Alternator problem

[bill dane]

Have a 160 amp Leece Neville alternator in our MH.  It was rebuilt at about 100,000 miles and now has 177,000+ miles.  Problem: for the first 30 minutes of driving , it does fine charging at 14.2amps.  Then it may drop to 12.8 amps, after a few more miles back up to 14.2.  Then it may jump to 15.5amps  for maybe 10 seconds, at which time the engine RPM will go up 300 RPM.  It will then drop back to 14.2 and engine back to cruse speed.  A drop back to 12.8 amps where it will stay for maybe 20 minutes and start the up and down same procedure again.  I would think it was a ground problem , but would that cause  it to go to 15.5 amps.
    Have to admit that when it comes to electricity , it either works or it does not.  Anyone know what might be wrong?  With its milage, am considering to just replacing with a new one.  If I go with a new one, any suggestions on where to buy.

Bill Dane  99 Country Coach  Allure

Edit: Removed white space.

 

[Gary RV_Wizard]

Do you mean "amps" or "volts"?  Those sound like voltage values for an automotive alternator. The voltage regulation circuit is built into the alternator but it depends on a feedback circuit from the chassis to tell it the system voltage. Typically that comes direct from the ignition key or close to it, but your '99 Allure Dynomax chassis is not one I'm familiar with.

I can't think of any reason why a change in alternator volts or amps would cause the engine to speed up (or down, either), as long as the alternator is supplying power in the 11-15v range. And even if it quit entirely, the battery would continue to supply the engine with 12v power for  a time.  If your engine runs oddly, I'm thinking you have some other sort of problem.

 

[John From Detroit]

On the other hand an increase in engine speed may cause the alternator output to increase if it's not spinning fast enough to start with.

 

[Mavarick]

Bill, I would also suggest checking your battery connections for cleanliness but it actually sounds to me like your built in regulator is starting to go bad. Like others I am assuming you are referring to voltage readings, not amps. All are normal except the 15.5v (this is too high) and the fact that it is working in a cycle of sorts with quite a bit of voltage swing in a short time. Because the alternator is being energized I think the feed circuit is probably ok. Can?t say on the engine rpm except maybe coincidence with the higher amp load.
I would drive the rig to the local rebuild shop for alternators ? starters etc. and they will check/test it for you for free. Or if you prefer, you could just pull it and bring it in to them. They will check it electrically, put in new bearings, brushes, regulator, etc and you are good to go.