G5200 Not Charging Battery

[Steve Corgan]

I bought a used G5200 that was very neglected, but I've been able to fix everything it needed, except I'm stumped on the charging system. I get only battery voltage when it's running, regardless of the engine RPMs.

Here's what I've done so far in trying to diagnose / solve the problem:

I installed a brand new battery.

I tested dynamo. Disconnected from rectifier, it's putting out about 11-12 volts AC at idle and 29-31 volts AC at high rpms. Tractor doesn't have a tachometer, so can't tell you exact rpms. I took dynamo apart and cleaned it. All looked well, but there was no change in performance afterwards.

I bought a new rectifier on Amazon. I connected new rectifier like old one was connected. Two blue wires from dynamo, red wire to battery positive, black to ground. Yellow and green wires were not connected. No change / still no charge. I returned rectifier as defective and they sent me a new replacement. Nothing changed, do I doubt I got two bad rectifiers. If I disconnect red wire to battery and measure output voltage at rectifier I get 10 volts DC.

I hate throwing parts and money and guesswork at problems, so I'm hoping someone can help. Any help will be appreciated.

Thanks,

Steve

 

[Dave_eng]

Lugbolt, a very knowledgeable forum member recently posted the following on your type of problem:

dynamo diagnosis

the books are jinglish, and IMO hard to follow.

thus I have my own tests

the regulator/rectifier has 6 wires. 2 are the same color, they end up at the dynamo. AC. One is a black ground wire. You will also have a +12v from the slow-blow fuse, and a +12v ignition (key on) and then a wire that runs to a charge lamp (if applicable, but it'll still have that wire).

Typically loss of charging performance is fairly easy to diagnose if you have the know-how, and a digital volt-ohm meter that has any quality whatsoever. A $10 one isn't that, just something else to throw into file 13 when it reads wrong.

The two dynamo wires (usually sky blue) are AC voltage, as said. Start engine, disconnect regulator and test ac output at the regulator connector, between the two dynamo wires. Should be 24V+ and I like to see more than 45 or so at full throttle. If it charges anything it's probably ok, they are a foolproof and extremely simple design that rarely fails outside of seized bearings. OK? Move on. Check your ground at the reg connector. One probe of the DVOM (set to ohms) on the ground pin in the connector and the other pin on a good ground, frame, transmission, etc. Must be clean. If you have more than a few ohms of resistance, your ground or harness is suspect

onward. Find your wire that comes from the battery. Backprobe the regulator connector. Now put your DVOM on DC volts. One probe goes to your connector, the other goes to the battery +. Should be under 500mv, or 0.500v. Ok? Move on. More than 0.5v? You have either a harness problem or a bad connection at the fuse, or whatever.

Last wire that will affect charging is what I call the "trigger" wire...it turns the reguator "on" so to speak, via the key switch. That one gets 12v when the key is on. Same as the last test, backprobe the connector with the key on. One probe of the DVOM in the connector and the other to the + battery terminal (use the post not the cable). You want to see less than 0.5v on the meter. If you see more than that, harness, fuse block, keyswitch, etc. Follow your wiring diagram. If you do see less than 0.5v, that circuit is not suspect, and there's a possibity you have a bad regulator.

Ideally you want to test everything AROUND the regulator because testing the reg itself isn't always conclusive. Thus, once you know you have AC voltage from the dynamo, you have good ground, you have +12v from the batt and ignition switch, the only component left is the reg. Process of elimination.

Electrical diag is not all that hard or it can be. It's all what you make of it. Don't put too much thought into it because it'll bite you. It's simple for the most part

speaking of being bit, be careful around the dynamo wires when testing. There's a little bit of voltage there and it's ac voltage, so it can bite you.

The problem is rarely the dynamo. far more likely a wiring or regulator problem

Dave

 

[BruceP]

I assume you have the 'owners manual' which contains the schematic. I just looked at it and here are the checks I would make:

1) Before starting engine, ensure that the RED wire on the RR (rectifier/regulator) is at battery-voltage.
(There is a fuseable-link between battery+ and the RR you are validating here)
2) Connect meter from battery+ to the RED wire on the RR. (use clips so the meter STAYS connected)
3) Start engine and observe reading (if over 50mv [0.05v]...you have found the problem)
4) With engine running - also check from battery- to the BLACK on the RR (if over 50mv [0.05v]...you have found the problem)
5) With engine running - check AC volts across blue wires on RR

IMPORTANT NOTE for #5 above: Your meter needs to be able to measure TRUE RMS AC volts. If your meter is only able to read AC volts at 60hz, it will NOT give accurate reading at the MUCH higher frequency which the dynamo generates.

ALSO NOTE: According to the schematic, the RR on the G5200 does NOT have a 'trigger' wire from the keyswitch....if you are using a RR which reqires 'trigger', you may need to customize things a bit to get it to work.

Let us know how this works out for you. Depending on your measurements, we may be able to direct you to other areas of the electrical system.

 

[Steve Corgan]

I assume you have the 'owners manual' which contains the schematic. I just looked at it and here are the checks I would make:

1) Before starting engine, ensure that the RED wire on the RR (rectifier/regulator) is at battery-voltage.
(There is a fuseable-link between battery+ and the RR you are validating here)
2) Connect meter from battery+ to the RED wire on the RR. (use clips so the meter STAYS connected)
3) Start engine and observe reading (if over 50mv [0.05v]...you have found the problem)
4) With engine running - also check from battery- to the BLACK on the RR (if over 50mv [0.05v]...you have found the problem)
5) With engine running - check AC volts across blue wires on RR

IMPORTANT NOTE for #5 above: Your meter needs to be able to measure TRUE RMS AC volts. If your meter is only able to read AC volts at 60hz, it will NOT give accurate reading at the MUCH higher frequency which the dynamo generates.

ALSO NOTE: According to the schematic, the RR on the G5200 does NOT have a 'trigger' wire from the keyswitch....if you are using a RR which reqires 'trigger', you may need to customize things a bit to get it to work.

Let us know how this works out for you. Depending on your measurements, we may be able to direct you to other areas of the electrical system.

Thanks so much Dave and Bruce. I'd already made continuity / resistance checks before posting, so when Dave and you mentioned the trigger wire, that was foremost in my mind.

The old RR had 5 wires, 2 blue dynamo, red to battery, and black to ground, plus it had a yellow wire that wasn't connected to anything. I looked and looked for somewhere to connect the yellow but couldn't find anything.

The new RR has 6 wires, all the aforementioned colors plus a green wire. So, I rigged a jumper wire from + side of battery and connected it to the yellow terminal on RR to serve as the trigger and voltage came up to 14.42 volts dc at the battery. I was delighted. I moved the provisional trigger wire to the green wire and got 14.54 volts dc at battery. I think this is all good isn't it?

Next I identified an accessory terminal on key switch that turns on and off with key (there's only one) and I made the trigger wire. My only question now is should I connect to the yellow or green wire on new RR? Or does it matter? Green is giving me .10 vdc more output, but yellow matches color on old RR. Thanks again for the help.

 

[Steve Corgan]

I forgot to mention that the G5200 doesn't have a charge lamp or gauge.