Thanks to Paul Malloy's contribution to the 120-130 M41 thread started by Erik on 9/24, I now have the best OD wiring hook-up possible -- one that automatically disengages the OD when I shift out of 4th and stays disengaged, till I pull the stalk switch again, when I shift back in. Though mostly a rehash of Paul's instructions, I'll explain how I achieved this "miracle." My excuse for doing so: a minor variation on Paul's theme.

The crux of this hook-up is to change the pull action of the turn signal stalk switch from momentary contact to ground into momentary power on/off, using a single pole/single throw, 240 door lock relay (Bosch #033204110) in combination with a 240 OD relay (Volvo part #1259750). The door lock relays (two) and the OD relay hang out in the upper regions of the 240 center console. The relay terminals are numbered, and the wiring goes as follows:

--Center terminal on the turn signal stalk switch (usually has a grey wire attached) to #85 on the door lock relay (DLR).

--Power from fuse box to DLR #86.

--DLR #30 to #15 on the OD relay (ODR).

--DLR #87, or 87a, to ODR #86.

--ODR #85 to one of the poles on the 4th gear lockout switch on the gearbox cover. Ground the other pole.

--From ODR #87, one wire to the OD solenoid and another to the OD light, wherever you installed that.

--ODR #31 to ground.

--If you have a two-pole solenoid (J-type), the second pole goes to ground, as if you didn't know. :-)

--ODR #15 to a power source through a 25 amp fuse.

If you don't want to use the stalk switch for the OD; because, for example, you trashed your foot dimmer switch and are now using your stalk switch for that purpose, you can, of course, route the power supply to ODR #86 through a dash-mounted, momentary contact, in-line switch; thus obviating the need for the door lock relay. That stalk switch is mighty convenient for the OD though.
Bob S.