Chassis Batteries not charging Alternator at 32 Vdc

[Wanderlust]

I have an 02 Dynasty 36.  I noticed my dash gauge was right at 12vdc so I put my meter on the batteries and they were right at 12 volts.  With the engine running, they remained at 12 volts.   I left the engine running and checked the input to the isolator that was labeled "Alternator"  and measured 32 volts!   I thought maybe the house and chassis batteries were somehow being put in series through the isolator so I lifted the cable from the post and started it again.  This time I was reading closer to 38vdc.  Any ideas?  

[tmw188]

Just to rule it out, are both battery switches ON? If not turn them both on.
House and Chassis

[MyronTruex]

It seems the diode isolator is defective. Connect the alternator (output),input(to isoltaor) ,directly to the engine battery post on the isolated and test again. There are come caveouts about remote battery sensors but no need to get into the weeds just yet.

In theory, you can connect all three posts together via jumpers for testing. But the single test will allow the alternator to "see" the battery load. I suspect your alternator input has a lot of AC components in it and can make a digital meter a little wonky. The battery is the filter for the Pulsating DC output of the alternator.

 

Edited July 15 by MyronTruex

[Rocketman3]

The alternator is a Duvac style. So it measures the battery voltage directly from a wire connected to the battery.

being it was outputting 32v - my suspicion is the regulator inside it may have failed. 
 

But I am by no means an expert- talk to one then maybe get the alternator rebuilt. Make sure it is done as a Duvac style.

[Wanderlust]

I was a little leary of possibly pumping excess voltage into my system so I disconnected the alternator cable from the isolator and ran it to a decent battery I pulled out of my boat.  I grounded it to the coach chassis of course.  I started the coach up and read a pretty steady 18.9 volts.  What do you think of the theory that the excess voltage fried the isolator?  With the Duvac style is it dependent on a feedback voltage on a separate wire or does it regulate based purely on the load?  When I bought the coach it came with a spare alternator but I didn't want to replace it just to find the issue was related to something else with the coach wiring.  

[Benjamin]

Agree with Myron, the alternator is using "remote sense" and is seeing the chassis battery needs more juice so it goes full output.  I didn't know it could reach 30V, but connecting to the chassis battery should show what's going on. The regulator is seeing the chassis battery, and doing what it's supposed to do. 

edit: I just read your bio, look up remote sense and DUVAC systems to understand what's going on.  There are alternatives to the diode isolator, or replacements if you want. 

 

Edited July 15 by Benjamin

[MyronTruex]

An alternator without a load, that is, connected to a battery, can easily reach 130 VDC pulsating. Like a modified sine wave inverter. Well, roughly speaking.

There was a kit in the dim days you could make your alternator into an AC source for some electrical things like a drill.

The output of the alternator was opened up via a switch that sent the output to an outlet. The same switch sent full battery voltage to the field of the alternator, bypassing the regulator. This put the alternator into a full output, based on engine rpm's. 

It was crude but worked.

Getting the 18 volts when connected directly to a separate battery is likely because the remote sensor voltage regulator is not (seeing) the battery it is charging.

If you have a meter with a diode checker on it or know how to use an ohmeter you can test the isolator. Pretty simple procedure. 

Your test with me indicates the alternator does indeed need to see a battery, which the bad isolator is not doing. The diode portion that feeds the batteries is open. 

Did the alternator kill the isolator. Highly unlikely. If high voltage was an issue you would probably have been boiling batteries and may have seen some extra bright lights.

I have seen some serious high charging voltages over the years due to bad regulators or misadjusted ones, but the owners would often be reporting having to change bulbs a lot. 

[Tom Cherry]

Lots of INFORMATION.  BUT, in my simplistic approach two thing stick out.

First, GREAT to put on a different battery.  Any alternator that is putting out almost 19 VDC is a BATTERY KILLER.  The Leece Neville alternator needs to be REBUILT.  PERIOD.  New OEM Parts, ordered directly from a Leece Neville dealer or distributor.  DO NOT USE aftermarket parts. DO NO TEST the Diodes....just replace them. Been there...done that... if you're going to restore it...do it correctly.  Properly rebuilt, it will last will in to the mid 2030's

Second.  I would NOT spend a PENNY on anything on the Isolator and such system.  That is really ancient technology.  The MH was built at the time where BiDirectional charging was just coming onto the Market.  Monaco, on the Windsor, in late 2001...early 2002, put in a Intellitec BIRD Module.  Some the MH's that see and the issues had an Intellitec IRD.  Now WHY did Monaco use the improved BIRD in the Windsor and the IRD in other models.  WHO KNOWS.  BUT if you have the Intellitec IRD with the FOUR Wires (Red, Black and Blue...Time to say GOODBYE.  If you have the BIRD Diesel or maybe (it could have been updated by someone) Diesel2, then TEST it.

BUT, bottom line...  The cost of replacing the IRD or BIRD and also putting in a new "Boost" or Battery Connection Solenoid...using OEM part will be around $150 or so.

Again, this is my PERSONAL opinion...but the number of knowledgeable member that have converted to the Blue Seas ML-ACR is growing...and they are really satisfied.  That system is around $225.  It is easy for anyone to install.  Your understanding and testing. now gives you "Can DIY" rating.  The Boost Switch will be replaced with the new Blue Seas Switch.  

Here's WHERE it gets a little tricky...but follow the narrative and look at your Rig.  The Boost switch provides a continuous 12 VDC signal.  It is Spring Loaded...but there is ONE wire.  That is needed for the new remote.  What is also needed is the "YELLOW" wire (in the Blue Seas schematic).  IF you have the IRD, at least on SOME models...then there may be a BLUE or the Solenoid wire that runs to the Boost Solenoid.  THUS, if your IRD is up front and there are TWO Wires going to the Boost...the RED from the Boost and the BLUE from the IRD, then, you have TWO wires to the ML-ACR.  It is easy to run the "BLUE" wire into the MH and use it as the Yellow.  The YELLOW is essential as it is the Status/Error circuit for the LED's

That's what many or perhaps MOST are doing.

Good Lucki...

[Benjamin]

5 hours ago, MyronTruex said:

Your test with me indicates the alternator does indeed need to see a battery, which the bad isolator is not doing. The diode portion that feeds the batteries is open.

Agree with everything else.  The diodes are open also, as the batteries are 20V lower than the alternator.  The isolator is not what connects the alternator remote sense to the batteries though, the remote sense wire bypasses the isolator and hooks directly to the chassis battery. So the voltage regulator IS seeing the battery voltage so far, the charge just isn't reaching the battery, so the regulator is saying "TRY HARDER".

30 minutes ago, Tom Cherry said:

...First, GREAT to put on a different battery.  Any alternator that is putting out almost 19 VDC is a BATTERY KILLER.  The Leece Neville alternator needs to be REBUILT.  PERIOD.  New OEM Parts, ordered directly from a Leece Neville dealer or distributor.  DO NOT USE aftermarket parts. DO NO TEST the Diodes....just replace them. Been there...done that... if you're going to restore it...do it correctly.  Properly rebuilt, it will last will in to the mid 2030's

I disagree, the alternator hooked directly to the chassis and house batteries at 12.0V will not produce 19V it will bring them up to 14V as fast as it should then continue slowly up toward 15-16-17-18V IF the alternator voltage regulator is bad.  You can add a jumper across the three threaded stud terminals, or connect the cables all on one terminal.  Nothing so far indicates the alternator is performing other than it should with a blown diode isolator, so I bet the battery voltage stops at 14V.  If you want to try this with the separate battery, run a wire back to the alternator's remote sense/DUVAC terminal, that wire can be a few inch jumper right from the B+ on the back of the alternator. 

If you want to replace the diode isolator, I can probably find my old one and mail it to you, or others here probably have the old one sitting around.  That should tell you how much better Tom's upgrade works.  But the offer stands if you just want this to keep working as it was, it should work fine.

Edited July 15 by Benjamin

[Wanderlust]

16 hours ago, Tom Cherry said:

Lots of INFORMATION.  BUT, in my simplistic approach two thing stick out.

First, GREAT to put on a different battery.  Any alternator that is putting out almost 19 VDC is a BATTERY KILLER.  The Leece Neville alternator needs to be REBUILT.  PERIOD.  New OEM Parts, ordered directly from a Leece Neville dealer or distributor.  DO NOT USE aftermarket parts. DO NO TEST the Diodes....just replace them. Been there...done that... if you're going to restore it...do it correctly.  Properly rebuilt, it will last will in to the mid 2030's

Second.  I would NOT spend a PENNY on anything on the Isolator and such system.  That is really ancient technology.  The MH was built at the time where BiDirectional charging was just coming onto the Market.  Monaco, on the Windsor, in late 2001...early 2002, put in a Intellitec BIRD Module.  Some the MH's that see and the issues had an Intellitec IRD.  Now WHY did Monaco use the improved BIRD in the Windsor and the IRD in other models.  WHO KNOWS.  BUT if you have the Intellitec IRD with the FOUR Wires (Red, Black and Blue...Time to say GOODBYE.  If you have the BIRD Diesel or maybe (it could have been updated by someone) Diesel2, then TEST it.

BUT, bottom line...  The cost of replacing the IRD or BIRD and also putting in a new "Boost" or Battery Connection Solenoid...using OEM part will be around $150 or so.

Again, this is my PERSONAL opinion...but the number of knowledgeable member that have converted to the Blue Seas ML-ACR is growing...and they are really satisfied.  That system is around $225.  It is easy for anyone to install.  Your understanding and testing. now gives you "Can DIY" rating.  The Boost Switch will be replaced with the new Blue Seas Switch.  

Here's WHERE it gets a little tricky...but follow the narrative and look at your Rig.  The Boost switch provides a continuous 12 VDC signal.  It is Spring Loaded...but there is ONE wire.  That is needed for the new remote.  What is also needed is the "YELLOW" wire (in the Blue Seas schematic).  IF you have the IRD, at least on SOME models...then there may be a BLUE or the Solenoid wire that runs to the Boost Solenoid.  THUS, if your IRD is up front and there are TWO Wires going to the Boost...the RED from the Boost and the BLUE from the IRD, then, you have TWO wires to the ML-ACR.  It is easy to run the "BLUE" wire into the MH and use it as the Yellow.  The YELLOW is essential as it is the Status/Error circuit for the LED's

That's what many or perhaps MOST are doing.

Good Lucki...

Firstly thanks for the info. When I bought tbe coach there was a "spare" alternator in the pass through slide.  It looked like a rebuilt unit, labeled for Duvac use.  I am now a little suspicious the prior owner was having issues.  He told me it was a goid alternator and I should have pressed him more.  I verified there is voltage on the sense terminal and the switched ignition terminal.  There is a third wire attached to the center terminal of the three that go to the windings that had no voltage with the key on or off.  I was measuring at the plug on the chassis side of the bundle. I installed the "spare" alternator and nothing is changed.  Tomorrow I will try bypassing the isolator and going right to the chassis batteries and checking the charge voltage again.  I think I will dig around for my old analog meter as it may take out more of the ac component.  Or is it the other way around for digital versus analog, I'm tired and can't remember.  You have a few acronyms IRD, BIRD, etc. I am not familiar with.  I will also check the isolator. I assume you just look for forward/reverse bias as required.  It sounds like it is a good idea to make some changes long term but for now I just want to know my chassis batteries will charge.  On a side note I did notice my Tach Drops about 100 rpm when I swith my headlights on.  Is that possibly because the alternator isn't compensating for the load? I just realized that third wire is probably for the tach? 

[MyronTruex]

All bets are off for the tach. It is probably seeing a lot of garbage. (dirty electricity), due to the batteries not filtering the alternator output. 

As suggested, if the remote regulator is seeing battery voltage go lower due to the lights being turned on, the alternator would likely be told to ramp up its output. The increased garbage from that may make the tach a bit goofy. 

[Wanderlust]

Thanks for all the help and suggestions.  Okay, so I tied the alternator output directly to the chassis  battery as suggested and it is charging at a nice 14.3 volts.   I read out the isolator and it reads wide open regardless of the bias so I assume it is bad.  I need to make a 5 hour  trip to have a couch installed soon so will not have time to upgrade or replace the regulator.  Would it be best to just feed the chassis batteries directly from the alternator or can I hook both banks to the alternator or would that be a bad idea due to the potential excess load and/or not having them isolated?

 

On 7/15/2024 at 5:43 AM, Benjamin said:

Agree with everything else.  The diodes are open also, as the batteries are 20V lower than the alternator.  The isolator is not what connects the alternator remote sense to the batteries though, the remote sense wire bypasses the isolator and hooks directly to the chassis battery. So the voltage regulator IS seeing the battery voltage so far, the charge just isn't reaching the battery, so the regulator is saying "TRY HARDER".

I disagree, the alternator hooked directly to the chassis and house batteries at 12.0V will not produce 19V it will bring them up to 14V as fast as it should then continue slowly up toward 15-16-17-18V IF the alternator voltage regulator is bad.  You can add a jumper across the three threaded stud terminals, or connect the cables all on one terminal.  Nothing so far indicates the alternator is performing other than it should with a blown diode isolator, so I bet the battery voltage stops at 14V.  If you want to try this with the separate battery, run a wire back to the alternator's remote sense/DUVAC terminal, that wire can be a few inch jumper right from the B+ on the back of the alternator. 

If you want to replace the diode isolator, I can probably find my old one and mail it to you, or others here probably have the old one sitting around.  That should tell you how much better Tom's upgrade works.  But the offer stands if you just want this to keep working as it was, it should work fine.

Thanks for the help, it does appear the isolator has failed.  I may take you up on your offer.  I am going to just run the chassis off the alternator until I can decide if I want to modify or keep it OEM.  I will let you know and will be glad to pay shipping and a fair price if I go that way. 

[Benjamin]

You can hook both directly to the alternator as long as you don't drain them so the engine doesn't start, or could add a length of 10g wire as a resistor to limit the charging to the house bank.  The alternator will not put out enough voltage to charge the house bank through the isolator with the chassis hooked direct, my guess anyway, you could check if it matters.  Or leave the house separate and charge from shore power.

[MyronTruex]

Combining them is fine and as mentioned, keep them charged. Shut the battery switches off is stored without shoreline for more than about three days. If you have solar you should be fine.

If you leave the coach set with the isolator bypassed and no shoreline, I suggest you start the generator and let it run a few minutes before attempting to start the coach. If you try to start with weak or run down batteries you may not get the generator to start. 

Did your Tach settle down? 

[Tom Cherry]

16 hours ago, Benjamin said:

You can hook both directly to the alternator as long as you don't drain them so the engine doesn't start, or could add a length of 10g wire as a resistor to limit the charging to the house bank.  The alternator will not put out enough voltage to charge the house bank through the isolator with the chassis hooked direct, my guess anyway, you could check if it matters.  Or leave the house separate and charge from shore power.

IF you add the JUMPER...be VERY CAREFUL.  FIRST...never mess (remove jumpers or nuts) with the switches ON.  TURN OFF BOTH Disconnect switches.

Next.  You can use a SIMPLE Auto Jumper Cable.  There is almost ZERO resistance in them.  There is zero resistance in the Battery Boost Solenoids.

There is no resistance....by design... in the contacts of the Boost Solenoid.

If you jumper the POSITIVE to the POSITIVE of the House and Chassis, that is essentially BYPASSING the boost.

NOW, FWIW, many members who have the Intellitec BIRD charging Systems or older, have used a DIRECT jumper...as in a cable or one member has a piece of fabricated copper tubing.  THUS we turn OFF our continuous BIRD "Big Boy" charging solenoid (disconnect a control wire) and store them with full power to the Inverter.

The Jumper Cables can, and have been OFTEN used from ONE BANK to the OTHER to start a MH.

SO, it is safe, and recommended to use a JUMPER CABLE.  The solenoids are usually rated at 100 or 200 amps so that a FULL Charge can be made.  You can jumper both banks with the #2 Jumper cable. The #10 wire is limited to 30 amps.  Thus, you can NOT fully charge, as you would with the Boost/Charing Solenoid.

The take away.  ALWAYS turn OFF the switches.  Connect the cable...then TURN BACK on the Switches.  This also is more important if you use a Vehicle as a JUMPER> 

The rationale  When you hook UP a live cable...then there could be arcing and a surge.

It is BEST to start the VEHICLE.  Then with the BANKS turned OFF, of course...put on the jumpers from the vehicle.  THEN turn ON the banks.  You have a positive CONNECTION...not one that is erratic.

Hope this clarifies it and answers your questions as well as how to properly connect both banks or JUMP START a MH..

Good Luck.