👋 Have a 1992 Volvo 240 Wagon automatic. Struggling to find any details of anyone with the same issue and possible same solution online so wanted to post here!

My overdrive off light is on, and after a mechanic visit, a lot of diagnostics on my own, I'm pretty confident it's not the relay, and probably not the solenoid, but a wiring issue in the shifter. Here's what's going on:

3 weeks ago the overdrive off light went on and the car wouldn't shift into 4th. Brought to a mechanic who after $200-300 diagnostics said it was just a blown fuse.Two days later it blew again. I found that he replaced the original fuse with a lower voltage fuse. Replaced, light went off as expected. Drove a couple small trips, and on the second trip, after parking and then restarting the car the light came on again.

Today I pulled out the relay - everything is fine. Tested the solder joints with a multimeter, and tested for relay functionality by running 12v of current through the relay - followed the instructions on a super thorough post I found here. Found that when jumping the pins as instructed the multimeter went off as expected for a properly functioning relay.

Visually inspected the solenoid - the mechanic said the solenoid was ok (but this guy replaced the fuse with the wrong one so 🤷‍♀️), and it does look ok. Checked this wire for breaks and/or missing insulation - wrapping that goes around it to protect it, that didn’t seem to extend, but there wasn’t an obvious break in the insulation.

Visually inspected the wiring around the shifter. It looks like the wiring insulation is worn and parts and the bare wire exposed.

Put the relay back in after zip tying down the switch down (per some hilarious yolo instructions here) to see if the overdrive would just stay on. Replaced the fuse. Light went out as expected and went for a 15 minute drive. Overdrive was functioning properly. Tried stopping, going into park a couple times to mimic the behavior that caused the light to go back on before taking out the relay. Was able to get the overdrive off light to go on the second time I went into park and turned the car off, which is making me think the issue is in the the wiring harness for the overdrive, and that installing a solenoid bypass won’t help.

Would installing the solenoid bypass help in this case? Has anyone gotten this far with diagnostics for this, and been able to install a new overdrive wiring harness, or even simpler, spliced in new wire or just wrapped some electrical tape around the problematic wires near the shifter? Struggling to find photos or videos of anyone doing this and at a loss at how to even get the gear shift head off. Any pointers would be appreciated!

 

OK - do you ever downshift from 4th to 3rd? (like maybe to help slow the car when driving in hilly country)

If you don't really use that feature - remove the solenoid, cut the wire going to it, grind a passage between the 2 oil ports and reinstall preferably with a new larger oring, leaving the small oring off.

That will provide oil pressure to the 4th gear circuit all the time - and the transmission will shift into 4th when needed.

Remove and throw away the OD relay. That will keep the light off.

That process is much cheaper than you have already spent.

Or keep spending money on a 30 year old car for a feature that you don't use or (for most people) need.

btw - if the relay is good it will "reset" - go back to 4 speed mode with the light off, every time you turn the car off. You can disconnect the wires to the shifter to make sure they are not shorting together and making the relay switch as soon as power is applied.

 

First and foremost ignore hoonky tonks advice he seems inexperienced to me
You mentioned in your post that you have bare wire exposed??? That is your issue it is grounding out against the frame of underbody and shorting out your overdrive!!

Tape up or solder and heat shrink the bare wire after cleaning it with electronic cleaner.
Or buy a bypass kit i have dozens available.
the grinding method is a waste of time and often doesnt work you feel me!!

Goldenblock

 

The thing that often goes with electrical solenoids is the contacts, they blacken and can make intermittent contact, ocassionally they weld together. Its not worth fixing thenm unless they are unobtainable so check the price on rock auto or similar, there are cheapo made in china ones. some are specific.

If you want to fix one because you are stuck make a spring hook, a tiny tie wrap will work, pull the spring off, unsolder the braided wire if it prevents disassembly then you can file the contacts. alternatively leave the spring alone and fold a piece of about 400 grit wet or dry sandpaper in half and only the size of a paper match . pu that in the contacts and then let the sping close and pull the paper out do that a bunch and then you can clean the contacts with alcohol to make sure they aren't greasy. a filed solenoid is never as good , it may have silver plating on the contacts but it can get you home if it's the fuel pump. and you are stuck.

if you found bare worn or damaged wires you can replace them , should I explain how to splice wires? you can do a western union splice
https://en.wikipedia.org/wiki/Western_Union_splice

get the heat shrink over the wire first, then twist like the diagram and solder them and then slde the heat shrink over the wire and heat it with a lighter if you aren't near open gas or similar..

the wires under the car get wet with oil then the casing of the wire gets hard , someties crack, splice in new wires as needed.

that console in the middle its hard to remove but you can the part near the shifter if its an auto has a clip that you remove if it has the box thing then look in the bottom for a part that removes , its hidden in the flocking but there is rectangle there.. the panels also have a metal strap and some screws that are hard to reach but if you persevere youll get them out, be careul and slow and patient wiht the plasstic parts.. with all that removed you can access the shifter wires etc..

manuals with overdrive have a transmission switch to tell the car you are in 4th, autos have either a switch or a button.. maybe the ones wiht a switch dont need the electrical solenoid, not sure.

my 122 has two circuits for the solenoid. one that does the work fo switching into overdrive. the other holds it on. I suggest accessing a schematic for your model and year and then you can follow the wires on the car and color them with a highliter pen.. it'll become more clear if you do and then you learn how the circuit works. someone else will know if the 240 has a two coil solenoid on the transmission , this is a solenoid actuator , it does work , lets make the differentiation between an electrical solenoid and the solenoid actuator used to switch into overdrive.. the one on the overdrive may be expensive if it fails or hard to get. I would not replace that unnecessarily. the electrical one , I would for reliability.

the other thing i\d check is not just the fuse but the fuse holder. take the plastic panel off, UNHOOK THE BATTERY 2 screws and the whole fuseholder strip comes loose. take it out as far as the wires reach, and use a little wire brush to clean all the fuse holders, replace any old chorroded ones , you can put some electrical grease on the tips to prevent more corrosion. even if the fuse is ok the problem can be intermittent if the fuse holder has that white stuff like the batteriy contacts in your old transistor radio after the battery leaked. also look at the wires on the contact strip if all the spade connectors are not clean , clean those up too. doing this will prevent a lot of issues even if it fails to fix this issue.

if you find bad wire you can cut it somewhere convenient and replce it now , or slip heat shrink tubing over the wire or if you like , electricl tape will work, never twist connections with no solder unless temporary.. some use the crimp connnectors or there is some sort of new fangled solder tape stuff so you dont need a soldering iron.. I hate crimps and always solder , it never fails then. if the insulation is cut
then some wires may be damaged so I like to make sure im not reducing the number of strands anywhere. strive for sa nice neat wrap like in the western union picture. I prefer heat shrink to tape, but do what you need to.

the fuses are rated by amps not volts , they do have a voltage rating but thats probably only adding confusion , they are 12 volts. so there will be a 15 amp or 20 orr somethign best to check the schemtic or the cover of the fusebox has a label. If it blows then dont just put a bigger one because the fuse is proportional to the amperage of the circuit and the wire size, youd rather it blow the fuse than cause an issue elsewhere.. if it keeps failing there is a reason. bad contacts like in the fusebox or a bad connection generate heat and that also increases the amp draw of the circuit. spring contacts like spade connectors or fuse holder tabs can loose temper ( springyness) if they get hot, then you get less spring tension and the contact is worse and thats called a slippery slope. they are color coded redor white you may find a couple of others like blue one that is a high rating. id take the fuse panel cover label to be correct. domnt be cheap with fuses they are a buck apiece but some are brass and seem to fare better than the newer ones.. its easy to disturb the fragile tips at the ends, check that they are all allright. you need good light maybe glasses.

if you want you can hook a little 12 volt indicator light bulb to the solenoid wires in parallel wiht the coil(s) so when the coil is on so is the lamp, that might help you troubleshoot it.

I agree first look at the bare wires you did find and around there , fix that first. I dont suggest modifications. I got a broken 122 overdrive from some nitwit that disabled the 4th gear switch and then bumped it when in first or reverse or something , and it snapped the whole cast iron housing in half. I spoke to a racer that rigged his manual transmission overdrive to work in 3rd, that's different he knew what he was doing and had a reason for it. and had probably added some switches for that. . the manual has a switch that looks like a backup light switch to tell when its in 4th and thats on the transmission.

while you are inthere lookingat the shifter wires, there is a lamp to tell what gear you are in , Id check if the bulb is good since its hard to get to otherwise.

 

Thanks! I'm going to try to get the shifter off - it's super tricky getting under there. I think the solenoid bypass kit is in my future if I can't seem to get into the wires, or it's too tricky to get splicing/electrical tape in there.

 

These are all helpful. Thanks you all - first post, wasn't sure what kind of help I might get

 

Right yeah - had thought hooking up the 12 volt indicator to the solenoid wires. I think I'm going to try splicing/wrapping with some electrical tape (first time trying to get in the wiring near the automatic shifter - it's a little tricky), and grabbed a solenoid bypass just in case. The other diagnostics sound super helpful. Really appreciate it. Will keep this thread up to date with where I ended up!

 

once you get the plastic cover off near the shifter there are some plog in connectors for wiring to the rear ashtray lamp and seatbelt lamps.
some screws might be behind the astray there are some visible phillips ones near the shifter. it has a split so after the clip at the front is off it can be opened enough to slide it out of there and free from the shifter. since the shifter moves it could rub through insulation. if you find yourself forcing anything stop , it will come without breaking stuff. you might need to really look at the flocking.in rhe little compartment. there might be a black plastic part that pops out. if there is a wire plug going to the shifter button you can unplug and check with your meter on ohms the switch should show near 0 ohms when on (closed) open circuit or OL when off (open circuit) if your meter has a beeper function you can use that rather than reading it, just touch the probes together first to see the meter working so you know your meter is working and what to expect.

you don't need the battery connected to check the switch.

what a relay usually, or often does is allows a low current circuit that energises or deenergises the coil in the relay so the switch just handles a low amperage.
the contacts, in turn handle switching on and off the hugher amperage needed
this allows the wire run to the switch to be thinner wire since it's not carrying too many amps.

your headlight , fuel pump and most things that reqire more amps will use a relay. some relays may have a bit more function and complexity there is one under the drivers feet carpet with a timer to delay wipers ,for example