First let me start out by venting.... Every car/truck that I have ever seen has either had 4 or 5 gears for a manual transmission. I have never, ever...EVER seen a button to push to engage into 5th gear, and I've worked on A LOT of cars in my life. So let me get this straight: These people sat around in the 1970s and 80s and said "Hey it's a great idea if we make 5th gear electronic instead of friggin NORMAL!"

That leads me to my car. I am "blessed" to have the last year where they used this awful idea for their manual transmission 240s. I honestly have no idea why it won't work so I figured I'd throw it out here:
1.) I replaced the overdrive relay.
2.) I used an overdrive switch from an automatic transmission 240 to see if it'll shift into 5th gear - of course no luck there...

3.) I checked the wiring running from the shifter to the tranny and it looks fine with no corrosion or cracks.
4.) My heated seats and rear view window defroster do not work. Those run into fuse #11 and even though the defrost switch lights up, it doesn't defrost and yes the connector is plugged into the grid.
5.) I've never seen that 5th gear light illuminate since I've owned the car as well.

So that's it. I'm at my wit's end here because I simply can't believe Volvo would do this with a manual transmission vehicle, and if I try to go outside and figure it out myself, I am going to get extremely pissed off..Haha...