My 1990 740 turbo wagon with 211,000 miles goes in and out of overdirve without warning. As I am driving, the little orange arrow indicator on the dash comes on, indicating that I am no longer in overdrive. I depress the small button on the transmission shifter, but this does not work. Usually, this button would activate the light and control the use of overdrive. I am hoping I can simply disconnect the switch and not have the problem. Does anyone have any suggestions?

sounds like you have a bad relay, easy fix, relays located behind the ash tray.

Resolder the OD relay. $0, 15 minutes, no risk, clean 'n easy work.

If it does nothing, you're out nothing.

Resolder your fuel pump relay and the "radio suppression" relay, too.

The fuel pump and suppression relays gave trouble in wife's '91 740. I got frustrated and resoldered every relay in the car.

Note -- you might have a chaffed wire from push button to relay, inadvertently causing it to shift in and out. But try resoldering the relay before you chase wires.
--
Don Foster (near Cape Cod, MA)

Before replacing the relay as suggested below, locate the relay from the description below, take a drive, and tap the relay as you are driving. This will usually make the overdrive kick back in if it is the relay.







AW-70/71 Overdrive Problems: Relay, Switch.
Relay Problems and Repair:
[See Relay Locations for a detailed picture of relay location and removal instructions.] [Symptom:]I have a friend with a '90 740 automatic and he is having intermittent OD problems that seem to be weather related. It won't go into OD when the weather is cold. Is the relay on the relay tray? If so, which one is it? [Diagnosis:] Yes it does sound like an OD relay. If I remember correctly on 740 it is by the Ashtray/FuseBox. It is pretty common component failure on the bricks. It will be a white Hella relay. Pretty simple to change. The relay is about $40-43 through Mail order from dealership. In my case I was "sure" it was the wiring, switch or solenoid, as the relay "looked" just fine. But as soon as I replaced the relay, all problems disappeared. The relay is about $40 from the dealer, or you can probably find it cheaper from a second source...it appears to be a standard Hella relay.
[Response 2: Michael Daley] I have just repaired the o/drive relay and rather than pay the UK£40 that the volvo dealer wanted for a new one, I took the top off the relay - all that was wrong with it was a cracked solder on the circuit board. Fixed with a soldering iron in 5 minutes, saving myself £40!!

For a more detailed discussion of relay repair, see Relay Repair vs. Replacement.

[Another OD Symptom:] I have a '93 940T with an AW71L transmission (or so I've been told...) Today I was driving on the highway and it momentarily dropped out of overdrive into 3rd, at the time I was at minimal throttle. I dismissed that as a hiccup. An hour later (after making a couple of stops)I began driving and I noticed that the tranny would not go into OD, 3rd gear was the max. All of the other shifts are perfect. I tried pressing the OD cancel button a few times, and I checked the related fuses - no changes. Am I looking at replacing the overdrive solenoid on the tranny? If so, can anyone give me a part# and/or approx. price? [Response: Abe Crombie] It is an AW71 no L. The turbos didn't get the locking torque converter feature. The trouble sounds like the typical OD relay failure. The relay is behind the ashtray in the fuse/relay panel. I believe it is white on that car and square in profile. The fuel system relay is the one to the left that is rectangular.

Most often the relay is responsible for the symptoms you describe. The relay tray is behind the ashtray and once you remove it and the small storage compartment you have good access to the relays. I believe you will find the overdrive relay on the right hand side of the second row. About 1" square base and about 2" tall. If you remove it and pry the cover off you would be able to resolder the circuit board and probably fix your problem. If you disable the overdrive by simply removing the relay it will never shift into fourth gear (overdrive) and fuel economy will suffer because the engine will operate at a higher RPM.

Randy