Alternator not charging

[Dave Blystone]

I changed alternators(reman) and it still doesn't charge.  Half of the dash lights up and house monitor doesn't light . I also changed echo charger and it did not light up. Any thoughts. Thanks in advance Dave

[Steve Huber Co-Admin]

Dave,
Does everything work normally when on generator or shore power?
Steve

[Dave Blystone]

Shore power makes no difference if is a cat 330   3126 it will start but not charge all the volt meter shows is battery voltage    thanks

[Gerald Farris]

Dave,
We need more information, like year and model coach. Also, since you said that you have an Echo Charger, I am assuming that you have a Duvac alternator, and if so, what is the voltage readings at the sense terminal and the ignition terminal on the alternator with the ignition on and the engine not running?

Gerald

[Dave Blystone]

It is a 2001 patriot 33  with a cat 3126   330 up   i will check alternator terminals as soon as I can umm not sure how but I will try to figure it out thanks again Dave

[Gerald Farris]

Dave,
The 2001 Patriot used a Duvac alternator because it had a battery isolator in the line between the alternator and battery. The Duvac alternator is a 4 wire alternator with two large cables (one for output that runs to the battery isolator and one for ground), and two small wires (one is the sense wire so the voltage regulator can read the chassis battery voltage, and the other is ignition voltage to supply a power source to magnetize the rotor). I need the voltage readings for the small wires. There should be no voltage on the large wires unless the engine is running, and when it is running the large wire next to the engine should have output voltage with the other cable at 0 voltage. If you can give me the voltage readings, I can tell you what your problem is.

If you do not have a volt meter (all coach owners should own a voltmeter) , you can get a cheap one for less than $10 that will work for this purpose from Amazon or Harbor Freight. 

Gerald

[Dave Blystone]

I will get that reading as soon as possible thank you again. Dave

[Gaetan Goyette]

Hello Gerald and Dave, I am new to posting so please excuse me if I am intruding, but I have the same problem and would like to know what are the possible outcomes of the voltage readings on the sense and ignition wires. Thank you for your reply in advance and again please excuse me for barging in
Gaetan

[Gerald Farris]

Gaetan,
This subject has been discussed many times here on the BAC Forum, so instead of trying to diagnose your problem by going back and forth here on the forum, just call me at 713-254-4156, and I will explain in detail how your engine alternator system works and how to diagnose or troubleshoot it.

Gerald

[Roy Boles]

    Dave I had a no charge problem not long after I had replaced my alternator. What had happened was the post on the battery isolator that the alternator was connected to had been arcing and burned in two. Be sure to inspect all cable connections at the alternator and in and around the battery compartment.

[Bruce Sieloff]

Hmm...Roy I thought this only happened to ME! If the alternator is solid and putting out voltage when the engine is running but the indicated voltage is erratic on the display, I would consider chasing it downstream to the isolator and checking for voltage there. Mine had the main power wire bouncing off what was left of the power stud on the isolator, giving readings from 18V to 11V depending on how it jiggled running down the road. Isolators are a cheap fix, about $100. All our issues should be so reasonable.