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Onan Generators

ONAN JB 7.5 new life


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  #61  
Old 03-15-2017, 10:01:40 PM
len k len k is online now
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Default Re: ONAN JB 7.5 new life

Other question is are you achieving the ~ 900 rpm ( 30 hz) required to activate the switch. That's why I say use a kill-a-watt meter to measure hz. Even if your AC reg is not working there are ways to make gen produce AC without it, so killawatt meter can tell you hz.
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  #62  
Old 03-15-2017, 10:10:32 PM
nothingbutdarts nothingbutdarts is online now
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Default Re: ONAN JB 7.5 new life

Len, I don't believe a Kill A Watt meter will work with that low of voltage @ 400 HZ. The display on mine will go blank when voltage is low.
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  #63  
Old 03-15-2017, 10:19:39 PM
len k len k is online now
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Default Re: ONAN JB 7.5 new life

When I did some voltage testing of my 7NHM , my killawatt accurately displayed ~ 60 hz till voltage got down to ~ 75 VAC . Display had steadily faded till I couldn't read it anymore at ~ 75 VAC.

400 hz ??? I just skimmed this thread , didn't notice 400hz, Could be wrong but believe he has 60 hz gen.

One trick I used to test my JB YD genhead is": with reg disconnected I applied a car bat ( 12V) to F1/F2 windings in place of reg output. ~12 ohms so draws ~ 1 amp. With gen at 1800 rpm ( 60 hz) I got ~ 140 VAC out the 120V gen leads.

So at ~ 32 hz ( 960 rpm) gen should make 75V which is ~ bare min to operate my killawatt. Just trying to see if he's over 900 rpm. Suspect meter will take 140 V, check your voltage with another meter first.


I suppose alternately could connect car bat and measure voltage out the 120 leads, may not be that accurate, but maybe in the ballpark . Ratio rpm from fact that my JB YD makes 140 VAC at 1800 rpm (60 hz), so 70 V = maybe 30 hz (900 rpm)

Last edited by len k; 03-15-2017 at 10:45:42 PM.
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  #64  
Old 03-16-2017, 01:45:20 AM
Vanman Vanman is online now
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Default Re: ONAN JB 7.5 new life

Have to remember that the YD generator has an exciter generator. So when testing with a fixed exciting current on the exciter at less than rated speed, exciter voltage will be reduced and therefore main generator voltage will be reduced not only by the amount attributed to the reduced speed but also by the amount attributed to the reduced excitation.
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  #65  
Old 03-16-2017, 05:22:48 AM
squidtrap squidtrap is offline
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Default Re: ONAN JB 7.5 new life

In manual 367-500 page 30/31 it shows the operation of the whole assembly and adjustments. Possibly weights or springs need attention?
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  #66  
Old 03-16-2017, 07:03:35 AM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

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Originally Posted by squidtrap View Post
In manual 367-500 page 30/31 it shows the operation of the whole assembly and adjustments. Possibly weights or springs need attention?
That's great information Than you.
Except I cant find that manual here
http://www.twinslan.net/~n0nas/manuals/onan/ .
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  #67  
Old 03-16-2017, 07:07:54 AM
Max Thompson Max Thompson is offline
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Default Re: ONAN JB 7.5 new life

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Originally Posted by fisherman81654 View Post
That's great information Than you.
Except I cant find that manual here
http://www.twinslan.net/~n0nas/manuals/onan/ .
Look for 367-0500
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  #68  
Old 03-16-2017, 07:36:20 AM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

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Originally Posted by Max Thompson View Post
Look for 367-0500
I don't see it there.
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  #69  
Old 03-16-2017, 08:15:38 AM
Kevin K Kevin K is online now
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Default Re: ONAN JB 7.5 new life

I think 367-0500 is a typo. Look for 967-0500 JB/JC Service manual. There are three versions available.
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  #70  
Old 03-16-2017, 02:54:35 PM
squidtrap squidtrap is offline
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Default Re: ONAN JB 7.5 new life

Sorry for the typo, to early, need to wait till after work, go to my post (possible new toy, page 1 post #5) it should be there, Ed
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  #71  
Old 03-20-2017, 08:12:27 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

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Originally Posted by len k View Post
Good sign that pushing centrifugal switch points closed makes relay in control box click, means at least that part of circuit is working. Next test would be to use a test light between frame and +12V lead of spark coil and confirm that you have power at coil when you manually close the centrifugal switch. From schematic looks like it should do that even if engine is not running and you don't touch start/stop switch.

I haven't had to take my centrifugal switch apart. But I'm guessing some weights spin and somehow push a rod outward to close the centrifugal points. IF engine is coming up to speed that switch trips at ( ~ 900rpm) and rod doesn't move then sounds like the rod is sticking. Also check gap.

If gen is making AC, 900 rpm corresponds to 30 hz. Most people here use a $22 kill-a-watt meter to measure hz, which is directly proportional to rpm.

I'ld say read the manual for details on how centrifugal switch works, I haven't.
I tore it down today and the problem was someone had bent the pin that the two springs attach to. They bent it in such a way that it would had to have MORE rpms to close the circuit. I bent it back straight and checked that each spring was about a inch and half in length, Aligned the two gears. put it back together and it now starts great. The rod was fine, set the gap to .020
It did have two waits that open up and there was no play to the mount.

Getting back to the fuel pump leaking oil,JB weld did not stop the oil leak for very long. I may take it off and look into some other way of fixing the leak.
I would like to keep it as original as possible. Got a cheap electric pump off eBay, hate to put that on it, we will see. Thanks everyone!
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  #72  
Old 03-20-2017, 08:44:57 PM
JohnnyC JohnnyC is online now
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Default Re: ONAN JB 7.5 new life

Glad to hear you got the centrifugal switch problem figured out. You are now one of the resident smart guys for centrifugal switch problems.

JohnnyC
New Jersey
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  #73  
Old 03-21-2017, 07:10:49 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

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Glad to hear you got the centrifugal switch problem figured out. You are now one of the resident smart guys for centrifugal switch problems.

JohnnyC
New Jersey
That's funny. But I'll go with that
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  #74  
Old 03-22-2017, 05:28:18 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

Quote:
Originally Posted by fisherman81654 View Post
I tore it down today and the problem was someone had bent the pin that the two springs attach to. They bent it in such a way that it would had to have MORE rpms to close the circuit. I bent it back straight and checked that each spring was about a inch and half in length, Aligned the two gears. put it back together and it now starts great. The rod was fine, set the gap to .020
It did have two waits that open up and there was no play to the mount.

Getting back to the fuel pump leaking oil,JB weld did not stop the oil leak for very long. I may take it off and look into some other way of fixing the leak.
I would like to keep it as original as possible. Got a cheap electric pump off eBay, hate to put that on it, we will see. Thanks everyone!
UPDATE
I took the fuel pump off again today and used a panel cut off tool to clean of the JB weld, cleaned it up with some lacquer thinner and used a different version of JB weld. So far so good.
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