Community Forums

u649024 · 07-28-2012, 01:35 PM

Started the MH (2003 Monaco Diplomat) up yesterday to go get new tires installed. After the low air pressure and jacks down warning beepers quit there was still a beep-beep-beep and the dash "ALT CHARGE" lite was on. The dash volt meter was reading less than 12 volts. I let it run for a while as I looked for any obvious reasons and found none. I shut the engine down and started checking all the chassis battery cables and connections, cleaned them all, reassembled and tried to start it to see if the warning condition had been corrected, it would not start, not enough voltage. I knew the batteries were not new so I called an Interstate store and found out how to read the date code. It turns out they were 2002 vintage, original I guess. I purchased two new batteries and installed them, same condition except now it will start, volt meter =12 volts but if I put any load on it at all the voltage drops so the voltage is all battery, nothing from the alternator. This morning I disconnected all connections (4), at the alternator, cleaned and reconnected, still get the warning beep-beep and the dash light is on. I disconnected and cleaned the main chassis ground connections, no change. At this point my assumption is a bad alternator, I know it was working when I parked it a couple months ago so I guess it went bad setting there. The alternator is a Leece-Neville 14 volt, 160AMP unit and the motorhome only has 31,000 miles on it. Any suggestions, experience with something like this?

SpringerPop · 07-28-2012, 01:44 PM

Almost always, the "field current" to the alternator is fused.

Get out the Owner's Manual to find the fuse chart......

It's a place to begin.

Do the easy things first.

Pop

Jim_HiTek · 07-28-2012, 01:53 PM

I'd recommend you remove it and have it tested at a truck parts house, I'd not use an automotive store.

Your newer rig might have an ECU that controls the output from the alt. Your alt does have a remote sense connection. It should read above 12V for your alt to output more then battery voltage, I believe.

Might be time to ask for a chassis electrical schematic from your chassis manufacturer.

RMinflorida · 07-28-2012, 03:18 PM

I have the same alternator on my rig. Mine would lose voltage as I was driving, had to run the generator to keep going. I pulled it out and had it tested TWICE ! it checked out good both times !
Two months ago I put in a aftermarket alternator, it has a little more amps to it (200 amp) and no core charge for $370. I'll keep the old one on board as a backup. You should change the belt at the same time and keep it on board as a backup as well !

Please note that on some rigs, you have to leave the "I" terminal disconnected ( like mine )

vsheetz · 07-28-2012, 03:50 PM

Quote:

Originally Posted by SpringerPop

Almost always, the "field current" to the alternator is fused.

Get out the Owner's Manual to find the fuse chart......

It's a place to begin.

Do the easy things first.

Pop

Also called excitation voltage. Agree - need to see if this is applicable to your coach (not call alternators have this, as they are self-excititing). 12v provided to the alternator over a small gauge wire, with a fuse somewhere inline. If fuse is opened or other reason the 12v excitation is missing, alternator will have no output. Many GM alternators and other are this design.

The fuse in my 95' Safari Trek has opened a couple times over the years causing no alternator output. Swap in a good fuse and all is well again.

Monacoach · 08-28-2012, 06:52 PM

No posts in one month so if I could chime in with the exact same problem as the OP..... would love to know the outcome...... I am experiencing the same symptoms.......... alt lite on dash illuminated with warning chime, gage reading below 13......... meaning alternator not charging ...

Dr4Film · 08-28-2012, 07:37 PM

Remove the alternator and have it rebuilt. It is shot.

If the dash voltage meter is not reading 14 volts or more with no load or 12 volts with a load then your alternator is not putting out any voltage. Also if you read across the chassis terminals and get less than 14 with the engine running and no load, your alternator is shot.

The last time mine went south I was about 400 miles from my destination. I drove those 400 miles over two days without a working alternator. I simply took a short battery cable and wired across the battery isolator then used my generator to keep the chassis battery up. I also did NOT drive at night requiring the use of headlights. My alternator is a Leece Neville 160 amp.

It always best to have your alternator rebuilt versus buying a new one off the shelf. That way you will know that it will fit and wire up perfectly versus a new one that may not. Most alternators built for motor-homes are not the same as ones for routine trucks.

Dr4Film ----- Richard

Monacoach · 08-28-2012, 08:14 PM

I suspect you are right about the alternator however I am also wishfully hoping it is something simpler such as a blown fuse or corroded battery terminal.

Papa_Jim · 08-28-2012, 08:31 PM

A quick easy way to check if the problem is indeed the alternator exciter circuit. The engine has to be running. Clip a wire to the big live post on the alternator. With the other end of the wire, briefly touch the exciter post. Don't hold the wire on it. Just lightly flick the wire on it quickly.

If the alternator kicks in and starts to charge, then you know there's a problem in the exciter circuit somewhere. You can make a little circuit so that you can manually excite your alternator every time you start the engine. This would work well until you can figure out what to fix in the exciter circuit.

If the alternator does not charge when you do this, then the alternator is most certainly in need of repair.

Monacoach · 08-28-2012, 08:47 PM

For me the only access to the alternator is through the bedroom floor and then its a long reach. Is there a fuse somewhere that could be blown? Still hoping for the simple fix......... I also wonder if corroded battery terminals would cause alt lite to come on.......... if no luck here I will make appointment with shop..... I appreciate the feed back....

Dr4Film · 08-29-2012, 02:46 PM

If your alternator is working correctly, putting out full voltage and amps to keep the chassis battery charged along with anytime you put a heavy load onto it, then it could be the special relay up in your front run bay that is no longer working correctly which turns your ALT CHARGE light off. It is a special Hamsar relay.

You may have to call Monaco Tech to find exactly where it is located or you possibly may have a set of wiring diagrams that will show it.

Dr4Film ----- Richard

koda59 · 08-29-2012, 03:48 PM

The way I check for either a bad battery or alternator is I disconnect the ground terminal from the battery. It the engine stlll runs it is a bad battery. If the engine dies it is the alternator. As we all know the battery is used just to start the engine and then the alternator takes over to charge the battery. Once the engine is started the alternator takes over and keeps the engine running.

rvjimmy · 08-29-2012, 06:48 PM

Take a multi-meter and check battery voltage, then start MH and see if it's the same or a little less. If it's not at least 13.8 volts when running it's probably a bad alt. Jim

sjholt · 08-30-2012, 12:35 PM

The best thing I did on my older MH was to take off that 160 amp Leece Neverworksright and put on a Delco 22SI 145 amp Alternator that I bought on line for $113 shipped. In fact the Delco has worked so good that I bought another Delco for a backup. The Delco was a direct bolt in in my 96 Monaco.
I've been using the Delco for 2 years now and 30,000 miles with no problems. There is a some .pdf on line showing how to wire it and make it remote sensing.