Sunrise Medical DeVilbiss 505DZ Service Manual page 43

C O M P O N E N T T E S T I N G , R E P A I R & R E P L A C E M E N T
If the left bed does pressurize first, observe whether pressure is shifted to the right bed once the shift point pressure is reached or if
the left bed proceeds to pressurize again. In either case, if either bed continues to pressurize without shifting, further testing is needed.
Refer to the Normal Operating Sequence.
4. Place the test leads of a volt meter across the terminals of the pilot valve. Approximately 12-15 VDC should be measured while
the green "4-way" indicator light is illuminated (voltage will be supplied for approximately 9-10 seconds or until the oxygen
accumulator tank is filled). If this reading is not obtained, check for loose or broken wires from the four-way valve to the PC
board. If no loose or broken wires are found, replace the PC board.
5. Test for pilot pressure. Refer to Pilot Pressure System.
6. If 12-15 VDC is measured at connecting leads to four-way and pilot pressure is normal, then four-way valve is either defective or foreign
matter has gotten inside valve causing it to malfunction. In either case the four-way valve must be removed to clean or replace it.
Four-way
valve
Pilot valve
Volt meter
test leads
Valve wire harness
Figure 40
43
Wires on pilot valve
Volt meter
on four-way