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620Doc

620/720 Charging System Failure

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620Doc

The charging system on my Allis-Chalmers 620 has had a catastrophic failure. Apparently, one of the magnets on the flywheel let go which then destroyed the stator. I'm wondering what happened. Did the glue holding the magnet to the flywheel fail? Did the main crankshaft bearing wear sending the stator into the flywheel magnet?

I have found a new stator online. And I have purchased a good used flywheel. But I'm a little leery about putting it all back together with the risk of another magnet on the flywheel letting go again.

Do you have any advise? Are new flywheels available? I don't really want to re-engine the tractor. And would like to keep it as original as possible. I've also seen many members that have fabricated alternators to these motors. Your opinions would all be appreciated.

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720nut

Here's a link to parts

onanparts.com

Would think that if crank were problem you would find excess play in bearings. would lean more to glue or what ever you call it failed

just my $.02

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phillobbezoo

I put a 12 volt alternater on one of mine there's a couple different ways to do it and it's alot cheaper then fixing the Onan charging system, mine fits under the hood with no modifications to the hood and it works great

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maxwood

Hello, here is a link to a site that deals in flywheel magnets and everything related. this site was started when tecumseh engines were popular.

I have reglued magnets on a flywheel using the info from this site.

http://d8491328.m200.plainhost.com/id2.html

http://d8491328.m200.plainhost.com/index.html?1414981750492

Thanks Ken in mi

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jverhaag
quote:Originally posted by phillobbezoo

I put a 12 volt alternater on one of mine there's a couple different ways to do it and it's alot cheaper then fixing the Onan charging system, mine fits under the hood with no modifications to the hood and it works great


id="quote">
id="quote">Any chance you have pictures of your setup?

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720nut

John, I've seen Phillobbezoo (phil) and midnightpumpkin (John) alternator setups and they look well worth the effort. Mine is working but if any problems I will convert to there setup. John is the man any questions on Powermax or Allis Chalmers he can help

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rmjens123
quote:Originally posted by 720nut

John, I've seen Phillobbezoo (phil) and midnightpumpkin (John) alternator setups and they look well worth the effort. Mine is working but if any problems I will convert to there setup. John is the man any questions on Powermax or Allis Chalmers he can help


id="quote">
id="quote">

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rmjens123

I am problems of like manner. I need info to correct charging problems.Have a Simplicity 9020. Owned 1 year.(replaced worn out 4041).Stator has output of 15.6-16.4 ac volts.Had bad rectifier. Bad stator. Used Als advice to check system.Had a spare stator. Rectifiers are pricey.No budget for repairs.Medical bills(thanks to Obama). I bought a regulator/rectifier and installed before replacing stator.I think I damaged it this way.Ran it for 2 months this way. Out put at reg.shows 1.6 now. Any clues whats next? replace reg/rec? Any help is appreciated. Reg/rec. is wired red stator output to ac white reg. output to center.2 black stator ac to other ac. Max9020

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720nut

Ralph, I documented the alternator build on my 620, It's under talking tractors, External 620 alternator. I went with largest lawn tractor battery I could get to give room , 70 amp alt off ebay and fabricated the rest. Very simple setup, one wire and good to go. Mine works very well will be converting 720 as well when time permits.

Try this link;

http://www.simpletractors.net/club2/topic.asp?topic_id=154806

Edited by 720nut

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macallis180

My magnet came loose, and ruined wiring on stator. Same as other members.

Just learn from me = bought a used stator and flywheel=$$$$= from a forum member that bought it from Sandy Lake that was supposed to be good.

Didn't work. Thought it must be either regulator or rectifier. After approx. ??? months, finally spent the big dollars for a new Onan regulator and rectifier = and, yes, you guessed it = still no charging. Apparently the stator is bad.

That was a year ago, and I can not afford any more expense to make the charging happen. Just charge the battery and don't go out after dark!

Hopefully, some day I can afford to put a little alternator on it.

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720nut

Merle, sorry to here that but if you watch Ebay you can pickup mini alternator very reasonable.I bought a new one $100 not cheap but like anything used is cheaper as for rest I built,pulley came from TSC about four bucks.

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JP

This is a common problem with the Syncro systems. They did NOT have the epoxy tech we have now when they built these systems. The biggest issue is debris. It gets packed in around the magnet plates & creates heat. The heat deforms the mag plates (there is >.40k clearance in there) it expands- POOF. The heat will also deform the mag cage & allow it to 'float' in the cast flywheel to slide out & drag on the case (IF you are LUCKY). Yes, You should loctite the screws on the stator AND DO NOT OVER TORQUE the flywheel bolt (Locktite it TOO).

I have used 'new' hi temp epoxy on both the mag cage & the plates with GREAT success. (none in 15 years have ever come back). I will probably start again when I retire.....

IT's a PITA to take the flywheel off.... IT should be done from time to time (depending on use) to clean the area.

Of course... just MHO

JP :D

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gp1200x

I have a Allis CHalmers 620 with a front loader so there is no option to add an alternator to replace my failing charging system. I have multiple sets of regulators and rectifiers and they tested okay so I wasted time thinking they were the issue. I have a spare new stator to install but haven't pulled the engine yet.  Here is what I think.....If I check the AC output on the two black wires it is 17V to 18V  at 1800 and NEVER goes much higher as I rev up the engine. At 18 V I don't think it will recitify (covert the 18V AC to a DC voltage over 9 Volts---correct?) I think either my stator or my magnets are the issue. I am hoping the stator is the problem.   I tried this several times with everything disconnected and I can never get the AC from the two black wires over 20 volts at full high rpm.  Range is always 16 to 20 Volts AC over the entire RPM range.   

Is it the stator or the magnets?   I had the flywheel off a while back and everything looked okay...no loose magnets but did not check each magnet for magnetism.

 

Thanks.....

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720nut

Thanks Wayne shows me real computer literate sm00

I did it with a hub pulley because mine was dedicated loader tractor need to make couple small changes for front clutch setup

Edited by 720nut

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midnightpumpkin
22 hours ago, gp1200x said:

I have a Allis CHalmers 620 with a front loader so there is no option to add an alternator to replace my failing charging system.

On my dedicated loader tractor, I simply replaced the electric clutch with a dual sheave pulley, one runs the loader pump, the other runs the alternator.

Here is a link to my setup Alternator on loader tractor

John U

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