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??? 20 hp onan not charging ???

Started by sawman, April 29, 2006, 11:20:55 AM

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sawman

 Our 20 hp onan seems to have quit charging? We have checked connections etc. Only getting 11 volts with engine running at battery.
Ammeter is not showing any charge, checked meter and it seems to be ok.
Where do i need to look from here? We do not have an external or seperate alternator.
'14 LT40 Hydraulic 26 HP koehler ,massey ferguson 2200 forklift, Case IH D40
Wallenstein FX85

woodbeard

I don't know anything about the non-alternator charging systems, but is it possible the battery is dying?

sawman

 brand new battery less, than 2 month old
last time we sawed about 2 weeks ago, was when we notice it wasn't charging, dad said it started ok yesterday, but did not have enough juice to start it today
'14 LT40 Hydraulic 26 HP koehler ,massey ferguson 2200 forklift, Case IH D40
Wallenstein FX85

johnjbc

I will be watching this one. I have the same problem with the 20 H.P. Onan in my Wheelhorse. ::)
I found a corroded plug pin in the B+  Circuit that I by passed. No help. :(
Then I found 2 cut wires down under the bottom of the dash. Still doesn't charge :(. The only thing is can find is some corrosion on the rectifier but I'm not sure how to test it, or what the reading of the internal charging coil should be ???
LT40HDG24, Case VAC, Kubota L48, Case 580B, Cat 977H, Bobcat 773

VA-Sawyer

There are two major parts to the internal charging circuit.  The first is the "altenator coil" located behind the flywheel. This coil is excited by magnets on the flywheel when the engine is running.  It produces AC current and the faster the flywheel is turning, the more voltage/amps the coil can produce.  You can do an initial check with a multimeter by disconnecting both coil leads from the regulator/rectifier and checking for continuity between the two leads coming from the coil.  There should be about .5 ohm of resistance between the two leads.  There should be a very high resistance between either lead and the case of the engine.  You can verify power output by connecting a fair size lamp ( 12V ) such an older style headlamp ( not the halogen type) across the two leads and running the engine at low to mid RPM.  It should have no problem lighting up the lamp. The coils output isn't regulated and it could produce enough voltage to burn out the lamp at high RPM so start low and slowly increase RPM until the lamp is lit. If the coil is open ( high resistance between the leads ) or shorted to ground ( low resistance between either lead and engine ground ) then the coil is bad and needs to be replaced. You will have to pull the flywheel to remove the coil. If it lights up the lamp then the coil is good and the problem is with the regulator/rectifier unit.
   The rectifer converts the AC ( Alernating Current ) from the coil into DC ( Direct Current ) and the regulator section limits the maximum voltage that is fed to the battery and electrical system.  The RR module is sealed and self contained.  About all you can do is verify that it has a good ground connection and that the other connections are snug. Some of them have cooling fins that stick inside the air baffle and are cooled by air from the fan on the engine. These cooling fins need to be kept free of sawdust and other grime so they can do their job.  Running too hot or shorting the + lead to ground can fry the RR module. They aren't repairable, you have to replace them. THEY ARE NOT CHEAP !
     Don't run the engine with the coil leads disconnected. The voltage in the coil could get high enough to arc across the windings and ruin the coil. I'm not saying it WILL ruin the coil, just that there is the chance. You want to have some kind of 'load ' on the coil such as the lamp used in the check above.
VA-Sawyer

Tom

I don't  know enough about this subject to comment in an educational way, but I had this problem with the external alternator on my 24 Horse Onan and fixed it.  There is a thread somewhere on the forum where someone explained what I did better than I could.

The "charge" light on the sawmill was used as a "tickler".  Without this light, the alternator didn't know to send a charge to the battery.  My light burned out.   I replaced the light with with an in-line resistor and the system began working again.


I did a search:  ;D

Link1

Link2

Link3





VA-Sawyer

Tom,
That is true for the external altenator. The current flowing through the indicator lamp is used to 'power' the initial elecromagnetic field for exciting the altenator. On the internal units the permanent magnets on the flywheel do the exciting.
VA-Sawyer

sawman

 Thanks for the input, will try and check it out next week.
'14 LT40 Hydraulic 26 HP koehler ,massey ferguson 2200 forklift, Case IH D40
Wallenstein FX85

MartyParsons

Alternator Output Test Onan
1. Check Battery Voltage with engine not running. If not within specifications Charge Battery before Proceeding to step 2 VOLTAGE ON ALL MODELS IS 12 to 13 VDC

2. With engine Running, check battery terminal voltage ( Regulator Output) Using a DC Volt meter. Voltage output should be within the values specified. If voltage is greater than specified replace regulator- rectifier assembly. If voltage is less than specified proceed to step 3. VOLTAGE ON ALL MODELS IS 13.6 to 14.7 VDC

3. Examine all wires for loose corroded, or broken connections. Check fuses. Repair is needed to assure continunity between Regulator-Rectifier B+ terminal to battery positive (+) terminal. Also Check ground path from battery negitive (-) terminal to regulator-rectifier case. Make sure ground connections are clean and secure. If battery voltage remains low with engine running proceed to step 4

4. Disconnect Both AC stator leads from regulator-rectifier and test the AC voltage at the stator leads with engine running. If AC votlage reads more or less than specified in table 1 proceed to step 5. If AC voltage is as specified but DC voltage is low. Replace the regulator- rectifier. SPEC A 20 AMP ( Approx. 21 VAC @1800 rpm and APPROX 41VAC@3600 RPM  Spec B 20 AMP Approx 29 VAC @ 1800 RPM Approx 57 VAC @ 3600 RPM     ALL 35 AMP  Approx 24 VAC @ 1800 APPROX 47 VAC @3600 RPM

5. Use the Rx1 scale on the ohm meter for detecting an open to ground in the stator ( unit not running) . Disconnect both AC Stator leads from the regulator- rectifier. Connect one ohm meter test lead to the stator lead, connect the other test lead to ground. Reading should show an open ( no continuity). If it doesn't the stator must be replaced. If the reading shows no continunity, measure the resistance of the stator windings by connecting one ohm meter lead to each lead coming from the stator. If resistance reading are as specified and winding are not shorted or open, Low AC Valtage may be due to loss of magnetism, If so, Blower wheel assembly must be replaced. SPEC A 20 AMP  0.06 to 0.10 Ohms Spec B 20 amp 0.10 to 0.19 OHMS        35 Amp 0.06 to 0.10 OHMS

Hope this Helps you guys. This is from the Onan engine service manual P216, 218, 220, 224
Marty
"A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty." -Winston Churchill

johnjbc

Well I did some checking and it looks like a bad Rectifier 8). Went out in the shed and located that old sealed beam headlight, you know the one I have been saving for years :D. Got my Simpson 260 meter out and tested it no resistance reading :(. Changed the 1.5 volt battery still no go. Changed the 9 volt battery . Now the R100x works :). Found the 1.5 battery terminal was corroded. Now the meter is ready  :D so all I have to do is find some jumpers and spade lugs.
First step is to check the resistance of the winding and it is less than 1 ohm (No expanded scale meter). So I hook up the sealed beam and hit the key and just with the starter turning over the light is coming on. :) :D
Thanks for all the help. The sealed beam tip from VA-Sawyer  worked great. And  I see Marty has all of the meter reading documented. :P
Now all I need to do is find the part number for a new rectifier and get it ordered. 


LT40HDG24, Case VAC, Kubota L48, Case 580B, Cat 977H, Bobcat 773

MartyParsons

Regulator part # 20 amp  WM PART # P07932 ONAN PART # 191-2106
35 Amp WM PART #  P09679  ONAN PART #191-1847
Marty
"A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty." -Winston Churchill

sawman

 went up to the farm this afternoon to see what we could find. When i went to pull the wires off of the rectifier one of them just broke off at the connector. checked the coil as per the instructions, it checked ok, re connected the wire that broke and everything is working again.
asked dad about checking things and he said he just did a visual and had not actually touched anything on the rectifier.

  Thanks to everyone for the suggestions, and thanks to Marty for the info out of the service manual.
'14 LT40 Hydraulic 26 HP koehler ,massey ferguson 2200 forklift, Case IH D40
Wallenstein FX85

sawguy21

Loose or corroded connections are very often the culprit. That spade connector is a lot cheaper than a new regulator.  :D Good job.
old age and treachery will always overcome youth and enthusiasm

Don_Papenburg

Get some of that corrosion inhibitor paste that is used on Al wire into the load center box.
Frick saw mill  '58   820 John Deere power. Diamond T trucks

VA-Sawyer

That Marty is pretty good.... He finds parts numbers, posts prices and even prints info from the service manual. If we could just get him to start buying the parts for us, then I'd consider him GREAT !   :D  :D  :D

VA-Sawyer

MartyParsons

You forgot about me coming to your place and install it also.
What ever it takes to keep you orange guys happy!  ;)
Plank from Ed, Ed and Eddie Says " Wood is Good"

Marty
"A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty." -Winston Churchill

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