The lower playfield general illumination stays dark in play and only comes on when the attract mode flashes all the lamps.

Lower GI only lights during attract-mode flashes: check the relay under the playfield

Cause: A relay under the playfield that switches the lower GI was faulty and had been wired incorrectly. It is an automotive-style relay that may not be factory fitted.

Checks

• First look for burnt or loose connectors in the GI feed.
• On the relay, pins 30 and 87 carry GI in and out, and the coil pins 85 and 86 need one positive and one negative to pull it in; check the wiring matches.

Fix

• Replace the relay and wire it correctly (or, if it turns out to be a later addition, remove it and restore the factory GI wiring).

Systems

• Williams System 7

Games

• Pharaoh

Related tips

• Some lamp columns over-bright: board or playfield?
• GI string out on a game with under-playfield GI relays
• A single lamp does not light
• No general illumination: trace the 6.3 V AC
• No lamp matrix voltage
• Light a lamp row by grounding its transistor
• Several lamps light together
• A whole lamp row or column dead or stuck on

Source: Pinball Repair help group!! (Facebook group)