I have a 81 240 dl 4 speed with electronic overdrive. When in 4th gear I hit the overdrive button, the O/D light comes on but the car does not shift. Just a few days ago the car would shift into overdrive and then would occasionally and briefly shift out and then back in, then for a while it seemed to not do it all. Well, Wednesday I was driving and it came out and hasn't worked since... any ideas? The wiring from the switch to the solenoid is in great condition considering it has just been replaced due to someone accidentally ripping the knob off going into second. Any advice would be great. Thanks

<Switches to Tarkin mode: I grow tired of repeating myself, so it'll be the last time.....Tarkin mode off>

Again, for the benefit of noobs, use the "search" option! light on means overdrive off, and vice versa. common probs include bad relay in dash, bad solenoid in gearbox, bad wiring near gearlever, poor servicing of gearbox and sludge buildup/filter failure, bad wiring at/near solenoid, bad fuse-dirty is enough 4 trouble-replace ALL aluminium fuses with copper or brass, or replace fuseblock with blade fuses.

okay...so then i am confused....how come when the little green light on the dash board is lit that says "OD" then the overdrive use to kick in? so how does light "on" mean over drive off?

http://new.volvocars.com/ownersdocs/1981/8...GLT_02.htm#pg37 says when button is pressed then overdrive is engaged....

"Overdrive (some models only)
Shift to overdrive at 45 mph (70 km/h) and disengage it when speed drops below 40 mph (65 km/h) or vehicle encounters hilly terrain. The overdrive can be engaged in 4th gear only. The overdrive is engaged by pressing in the switch on the top of the gear lever. If the switch is pressed in once again the overdrive will be disengaged. In addition, the overdrive is disengaged when downshifting.
No extra operation of clutch or throttle pedal is normally necessary. Engagement is facilitated if the accelerator pedal position is maintained steady.
When disengaging, depressing the clutch pedal slightly makes a smooth transfer.
The overdrive should be used after the engine has reached normal operating temperature (minimum time is five minutes) and the vehicle is being operated on relatively level roads.
Downshifting to a lower gear will disengage the overdrive"

I just checked and I can hear the relay clicking so it is good. Any advice?

I appologize, I'm using my 88 240DL as reference which is amber arrow on for no overdrive. I accept that other models may be different. relay sounds ok, now open left side front door, motor off, ign on, and click the OD switch. Listen towards underside of car for solenoid clicking-if OK, then plumbing blocked in gearbox-if no click, then failed connection or solenoid (perhaps blockage too). repair/replace. Check gearbox oil quality. Change at least every 50,000 mi, and prob sooner on some models-see handbook for your model. If no proof of last change, do it now anyway, so you have a benchmark & write it down and keep it for reference. Mark calendar 2 yrs ahead for approx next gearbox oil change date.-gear oil is cheaper than gearbox. BTW ditto Differential with it.

awesome! thanks for the advice, will try right now and let you know how things go.