How do you fix overdrive button on 91 Volvo 740?

Answer 1

Chances are very good that there's nothing wrong with the pushbutton itself. Most likely the OD relay has gone bad. They are notoriously unreliable pieces of crap and I cannot understand why they ever installed these. . . but they did. Remove the ashtray in the center console. If you can reach into the relay tray, put your hand in there and feel around toward the firewall for the tallest relay. It'll be to the right and all the way forward on the tray. While driving, try to jiggle this relay and see if the OD goes on or off (whichever you can't get it to do now). To change it, you'll probably need to remove the cigarette lighter and the junk compartment above the ashtray.

IF your switch is actually bad (which is rare), just use a very small straight-tip screwdriver to pop it out of the shifter handle. I believe the wires detach at the switch itself. If not, you'll have to chase them into the tranny tunnel to find the connection. . . or you can do the shadetree half-ass method of cutting and splicing with electrical tape.