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Ranger Smith

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Posted: 03/22/21 02:20pm Link  |  Quote  |  Print  |  Notify Moderator

Mine would prime then nothing. There are 3 separate relays in there. Search the internet for your model of generator and you will find a maintainence and troubleshooting manual.


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time2roll

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Posted: 03/22/21 02:58pm Link  |  Quote  |  Print  |  Notify Moderator

Most Onan experts want the full serial number to avoid playing 20 questions about what you have.


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DouglasC

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Posted: 03/22/21 03:14pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Most Onan experts want the full serial number to avoid playing 20 questions about what you have.


Model #4KYFA26100K

Serial #B060888956

Built in 2005


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DouglasC

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Posted: 03/23/21 01:49pm Link  |  Quote  |  Print  |  Notify Moderator

DrewE wrote:

Have you checked the 12V fuse on the generator? It's an easy, low-hanging fruit sort of check. Checking that all the connectors in the guts of the generator (through the firewall) are clean and tight is also worth checking/trying.


Double checked my incoming voltage at the generator today and got a reading of 13.55VDC. All connections in the generator look clean and tight.

Never knew that an Onan 4000W generator has a 12VDC fuse. I don't see one. Where is it located?

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Posted: 03/23/21 03:14pm Link  |  Quote  |  Print  |  Notify Moderator

DouglasC wrote:


Never knew that an Onan 4000W generator has a 12VDC fuse. I don't see one. Where is it located?


On mine, it's in plain sight, on the generator itself, right next to the generator-mounted start/stop switch. Looking at some parts manuals, it seems that your spec level (spec K, the last character of the model number) they omitted the fuse. Mine's a spec H generator.





craz z

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Posted: 03/24/21 10:22pm Link  |  Quote  |  Print  |  Notify Moderator

A few questions
On prime does the fuel pump hum like normal?
Checking 12v input is fine what about output to starter?
Can u take out plug to release compression maybe reach in deep an bang on starter?
I'm thinking starter the bendix on the Onan is plastic trash that locks up an falls apart a current meter on the output should help.

I had a bad starter that would work half ass then finally nothing the starter needs to wind up to throw out the gear into the flywheel once locked out nothing happens and seems to go when you least expect it.

If you don't have a slideout Gen it sucks to get to the starter as it's on the back side.

Another option is to see if you can gain access to the fan an turn the flywheel it may unlock the bendix you may get a few more starts but will indicate its time to change the starter.

DouglasC

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Posted: 03/25/21 04:39am Link  |  Quote  |  Print  |  Notify Moderator

The generator is dead! No prime, no starter - - nothing! I checked the voltage at the starter solenoid when the "Start" switched is pressed - - zero volts. So the signal from the control board to send voltage to the starter isn't happening. That's a control board problem. This happened to this generator once before about 7 years ago. A new circuit board fixed the problem then.

DrewE

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Posted: 03/25/21 08:27am Link  |  Quote  |  Print  |  Notify Moderator

craz z wrote:


I had a bad starter that would work half ass then finally nothing the starter needs to wind up to throw out the gear into the flywheel once locked out nothing happens and seems to go when you least expect it.


I had a bad starter for awhile, with what sound like similar symptoms: it had trouble getting the engine over the compression stroke, and would sometimes need a running start to do that. It also cranked over the engine without much vigor. Eventually, it burned out and I had to replace it.

On examining the remains of the bad starter, I found that one of the four brushes was not working properly, which meant the starter had been operating at half power for quite some time. (The starter has four brushes and four poles, unlike many motors that have but two.) It finally died due to some of the coils on the armature burning out, probably due to being stalled or nearly stalled since it lacked torque. At any rate, before that happened, I probably could have repaired it simply by fixing the bum brush.

craz z

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Posted: 03/25/21 04:30pm Link  |  Quote  |  Print  |  Notify Moderator

I'm struggling to find the documentation on the spec K it sucks cause this particular spec is on like every motorhome made in the last 20 years.

I tore one of these down but its been a couple of years. There is a possible fuse to the control board maybe F1 is number.

You could try to take out the switch panel where the start stop is on the genny it could be hiding behind it.

early models (not spec K) did have this fuse near the switch in plain view.

Option 2 is to start taking out the stuff around the control box as there could be another fuse hiding near it.
Bat+ comes direct to starter solenoid ground is on the outside of the frame where all the wires enter the genbox. that solenoid also has the signal to fire the starter I would trace any smaller wires to see where they lead hopefully to a fuse.

there is a pinout to the J1 P1 connector you could backprobe to verify voltages to the control box.

After that control box could be a possibility just cover all your basis as those are silly expensive. the fact you have already replaced it once indicates a short could be hiding in the wiring somewhere.

Onans are great until they are not and if it wasn't for the fancy switch in the cab i would rip it out and use the space for a portable gen as for the cost of the control box alone you can buy any cheappy genny on the market.

DrewE

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Posted: 03/25/21 09:24pm Link  |  Quote  |  Print  |  Notify Moderator

Download your Cummins/Onan RV generator manuals here. You'll have to register (free account) to download them, but they're all there for whatever spec level you happen to have.

The "parts manual" also generally has some service information (troubleshooting guidance, valve clearance specifications, that sort of thing).

* This post was edited 03/26/21 08:33am by DrewE *

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