The one thing that bothers me is the guy who has more experience than me, said he tested the red wire on the other side of the voltage regulator and he found that it was putting out 29 volts and he said that that meant the regulator was not working properly. Does that make sense and could it have anything to do with the DIODE and SAFETY RELAY being bad?

thanks again

 

[mitch becton]

the john deere 4100 came from the factory 12v it does not have a alternator as most of us know them as. it has a permanent magnet chargeing system which means if you can get you magnet alternator open all you are going to see is a rotor and magnets they are only set to to put out enough power to charge battery and possibly run lights if you have them. if your friend got a reading of 29amps or volts either one the possiblity the alternator/magnet is charging wide open over a period of time wires will burn parts will suffer meaning the regulator/rectifier combo i think you said you already replaced the regulator/rectifier i feel it maybe time make sure magnet alternator is working and if it is start looking at wiring. as far as i know the magnet alternator has only 2 serviceable parts that is the bearing if magnets break or rotor get open wires it has to replaced. and the newer ones you cannot even get open to replace the bearings.

mitch becton