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I've been parked for a few weeks so only 2 weeks since last start of gen.  Tried today getting 3 blinking code clicking on prime and clicking on start not even trying to turn over. Tried from dash, from power wall and from gen itself.  Reset gen breaker? Still no start?? 

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I would check cable connections, especially the ground.  Did you try the battery boost? 

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Check the chassis battery voltage.  You will probably find it's low.  Charge it, or jumper the generator and charge everything back up.  

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OK....here is HOW it should work...

IF you start or crank the Genny from the HOUSE batteries, then this should do it....

Crank the Engine.  Let it run a few minutes.

Hold in the BATTERY BOOST button.  THEN immediately start the Genny.  If that does NOT do it....then you have really DEAD HOUSE batteries.  WHY????  The Battery Boost control voltage is HOUSE.  SO, it the House Batteries are really drained.....guess what?  You have NO voltage to close the Big Boy or whatever the Battery Boost Solenoid is called.

THEN....next step.  Find a Car or Truck Jumper cable.  You only need ONE.  Connect the Positive on the Cranking to the Positive on the House.  THAT should do it.  Assuming you have the Engine running.  From there....you need to trouble shoot.

WELL NOW>>>  Still no JOY.  Then it is time to call a tech or IF YOU ARE ABLE.....then shinny or slide UNDER the Genny.  Take TWO jumper cables with you.  There is a Positive and Negative on the back side.  Attach the Jumpers RED to Positive and BLACK to Negative.  I suggest that you stay UNDER there and hold them in place.  The terminals are small.  Then have your assistant crank the TOAD, where you hooked up the Battery Cables.  Then have them START the Genny.  It should start.  THAT tells you that you have a BAD cable or a bad Connection (the Ground Studs are the most common cause) issue.

I was FINE with all my House Power.  Problem was....I had a BAD Ground Stud Connection behind the Battery Box.  I could see the voltage change or the resistance as I moved the battery tray in and out.  I got it where it would start (was on a long trip).  I NEVER moved the battery tray.  When I got home, i pulled the Ground stud nut off on each connection and cleaned them.  Have NOT had an issue since then.  

NOW.....you coach MAY have the Genny starting circuit "wired" through the House Switch.  Some did....some did NOT.  Mine does NOT.  The Genny is fused....but not connected via the House Disconnect switch.  If your genny cranks via the House Cut Off Switch, then THAT is a place to look.

Good Luck....let us know....

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Tom, problem is my house batteries were at 12.9 and float charging just before I disconnected shore to start genny.  Battery boost also didn't work. Same clicking.  I did decide to leave the CG and 15 min down the road tried the gen start and voila it started while driving. Would like to know why it clicked and wouldn't turn over? 

Thanks so, it all points to batteries but boost didn't work and charge was at float before disconnecting shore.  I mistakenly didn't get the secondary code, thanks for that link, saving that one.  After moving a bit and it starting without the boost indicates low volts but the meter didn't tell that story. Thanks again for the responses.  Stay safe all. 

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2 hours ago, Joel Sheriff said:

Tom, problem is my house batteries were at 12.9 and float charging just before I disconnected shore to start genny.  Battery boost also didn't work. Same clicking.  I did decide to leave the CG and 15 min down the road tried the gen start and voila it started while driving. Would like to know why it clicked and wouldn't turn over? 

Thanks so, it all points to batteries but boost didn't work and charge was at float before disconnecting shore.  I mistakenly didn't get the secondary code, thanks for that link, saving that one.  After moving a bit and it starting without the boost indicates low volts but the meter didn't tell that story. Thanks again for the responses.  Stay safe all. 

OK....my hunch.  You have a BAD connection.  Remember my problem.  My House batteries were at peak.  I had plenty of power.  NOW, one does not USUALLY load up their house batteries to full capacity to use the 2000 Watts that our inverters need.  2,000 watts equates to about 160 Amps.  Most of the books for the Onan specify a 650 CCA battery.  That is about 4 times what the Magnum will draw.

MY BET....You have a CONNECTION (or maybe a cable end) issue.  Problem is.....where.  It takes a lot of perseverance to chase it down and a good VOM and an assistant.  What you describe is what happened to me.  And it happened AGAIN on my Hydraulic Pump.  The FIX (or shotgun approach).  

Start with the battery (House) bank.  Make sure that the connections on the battery are tight.  Then make sure that the ground studs are clean and that they have been "serviced".  By that, you loosen the nuts.....then rotate the cable ends to polish or burnish....then retighten.  

Next up.  You have to get UNDER the Genny.  You do the same for the Positive and Negative there.  WORD OF CAUTION.  The studs or terminals are Brass.  DO NOT overtighten....I did not but someone told me that he did and it took all day to get off the cover and put in the new bolt.  

Finally....trace the Genny Negative to the Ground stud in the front.  Clean or burnish or polish it.  

Odds are....that will fix it.  

NOW....why is this guy so confident.  I have (or hope it is HAD) a similar problem.  I could drive 15 miles....and my hydraulic pump (slides) would NOT work.  OK....it worked a a little, but slowly  Drive another distance....BINGO perfect.  I traced and tightened and found a few suspects.  i spent hours measuring the voltage across each connection or cable or terminal.  I tightened the two suspects....but I recabled so that if the primary line from the House was bad, I had a switched alternative to the Chassis.  It has NOT failed me yet.

BUT, the Genny did....and it was the Ground stud.  After I fiddled with the tray, I "got it in the right position". You driving it vibrated it to the RIGHT position.  Could have been a little corrosion and your vibrated the loose connection so it worked.

I would fix or have the cables fixed FIRST.  NOW.....you might call a good ONAN tech (or call Tech Support).  That is my advice....based on a LOT of circuit testing...

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Tom, all you said makes a lot of sense.  I will start with changing out my AGM connections, clean and Tighten all. They are relativity clean with no corrosion but are 4 yo with very little attention. Then I'll follow your assumptions on genny but for that I'll have someone go under the 8k. I don't do ground work very well any more.  At least now, if it happens again I know where to start to look if I haven't gotten to the fix yet.  Thanks again, stay safe regards Joel 

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As stated start cleaning connections.  If you start with the batteries and clean the cut off switch connections, bulkhead connections, battery chassis ground, front run bay bulkhead connections (if power runs that way on a Diplomat), generator ground and generator + & - at the generator you will not only cure your current issue but will also avoid other electrical issues for a long time.  Don't forget to check the cable ends for corrosion where the wire enters the connector, green is not a good thing.

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This may be mentioned already, but check the generator starter connectors too. And it could be your starter is going bad.  Happened to my Jeep. 

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5 hours ago, Steven P said:

This may be mentioned already, but check the generator starter connectors too. And it could be your starter is going bad.  Happened to my Jeep. 

Totally agree.  But, the easiest test is by using a pair of Jumper Cables and trying to start the Genny from the main DC terminals on the lower back end of the Genny. 

Joel,  I crawl around less and less and am very cognizant that you don't do the same things that many of the young whipper snappers do.  However, doing the simple things like battery connections and such is easy.

IF you can find a helper to shinny under there, the Terminals are in plain site.  The are RED and BLACK and have a RED and BLACK cable going to them.  If the helper puts the jumper cables  on the terminals and holds them in place....then you can attach to your Toad and start the Toad and then crank the Genny.  IF it cranks.....VIOLA.....you have a cabling or battery or whatever issue and can find someone to help.  Otherwise, you need to get a Genny Tech to look at it.  That points you in the right direction.   

 I CAN offer one more little TRICK.  Your Motor Home Cranks.  Remember, you have TWO ground Studs that complete the circuit to the Genny.  There is a Ground Stud behind the Battery Box.  There is one UP FRONT.  MY MEMORY....and yours may be different is that the Genny Ground and the Hydraulic Pump Ground use a COMMON Ground.  That is on the frame in the Genny compartment and easy to get to.  If you clean THAT ground....then you would expect to have a good connection to the Genny's negative.

NOW....since the Genny cranks off the HOUSE....if you have a bad Ground Stud connection on the House....throw a Jumper Cable from the Negative of the House to the Negative of the Chassis.  That eliminate the ground stud....if it cranks then....you look at the NEGATIVE cable and grounds....if not....it is somewhere else.  Many of these you can see and get to yourself....if you are so inclined.

Good Luck...

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Thanks again Tom, more good info. My son is coming out to visit. He'll do the "ground" work. 

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