Weird electrical puzzler - breaker pops, the PT1850 runs better until it's shut off

[Coyote machine]

The existing alt is dirty, and as excess heat, often from dust/dirt stuck to fan blades etc. can cause electronics to run erratically, and or fail due to lack of cooling needed to dissipate excess heat from the voltage regulator, diodes and the like.
The voltage regulator is at the top of the alt, with the 2 torx screws holding it's rectangular shape in place. If it were my machine I'd thoroughly blow out all evidence of dust and dirt from the existing alt, and fan blades, including using contact cleaner or small doses of Brakleen on the various terminals and connections going to/from the alt.
This might not solve your problem, but it might show visible signs of burnt sections of the alternator that another pic after cleaning could help us verify what may be happening.
Or you could just bolt up the new one and be done with it at this point, hoping that the alt is the culprit.
Do they core charge on those puppies? If not, I'd keep the old alt for possible use by someone else who might be able to get yours rebuilt for a fraction of the cost of a new one; or for you as a rebuildable spare, just in case.
And whatever you do, try like h^5l to keep the new one clean by periodic compressed air use.

 

[Soundguy]

Remember the old days when generic button diodes were in packs on part house floors. If that trio just lost a single button, it could very well be rebuildsble. Heck, in a pinch it could be externally bubba'd with a suitably large piece of silicon, or an old style cutout even

 

[ponytug]

As Mike mentioned, these alternators contain significant quantities of unicorn hair and diamonds.

Deutz is superb at making reliable, compact engines. The flip side to that is that this isn't a New Holland with an extra six inches of room to hang stuff. Also being air cooled, these Deutz engines have rather high air flow over the alternator as it is the primary air source for cooling the engine, and adding extra hardware is likely to cause some part of the engine to get hot because the cooling air is now being deflected. I've done my share of Bubba fixes, but these engines aren't the easiest engines to bubble gum and duct tape things, though I recall another Power-trac owner putting on an external alternator and hanging out the side of the tractor. Sometimes necessity is the mother of invention.

It is hard to find people to rebuild these alternators, but worth it because they are very high quality- look for Iskra/Letrika brand parts, if you can't find Deutz. The diode pack is about $60 on Amazon at the moment. There is a nice troubleshooting article about a similar design alternator here, just bear in mind it is for a car, not this tractor. These alternators function very differently from most US alternators and are therefore wired significantly different from the typical US engine. That makes troubleshooting them a bit different. They are wired to get their starting magnetism through a current draw on a defined source, usually the "Charge" light on the dash. This simplifies the design, and improves the reliability in harsh environments, but it does mean that they behave a little differently. That's why I suggested double checking the battery and ground cables- if they float, it can trash these alternators in nothing flat. If you haven't worked on one of these before, you are likely to find yourself in the swamp in short order. Trust me, I've been there.

For details see the above article. If it were me, I'd replace the brushes and bearings at the same time that I replaced the diode pack.

All the best,

Peter

 

[MikeOConnor]

The new alternator is in. I've attached the photo I took at the "what could go wrong??" moment where the old one was out and the new one was on its way in.

Drum-roll.... Not much change. The charging voltage is 14.6 instead of 14.8, which makes me a little calmer (but probably isn't significant). Tractor starts, runs, didn't pop the breaker while I stood there (about a minute).

So I think I will button it back up, head out to do a project with it and see if I can figure out what accessory isn't working (back to the "fail open" theory).

If all the accessories work, maybe the elves came and fixed it?

 

[MikeOConnor]

Wow! All those posts rolled in while I was typing that last one.

Yes -- the alternator and all the housings were *VERY* dirty. I've been cleaning it wrong for all these years, not realizing that I need to blow out the alternator in addition to the cooling fins. I had to take the housings outside so that I didn't choke to death when I blew them out.

I think I may have replaced an operational alternator, but that's OK. Now I've got a backup.

The weird voltage drop and popping breaker disappeared a few days ago -- so now we have the dreaded "intermittent failure" puzzler. I think I'll just whale on it for a while and see what happens.

Here's a demonstration of how much I love using this machine -- I just bought another one as a backup. Should be here in a week or so.

 

[MossRoad]

You are officially an addict....

 

[Coyote machine]

You are officially an addict....

That's code for: crazi :confused2::laughing:

 

[Coyote machine]

Wow! All those posts rolled in while I was typing that last one.

Yes -- the alternator and all the housings were *VERY* dirty. I've been cleaning it wrong for all these years, not realizing that I need to blow out the alternator in addition to the cooling fins. I had to take the housings outside so that I didn't choke to death when I blew them out.

I think I may have replaced an operational alternator, but that's OK. Now I've got a backup.

The weird voltage drop and popping breaker disappeared a few days ago -- so now we have the dreaded "intermittent failure" puzzler. I think I'll just whale on it for a while and see what happens.

Here's a demonstration of how much I love using this machine -- I just bought another one as a backup. Should be here in a week or so.

You do have a good used alternator. I believe your issue is solved, and an expensive lesson learned, regarding the alternator replacement, unfortunately. But if you have solved the problem then all is well, and you'll know to keep her clean, including the new one coming in soon.
Post some pics of the new unit. Where did you find the 2nd one?

 

[MikeOConnor]

Yup - crazy addict is definitely a match.

I found it the hard way -- called Kristy and sent a check.

 

[Coyote machine]

So next time I tell you not to open the box and to not replace the alternator- what ya gonna do?:confused3: