Hey all, I have a 1986 volvo 240 DL with the 4 speed manual gearbox with electronic overdrive.

The overdrive has never worked for me the way it should. Although I can jump the correct wires (yellow and blue i believe) with the relay out and get overdrive to engage. when doing this, the solenoid works well and the overdrive sounds good. I have a repair manual, but it lacks any useful wiring diagrams for the overdrive system. I have a 5 volt reference and a 12 volt power supply to the relay, the ground is good, and the switch on the shifter works as well. I got another relay (new) and still no overdrive.

are there any other weird parameters controlled by the ecu that would not allow my overdrive to work correctly?

and, will there be any damage if i just connect a hard switch to the overdrive solenoid wires to directly control it?

Thanks, Ian

 

Since it sounds like everything else is working : it might be the gearbox switch which connects the red wire to ground when you are in 4th gear (OD enabled). When you down shift, the switch opens and ground is removed, and OD is disabled.

And yes you could hard-wire around the relay with a switch, but wait until the wife/girlfriend presses it while in first gear :-)

 

ahh, excellent, so I should have continuity to ground through the red wire when in 4th gear...is this switch inside the gearbox or external of it.

if its inside I could put a simpler switch in the red wire to connect it to ground once in 4th gear,then use the switch on the shifter to engage overdrive...and it wont be so tempting to hit overdrive in first gear.(by the way what happens? stall?, grinding?)

thanks, Ian

 

Where did you get that diagram? that is exactly what my repair manual DOES NOT have, and would have made it much nicer to know what wires were what earlier on.

Thanks again.
Ian

 

The switch is shown in this picture. These diagrams are from the "green books" published by Volvo. You can find them here:
http://www.k-jet.org/documents/greenbooks/200-series/

I would measure ohm's to ground on that red wire when/when not in 4th gear. What did you mean by the "5 volt reference" in your first post? Nothing in this circuit should be 5 VDC ...

 

Hey, awesome again.

it wasnt exactly 5 volts, i think it was 3-4 volts. and where i measure it was at the relay connector with the relay out, and the key on. I believe it is for the low amperage switch of the relay circuit. I think it was the middle "87" terminal to the black wired ground "31" i believe.