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Topic: Battery Isolator Question - 1993 U-280 (Read 1146 times) previous topic - next topic

Re: Battery Isolator Question - 1993 U-280

Reply #25 –
Wow, quite the discussion!

I have the isolator installed and now no power to the alternator exciter to the alternator won;t come on line. Looking down the wiring diagram i have a 15 amp CB in line to a relay with a/c related items on it. Anything else to flash the alternator? I now have found another problem or worse, caused one!
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #26 –
Crimp on connections at either end of the excite and sense wires are common failure points. If they are suspect, replace them.  Use heat shrink adhesive filled crimp on connectors or an adhesive filled heat shrink tubing to seal and reinforce the connector. 
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Battery Isolator Question - 1993 U-280

Reply #27 –
Brett:
I experimented with different alternator voltage settings to keep refer powered and batteries charged.
I found less than 14.0 volts would result in undercharged batteries by the end of the day (based on Amphour meters).
I live and travel in Canada during the summer when ambient temperatures are low compared to Texas, but spend winters in California, Arizona, or Mexico when ambient temperatures are similar to Canadian summers.
The fridge, when heater is "on", requires 40 amps to the inverter, while the freezer compressor (for ice maker) requires 10 amps continuously to the inverter.
Note that the solar controller is helping the alternator, but is temperature compensated.

Now for something most folks do not know about constant desulfating. Each of the three batteries have a desulfator most of the time, which raises the fully charged voltage of the batteries about 0.2 volts, so 13.0 volts, rather than 12.8 volts.

I am concerned about overcharging the batteries so do check "state of charge" on every trip and can adjust the alternator charge voltage down when ambient temperatures are very high.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Battery Isolator Question - 1993 U-280

Reply #28 –
The refer on inverter is the unusual draw.

Thought about it.  I do not think most rv's turn off propane on the road. 

At higher voltage I would routinely check capacity myself just to verify no long term capacity loss.

I almost feel stupid advising Wyatt about electrical stuff. 

Added a magnum BMS.  It's source and feed in is at the batteries.  Not a long cable run away. 

.1 to .2 voltage variation from the Xantrex power pro remote voltage sensing versus the BMS 5' run location with its thicker twisted pair hookup
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Battery Isolator Question - 1993 U-280

Reply #29 –
The voltage sense wire to the alternator on my 1996 U320 was connected to a terminal on the A/C relay which was located behind the driver side rear tires, so constantly attacked by water, salt, and sand. This sense wire was corroded off at the alternator. I moved all relays and the battery isolator to under the foot of the bed. I also moved all + 12 volt wires to a common brass bolt under the bed, including the sense wire to the alternator. Now, wiring stays clean and corrosion free while being easily accessible.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Battery Isolator Question - 1993 U-280

Reply #30 –
I'm definitely moving the panel inside. Just not today.

I did find the exciter wire broken at the alternator but don't know what lug it should be attached to. there are 3, two yellow that have wires going into the alternator and the main power lug that carries the current out of the alternator. There are no wire terminal ends left from the broken wire. where does this wire go? The wiring diagrams are not that specific for the alternator connection.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #31 –
Correction on my last. I have four lugs. One with nothing on it next to the output lug
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #32 –
Remember, the sense wire can originate from any place that is electrically on the chassis  battery side of the diode-based battery isolator.  There is no "here is where it has to connect". So, chassis battery, chassis battery lug of the battery isolator, chassis battery side of the battery combine/boost solenoid, etc, etc.

And as others have mentioned, one of the first things I did was move the "behind the driver's side rear wheel" electrical panel to under the front of the bed electrical compartment. Yes, from wet and muddy to clean and dry.  As I recall, did not have to cut/splice a single wire.  Just disconnect battery grounds, label all wires VERY CAREFULLY, move the panel (replacing corroded or questionable relays, etc) and reconnect.  I drilled a larger than needed hole through the driver's side floor of the "under the bed compartment", installed a hose through which all the wires could be fed and sealed it in with polysulfide.

Mike probably has pictures of this.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Battery Isolator Question - 1993 U-280

Reply #33 –
Thanks Brett. I have 12 volts from the battery to the alternator. The wire going to the alternator was removed at some point. I was going to re attach it but don't know what lug to put it on. I have 4 and one next to the output has nothing on it.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #34 –
Look closely at the back of the alternator.  Quite likely there will be some embossed markings for things like IGN, Sense, etc.

If you don't see them, do a search for your alternator make/model installation instructions.  Should give you exact connection details.

This approach is better than ASSUMING that you have exactly the OE alternator that was fit in 1992 with exactly the same connections.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Battery Isolator Question - 1993 U-280

Reply #35 –
On the back of your alternator will be four lug bolts, two heavy and two light.
The heavy lug bolts are for charging, one negative with cable to engine block and one positive to the diode isolator.
The light lug bolts are for ignition power (hot when ignition is in the "ON" position) and for battery sense wire.

Note: it is very possible that you will not be able to easily remove the nuts from these four lug bolts because they are corroded and imbedded in plastic. I had to use penetrating oil and a lot of patience to remove all the nuts without breaking the lug bolts.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Battery Isolator Question - 1993 U-280

Reply #36 –
Solid advice Brett.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #37 –
Ian,

After seeing the "custom" wiring on your old isolator, I am guessing there is a good chance that the alternator on your coach has been replaced at some time.  If so, there is also a good chance that it is not a DUVAC alternator.  A DUVAC alternator has the proper configuration to allow the use of a remote "sense" wire, which is required when you have a diode based isolator.  The "sense" wire is connected to "always hot" source that sees START battery voltage.  Some Duvac alternators may also require a "excite" wire, which is connected to a "hot with ignition" source.

What is DUVAC?

SO, as Brett has suggested, you must first determine exactly what model alternator you have.  Google the model number to find the technical info and installation instructions for that model.  You are looking for something that says it accepts "remote sense" input.  If it has that feature, you are in good shape.  If it does not, we can offer you some alternatives.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery Isolator Question - 1993 U-280

Reply #38 –
Thanks Chuck. I could not find the data plate on the alternator and just put everything back the way it was for now. Its pushing 100 degrees here so I figured I had enough. Its putting out 14 VDC just not with isolated batteries. More tomorrow early, before the high temps get here.
Ian Minaert
1993 U280 Build #4324
Cummins 8.3, 6-Speed, Exhaust Brake, Aquahot
Valley Center, KS

Re: Battery Isolator Question - 1993 U-280

Reply #39 –
Very likely you have a "one wire" alternator that is self-excited.  Very common on GM vehicles, and many others.  All it requires is a single positive cable to the battery, and a negative ground.  The way your isolator was wired, with the alternator output connected to the start battery post, that type alternator would be perfectly happy.  Once you move the alternator output cable to the center post on the new isolator, the alternator is no longer "seeing" the start battery voltage, and it will not initiate charging.

Let us know if you are able to I.D. the alternator, and we can go from there.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Battery Isolator Question - 1993 U-280

Reply #40 –
Quote from: wolfe10 –
Remember, the sense wire can originate from any place that is electrically on the chassis  battery side of the diode-based battery isolator.  There is no "here is where it has to connect". So, chassis battery, chassis battery lug of the battery isolator, chassis battery side of the battery combine/boost solenoid, etc, etc.


I'm going to stick my neck out here and, even after all of the help Mr. Wolfe has given me, respectfully disagree with Mr. Wolfe on this one.

The (A) voltage sense wire is essentially one lead from a voltmeter built into the source (alternator.)  As such it needs to be connected as close, if not directly to, the load (battery,) so that the load is given the voltage it requires regardless of line losses.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.
 

Re: Battery Isolator Question - 1993 U-280

Reply #41 –
Quote from: Old Toolmaker –
I'm going to stick my neck out here and, even after all of the help Mr. Wolfe has given me, respectfully disagree with Mr. Wolfe on this one.

The (A) voltage sense wire is essentially one lead from a voltmeter built into the source (alternator.)  As such it needs to be connected as close, if not directly to, the load (battery,) so that the load is given the voltage it requires regardless of line losses.


Agree in theory. And on our sailboat also a practical one, as cabling size is "not robust".

But, on the Foretravel, from a practical standpoint, those very large gauge cables from chassis battery to battery isolator, boost solenoid, etc show exactly the same readings as at the batteries. If not, there is a (serious) connection or cable issue.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020