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M46 Manual swap Over Drive wiring issues

johnmofiemd30

johnmofiemd30

Member
Joined
Jul 6, 2023
Hey all. I’m wrapping up a m46 manual swap
In my 92 245 and I am having the hardest time wiring the overdrive. It’s going in an Auto car that had OverDrive. The basic concept seemed easy enough but I noticed the relay’s terminals that came with the M46 were slightly different than what I was seeing on diagrams and videos for the M46 harness. Well it looks like the guy I got the m46 from included an Auto OD Harness by accident. I checked my car and it’s identical to the OD Harness currently in it . On top of that there was no relay and it looks like they looped the 12v power to the Solenoid wire on their conector (pic included). (My guess is he was trying to bypass something) when I pulled the Auto trans, the OD solenoid wire (white) was in pretty bad shape, maybe he had OD problems and pulled the relay because he didn’t want to deal with getting under the car? Idk haha

So with that, I’m having to wire it from scratch and figure this out. I’m bad at wiring and I have questions.

What fuse block terminal do I run 12v power from, I’ve heard 11 and 12, but I’m not sure.

Where in the instrument cluster do I plug in for the indicator light? All of the diagrams im seeing are with the old mechanical speedo cluster, mine is the newer electronic version. Everything else im seeing says a (yellow wire) on the “number 4 terminal” of the main half moon key plug on the back of the cluster. But my number 4 is brown and black, and there is a yellow wire, but it’s on the the number two terminal.

Below is a link to a folder with photos I took, and diagraman I’m looking at. I’ve also been referencing pretty much the only “how to wire an M46 overdrive” video I’ve seen on YouTube. This guy does the wiring from scratch, but again, colors don’t match up in my car to what he’s saying.

Below are two links, a google drive link to the photos I took and diagrams, and the link to the video I’ve been referencing.

Photos/Diagrams

YouTube video

Would love some insight, also I’m supposed to move in a week and drive it cross country, so it’s sort of time sensitive, DM me and we can jump on a call, which is more efficient sometimes. Also saves the ole thumbs.

Thanks
 
Have you browsed Dave Bartons web site? He has wiring harnesses ready to install for the M46. You can also buy connectors, pigtails of wire with connectors installed. All the stuff you need for what you are doing. In the dash cluster you are going to snip the wire that goes to the o/d light in the cluster from going to the automatic o/d relay. then you connect that to the wire that is going to the new M46 o/d relay. You will also need to add the bypass jumper wire to the wiring for the neutral safety switch so your starter will run.
 
1) OD Wiring Harness:
From my experience there is an earlier and later harness, the earlier type uses a 5 pin relay (blue) and the later ones use the 7 pin relay (reddish.) The 7 pin relay set up I believe is shared with the automatic cars starting around 1986, I assume this is to reduce the amount of unique parts between the cars but that is only speculation. Recently scavenged an OD harness out of a 1983 245T in the Oakland junkyard to put into a friend's 122S Wagon which is getting an M41 installed. Below is a picture of the harness I pulled and with notations of their destination (Edit: The red wire listed as "solenoid" attaches to the 4th gear switch at the front of the transmission.) The wiring diagram is from the 1984 service manual.

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2) Dash Light:
In 1986 with advent of the electronic speedometer, the wiring of the cluster changed to account for that. What you can do is to hook the yellow wire onto the single connector in the bottom corner (34 in the diagram.) This activates the up arrow light for the OD light for the automatic transmission. Below are the wiring diagrams for the 1993 240 instrument cluster which should be pretty close to the 1992 model. As for where to power it the automatic wiring hooks into fuse 11 so that would be my target.

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3) Lockout Wiring:
When going to a manual, don't forget to transmission lock out wiring. This is a two connector plug along the drivers side of the transmission tunnel and you need to just put a jumper between the two leads.
 
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Wow this is so helpful holy cow! Thank you so much. I’ve got a blue manual relay arriving on Monday, I’m just going to wire it from scratch to avoid confusion. What is the lockout wiring? This is the first I’ve heard of this.
 
johnmofiemd30 said:
What is the lockout wiring? This is the first I’ve heard of this.
Click to expand...

A misnaming on my part, the lockout is only found on the 1993 240 automatics. What I am refering to is the "Neutral Safety Switch" previously mentioned by dl242gt in the second post, aka "Start Inhibitor Switch" (F) in the wiring manual (see below.) The jumper wire needed for a manual transmission swap is connector "E" in the diagrams. Did you also get the M46 driveshaft as part of this conversion as that is a different length than the AW70 driveshaft.

If this information/wiring diagrams saved you time and effort in getting the your new transmission in, consider donating to the Hi Performance Auto Service GoFundMe effort. They are one of Turbobrick's cornerstones of information on keeping Volvos on the road.


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Oh awesome, yea I already looped the neutral safety switch and she starts right up so we are good there!
 
OK I have another question and I’m hoping this one will be the last one. The overdrive is hooked up, but it seems like something is reversed in regards to the fourth gear sensor. I can shift into overdrive in every gear except fourth when I’m in fourth the overdrive light just stays on, when I am outside of fourth I can toggle on, and off. This is just in regards to what I’m seeing on the dash with the light coming on and off. It seems like I have something swapped because it should be the opposite. The light should only come on and be a bailable to toggle in fourth gear.
 
Seems to me like you wired it so the circuit gets ground all the time except in fourth. So I would look into your fourth gear wiring and also where you put the ground for the relay.
 
Okay, the 4th gear wiring is just one wire, from the trans switch to the relay. I’m not sure how that one can be wired wrong. I replaced the wire with a new one and I’ve checked the continuity. The being grounded all the time suggestions defiantly sounds like that could be it though. Is it possible the relay isn’t getting ground?
 
dl242gt said:
Seems to me like you wired it so the circuit gets ground all the time except in fourth. So I would look into your fourth gear wiring and also where you put the ground for the relay.
Click to expand...
Okay, the 4th gear wiring is just one wire, from the trans switch to the relay. I’m not sure how that one can be wired wrong. I replaced the wire with a new one and I’ve checked the continuity. The being grounded all the time suggestions defiantly sounds like that could be it though. Is it possible the relay isn’t getting ground?
 
Try verifying each wire is going to the correct numbered location on the relay. If that checks good. Then I would suspect the relay. There is also supposed to be a ground wire to the dash for the relay. Not sure how it would work if that isn't connected. You can also use your ohm meter to make sure the fourth gear switch is working properly. With power off you can connect to the wire in the connector and put the shifter in fourth and it should beep on the continuity checker.
 
dl242gt said:
Try verifying each wire is going to the correct numbered location on the relay. If that checks good. Then I would suspect the relay. There is also supposed to be a ground wire to the dash for the relay. Not sure how it would work if that isn't connected. You can also use your ohm meter to make sure the fourth gear switch is working properly. With power off you can connect to the wire in the connector and put the shifter in fourth and it should beep on the continuity checker.
Click to expand...
Okay I’m going to put a meter on it now stand by haha
dl242gt said:
Try verifying each wire is going to the correct numbered location on the relay. If that checks good. Then I would suspect the relay. There is also supposed to be a ground wire to the dash for the relay. Not sure how it would work if that isn't connected. You can also use your ohm meter to make sure the fourth gear switch is working properly. With power off you can connect to the wire in the connector and put the shifter in fourth and it should beep on the continuity checker.
Click to expand...
okay, when car is off, and it’s in neutral, there is continuity and a beep. When it is in fourth, no beep.
 
dl242gt said:
That is the excact opposite of the way the fourth gear switch is supposed to work.
Click to expand...
I know, that’s why I was thinking there has to be something reversed, but I have no idea. And everything seems to be wired up properly. There is only one wire coming from the 4th gear sensor correct?
 
Somehow the switch is grounding when you aren't in fourth. Are you sure it's the correct switch in there? It takes the shifter moving over to that side of the trans to ground the switch. Seems like your switch is grounding then going open circuit when the shifter moves into position. I would want to have a good look at the fourth gear switch. What version did you use? Early type is two terminals, later type is one pin contact.
 
It’s the later type. There is a two pin on the driver side (reverse lights) a one pin on the passenger (4th gear switch)
 
Yes only one wire to the relay controlled setup. The shifter should ground in fourth only. The early switch on the trans is a pass through type made to work without the relay. Later they added the relay and it gets the circuit grounded via that single contact. I suspect that switch somehow.
 
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