This Volvo is a 1991 740 wagon: AW71 automatic transmission (w/button on shift knob to disengage 4th "overdrive" gear). Problem: no 4th gear.

When I have had Volvos with overdrive problems in the past it was because the fluid was low. When it wouldn't upshift into 4th I topped off the fluid. It is now a little overfilled. I resoldered the OD relay. I swapped a good OD relay from another 740. Still no 4th gear.

It was below freezing outside & raining on me. I have no garage or concrete to park on; no cash & two family Volvos needing Dad's attention. I am fighting the clock because I have to leave town for a few days & I am now about 48 hours late. Sufficiently stressed, I reluctantly got under the Volvo in the cold wet mud --- the solenoid insulation was cracked & loose & when I wiggled the wire it was not making contact anymore.

I replaced the $250 solenoid. It still won't upshift into fourth.
I presume that this means there is no voltage getting to the solenoid.

Symptoms: The arrow light stays on. The relay makes an audible on/off "clicking." There doen't seem to be any voltage reaching the solenoid regardless of the shift knob switch position. No 4th gear.

I disconnected the battery for about 30 minutes just to see if there was a curable computer glitch... of course, it didn't help.

I'm stuck --- troubleshooting, here's what I see:
Took off the plastic & started digging around. Stripping insulation & wires looking for strange readings.
(1) The solenoid connector wire shows continuity to ground. No power. Just like it was switched off.
(2) Snipped wires to shift knob ...there is voltage on one side of the shift knob switch but it doesn't switch in & out like you'd expect. I presume it is power to the switch & could be a bad switch.

QUESTION: How do you r/r the switch in the shift knob?
There is no obvious way to look inside it.

I isolated checked the connector wire from the solenoid; it does not seem to have any open or short; okay up thru the connector, and on up to where it disappears under the fuse box. BUT I didn't clip-it so it could be shorted under the fuse box. Checked fuses with a fuse checking tool.

QUESTION: How do I get under the relay tray & fuse panel?
(I know that there is supposed to be some plastic clips to move but I had a hard time changing out the relay. No room for my hands).

Help!