Re: Ping Alan Robinson
- From: "Alan Robinson" <alr@xxxxxxx>
- Date: Mon, 17 Sep 2007 16:30:08 -0700
"Frank Howell" <fphowell@xxxxxxxxxxxx> wrote in message
news:46ebe5c0$0$5075$8d2e0cab@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi Alan
I have a Onan Emerald Plus generator. Model 4BGEFA26100F. It's a circa
1990 build.
I was doing my monthly engine run, when I saw a decrease in the coach
lighting. I decided to measure the voltage of the house lighting and it
was 10.2 volts. Not good. I then decided to measure the AC voltage and it
was 152. Dang! I then decided to gracefully shut down the generator and
then started it up again. This time the lights looked normal and a
subsequent DC voltage check showed 12.2 volts. I then measured the AC and
it was 120 volts. I ran it for awhile and then shut it down and started it
backup later in the day with normal results. I am going to start it up
today for more tests. My question is, given the measurements of 10.2 VDC
and 152 AC, what could this be a symptom of?
Oh, about 290 hours on it and I have owned the MH about 6 years, so don't
know of previous maintence or lack of by first 2 owners.
The DC voltage problem is something to do with the convertor in your coach -
it evidently didn't like the high AC voltage from the genset.
The high AC voltage from the genset is most likely a connection issue. The
electronic voltage regulator in your set 'reads' the output AC voltage, and
adjusts field voltage/current as needed to maintain 120v output. If it can't
read the voltage, it will go to full field - which with no load, could be as
high as 165v. Later Onan regulators were 'capped' - if they couldn't see the
AC output, the maximum field voltage they would allow would give about 135v
no load. Of course, it's also possible that something in your regulator is
starting to fail....
Unplug the remote connector from the right end of the control box, undo the
two screws holding the control panel in place (you'll need a torx driver),
and carefully pivot the top of the control panel towards you, then lift the
bottom tabs out of the slots in the control box and get the control panel -
and the control board mounted on its back - clear. Mark the board
connectors, then unplug the board and set it and the control panel aside.
The voltage regulator is mounted on the bottom left of the control box,
and has wires coming from it to a 12-pin plug that plugs into a 12-pin jack
connected to the rest of the control box wiring. The voltage sense wires are
pin 2 (wire from the jack runs to the L1 -hot lead- terminal strip in the
back of the control box), and pin 3 (wire from the jack runs to the
L0 -neutral- terminal strip in the back of the control box). Make sure the
pins in the 12-pin connector are clean, and the lead connections at the
terminal strips are clean and tight.
While you have things open and unplugged, set your meter to read ohms,
and measure from pin 9 to pin 10 on the wiring harness connector - should be
about 25 ohms. This is the circuit to the brushes/slip rings and rotor field
winding - if tarnish builds up on the slip rings, the extra resistance can
cause the voltage regulator to have to work harder, and may cause problems
with the early non-capped regulators. Anything over 35 ohms is a potential
problem, anything over 50-60 ohms will cause problems.
Once everything is clean and making good connection, put all back together
and test - hopefully, it will be ok, and continue to be ok. Do keep an eye
on the genset voltage when you run it, though - if something in the
regulator is getting ready to fail, you may have more hi-voltage episodes.
Alan
.
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