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Onan LT II Transfer Switch JB 7.5


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  #1  
Old 06-04-2017, 12:13:44 AM
JohnnyC JohnnyC is offline
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Default Onan LT II Transfer Switch JB 7.5

I hooked up an Onan LT II transfer switch to my JB and seem to have a slight issue. I could write it up in several paragraphs and screw it up, so I made a 7 minute video detailing the problem. The video can be seen by clicking on the following link.

https://www.youtube.com/watch?v=8eVV...ature=youtu.be

If you have any experience with these transfer switches or have any idea what may be the cause of the problem shown in the video. please let me know.

Thanks in advance,

JohnnyC
New Jersey
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Old 06-04-2017, 01:44:42 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Johnny,

Do you have another 120 VAC cube relay handy? I see some of the other modules have been replaced with regular relays.

Stick another 120 VAC relay in the K6 position, the black sensor in the lower left of the relay board. K6 has a full time duty, as it is normally energized as long as utility is present, and has to be energized to, among other things, energize K3 Start Relay, which is also a normally energized relay (Cube relay all the way to the right side of the pack). K3 has to be energized to keep genset from cranking in Auto position.

If you stick a good relay in the K6 position, and it, and the K3 relays pick up, that might be all there is to that particular issue. Retest to confirm at that point. If that cures it, you could find a "reasonably" priced voltage sensor relay to plug in to the K6 position. Also, perhaps consider a time delay relay for the K4 retransfer relay position, if you find out through further testing that the orange one doesn't work.

LT II was never one of my favorites. Used to carry all the time delay relays and sensors on the truck, but they are being obsoleted.
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Old 06-04-2017, 05:08:44 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

I agree with Eric. Problem will be K6 or K3. K6 is the line side sensor. Which feeds power to the control system. K3 is the start relay. I have seen them fail allot. I always put a cube relay in it's place. I have also seen the main board burn the tracts off the back.

LTII was not a very good switch. I carried a box of spare parts on my truck. I would also pull the shields off of the transformers. They had a bad habit of starting fires. Check them over for proper voltage.

Just be glad you don't have the LT26K. A real nightmare.
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Old 06-04-2017, 07:20:24 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Eric and Billy, thanks for the information. I too targeted the K6 relay after reading the Service Manual the other day. The manual says K6 is an adjustable voltage sensor relay. The relay that was in the switch was a cube and I believe it was either factory or replaced professionally since there was a factory plastic wire tie properly in place to hold the relay from coming out. None the less, I had an extra adjustable voltage sensor relay that I saved from another Onan transfer switch that I junked last year and plugged it into K6 relay socket. The results are the same....... In both cases (cube and adjustable relays in the K6 socket) they made a strong click sound when utility power was applied which appropriate. I did not focus on the K3 relay which I will do today. I may have another cube relay laying around somewhere, but I will have to look into the deep dark corners of my workshop.

One observation that I noticed with the clear cube relays is what appears to be slight moisture build up on the clear shell walls inside the cubes after I played with the transfer switch for a while. I can't be 100% sure, but it was enough to catch my attention. So, my mission is to attempt to unbury any cube relays that I may have saved and focus on K3 and try a third relay in K6.

I like these challenges. If the LT II transfer switch worked the first time there would be little to learn. By resolving problems, you get to know how these things work in detail.

JohnnyC
New Jersey
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Old 06-04-2017, 10:07:22 AM
akirkland akirkland is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

The most common failure points on an LTII are the time delay retransfer relay and the time delay stop relay. So common , in fact, that there are dip switches to bypass them. Look in upper right hand corner of printed circuit board. Push retransfer dip switch to on position, then try testing switch. Try same test with stop bypass switch.
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Old 06-04-2017, 11:27:26 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

On K6 make sure it is a single phase relay. Because there is a 3 phase also both look the same.
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Old 06-04-2017, 12:08:12 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Well, I went to the garage and played with the bypass switches. No positive effect. I swapped K8 with K3 and the transfer switch worked perfect on start up for ONE cycle only. I was going to shoot a follow up video and when doing so, the switch then behaved as it did before- not working correctly.

I went to my Onan box of parts and found 5 identical relays. They look good, but that is no guarantee if they are electrically good. I will try them out after lunch.

I attached 2 pictures below. One of the pictures shows one of the original relays up close and it looks scuzzy. The other picture shows the parts I got from my box of junk parts.

I will report back later .

Thanks,
JohnnyC
New Jersey
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Old 06-04-2017, 12:28:33 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Billy, the voltage sensor that I swapped in is the same as the other voltage sensor. K8004 120 vac. Thanks for making me aware of the possibility of others.

JohnnyC
New Jersey

I swapped out all the original relays one by one and then all with the relays I got from my junk box. No luck..... I can easily (but time consuming) bench test each cube relay which I may do, but I am thinking that maybe there is a problem with the PC board that I can't see from the top. All hard wiring looks good though... Anyway time for lunch. I will think what I'll do for my next step..

JohnnyC
New Jersey
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Old 06-04-2017, 10:27:36 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Update
10:25 pm - Since my last posting, I got nothing done in regards to the LT II transfer switch testing. I had several scheduled minor repairs for my tenant's apartment this afternoon and afterwards we ended up chatting (I don't see this tenant too often) and drinking a bottle of liquor. Feeling too good to play with electric now. Tomorrow is another day.

JohnnyC
New Jersey
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Old 06-05-2017, 10:30:57 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

This evening I got back to troubleshooting the LT II transfer switch. Following Ericwood, Billy's and akirkland's advice regarding the relays and the fact that they are the common cause of failure, I removed all the relays for a closer look. Yesterday I reported that there may be moisture inside the clear plastic cube relays. I was wrong. It is actually some kind of corrosion dust or dust from eroding contacts inside the 3PDT cube relays (see first and second pictures attached below). Some cube relays look better than others, but they are not healthy.

I have industrial/professional grade contact cleaner, but before I clean the relay contacts I want to bench test each relay to find out if I have relay with bad contacts due to corrosion. They are nothing more than 3PDT relays that require 120 vac for switching. easy to test these relays - even a trained chimpanzee can do it...

Lastly, I pulled the relay PC board and examined it very closely under a powerful magnifying glass as seen in the last picture below. I did not see any breaks in the foil traces and no cracks on the PC board.

Almost forgot to mention - I could not open the adjustable time delay relays. I need a small allen key to remove the knob before removing the relay's plastic shell. I am too lazy to leave the house and walk 100 feet to the workshop to get the allen wrench key (JohnnyC is lazy tonight). I wonder what surprises I'll find inside those relays.

JohnnyC
New Jersey
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Old 06-06-2017, 09:08:53 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

This evening I serviced all the relays. Many were bad. Some of the relay contacts show absolutely NO continuity while others showed high resistance. Very few of the relay contacts had good continuity.

I took each relay apart, sprayed a commercial grade contact cleaner on all contact surfaces and retested. They now all show perfect continuity in both energized and open states. I also tested the functionality of the time delay relay and voltage sensor relays. Most of the problems were caused by oxidation and the effect was similar to point sets that go unused for a long period of time.

I doubt I'll have time after work Wednesday to reinstall the relay PC board and relays since I have a drywall side job to do. I am looking forward to completing the job on Thursday and hopefully I'll get the stupid LT II switch working although I will be playing with the sensor and time delay adjustments afterwards if the basic functionality is fixed.


**** Should I repaint the box?? I can gut the rest of it in a few minutes.

JohnnyC
New Jersey
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Old 06-06-2017, 11:46:51 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

So, you fixed those relay contacts just with contact cleaner and no physical cleaning? I've got to get some of that! The equipment I work on WAY predates enclosed relays, at least commonly available ones, and a good contact cleaner would be very useful.

Keith
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Old 06-07-2017, 05:48:17 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Vanman, I was amazed too. My Fluke meter does not lie. I double and sometimes triple checked my reading before and after the cleaning. Most of the problem seemed to be heavy oxidation. The stuff I used is made by Wurth and called "Contact Cleaner OL". You will see it in my previous picture postings. This stuff is the only contact / electrical cleaner we use at work. It leaves a film that prevents oxidation.

I hope this is the answer to my LT II switch problem, but knowing how things work for me it won't be. I'll find out Thursday after work because I will be too busy today to play in the garage.

JohnnyC
New Jersey
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Old 06-07-2017, 06:38:11 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

Johnny, thanks for the tip on contact cleaner. I am presently using GC Electronics Jiffy Bath contact cleaner, part # 19-638-A, which seems to work well.

So I Googled the Wurth "Contact Cleaner OL" and came up with a number of sites.

You can buy it directly from Wurth for $10.99/can, minimum order two cans.
http://www.shopwurthusa.com/wurthsto...L/p/0890101101

I found an eBay link, selling three cans for $69.99! http://www.ebay.com/itm/Wurth-Contac...-/302256477439

Like that's going to happen! I'm starting to see more of this nonsense on eBay, ridiculously high prices on items that can be purchased elsewhere much cheaper. These sellers know many people search eBay first, and they can double or triple their money with little effort.
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Old 06-08-2017, 09:57:04 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

This evening I slapped the relay PC board back into the LT II switch and retested. It still ain't working. Without doubt, the relays had problems. You all seen the corrosion on the relays in my earlier pictures and the cleaner fixed it good and they tested good afterwards, but there is another problem that I have not pin pointed yet. It is kicking my azzzzzz, but I think it is a short in the exercise clock circuit wiring which is causing the generator to fire up immediately after flipping the switch to auto. I am currently going over the wiring schematics.

JohnnyC
New Jersey
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Old 06-09-2017, 05:45:29 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

JohnnyC is happier than a pig in mud. I figured out the remainder of my transfer switch problem by which the transfer switch would immediately signal the startup the generator when the Generator Selector Switch was set in Auto mode regardless if there was grid power or not. There should be a jumper between 11 and 12 on the TB1 remote start block. It was MISSING. I jumped 11 and 12 and the LT II transfer switch functions 100%. How did I find the problem? Simple ...... I read the schematics. JohnnyC is a happy dude tonight...

JohnnyC
New Jersey
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Old 06-09-2017, 06:41:43 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

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Originally Posted by JohnnyC View Post
JohnnyC is happier than a pig in mud. I figured out the remainder of my transfer switch problem by which the transfer switch would immediately signal the startup the generator when the Generator Selector Switch was set in Auto mode regardless if there was grid power or not. There should be a jumper between 11 and 12 on the TB1 remote start block. It was MISSING. I jumped 11 and 12 and the LT II transfer switch functions 100%. How did I find the problem? Simple ...... I read the schematics. JohnnyC is a happy dude tonight...

JohnnyC
New Jersey
So if one was to wire up a toggle switch across 11 and 12, the ATS could be controlled manually? If so, bingo to what I've wanted on when I install my ATS. Basically, I don't want to be away and have my generator starting when nobody is home. Also, if the power goes out for just a few minutes, I don't want the generator starting. I want to control when it starts, but have the start and transfer be auto.

On the timer, it's a cool down timer in my eyes. You never want to shut and engine down without cooling it down first.
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Old 06-09-2017, 07:01:40 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

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Originally Posted by LRomero View Post
So if one was to wire up a toggle switch across 11 and 12, the ATS could be controlled manually? If so, bingo to what I've wanted on when I install my ATS. Basically, I don't want to be away and have my generator starting when nobody is home. Also, if the power goes out for just a few minutes, I don't want the generator starting. I want to control when it starts, but have the start and transfer be auto.

On the timer, it's a cool down timer in my eyes. You never want to shut and engine down without cooling it down first.
From what the schematics list the use for the two terminals is a "remote test switch". With the circuit open between the two terminals (no jumper), you could essentially manual start the generator as well as shutting it down at the generator rather than having the automatic function of the transfer switch doing it. The transfer switch will automatically cut the output over between the grid and generator depending if the generator is running or not.

To make things easier if you have an LT II switch, I think you would want to run the switch set to "Hand Crank" mode (see picture below) for what you want... For me I want to run it fully automatic mode. It is nothing more than a flip of a toggle switch on the ATS.

Below is a quick video that I shot this evening after I installed the missing stupid jumper.

https://www.youtube.com/watch?v=5ink...ature=youtu.be

Thanks for the clarification on the timer.... I guess it could work both ways - for cooling down period and to ensure the power is back on and stable. There is a second adjustable relay that is a voltage sensor too. On the label inside the ATS, the Onan tech noted that it is set for 80%.

I never played with an ATS until recently. I am having a blast and learned a few things, but there is more to learn in order to set everything correctly. Right now, my garage is like a mini learning lab with all this crap hooked up. I think people pay money to take courses in this stuff.

JohnnyC
New Jersey

p.s. - you may notice the exercise clock in the video above is missing. I simply bypassed the clock by using a jumper to eliminate the possibility of a defect clock that may be triggering the starting of the genset no matter how programmed the switch is or not. The clock is nothing more than a DPST switch ran on 120vac.
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Old 06-09-2017, 10:59:53 PM
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Default Re: Onan LT II Transfer Switch / JB 7.5

After I finished my yard chores (finish cutting the lawn and trimming) I played some more with the transfer switch after closing it up I simulated power failures by cutting grid power and doing various tests. The ATS seems to work A-1.

Now that it is done, I have absolutely no clue what I will do with the switch, but it was fun to play with the switch.

JohnnyC
New Jersey
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Old 06-10-2017, 06:00:47 AM
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Default Re: Onan LT II Transfer Switch / JB 7.5

I thought about that. But in all my years with Onan. I have never seen the remote test switch used. Even at places where they were supposed to have one.
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