So one day I clicked the Overdrive on/off switch on accident, turning overdrive off, and now it wont go back. The "up arrow" light on the dash is constantly on, and whenever i would click the OD on/off switch to try and get overdrive back on i wouldnt hear any click coming from the OD relay. I was reading a while ago that this could mean a bad relay so i bought one on ebay and replaced it, and still no click from the relay. What could be causing this? Is the OD on/off switch broken possibly? If i cant figure it out, im probably just going to buy one of the Bypass kits and never have to worry about it again!


UPDATE: So it turns out the fuse was bad. Bought extras, and when i put them in, they break when i turn the car on. Looks like I have to find out where the short is coming from? I have no idea what could be causing the fuses to break every time

 

Specifically its fuse #12 which is responsible for Back-up lights, cruise control, and
disengagement of 4th gear on automatic transmission

 

on a 91 (I don't have 1990 schematics), it also shows fuse 12 as being the bulb failure warning light circuit, at least on some cars (maybe not US models?).

that fuse blowing suggests one of those circuits is shorting to ground.

turn off everything you can. remove the OD relay, and replace that fuse, does it blow immediately ? no, then the problem is in the OD circuit

yes, then under the steering column, find the 4-pin connector for the cruise stalk, and unplug it, and switch the car on, does fuse 12 blow now? (this connector has a bunch of color wires to it, like blue-orange, blue-grey, orange-white, green-orange, blue-red. that blue-red wire is the power from fuse 12.)

if that fuse still blew, then...

hmmm, the plug for the reverse lights is a connector with a blue-red and a black wire (the other side of this plug might be green and white) thats somewhere near the fuse panel or under the carpet near the ashtray... this goes to the reverse switch which is on the side of the shifter for an automatic, or on the top of the transmission for a stick-shift. that black wire is NOT ground, its the wire to the backup lights.

if you've disconnected all this and its STILL blowing, well, color me confused. maybe the short is under the fuse panel itself on the '+15' rail (which is where all the blue-red wires go). see Electrical: Circuits, Relays

 

Dude, today is the OD day haha
Check my post: https://volvoforums.com/forum/volvo-...erdrive-81453/

Basically go like this:
1) Button
2) wiring to overdrive solenoid
3) overdrive relay
4) overdrive solenoid with new 2 o-rings.
5) Transmission(which i'm having problems with...)
Also, possible cause kickdown cable, see if your car drops in lower gear when pushing pedal to the metal.

 

the wire that comes out of the shift lever and goes to the dash loops down into the shifter well in front of the shifter. for some reason it gets all hard and cracks where its stuffed down into the shifter well, might be the heat from the exhaust i guess, but worth a look..