Practical troubleshooting your RV, 101 #1

[Bob Lawrence]

Hi Ralph,
On our trip here to South Padre Island, we stopped at a campground in
Rockport.
I was working outside with my Dremel plugged in and it bogged down. I
heard a pop and I lost all the grounds in the bus and blew 6 surge
protectors.
Where do I look?
Could the ground have melted off at the bus 50 amp inlet?
Bob Lawrence
84 PT36
South Padre Island, Texas

> Hello everyone;
>
> Electrical systems in any venue, to many, is confusing and it does
not have
> to be. With just a few simple rules, one can do a systems check no
matter
> if it is a 12vdc/24vdc or an 110vac system.
>
> The words, what? where?, how? and why? come to mind as the very
basic start
> to finding a problem with systematic troubleshooting.
>
> What? equates to, What is the real problem? (does not mean what the
problem
> appears to be.)
> Where? equates to the physical location of items along a "path" in
a given
> system.
> How? equates to how does it or is supposed to work?
> Why? (remember when Dad used to say "there is no such word as why."
The why
> equates to why did it happen in the first place.
>
> It is important to try to learn how a system is designed to work or
the
> right way to say this is "know the sequence of operation." If you
know how
> it is supposed to work then you are ready to start trying
to; "recognize"
> "localize" and "isolate" a problem.
>
> Ok lets pick a simple system; 12vdc fan. Problem, fan does not run.
Ok so
> now we know it is a fan not coming on, so the problem
is "recognized." So
> what do we really know about "where it is." A switch on a dash, the
fan is
> located behind a panel near the co pilots feet, but is there more
in that
> system besides a switch and fan motor? Could there be a "relay" in
line
> between the switch and fan? Could there be a circuit breaker or
fuse,
> between the switch and fan motor? All are valid questions and can
be
> answered with a "sequence" of operation.
>
> "Sequence" of operation for the system above; 1.it is a 12vdc
system so
> from the system circuit breaker, 12vdc is supplied to a switch and
from the
> switch to the coil of a 12vdc relay then 12vdc passes through the
contacts
> of the relay to the fan motor and the fan motor runs.
>
> Now we know the "how" it works, we can start to "localize" the
problem.
> Starting at the circuit break we are going to check for 12vdc to be
sure
> the switch is in fact getting power. Yes voltage is present. Then
go to the
> switch and check for 12vdc, yes voltage is present on one side,
then switch
> the switch to the run position and check for voltage. It is found
that
> 12vdc is present on the out put side of the switch. Next stop is
the relay
> coil, check for 12vdc at the coil of the relay, yes 12vdc is
resent, then
> check the out put side of the relay, no voltage found, hmmm,
interesting,
> now it is time to find out how the relay works, 12vdc goes to the
coil of
> the relay then passes through the coil to ground and the relay
energizes
> and the contacts are changed in state for open to closed, but the
12vdc
> power source is from some where else going to the 12vdc fan motor
and not
> the switch on the dash. Now one must check the voltage patch the
flow
> through the relay to the 12vdc fan motor, and find the "why" it is
not
> present. So we have isolated the part of the 12vdc circuit that is
not
> working to turn on the fan with the switch. Checking the "source"
circuit
> breaker, it is found not to have 12vdc present. So the circuit
breaker is
> the bad part, it must be replaced. Now switch on the dash switch
and the
> fan motor runs. Great! you have fixed the problem, or have you? Did
we look
> into the "why" the circuit breaker went bad? This part of trouble
shooting
> is not always well defined and in fact may not be found. So that
brings up
> the question, what must happen to make a circuit breaker fail? Lose
> connections are a cause. Bad ground is a cause, age of the part
will
> contribute to the cause of failure.
>
> As you can see there can be several steps and items in a system
even one as
> simple as this one. Trouble shooting can be VERY time consuming,
but it has
> to be done to make a system work. Once you have been through a few
> troubleshooting procedures like this, you learn some short cuts
here and
> there that helps to "cut" the time factor down a bit.
>
> Also a thing to remember. Nothing is set in concrete when trying to
find
> out and repair what does not work. What I am trying to do here is
show a
> process that is practical, saves time and effort and cuts the cost
of a repair.
>
> Let's not throw money at something in hopes that is will make it
run. You
> can sure go through allot of money doing that and still not find
the
> problem let alone fix it. So with a few trouble shooting steps we
have
> spent $3.00 on a part to make the system run, instead of spending
$225.00
> in parts like new switch? new fan motor, new relay and so forth.
Yes it has
> cost the time to troubleshoot the system but is still cheaper on a
repair
> bill than throwing money at some thing.
>
> Will stop here for this first post and wait a few days and answer
any
> questions anyone may have.
>
> Ues I know it is a VERY simple system noted above, but there are a
large
> percentage of people that do not have any idea what or how. Please
keep
> that in mind when posting on this first post.
>
> Safe travels,
>
> Ralph and Charolette Fullenwider
> 84FC35 "Ruff Diamond"
> Duncan, Oklahoma
>