The trap door on the main playfield stays shut, or opens and burns its coil.

Haunted House trap door won't open

Cause: The trap door coil is driven by MPS-U45 Q17 on the driver board switching a playfield-mounted 2N5879. It is a two-winding flipper-type coil: the strong winding pulls the door and opens a normally closed end-of-stroke switch, which drops it to the hold winding. A dirty EOS switch stops the door from opening. A failed transistor or missing pull-up also stops it.

Checks

• Test Q17 and the playfield 2N5879.
• Clean and gap the EOS switch on the trap door coil.
• Check the 4.7k pull-up on the playfield transistor base.
• Check fuse F14.

Fix

• Clean or adjust the EOS switch, replace failed transistors and add the pull-up.

Systems

• Gottlieb System 80

Games

• Haunted House

Related tips

• Coil stuck on that is driven through a playfield-mounted power transistor
• Flippers dead during play: check the "U" relay
• System 80 driver board transistor types
• A CPU-controlled lamp or coil stays on
• Replacements for the 2N5875 under-playfield power transistors
• Adding the 4.7k base pull-up to playfield power transistors
• Haunted House driver board: which transistor runs which coil
• Backbox chase lights not running

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part Two, Clay Harrell (pinrepair.com)