I am pretty sure my 4th gear switch for the OD is shot. I can ground the wire going to it from the relay and hear things clicking. So it seems that this needed ground is not being supplied.

I have called/checked everywhere and this item is no longer available. There is a guy on EBay who claims to have them but after making a purchase he responded 5 days later saying he doesn't have them after all. So that isn't an option.

I have considered adding a manual switch to ground on the dash panel somewhere. But with my aged, addled mind I am concerned that I might not always do the right thing and mess up the OD unit.

I may be able to get one from a junkyard somewhere. But I would really like to get a new one. Any suggestions?

A guy at IPD said that some Datsun cars used the same switch. But I don't know which models/years/part number. And this could be an urban myth.

Thanks for any pointers.

Try this while safely cruising at a speed that you would normally use the OD:

press and hold the OD button on the shift knob while pressing the gear lever to the right and back. If the OD then engages, you have confirmed that the 4th gear switch or (much less likely) its mechanism in the transmission is faulty. If it doesn't engage there are other components that could also be faulty, but your shorting of the switch wire seems to eliminate them.

My 1983 M46 also has this problem. Wiggling the lever as above worked...for a while. As a temporary fix, I rigged up a switch on the dash panel beside the 4-way flasher switch, that provides a short to ground for the OD relay terminal 85 (Red wire). Works just fine BUT....

You MUST remember to turn off that switch (or trigger "off" the OD using the gear knob switch) when you slow down in 4th gear. You can destroy the OD if you use reverse gear with OD engaged, and that is easy to do if you forget to disengage it.

I have a new 4th gear switch sitting in my parts box - bought it a couple of years ago from FCP. That's the problem with "temporary" workarounds; they trigger my "lazy gene" and the proper job gets postponed - or not done at all!
--
Bob: Son's XC70, my 83 240, 89 745 (V8) and XC60. Also '77 MGB and some old motorcycles

Thanks for the pointers. It is somehow helpful to know I am not alone or crazy here. I have considered a manual switch to ground on the dash for relay terminal 85. But I was concerned about the items you caution about and thought that my aging brain might not be able to do the right thing every time. The results of such a brain fart could be pretty unpleasant, I fear.

I have tried jiggling the shift lever while in 4th and really trying to pull harder back and to the right. It doesn't seem to make much difference. But the fact that the OD worked on yesterday's test run has me quite confused about my hard-won conclusions thus far.

Cheers

My OD worked sporadically too, after it started showing the problem. And the 4th gear lever wiggle worked for a time too.

My aging brain has forgotten to disengage the OD a few times, but fortunately reverse gear was never used at those times. Scared myself though, when the OD would unexpectedly engage as I was accelerating in 2nd.
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Bob: Son's XC70, my 83 244DL, 89 745 (V8) and XC60. Also '77 MGB and some old motorcycles

I have finally been able to convince myself that the problem is indeed the 4th gear switch (or the wire going to it from the relay - which I doubt since all the other wires in the system are fine).

I cobbled together an alternate ground for the one normally provided by a working 4th gear switch. I put a toggle switch inline on the alternate ground. And I added a test lamp to replace the OD dash indicator since my bulb burned out long ago and I have been afraid to pull the instrument cluster to replace it. I have posted a photo of this horrible contraption so you can all know how little experience I have with stuff like this (https://www.brickboard.com/IMAGELIB/volvopic.htm?js_link=1&id=12057).

On a good test drive with my alternate ground disabled via the switch I got no overdrive engagement. A quick flip of the toggle switch enabling the alternate ground and I can (a) hear the OD relay click, (b) see the test lamp light, and (c) feel the OD engage. Flip the toggle switch back and nada. I was able to do this about 10 times with exactly the same results.

So now all I need is a new switch (my search continues) and a procedure to replace it - hopefully without having to lower the transmission. I have been told that it is possible to do this. Maybe I cannot since I don't have a lift. But it sure would be nice.

Thanks for all the help. Cheers!

The switch will require a 22mm deep socket. 7/8" will work but fits a bit loose.

I'd suggest lowering the gearbox. By the time you finally decide you have to you will have spent more time than if you had just done so in the first place.

It only has to come down a little on the right side.

Make sure you know what you are doing and take all necessary safety precautions.

--
'80 DL 2 door, '89 DL Wagon

Thanks for the info. I will start researching lowering the tranny. The only socket I have that might work is an O2 sensor socket similar to this (http://www.harborfreight.com/78-in-oxygen-sensor-socket-69022.html). It is marked both 7/8" and 22mm. Do you think that would be sufficient? Cheers!

That should work. But even though it may seem like you can leave the wire connected, disconnect it.


--
'80 DL 2 door, '89 DL Wagon

Further to Bulletproof's post above, a good description of the procedure has been posted on this BB some time ago. If you type "4th gear switch" into the search box at the top of this page, a slug of threads come up on the subject and somewhere in there is a go-by for partially lowering/tilting the trans and accessing the switch.
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Bob: Son's XC70, my 83 244DL, 89 745 (V8) and XC60. Also '77 MGB and some old motorcycles

All I can say is "wow".

And your interior is exactly the same as my 83.
--
Bob: Son's XC70, my 83 244DL, 89 745 (V8) and XC60. Also '77 MGB and some old motorcycles

Thanks for all. I think I will try to hook up some form of temporary bypass for the ground normally supplied by the 4th gear switch to see if all works as expected. But I don't think I want to go that route for long. I am pretty sure that I or someone else may mess up. However, finding a replacement switch seems impossible at this point. I have contacted all sorts of suppliers including Volvo in Sweden and none have any in stock and it is indicated that this item is discontinued so the likelihood of getting any more any time soon seems remote. Maybe someone will start making these again. But the wait could be quite long leaving only used parts from junkyards as an alternative. Cheers!

I bought one from IPD last October 2014. Do they not carry them any longer? While at Midas for a new muffler I asked the tech to replace the no good original one with it and now OD works every time.
Dukester
'85 244 M46

Just got my new 4th gear switch installed. Works perfectly now - every time. Thanks to all!

Thanks. But IPD (and it seems everyone else) is out of stock and have no idea or expectation of when they can get any more. I hope this will solve my problem. But today I got the car back together enough to drive it a bit. And darn it if the OD didn't work much of the time. It did seem however, that at higher speeds (say 55) it did not want to engage. But at slower speeds (say 45 which is not when you really want OD) it did engage 80% of the time. I have no idea what that means except that the 4th gear switch is working at least some of the time. Darn it!

I understand that you hear clicking, but you may want to do a little more diagnosis before springing for a new switch.

Did you check the switch with a meter? It's a pretty simple momentary switch and easy to check.

How about the 4th gear lockout switch?

Did you check the wiring at the gearbox for any that have corroded or fallen off?

Not saying it can't be the switch, just trying to give you other items to check.
--
"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig

Hello and thanks. I do believe the problem is what you call the 4th gear lockout switch. That is why I am seeking one. Right now I am not 100% sure if it is the wire going to it from the relay or the switch itself. I am also not sure how the switch itself grounds (perhaps to the engine and its ground strap?) but I know that if I provide the needed ground to the relay, I can hear the solenoid actuate when it does not if I do not provide the ground when the shifter is in 4th gear.

I can't provide the answer to your problem as it will take some amount of thought and I was just heading out the door--but--I can see you are on the wrong track if you suspect the 4th gear lockout switch because of a ground problem. That switch is the last stop for power before it heads to the actuating solenoid for the OD--has nothing to do with grounds in the system. Another poster has suggested things to check--you should go ahead and check those things. In politics they say to follow the money. You need to follow the power. -- Dave

Hi and thanks for your time and response. I have been working with the wiring diagram in my Bently for my 1983 and it corresponds exactly with this diagram . This is in addition to following several test paths including this one from Duane .

I will certainly not claim to be expert (or even knowledgeable here). But I think I have eliminated everything else at this point.

(a) I checked the fluid level. Thought at first that was it since I recently changed fluid, the thing worked better than it had in a long time, but I saw some leaking from the OD area and assumed that I had messed up. Turns out to not be the case, just "normal" leaking for this thing I guess.

(b) Applied 12V to the solenoid itself and can hear it click in response.

(c) Pulled and tested the push button switch on the shift knob. Works fine.

(d) Visual inspect (from above) and test continuity of wires from the shift knob to the relay. All fine and it seems like the wires were at some point well wrapped with tape and it all seemed well armored.

(e) Open up and inspect the relay for burnt or cracked connections on the circuit board. None found. However, I understand they can be hard to see so I could be wrong here.

(f) Test for 12V at relay terminal 15 (and the push button switch. No problem.

(g) Test for continuity to ground on relay terminal 31.

I could find no way to get the 12V to relay terminal 87 making the dash light to illuminate or the solenoid to respond until I provided an alternate path to ground on relay terminal 85 (the red wire that goes from relay to the 4th gear switch). When I do this, both dash light and solenoid do the right thing. This indicates to me that the relay is doing its job.

So from this I am concluding that:

1. The red wire to the 4th gear switch must supply a ground to the relay. It can hardly provide power. It is a single wire to a single connector on the switch itself. So it must ground to the transmission housing into which the switch screws (I am not sure exactly how this grounds though - maybe to the engine housing and then the ground strap?).

2. Either the red wire from terminal 85 on the relay to the 4th gear switch is bad or the 4th gear switch is bad. I am not sure which but if I am getting under there and possibly having to lower the transmission, I'd just as soon install a new switch along with a new wire if that is needed.

3. It is clear that these switches do fail. They are listed for sale in many places and I have read many postings where folks have done this task. I have also spoken with some really knowledgeable mechanics at Rainbow in Bellingham, WA (not that far from me) and they replace them regularly.

Of course, I could be totally off base.

Please---totally ignore what I wrote before--guess I was in too much of a hurry---thinking of my 144S w/M41 and '80 245 M46. If grounding the wire at the lockout switch gets things to work--then yes, the switch probably is bad--only the tang on the shift rail not working could be the other possibilty--however uncommon. One test you can also do to confirm that would be to put a continuity tester between the switch terminal and the transmission (ground). Should show continuity with the shifter in 4th. -- Dave

Thanks for pointing out that the 1980 (my wife has one) is different. I had assumed they are the same. But lacking the relay it figures it would be different. So I just checked the wiring diagram for that year and it is quite different (much simpler). And the switch does indeed have 2 leads and sits right before the solenoid.

Of course, having said and gone through all of this, I got the car back together enough to drive it a bit today. And darn it if the OD didn't work much of the time. It did seem however, that at higher speeds (say 55) it did not want to engage. But at slower speeds (say 45 which is not when you really want OD) it did engage 80% of the time. I have no idea what that means except that the 4th gear switch is working at least some of the time. Darn it!

Which exact transmission do you have?

The early M46 has a lockout switch with 2 or 3 poles.

The later lockout switch has 1 pole.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Sorry, should have been specific here. It is a 1983 240 with 2.3L and M46. Everything I have read said it should be a single pole. My wife's 1980 also has OD with a slide switch. Maybe that uses the dual pole. Thanks