Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan LT II Transfer Switch JB 7.5


this thread has 105 replies and has been viewed 4409 times

Reply
 
Thread Tools Display Modes
  #1  
Old 06-04-2017, 12:13:44 AM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Reply With Quote
Sponsored Links
  #2  
Old 06-04-2017, 01:44:42 AM
EricWood's Avatar
EricWood EricWood is offline
Registered-III
 
Join Date: Oct 2005
Location: West Concord, Minnesota USA
Posts: 1,923
Thanks: 240
Thanked 1,413 Times in 761 Posts
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.
Reply With Quote
The Following User Says Thank You to EricWood For This Post:
  #3  
Old 06-04-2017, 05:08:44 AM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is offline
Subscriber
 
Join Date: Nov 2004
Location: Centerville, Texas
Posts: 17,159
Thanks: 8,885
Thanked 14,501 Times in 6,845 Posts
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.
__________________
I don't talk to myself. This early in the morning. Why the hell should I talk to you.
Reply With Quote
The Following User Says Thank You to Billy J Shafer For This Post:
  #4  
Old 06-04-2017, 07:20:24 AM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Reply With Quote
  #5  
Old 06-04-2017, 10:07:22 AM
akirkland akirkland is offline
Registered-I
 
Join Date: Jan 2016
Location: Portland, Oregon, USA
Posts: 406
Thanks: 82
Thanked 214 Times in 154 Posts
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.
Reply With Quote
  #6  
Old 06-04-2017, 11:27:26 AM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is offline
Subscriber
 
Join Date: Nov 2004
Location: Centerville, Texas
Posts: 17,159
Thanks: 8,885
Thanked 14,501 Times in 6,845 Posts
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.
__________________
I don't talk to myself. This early in the morning. Why the hell should I talk to you.
Reply With Quote
  #7  
Old 06-04-2017, 12:08:12 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Attached Thumbnails
Click image for larger version

Name:	20170604_114634.jpg
Views:	79
Size:	89.8 KB
ID:	283627   Click image for larger version

Name:	20170604_115545.jpg
Views:	91
Size:	157.9 KB
ID:	283628  

Last edited by JohnnyC; 06-04-2017 at 12:25:46 PM.
Reply With Quote
  #8  
Old 06-04-2017, 12:28:33 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Reply With Quote
  #9  
Old 06-04-2017, 10:27:36 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Reply With Quote
  #10  
Old 06-05-2017, 10:30:57 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 4,945
Thanks: 1,739
Thanked 2,481 Times in 1,430 Posts
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
Attached Thumbnails
Click image for larger version

Name:	001.jpg
Views:	71
Size:	144.9 KB
ID:	283772   Click image for larger version

Name:	002.jpg
Views:	68
Size:	144.1 KB
ID:	283773   Click image for larger version

Name:	003.jpg
Views:	77
Size:	120.9 KB
ID:	283774   Click image for larger version

Name:	004.jpg
Views:	85
Size:	195.3 KB
ID:	283775  

Reply With Quote
The Following 2 Users Say Thank You to JohnnyC For This Post:
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Onan Transfer Switch saggys Onan Generators 5 01-24-2015 12:07:53 AM
Onan OT 150 transfer switch jurick Onan Generators 9 08-26-2013 11:51:48 AM
onan transfer switch bswalsh55 Onan Generators 5 02-07-2013 10:00:53 AM
Transfer Switch for my Onan BigBlockChev Onan Generators 6 03-08-2012 04:19:38 PM
Help on Onan OT Transfer Switch hoghunter69 Onan Generators 11 12-07-2011 08:25:19 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 10:17:33 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277