Alt alarm on dash

[Sspdiesel]

Cummins , used many types of alternator brands , and not sure some oems put there own brand on the engine ..
Here is the thing about the alternator many people go online and get a cheaper China brand , it’s super hard to get a new delco , or balmar , or etc .
The key to getting the right part get engine serial number of Cummins call Cummins parts get a recon from Cummins ..it’s cheaper then you think .
Last the Oem altnator has a sense wire for light usually supply’s light in dash with a ground to turn it on . I would say , when the first , altnator was changed they swapped it for a cheaper unit not Cummins ..

Easy way to check get serial number goggle quick serve Cummins , put you info in
Look at the parts diagram , and seek if it’s your alternator you have .

The way I see my coach wired to charge house batteries and engine is very old school now when we have multiple banks of batteries we use a a c r or a battery isolator .. the worst thing you can do to alternator regulator is to apply another charger at the same time it’s running ..

So the fix , check alternator , if it factory , look at harness to it for short go ground .
Rub marks . Disconnect sense wire see if light goes out of it doesn’t go out there a short in wire from unit to coaches oem harness .

Like some one posted 13.8 to 14.2 when running it’s charging , easy check is on your panel where you can control hose like water pump there a bolt gauge for house battery and chassis battery ..make sure you in plug and shut off inverter .

Hope this works ..

if it’s not a Cummins , same way to trouble shoot ..need the brand of alternator
Can send you wiring diagram .. or goggle it ..

[YC1]

https://1drv.ms/u/s!Aqrv2TUdbV6xjkau...xMPJS?e=TU0dGr

Here are several files that may be useful. There are some extras but might be handy some day.

As suggested, it could be a small fuse near the alternator that feeds back power to the alt fail relay. That is located in the compartment below the driver in the outside compartment. Mine is a 2008 HR Endeavor. Your setup may be different of course but it seems this is a very common setup.

[ronbunge]

On my 05 Cayman 36PDQ my ALT light and beeping will come on. If I turn on the headlights it goes out. Seems to go into alarm if overcharging.

[Jchemie]

If your coach has a Reese-Neville alt it puts out 14.3 vts when running correctly. My idiot light came on and the alt was putting out 13.5 vt, thats ok for a car but not good for a motorhome with all those batteries. Get it rebuilt at a good altenator-generator shop, lower cost than new. Or get a new one if you can’t wait, just a lot more cost. Also check the single wire at the top or bottom (depending on how it is installed) between the pos & neg posts. Make sure it is connected, and should register about 6-9 volts with a volt meter with the ignition on. This wire “excites” the alt and makes it produce big volts. There was a thread recently in this forum where someone said there was a fuse in on this line. Well hidden, too. Anyone remember that thread?

[Notn2bars]

Our alternator relay is located in the rear run bay.