Diagnosis rectifier failure

[Dgilmored 2]

   I acquired my B80 a couple of years ago. It had several issues one of which was electrical. Mainly loose connections and shabby repairs. I cleaned up the wiring and that fixed all the issues. The one thing I noticed was when running, the amp gauge was very erratic, jumping all over the charging side of the scale. Is this normal? I tested at the battery and all was good charging at 14v.

   I haven't had any issues until last April I noticed the amp guage was not moving off 0 volts. I replaced the  rectifier which I believed to be the original with an aftermarket one. I had about 22 hours of running time with the new one when I had a no crank, no start  problem. I chased the issue to the amp gauge. I bypassed the guage and it started right up. While continuing with my fall cleanup I noticed smoke coming from the rectifier area. The rectifier over heated melting the connector plug. I made sure the ground was good on the rectifier. I removed the rectifier knowing it's junk. I tested the stator with a multi meter. This is the first  time I've ever done this and I have some questions. I have read manuals  and viewed some videos for this procedure. The readings on the meter where jumping rapidly all over between 33 and 27 volts and periodically a "1" would appear in front of the  readings technically changing them to 133 - 127v . I don't know if I have a problem with the stator or my  meter  is not giving me a accurate reading.  It's  new , I think I paid about $20 .

     Any thoughts would be greatly appreciated .  Either way I'll  need to get  a replacement rectifier. Has anyone  experienced issues with an aftermarket rectifier. I know oem is the way to go but I can see sellers are very proud of them. 

   

[Ed Kennell 43,119]

It sure sounds like your stator  is putting out an erratic high voltage that is melting the electrical components in the charging circuit.

The stator should put out a steady 25 to 35 AC volts and vary with the engine rpm.      

Is there a fuse in the charging circuit?     Is your meter on AC setting when measuring the stator voltage? 

[ebinmaine 74,611]

Ed has you headed the right way with the issues so I'll say this about the rectifier purchase.

IMHO you may be better off getting a used Good original from somebody like Lincoln at A to Z Tractor in PA.  

[Gasaholic 334]

1 hour ago, Dgilmored said:

 . The rectifier over heated melting the connector plug.

   

This is classic high resistance issue, more so than a voltage issue. 99.9% of the time a melted plug like that is either A) a short circuit in the wiring to whichever terminal in the plug shows the melting, or B.)  a Packard terminal failure (If you look close at them, you'll notice the part that slips over the male terminal tank has a "folded over" tongue that works like a spring clip to give positive contact over a wider area.... and what usually happens is metal fatigue at the area where it is folded over and the tab cracks and/or breaks away resulting in the terminal no longer making solid contact, which introduces the high resistance that caused overheating and melting terminals)   

 

So as above I'd first verify that you are checking AC volts using a meter properly set on AC and connected across the two AC charge wires and getting relatively steady 25 to 35 AC volts -  Meter jumping around can be due to a bad meter, but if it smoothly swings voltage variations (as opposed to "jumping around" instantly) then I'd be wondering if the flywheel magnets came loose (not at all uncommon, especially on engines that have experienced overheating, poor maintenance, or excessive machine vibration)   Cheap meters can of course give suspect results so if you only spent 20 bucks on the meter, throw another 20 bucks into a second meter and compare results .. or buy a GOOD meter (Actron is OK.. Fluke is the best) its a "buy once , cry once" purchase that can last you a lifetime.. My fluke meter was new in 1994 ($98) and still going strong.  

 

If you actually get solid reading you can trust in, then your stator's fine and your issue is likely either a short or a bad terminal - So I'd take a closer look at the Packard terminals first (easiest to diagnose) before suspecting the aftermarket regulator (Though they can have inconsistent results - I got one that was allowing 15.3 DC volts output! - not very good, but usable given I don't run that machine all that much for extended periods... Were I to change uses on the machine I'd probably buy an OEM regulator...(new style ones that bolt to blower housing, can still be adapted to fit where older style "box" regulators were used.)

[Handy Don 14,697]

Good advice there. 

I can (sheepishly) admit that testing AC with the meter set for DC and not being sure of clean, solid connections has thwarted me more than once.

[rmaynard 16,589]

My first guess is that the regulator/rectifier is not grounded properly any longer. Common problem. But first, check the AC voltage coming from the stator. It should be in the 28 to 40 volts AC at 3600 RPM, not connected to the regulator. Remember to put your meter in the AC mode. Next, I would install a known-good or new regulator. The output voltage should be about 13.8 VDC. Check charging voltage with the battery connected as the battery is part of the charging system. If all voltages are correct, see what the ammeter is doing. If it's steady, good. If not, replace it. All of my ammeters on B-80's, B-100's, and C-120's all jumped around. As long as you are charging, just bypass the meter if it bothers you.

[Dgilmored 2]

   Thank you all for reaching out. At least now I have a direction to move which eliminates some of my frustration. I thought I was already for winter 

I did suspect an issue at the rectifier plug. The aftermarket rectifier is slightly larger than the oem so the plug was close, if not touching the amp gauge. I'm also replacing the ignition switch plug and new connectors and wires. A couple of connectors were questionable by not locking in. It was all original. 

   An investment in a new multi meter will help me sort things out with more confidence.