9
Dometic Vacuum Holding Tank
Troubleshooting
Problem
Possible Cause
Service Instruction
3 . Vacuum pump will not run .
a . No electrical power .
b . Loose or broken electrical
wiring .
c . Improper electrical
connections .
d . Faulty vacuum switch .
e . Faulty pump motor .
a . Check input power, circuit
breaker and fuse .
b . Tighten or reconnect wires at
vacuum holding tank .
c . Make certain wires at vacuum
switch are connected to the “B”
terminals . (Refer to Wiring Sche-
matic included with parts list .)
d . To check vacuum switch, short
across “B” terminals with jumper
wire .
e . Replace motor .
4 . Vacuum pump will not shut off .
a . Insufficient vacuum .
b . Excessive vacuum leak .
c . Faulty vacuum switch .
d . Improper wiring .
a . Verify pump pulls minimum
10 in . Hg of vacuum .
b . See problem 1 .
c . To check switch, remove one
“B” terminal wire .
d . Check wiring . Refer to Wiring
Schematic included with parts
list .
5 . Vacuum pump is making a loud
noise .
a . Loose set screw in crank
assembly .
b . Pump bearing is worn .
c . Dirt or debris in pump body .
d . Worn or defective motor .
e . Motor loose from mounting
bracket .
a . Remove cover from pump and
check crank assembly setscrew
for tightness .
b . Check pump bearing for wear .
Replace if needed .
c . Disassemble vacuum pump
assembly and inspect inside of
pump body for foreign objects .
d . Replace motor assembly .
e . Tighten the four screws that
secure the motor to the
mounting bracket .
6 . Vacuum pump is running too
slow, overheating, blowing fuses
or tripping circuit breakers .
a . Improper voltage .
b . Loose or broken electrical wiring .
c . Improper wire size .
d . Motor worn or defective .
e . Tank is overfilled – vacuum
pump forced to pump water .
a . Check input power for low
voltage .
b . Tighten or reconnect wires .
c . Wire size too small – check
electrical diagram for proper wire
size for voltage of pump used .
d . Check motor and replace if
necessary .
e . Disassemble vacuum pump and
empty out water .
7 . Difficulty in emptying waste from
holding tank .
a . The toilet pedal is not open
during holding tank pump-out .
a . Keep the toilet pedal open
(see “Holding Tank Pump-out
Operation”, page 7) .
8 . Vacuum pump emits odor .
a . Worn, torn or punctured pump
diaphragm .
a . Replace pump diaphragm .
9 . Toilet system emits odor .
a . Check for improper flexible
sanitation hose .
a . Replace hose where necessary .
