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DEC 2012 DANIEL MODEL 788DVC DIGITAL CONTROL VALVES
TM
TROUBLESHOOTING6-2
Table 6-1 provides information for identifying and correcting operational problems you may
experience with your control valve. Please keep in mind this information is not exhaustive and that
system abnormalities may result from causes other than valve error. This information is provided
to assist in general field repairs.
Table 6-1. Troubleshooting
Condition Probable Cause Correction
Valve will not open Upstream valve is closed. Open valve.
Pump is not operating. Start pump and check for cavitation.
Downstream valve is closed. Open valve. (Check coupler on bottom
loading units and internal valve in
truck.)
Insufficient pressure. Check pump. Check bypass and strainer
in line.
Clogged strainer. Clean strainer.
Swollen o-rings. Disassemble valve and replace o-rings.
Check compatibility of o-rings with
product.
Pilot malfunction. Consult pilot manual.
Valve opens too slowly Valve inlet pressure below normal. Check strainer and pump for
obstruction.
Swollen o-rings. Disassemble valve and replace o-rings.
Check compatibility of o-rings with
product.
Pilot malfunction. Consult pilot manual.
Valve will not close off tightly Bent indicator stem. Replace indicator
Foreign material lodged in main
valve piston seat.
Disassemble valve and inspect piston.
Swollen o-rings Disassemble valve and replace o-rings.
Check compatibility of o-rings with
product.
Piston or seat o-ring cut or
defective.
Disassemble valve and replace, if
necessary.
Pilot malfunction. Consult pilot manual.