Re: [A/S] A/C - A continuing saga

["Don (MI)" <dash7_@xxxxxxxxxxx>]

Hi Tom et all,

I've been following your saga and have a feeling you may be 
experiencing two separate problems that individually would probably 
go unnoticed or would be only an annoyance but together are eating 
your air conditioners.  One is campground voltage and the other is 
trailer wiring.  

Having the same problem with the fourth a/c unit is an indication 
that the a/c is not the problem.  Everyone using this model a/c faces 
the voltage problem in campgrounds. If it was the a/c, there would be 
a line of unhappy campers at the dealer every Monday morning!  After 
reading all of your postings I have come up with a SWAG (Scientific 
Wild A$$ Guess) as to what may be going on.

AC Electric motors must have their rated voltage present at the MOTOR 
TERMINALS to perform properly.  If this voltage is low the motor will 
draw higher than normal current and that will increase the amount of 
heat generated within the motor.  The lower the voltage, the higher 
current, which = more heat, = eventual motor damage. Proper voltage 
at the motor terminals depends on the correct voltage at the 
receptacle the trailer is plugged into (campground power) AND also a 
low resistance path from that point to the air conditioner (trailer 
wiring). Poor connections between these points (loose or corroded 
connections at the plug, beaker box, a/c terminals) or a defective 
circuit beaker or GFI (higher than normal resistance) will result in 
a voltage drop and lower motor voltage.

Suppose your trailer has a wiring problem that is causing a 7volt 
drop in the line.  When plugged into a solid 115volt source at the 
dealer, the a/c would APPEAR to function properly.  However, with 
only 108 volts at the a/c, the motor would be running hotter than 
normal.

Now take the trailer to a campground. Even if the line voltage is 
115volts, you're a/c is running on marginal power (voltage).  As
the line voltage drops due to other RV's being plugged in, the
power at your a/c will be heading for disaster. If you are lucky, the 
breaker will trip and not reset.  If not, the motor will overheat and 
self-destruct.  

With the campground power at 108-110 volts, other RV's would
probably not have obvious problems with their a/c, while you would be 
having repeated circuit breaker trips or worse.  The campground 
manager would probably ignore your comments on low power solely on 
the fact that no one else seems to be having trouble.

Measuring the line voltage at a receptacle inside of the AS will tell 
you the campground voltage but it won't tell you the voltage at
the a/c because the a/c wiring is a separate circuit.

What to do?  The first step is to determine if there is a wiring 
problem in the trailer.  One method would be to measure the line 
resistance between the trailer plug and the a/c.  This method could 
be deceiving as typical ohmmeters use a very low dc current for this 
measurement and the problem is in a high current ac circuit.  A 
measurement under actual operating conditions would be preferable.  
Plug the trailer in, turn on the a/c and measure the voltage at the 
receptacle where the AS is plugged in and then measure the voltage at 
the power terminals on the a/c.  The readings should be the same.  
Any difference is a voltage drop in the trailer that subtracts from 
the power available at a campground. 

I would have an AS dealer do this for me as they have (or should 
have) the equipment needed to safely measure the voltage at the a/c.

Don (MI)