There is a 1-wire temperature activated switch on the front of the thermostat housing that does not allow O/D operation until the engine is at operating temperature. Remove the connector and ground it. An easy way to do it is to stuff a piece of small wire up inside the connector, reinstall it and ground the other end of the piece of wire. If the O/D now works, replace the thermo switch.

If that doesn't work, the issue is probably with the O/D OFF relay, but odds are it's the thermo switch.

Frank

'89 [color:"white"]G-Raider[color:"white"] [color:"black"]Supercharged 3.0L, MegaSquirt 2, lockup A/T, 2.5" exhaust, 172k, Cibie H4s/Oscar SCs, Hella Micro DE fogs, Cobra CB, Superwinch hubs, LSD rear/Aussie Locker front, Bilsteins, Lifeline AGM, Rust-Oleum