Graco Magnum DX 232735 Service Instructions Manual page 16

General Problem: Excessive Pressure is Building Up
SPECIFIC PROBLEM
Spray–Prime/Drain valve
actuates automatically,
relieving pressure
through drain tube.
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Advanced Troubleshooting
CAUSE
Pressure control switch is worn.
Water or paint entered pressure control switch
or shorted control board.
Control board has failed.
SOLUTION
Replace pressure control switch using Pressure
Control Switch Kit 244266 for DX models or
244267 for XR models.
Clean out and/or dry out, and retry. Replace if
necessary using Pressure Control Switch Kit
244266 for DX models or 244267 for XR models.
See Control Board Diagnostics on page 19, and
replace control board if damaged using Control
Board Kit 245079 for DX models, 243228 for XR5
and XR7 models, or 243229 for XR9 models.