Onan 6.5 NH-3cr Won't Crank

[Ken Loggains]

Hi Everyone, Newbie that really needs your help.. I have a Onan Model # 6.5 NH-3CR/16004P ser# K833725027 that will not crank.. It's in an RV that was parked for about 3 months. The generator worked before, but now will not turn over.. It has a little less than 1000 hrs on it.. I read through all the post here and couldn't find the answer, so I need your expert help.. I have the Operators manual and have been through the troubleshooting part.. I have a new battery, I have replaced the start solenoid with the correct Onan part, checked fuses, resistors, low oil switch, diode, and brushes - all good.. I have 13V on the B+ terminal when I push the start switch and it drops to 2.5V. Last night I pulled the brushes and cleaned the collector rings with #200 sand paper. Checked collector rings to ground and no shorts. After I did that the solenoid just rapid clicks.. So I'm hopeing now that someone can point me in the right direction.. I do have the scematics and parts lists just need some pointers.. Thanks in advance for all of your help..

[Billy J Shafer]

The brushes nearest the engine are the starter brushes. So make sure they are free and in good contact with the slip rings. But with that much of a voltage drop I would recheck the ground and battery connections.

[Ken Loggains]

Billy thanks for the reply! What kind voltage drop should I be seeing?? I did look at the front brushes and they look fine and move freely. I also cleaned the collector ring..

[Billy J Shafer]

I would say not more than three volts.

[Ken Loggains]

Thanks again Billy.. I'll check all my grounds in the morning and see if that is causing my problems..

[Dave Edmonds]

I would agree - get your voltmeter out and find out where the voltage is going. I had a ground terminal that "looked" great - when I took it loose, everything between the terminal and the frame was rusty! Didn't show from the front. A little wire brush work, and all was well.
Dave Edmonds

[Skytruck]

I would also check the "new" battery with a load tester, once all the other connections are clean and tight. Once in a blue moon you can and will get a bad battery off the shelf "new".
Jim

[lokay5]

I agree with Skytruck. My money's on a low battery.

[Billy J Shafer]

As my daddy always told me New don't mean squat.

[Mikisan]

I agree with all replies above. Some good voltage drop testing is in order. Stick your meter's test leads directly on the Batt posts (not the clamp or connector) and touch 'start', If the voltage drops to 3vdc then it's definately the battery. If not, next move the pos. test lead to the pos. cable end or clamp while leaving the neg test lead wher it was on the neg. post, hit 'start', if the volts then drop way down the problem is the connection between the pos. post and pos. cable end. Continue in this manner untill you've located your drop. Note: don't skip over factory crimp or leaded connections on batt cables assuming they will be good, they can go bad inside where you can't see.


Oh, one other thing. Gensets in RV's are usually connected to a batt a long way away by one pos. cable and then grounded by a shorter cable to the frame somewhere. Be suspicious of the connections to the frame both at the genset and the batt.

Hope this is helpful

Mike

[Ken Loggains]

Thanks Guys for all the input.. I went out yesterday to start tracing my battery voltage back to the source, but noticed I didn't have any voltage on the generator solenoid, long story short I had unplugged the RV from the house source, so I have an inverter that was suppling the 13.5VDC.. I then hooked up a stand-alone battery to the gen and it started right up and runs like a top.. So now I know that I'm not getting voltage from the battery and all it have to do is get under the RV and trace my B+ back to the battery.. My Battery goes to the motor start solenoid and then piggybacks across the frame to another solenoid and then heads to the gen box.. I've got B+ to the second solenoid, but thats as far as I've gotten.. So again thanks for all the inputs - they really helped and I should be back up and running in no time!!!!

[Billy J Shafer]

Sure wish I could be there with you. But then you would not have all the fun to yourself. I will be thinking about you on this nice warm Texas day.

[Ken Loggains]

Billy - I think your pullin my leg... But on the other hand what's not to love when working on RV's... No schematis, can't reach anything, can't see anything, and everything is bundled together for convenience... Throw in 95+ temps and mosquitoes - you gotta love it..

[Billy J Shafer]

Ken you forgot the I can see it,I just can't get to it items.

[Wayne 440]

And the "I know its back there, but can't see it because of all the other $%^&* in the way items".

[Mikisan]

Ken, It might be usefull to have some basic "RV" wiring theory. Motorhomes essentially have two seperate battery systems that are not connected together while "parked". The "Engine" battery and the "House" battery-bank. The engine or truck battery is usually a typical 900 cca starting battery and the house battery(ies) usually two deep cycle 6v batteries wired in series or one large 12v deep cycle. The engine battery is kept seperate from the house so that while "Dry Camping" the 12v lighting and controls in the house will not deplete the voltage neccessary to start the truck and recharge all the batteries. When the truck's ignition switch is turned on you energize a large constant duty solinoid which "Ties" all the batteries together to be recharged by the truck alternator. When the RV is "camped" with engine off and connected to 120v AC "Shorepower" the houses CONverter supplies the 12v DC power for all the lighting and controls and also charges the "House" battery, unfortunately to save cost most RV manufacturers did not include a large battery isolator to also charge the engine battery while connected to "Shorepower", especially when there is a generator installed. This is simply because when most consumers "Dry Camp" the generator is in use which leads us to where the generator starting voltage comes from, The RV's Engine battery. So, you can see how sitting plugged to an extension cord would allow the Engine battery to eventually trickle down to not enough. Also (as if this post isn't long enough) some RV's have another solinoid called a "jumpstart" switch, which is just a button on the dash to TIE the house batteries to the Engine Battery to Jumpstart the RV.

PPHHEEWW, Did I cover everything? Sorry if this was to long or to far off topic.

Cheers,
Mike

[Billy J Shafer]

Yea Mike but he still can't see it.

[Mikisan]

Yes, I've prayed many times for an extra joint near the wrist and an eyeball on a string.

[Ken Loggains]

Thanks Mikisan for the theory.. I knew there were two DC systems, but didn't understand how they were tied together. It also explains the second solenoid and why my engine battery was ruined when I left the RV unattended at the deer camp for several months..
Anyway I appreciate all the good humor - sounds like you guys have been down this road before.. The extra wrist joint & eyeball on a string would really be the ticket..