Sabre 1438HS dies when engageing pto and deck is not under mower

Replaced seat and splice the two seat wires together ,removed deck to fix out of line pulley. Deck is still out from mower. When I start mower it dies when I engage pto (blade drive) . Seems to work in reverse how do I check out problem
Un hooked the two seat wires and mower will not start

Sabre 1438HS dies when engageing pto and deck is not under mower