I would appreciate some help in diagnosing overdrive. Today when I started my 240 wagon ('87, automatic) the yellow arrow lit on the dashboard and overdrive stopped working (tested on the highway). Pressing the small button on the gear shifter does not help -- nothing happens and I don't hear any sound. How would I start diagnosing the problem? The relay seems to be the easiest thing to get to -- but what should I do once I am there?

 

Change the relay--in most cases that solves the problem.

 

yeah, if the light is stuck on and OD is disabled, then its quite likely the relay. if a new relay doesn't fix it, it might be the wiring and switch on the shift ****. thats hard to fix.

if you have a digital volt meter and know how to use it, you could try this....

... find the OD relay, leave it plugged in... find pin 86, which has a grey wire (not pin 15 that has a grey and blue wire). insert your volt meter probe into the back of pin 86 so it makes contact, connect the other probe to ground (or pin 31, black). turn the ignition on (don't have to start the car), and push the button on the shifter. when you push it, you should see 12V on pin 86, when you let go of the button, it should drop to near zero. if it doesn't, then the button and wiring is suspect. if it does, and the light isn't toggling (and fuse 11 is good) then odds are even higher your OD relay is dead

the OD circuit is a bit confusing, btw. when the light is ON, the overdrive solenoid is OFF, and the overdrive is disabled. when the light is OFF, the OD solenoid is ON, and automatic OD (4th) is enabled.

 

Thanks for the detailed instructions. The problem was from fuse, which I blow out myself... I've tried to diagnose the rear window defrosted and found that its switch was disconnected. My idea was that this has happened accidentally (apparently, previous owner did it for purpose), thus I connected the switch and put it into on position. This immideately blow up fuse #11, causing the overdrive arrow to lit (it seems a bit strange engineering solution to put overdrive and defroster on the same switch...).

Now when I've put new fuse, the OD works.. I wonder why activating defroster destroys fuse.. My guess is the short circuit somewhere in the defroster circuit?-- am I wrong? Even when the fuse 11 was dead, pushing defroster button caused relay to click..

Another follow up question is that OD did not work that well even before all this happened. When on highway, I often have to floor the gas pedal and then release it so that OD kicks in. Without doing so, the car may go at 50mph and 3000 rpm without shifting to the 4th gear. I wonder if this means solenoid that is failing or can it still be caused by dying or old relay?

 

do your other gears shift normally (1->2, 2->3) ?

 

They do. May be not that smoothly as in the new car, but they shift well.

 

oh, re: your defroster, odds are you've got a short somewhere in the wiring.

#1 candidate for the short is at the hinge... the power wire looks like it travels down the left side of the car, up and over the left rear wheel hump, then goes up the left D pillar to the left hinge. my diagrams show it as a yellow wire, 2.5mm for most of its run, 1.5mm for the last bit through the hinge down to the left side of the window. there is a connector 'E' shown just before the hinge.

 

btw, the OD solenoid... its a solenoid valve... when its powered to enable OD, a passageway opens that allows ATF to flow, when its depowered to disable OD, this passageway closes. its quite possible yours is somewhat plugged up.

when was the last time your transmission fluid was flushed and replaced? it should be clear red on the transmission dip stick, if its dark brown and/or smells burned, time to flush it !!

 

After this leak the transmission fluid was replaced (they also replaced the pan gasket) in a shop.. Thus the fluid there is in a very good condition.

 

how was your OD prior to this work?

 

I am not sure I remember this well -- the leak happened days after I got the car.. Also the car didn't have the tach installed then.. Anyway it is probable that the OD had similarly strange behavior even before the leak.

Could this be caused by a slight overfill of the transmission? I.e. those guys filled the fluid so that it goes to the hot line in the cold transmission.

 

someone else reported their tranny was shifting sluggish when it was overfilled, so yeah, maybe. too much pressure or whatever.

I asked earlier about 1-2 and 2-3 because if they were ALL shifting late, the transmission throttle cable might need adjusting.

 

Well, I just noticed with my eyes that the yellow wire is broken. The place where it is broken is at the hinge on top of the car -- there is a small slit through which I can see wires. Do you have any idea how to get there?

 

I believe to work on those wires, you remove the interior trim panel across the top, this probaby requires removing the D pillar interior trim too. I have a 740 wagon, our 240 is a sedan, so I can't say for sure.

note that wire that runs out the hinge is NOT ordinary wire, its got extra fine stranding and extra tough insulation.

I believe this is the aftermarket replacement harness
Volvo Tailgate Wiring Harness Left (240 245) - Pro Parts 3544695 | FCP Euro

and this is the factory part
Cable harness, Cable harness, bottom rail- boot LID/TAILGATE. Fits: Volvo | VolvoPartsWebstore.com

note the harness is not just the window defroster but also the license plate and 3rd brake lights...

 

When I tried to get to the hinge from the bottom, I didn't manage to detach the fabric lining on the car roof. I was too afraid to tear it... What is the best way to detach the lining? Sorry for noob questions.