Wanderlodge Owners Group  
BuyByeBlueBird.com
Donate

Go Back   Wanderlodge Owners Group > Mechanic's Corner > Electrical

Electrical Discussion of preventative/corrective maintenance and other technical issues regarding your coach's electrical system.

Site Search:
Reply
 
Thread Tools
  #11  
Old 09-15-2019
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

I found an old post from ac7880 about his alternator and it seems mine is wired the same way. “Alt output” wire sees 12v from the chassis bats. “Ign to reg” wire sees 12v when key is in run position. I checked at the alternator, bus off 12.94 volts, bus on voltage jumping wildly from about 13.2 to 14.2. Reving the engine same result. From there I checked at the isolator.

Bus on: chassis 13.9, alt 14.2, coach 13.6
Bus off: chassis 13.5, alt 13.5, coach 13.1

Plugged in/aux off: chassis 13.3, alt 13.3, coach 14.6
Plugged in/aux on: chassis 13.7, alt 13.7, coach 13.7

I’m thinking a new alternator is in order especially if it’s a Chinese knockoff.
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”
Reply With Quote
  #12  
Old 09-15-2019
badandy badandy is offline
Senior Member
 
Join Date: Dec 2016
Location: delavan
Posts: 2,377
Default

What kind of isolators do you have? It could be fragged alternator doing that, but it could be a screwed up wire, too. Isolators don't often go bad, but it can happen.
__________________
Reply With Quote
  #13  
Old 09-15-2019
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

The isolator is a sure power 1602 160 amp model. The alternator has the j180 short mount. It looks like the original would have been a long mount from reading other posts. Does anyone with a long mount alternator know your belt number? I figure I’ll put it back to the correct mount size. It was a bear getting the belt off now and it definitely won’t work with a long mount.

I have two spare belts in the basement a gates k080610 and a Cummins 3911572. They seem to be the same length. I didn’t pull the one from the engine to compare sizes and it doesn’t have any markings left. The Cummins belt says it was made in 2000 so likely was for the original alternator. Crazy it has been riding around in there for 19 years.
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”

Last edited by LeRoy; 09-15-2019 at 04:33 PM.
Reply With Quote
  #14  
Old 09-15-2019
dthollis dthollis is offline
Senior Member
 
Join Date: Jan 2008
Location: Sherman
Posts: 582
Default

K080610 is the correct belt for my 1994 BMC. Your alternator looks similar to the Delco unit that was on our BMC when we bought it. I bought a new Leece Neville DUVAC alternator, installed it and put the Delco in the bay for a spare.

As originally equipped(at least for 1994), the large Alt+ terminal that runs to the center post of the isolator should not show voltage when the engine isn't running. I've read on irv2.com about guys replacing alternators with a "will fit" and then finding goofy electrical issues such as things being energized when they should not be. Wouldn't your engine not shut off once upon a time? That and the hot Alt+ terminal make me think you've got other issues besides just Alt output.

Here is a basic DUVAC troubleshooting chart that may be helpful:

https://www.dixie-electric.com/tsb/TSB_704.pdf
Attached Thumbnails
Click image for larger version

Name:	IMG_20190915_180711012.jpg
Views:	15
Size:	207.2 KB
ID:	64160   Click image for larger version

Name:	IMG_20190915_180114147_HDR.jpg
Views:	14
Size:	209.3 KB
ID:	64161  
__________________
David and Dawn Hollis. Sherman, IL

217-720-3608
dthollis@sbcglobal.net

1994 BMC37
1991 SP36(sold)
1984 FC35(totaled)
1978 FC33(sold)
Reply With Quote
  #15  
Old 09-16-2019
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

Quote:
Originally Posted by dthollis View Post
As originally equipped(at least for 1994), the large Alt+ terminal that runs to the center post of the isolator should not show voltage when the engine isn't running.
Wouldn't your engine not shut off once upon a time?
That and the hot Alt+ terminal make me think you've got other issues besides just Alt output.
I will confirm the path of the alt + wiring to the isolator and let you know where it goes.

It is true, for a while my engine did not like to stop playing. That stopped after I replaced all of the batteries and replaced the cabling in there.

Sounds logical. I’ll report back on what is in the path of the alt to isolator circuit tonight.

Thanks.
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”
Reply With Quote
  #16  
Old 4 Weeks Ago
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

Okay guys I need the think tank to activate. I checked just installed the new 28si 160 amp alternator. I checked on what Dave said above about the isolator center post not having 12v when the engine is off. The wire from the alternator to the isolator center post seems to be a uninterrupted run and now doesn’t have 12v when the engine is off. I guess there was a problem internal to the old alternator. I thought it was fixed. However when you start the engine you get a solid 3v output regardless of rpm. I then removed the sense wire and ran it to see if maybe it just doesn’t output if the bats are full, solid 3v. Next I watched a delco video that shows that the sense circuit compares the bat voltage on the output to the bat voltage on the sense input to regulate output. I thought maybe the issue was the isolator in circuit so I moved the chassis bat wire from its isolator post to the alternator post to tie the alternator directly to the battery. Shebang the alternator is putting out a solid 14.3 at idle. So here is the question. Is my isolator bad (it seemed to test fine) or is the alternator not compatible with a isolator system? Obviously I can’t leave the connection as is or the coach bats could draw down the chassis bats. Thoughts?
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”
Reply With Quote
  #17  
Old 4 Weeks Ago
badandy badandy is offline
Senior Member
 
Join Date: Dec 2016
Location: delavan
Posts: 2,377
Default

Isolator could be bad, they are just big diodes. The alternator doesn't care about the isolator and there will not be any compatibility issues between them.

Honestly I would toss the isolator(s) in the garbage and run an Eaton Surepower 1315-200 in its place. The diode isolators will drop any voltage going through them 0.7 volts on top of whatever loss you have in your wiring, but the Surepower doesn't because it's a giant solenoid with some smarts built in. The reason they run the sense wire from the alternator down to the isolator is to have the regulator make up the voltage drop while charging.
__________________
Reply With Quote
  #18  
Old 4 Weeks Ago
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

Found the issue, now I have to come up with a solution. The 28si requires bat voltage on the output initially to start the exciter. So it you bridge on of the battery terminals to the alternator post briefly it will take off as intended. I guess they make isolators with an excite terminal for this. I’ll compare the cost of that to installing a circuit that brings power to the post briefly at startup. Has anyone else gone down this road?
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”
Reply With Quote
  #19  
Old 4 Weeks Ago
badandy badandy is offline
Senior Member
 
Join Date: Dec 2016
Location: delavan
Posts: 2,377
Default

LeRoy - don't do all that monkey business. All a 28si needs is a power wire on its output directly to a battery (or isolator if you still use them) and a ground strap. It will not discharge the battery by being connected like this.
__________________
Reply With Quote
  #20  
Old 4 Weeks Ago
LeRoy LeRoy is offline
Senior Member
 
Join Date: Apr 2018
Location: Lawson
Posts: 331
Default

Quote:
Originally Posted by badandy View Post
LeRoy - don't do all that monkey business. All a 28si needs is a power wire on its output directly to a battery (or isolator if you still use them) and a ground strap. It will not discharge the battery by being connected like this.
The problem is there is not 12v on the isolator terminal until the alternator begins producing power.
__________________
LeRoy Brown
Lawson, Missouri
1995 BMC 37 “MockingBird”
Reply With Quote
Reply

Bookmarks

Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
battery charging issue Mikenjackie Electrical 26 09-16-2017 12:01 PM
Charging batteries Kevin Brown Electrical 7 04-06-2017 08:29 AM
Alternator charging house batteries issue Jay Shelley Electrical 4 05-07-2012 03:22 AM
No charging atckip Electrical 16 04-25-2010 08:59 PM
explain charging? Luvoekars Electrical 13 02-15-2009 09:06 PM

Web Search:

All times are GMT -4. The time now is 03:31 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.