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Onan 4000w 4.0bf3cr16000b (R1 resistor)


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Old 10-10-2017, 11:49:59 AM
JohnnyJeeper JohnnyJeeper is offline
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Default Onan 4000w 4.0bf3cr16000b (R1 resistor)

Hello all,
I had an issue with my old gen...only run while holding start button, traced it to a bad R1 resistor replaced it and it started right up and ran great for a few hours then started the same symptoms, only run while holding the start button, the new resistor I put in looks like it started to melt...what would make the new resistor fail like that? Should i be looking at some other source of the issue? Any insight here would help a lot, been workin on this old thing fo awhile.
Thanks, J
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Old 10-10-2017, 01:16:18 PM
len k len k is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

If it was same type and size as original you might need to put it into an airflow. I'm not too familiar with which one R1 is on a BF. But if it's the bat charge resistor, it may be a 25 watt resistor dissipating 50 watts, and needs forced cooling from an airflow. Bat charging resistor on similar NH models are by the fan near the brushes.
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Old 10-10-2017, 04:13:55 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

On my BF 3CR/ 16002b 4KW The R1 charge resistor is onan part number 353-0057 and it is back on the generator end by brushes Maybe check to see if you got a bare wire causing a short be sure all brush wires are in the right place check wiring diagram.
I am thinking 5 ohm 25 watt resistor
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Old 10-10-2017, 04:28:01 PM
JohnnyJeeper JohnnyJeeper is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

I checked all brush wires good no bare wires that i see...all checks out good except the resistor, that is the exact one I installed 353-0057...could a bad voltage reg cause the resistor to heat and fail? Doesnt seem like it would be the issue but i am stumped at this point, could it just be a bad resistor out of the box? I think it said on the box it was made in 2009.
Thx
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Old 10-10-2017, 05:07:21 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Johnny you change the resistor start it and with your volt meter see what the dc voltage is I have not looked at my BF charge for sometime I am thinking it may of been like 18 or 19 volts dc kind of been taking care of my wife and have not been in the garage for sometime I hope she gets better still and then I can get back to my true love GREEN MACHINES but do not tell my wife
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Old 10-10-2017, 05:18:57 PM
JohnnyJeeper JohnnyJeeper is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Thanks Dan,
Hope all is well with the wife...and hope you can get back out in the garage soon!
So install a new resistor and while running test DC voltage from where? Sorry to be stupid here just learning about this old girl...
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Old 10-10-2017, 05:28:19 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

No voltage regulator on a BF. Diode and adjustment (two choices on wiring hook up) on the resistor you changed.
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Old 10-10-2017, 05:41:34 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Check that CR1 charging diode is good. If shorted then resistor may draw hi amps when engine is off.

How's your bat, dead cell maybe and bat only making 10V instead of 12V?? That would increase current thru resistor. Check bat voltage after bat has sat for about a day without use or charging.

If RPM (hz) are high that would increase bat charging amps, but 120VAC voltage would be high also.

Last edited by len k; 10-10-2017 at 06:05:38 PM.
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Old 10-10-2017, 06:36:00 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

like was mentioned there is no voltage regulator on the BF easy to check 12 vdc currant you can check it at the resistor positive on the resistor wire and grd to grd also when running you can test for dc volts at the fuel pump or on electric choke the running speed of the generator determines the voltage ac or dc 1800 rpm 60 hertz 30 rpm per hertz times 60 equals 1800 rpm I run my BF around 124 volts ac so it would be a little over 1800
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Old 10-10-2017, 06:37:33 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Just installed 2 new 6v golf cart batteries those are good to go...could a bad charge diode cause the resistor failure?
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Old 10-10-2017, 06:45:55 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

yes it is possible that it could .. to get hot to the point to melt the resistor you must be getting some really high currant somehow like you said to maybe a bad resistor. I would double check all the wiring and be sure you do not have a hot wire somewhere to ground. The diode is what keeps the battery from discharging when setting dc currant goes one direction.
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Old 10-10-2017, 09:48:22 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

If diode is shorted you will get high amps and no cooling from fan since engine is not turning.

Easy to test the diode, disconnect one end and measure with ohms meter. Should get conduction in one direction and none in other. https://www.smokstak.com/forum/attac...4&d=1344478607
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Old 10-11-2017, 10:23:53 AM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Thanks for all the info, I will recheck all my wires and test that diode and take it from there...I will post what I find.
Thanks again, J
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Old 10-14-2017, 03:29:30 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Ok, all wires are good tested the diode it reads 0 in one direction and around 7.68 in the other direction, so i guess its good, i found a new diode online so i went ahead and ordered it (discontinued part not easy to find so got one anyway) any other ideas or suggestions?
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Old 10-14-2017, 11:00:04 PM
JRinkenberg JRinkenberg is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

I am having the same problem on my generator (4.0 BF-3CR16000B) as you. An open diode and a burned out resistor R1. I checked the parts list and it is part #353-0057 as stated but it is listed at 3.4 ohms and 75 watts. My question for you is where did you pick up/order the resistor and diode? I am looking to buy one of each to fix my same problem.
Thanks
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Old 10-14-2017, 11:37:53 PM
JohnnyJeeper JohnnyJeeper is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Hello,
I found the resistor on ebay ( tims truck mobile truck repair) the diode was harder to find i found 1 one ebay but it was the last one and it was $38 there is another place online that had it for around $50 try searching part number 305-0673 that replaced the old part number...
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Old 10-14-2017, 11:48:27 PM
len k len k is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

A resistor is a$5-8 comodity item item, before you add many layers of excess profits.

Find the ohms, wattage, and convient mounting and look on ebay for a generic.
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Old 10-14-2017, 11:57:41 PM
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

I paid $11 For the resistor but the diode was harder to find and was $38 i think the extra $$$ is for the fancy Onan box it comes in...
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Old 10-15-2017, 01:49:40 AM
len k len k is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Same issue for a diode it's a commodity item, they are sold by PIV voltage , amps, and style of mounting terminals $2-5 item. Maybe 30 cents in high quantities of 50,000 units that manufacturers buy in

Last edited by len k; 10-15-2017 at 12:42:18 PM.
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Old 10-15-2017, 08:36:39 AM
Chas183 Chas183 is offline
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Default Re: Onan 4000w 4.0bf3cr16000b (R1 resistor)

Can't recall which staker posted this link, but a bridge rectifier has four diodes,
With this model in the link. You can mount it and have a spare.
Just use two terminals of the bridge rectifier in the correct direction.

http://www.ebay.com/itm/4X-4-PCS-50A...19.m1438.l2649

chas183
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