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Another Onan JB


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  #61  
Old 01-10-2018, 09:29:22 PM
Leon N. Leon N. is offline
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Default Re: Another Onan JB

Just my opinion, but I would not apply sandpaper to any relay in the control box. Too delicate and I do not think they are pitted. I have cleaned the ignition start relay, which is of open construction, with contact cleaner which comes in an aerosol can. I can see using sandpaper to clean the starter relay power contractors which are big buttons. But that relay contactor is sealed so unless the contacts are worn down it is probably ok.

As for the ignition points, for reliability reasons, I would not file or sandpaper them but replace then and the associated condenser. There should be no sparking at the points. If so, this means the condenser needs to be replaced.
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  #62  
Old 01-10-2018, 09:30:52 PM
len k len k is online now
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Default Re: Another Onan JB

Leon had a thread about testing and replacing his solenoid a few months ago. He went to local car starter shop, they sold a "heavy duty"?? solenoid. What ever that means.
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  #63  
Old 01-10-2018, 09:40:52 PM
RETCPO RETCPO is offline
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Default Re: Another Onan JB

You do have the option of replacing the starter!
https://www.ebay.com/itm/182339499051
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  #64  
Old 01-10-2018, 09:43:47 PM
EnginePat EnginePat is offline
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Default Re: Another Onan JB

Thanks for the info on the replacement starter, the starter works good the solinoid is burnt out so just a replacement part is needed.
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  #65  
Old 01-10-2018, 09:49:42 PM
len k len k is online now
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Default Re: Another Onan JB

I think it was Mitsubishi one that was supposed to be lot better one than the Prestolite one.
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  #66  
Old 01-10-2018, 09:57:35 PM
Leon N. Leon N. is offline
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Default Re: Another Onan JB

Yes! Len is correct. Back in 2011 I had my JB Prestolite starter was refurbished at the local auto electric shop. I was surprised to hear that those old Prestolite starters are still serviceable. Apparently parts are still available. What I did not realize until I had a second starter solenoid failure last September/October that it was a Chinese made product that was put on my Prestolite starter back in 2011.

So I insisted on a "American" made starter solenoid/contactor. Not only that I opted for a beefier one. It was made in Canada. The invoice show a p/n of RCP 12630. Not sure that is helpful but so far the JB starter along with a new Bendix is working fine.

The Onan parts manual does not breakout the starter solenoid/contactor p/n and any ways it does not matter because the shop knows exactly is needed.

What is important is the shop is going to install the cheaper "Chinese" made product unless you inquire and want to pay a little bit more. Beware my friend.

P.S. Yes it was sold as a heavier duty solenoid. Form, fit, and function were identical. So I opted for it. What was interesting is it draws less current on the pull-in coil that the cheaper one, but there must be more amp-turns giving it more pull-in power than the cheaper one from China.

One more thing to be aware of: If you decide to replace the starter mounted solenoid/contactor, you should make a copy of page 40, Figure 52 in 967-500. Figure 52 shows how to properly adjust the solenoid plunger linkage so that you retain the proper starter pinion clearance.

Last edited by Leon N.; 01-10-2018 at 10:44:33 PM. Reason: more data
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  #67  
Old 01-11-2018, 10:58:12 AM
EnginePat EnginePat is offline
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Default Re: Another Onan JB

The solenoid number is SAD-4403. There$45.00 give or take couple bucks.
Standard motor products SS-202
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Last edited by EnginePat; 01-11-2018 at 11:47:28 AM.
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  #68  
Old 01-11-2018, 05:57:24 PM
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Default Re: Another Onan JB

I picked up a starter solenoid, that took care of the starter. Now the starter turns with the switch. Removed all the cut wiring that was not going to be used. Pulled off the oil pressure gauge just to confirm that oil is flow g thru the hole and it is. Just quickly cleaned the gauge. Figured I could give it a whirl, but no spark so tomorrow I will check the coil out.
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Old 01-11-2018, 06:02:28 PM
len k len k is online now
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Default Re: Another Onan JB

Spark coil is 6V.

To test mine I took it off, bent up some paper clips toplug in and make a spark gap.
Then wired up a 6V gel cell , condenser and coil in series then intermittently shorted out the condenser. I got a strong spark, ~ 3/4 inch. (Others say don't make the gap that large as it stresses the insulation inside the coil)

Only hold ONE wire, if ANY, so you won't be in the circuit and get ZAPPED.

On mine the terminal nuts were green and slimmy. I cleaned then with a wire wheel on a dremal and it worked great. Coil primary is ~ .9 ohm
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  #70  
Old 01-12-2018, 03:34:31 PM
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Default Re: Another Onan JB

The coil is fine, but no power to it.the power wire runs to no 10 on the strip on the bottom of the control box. Then to the start solenoid in the box,then to the k12 contactor.
I can get power to the points only with a jumper on the coil.
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  #71  
Old 01-12-2018, 05:23:02 PM
Leon N. Leon N. is offline
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Default Re: Another Onan JB

You should have the correct wiring diagram for your particular JB and just trace the wires through and do not alter any resistor values in the coil circuits. The values used are important for proper operation and spark performance. I would suggest putting a spark plug on each hi tension lead so that you do not over stress the coil windings insulation as mentioned by Len.
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  #72  
Old 01-12-2018, 05:31:39 PM
EnginePat EnginePat is offline
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Default Re: Another Onan JB

Quote:
Originally Posted by Leon N. View Post
I would suggest putting a spark plug on each hi tension lead so that you do not over stress the coil windings insulation as mentioned by Len.
That is just what I did ,I don't want ruin any expensive parts.
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  #73  
Old 01-12-2018, 08:42:51 PM
EnginePat EnginePat is offline
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Default Re: Another Onan JB

So I have been trying to get the schematic for this jb.

7.5JB 3CR14081AD
OTCU40-B/14G
B870876050
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Last edited by EnginePat; 01-12-2018 at 09:32:29 PM.
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  #74  
Old 01-12-2018, 09:39:40 PM
Leon N. Leon N. is offline
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Default Re: Another Onan JB

It might be listed on the factory build sheet. Maybe someone on the Stak can provide that, I cannot.
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  #75  
Old 01-13-2018, 06:27:49 PM
EnginePat EnginePat is offline
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Today I did some work on the jb, I had to get the top of the enclosure off and there was no moving the elbows on the muffler ,so the east way was to use a cut off wheel and cut the elbow in half.then cut it down to the threads and knocked it off. The muffler came right off and the top. I cleaned all the crap out of it, sand everywhere. Blew out the cylinder fins (old mice insulation ) I put a different demand regulator on it and shut off valve.
So I started trying to figure out why no power to the coil. I hooked the battery up and started checking. First i cleaned all the connections. That did not change anything. The gas solenoid has no power. I jumped from the battery to the gas valve and that works, I pushed the start lever and the points had power also by jumping the gas valve. So I went to the k11 black start solenoid, this one has 2 small connections on top and 1 on each side. So I jumped battery power to the left side small connection. At that point I had power to the coil and the gas valve. I do not know the procedure to check the start solenoid but it may be the problem, if anyone knows the way to do it please school me.
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  #76  
Old 01-13-2018, 06:43:56 PM
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Default Re: Another Onan JB

The "I"terminal on top of the big starter solenoid should have 12V on it when the starter switch is pressed. It is an auxilliary contact which activates when the main relay is pulled in. You can test this by hooking your volt meter to it and pressing the start switch. no volts means it is probably hooped. That part of the circuit is energized only while the starter is turning, once the centrifugal switch kicks in it takes over supplying 12V to the circuit. Hope this is what you are asking about. Cheers Dan
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  #77  
Old 01-13-2018, 06:51:37 PM
Max Thompson Max Thompson is offline
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Default Re: Another Onan JB

Sorry the print is so poor, it is pot luck with the scans, some are great some like this. Some prints do not exist, so I guess this is better than nothing.

During starting ignition power is supplied through K-11. When the centrifugal switch closes and K-11 opens, power must flow through K-12 contacts. Battery - from the start switch to pull in K-11 must also pass through K-12 contacts to pull in K-11.

If K-12 has been abused by the rodent population, it can cause you fits.
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File Type: pdf 75 JB Pat 612-6070.pdf (374.1 KB, 9 views)

Last edited by Max Thompson; 01-13-2018 at 07:11:05 PM.
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  #78  
Old 01-13-2018, 07:12:12 PM
len k len k is online now
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Default Re: Another Onan JB

That's interesting on the schematic, whats does the vacuum switch do?
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  #79  
Old 01-13-2018, 07:19:04 PM
Max Thompson Max Thompson is offline
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Default Re: Another Onan JB

After re-reading above, it sounds like you have a contact in K-11 that is not good. You can drill the rivets out of the bottom of this relay and take it apart, if you can not find a replacement near by. Replace the rivets with 6/32 screws when done.
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Old 01-13-2018, 07:46:33 PM
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Default Re: Another Onan JB

The large starting solenoid on this unit has 2 terminals on top. I jumped bat power to the left small terminal and that gave me power to the coil and gas solenoid.

Ls......Rs
●| • • |●

K12 seems pretty clean and corrosion free, I did not find any rodent dropping in the control box. I did find a wire that went the the gas valve chafed, it was put thru a small hole that was drilled in the bottom ,it was arched in the spot.
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Last edited by EnginePat; 01-13-2018 at 08:07:16 PM.
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