Pre-Infusion Solenoid Troubleshooting - Steam LP
Pre-Infusion Solenoid Troubleshooting - Steam LP

SLAYER recommends all service be performed by an experienced SLAYER Espresso trained technician. For a technician reference near you, please contact SLAYER Support at (206)-284-7171 (#1 in Directory) or email support@slayerespresso.com.
SLAYER Steam LP's Pre-Infusion solenoid is a 24v DC 3-way solenoid which enables a group to efficiently switch between between two brewing phases.

The Pre-Infusion inlet is the feed hydraulic path for maintaining a fully saturated brew tank. Additionally, the Steam LP utilizes one rotary vane pump, each group has it's own independent hydraulic path featuring a check and expansion valve to maintain pressure and temperature stability among the brew circuit.
Parts:
- 99015-10035 Preinfusion SV Assy. Steam LP
Group Cap Magnetic Reed Switches:
Refer to illustration below for magnet activation phases:
- Normally Closed:
- Pump OFF
- No water through group.
- Activates Autoflush feature if enabled.
- Normally Open:
- Manual Mode
- Idle: Pre-Infusion solenoid circuit is closed.
- Active: Pre-Infusion solenoid opens and allows through valve for Full-Brew extraction phase.
- Volumetric Mode
- Activates SHOT 2 Volumetric Recipe.
Actuator Positions:
Refer to illustration below for group activation phases.
- IDLE:
- Right, OFF (ghost actuator in POS 1 illustration).
- POS 1 (Pre-Infusion):
- Indexed actuator magnet moves away from N/C switch.
- Pump activates. (Does not contribute to water pressure during Pre-Infusion phase.)
- Water is moving through the Pre-Infusion brew circuit at 2.5bars of regulated line pressure.
- POS 2 (Full-Brew):
- Pump remains active.
- Indexed actuator magnet activates N/O switch.
- N/O switch sends signal to board to charge 24v DC Pre-Infusion solenoid.
- Solenoid opens and pump pressure water travels through valve.
Troubleshooting:

Deactivate Autoflush while troubleshooting brew group functionality!
Tools:
- #2 Philips Screw Driver
- Multimeter
Parts:
- 99015-10035 Pre-Infusion Solenoid Assembly, Steam LP
- 30000-20042 MAG SWITCH, N/O, PINNED
Symptoms:
Hydraulic path stuck in either Pre-Infusion or Full-Brew, unresponsive POS 2 volumetric program, 'chattering' Pre-Infusion solenoid.
Solution Measure 1:
Verify N/O Magnet Switch is functional.
- Identify respective group switch. Labeled: SW-L.
- Set multimeter to continuity mode and place leads on male molex.
- Actuate group to Full-Brew. Circuit closes, continuity should be present.
- Adjust or replace N/O magnet switch.
Solution Measure 2:
Verify Pre-Infusion solenoid receives 24v DC when group is actuated to the far left, Full-Brew, position.
- Raise display hood:
- Removing Upper Front Panel - Steam Series
- Remove Pre-Infusion solenoid boot and reattach exposed terminal to valve.
- Set multimeter to DC and place leads on solenoid.
- Activate manual mode.
- Actuate and observe.

Video: Actuating through brew phases. Notice 24v DC is absent during POS 1 and OFF positions and present at Full-Brew position.
Questions or concerns? Please contact: support@slayerespresso.com
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