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Wire diagram for 1985 M46 OD Relay

DStarratt

Member
Joined
Jun 4, 2017
Location
San Antonio
Hi, I am trying to fix an OD that will not engage until the car gets warm. It takes about 20 min. There is no power to the solenoid while cold. I do have power to the OD relay. I think I'm getting power from the shifter button too. In order to diagnose I need to figure out which wires to the OD relay harness go where in the system. I have a wiring diagram for 1984 but 1985 is different. Im hoping someone can post a picture of an 85 wiring diagram or even identify the color wire and where it goes. Thanks.
 
Sounds like the classic fourth gear switch that is intermittent until the trans gets warmer and expands. When it's cold try moving the shifter sideways and see if that makes it work. Also clean up the ground on the overdrive. Best to also do a visual inspection of the wiring and make sure the insulation hasn't decayed off the wires.
 
Thanks. Tonight I tried pushing the shifter way down and as far to the right as I could. No luck.

That wire diagram is off a little. My OD relay connector has a couple wires that aren't in the diagram. Does anyone know what the orange wire goes to? I think it's either the indicator light or the solenoid. I think the yellow wire will go to the other. I also have a brown wire that I can see comes from the shifter button.

The wiring looks pretty good. I'll clean the ground on the OD. I'm guessing it is the OD switch on top of the OD. Is there a way to test it with a multimeter where it sits? I'll probably just replace it but it would be nice to test it first while it's on the car.
 
The '86 wiring diagram shows the orange wire goes to the indicator light in the cluster and the yellow wire goes to the solenoid. The OD switch has a blue and a brown wire. The blue wire comes from the fuse box and the brown wire goes to the relay.

The OD relay is known to suffer from the same solder joint failures as the fuel pump relay. Try re-flowing the solder connections in the relay if all the wiring checks out.
 
The OD relay is known to suffer from the same solder joint failures as the fuel pump relay. Try re-flowing the solder connections in the relay if all the wiring checks out.
:nod: Especially the row of little chair-shaped connections connecting the external spade connector board to the inner circuit board.
 
Thanks I will try that. I tried soldering a few other relays and I think I’m getting the hang of it. I ordered a fourth gear switch last night. Between the switch and the soldered relay I should be OK.

Just out of curiosity though, what sort of charge should I get from the red wire (4th gear switch) with thetransmission in 4th gear vs say 3rd gear? The diagram shows a pink flow.
 
The fourth gear switch is ground for the relay. That way it only works in fourth. The volvo diagrams show you the various operating conditions of the circuit. So the one with third gear would be an interrupted circuit since the fourth gear switch isn't grounded.
 
The red wire is grounded when the trans is in 4th. It should be open (no connection) in any other gear.
 
You might also want to make sure the red wire is firmly attached to the 4th gear switch. I went through this with my 242 when it had the engine/tranny that are now in my 245. Frequently, it wouldn't work at all when stone cold, then sometimes would click on and off quickly if you did the shifter trick, until it was finally warm enough to work properly. When I took the engine out, I noticed that the 4th gear switch wire was barely making contact.

If you have a multimeter handy, put it on continuity or resistance (ohm) measurement mode. With the transmission in 4th gear, disconnect the harness at the center console and connect the (+) probe to the red wire, then the (-) probe to a good ground. If there's no resistance, then the wire and the switch are fine. Put the transmission in neutral or another gear. You should have infinite resistance. With respect to the relay wiring, the '85-'86 cars were wired differently, partly to make things more modular than they were before, and partly to allow usage of the OD OFF light as both that, plus, on B230F M46 cars, as the upshift light. That's why there's an extra wire (or two) coming off the blue relay plug on a later 240, compared to a 1981-84 car. Works with the small "b" shaped relay to provide the upshift light feature. Otherwise, if you went from 4th to overdrive and didn't disengage the clutch, the light would keep glowing, which apparently was a problem on late 1984 DL and GL cars with the upshift light. The extra wiring isn't really needed on a 1985 240 Turbo car, since those vehicles don't use the upshift light. On my old '85 245Ti, I actually switched to the 1981-84 relay. The orange and yellow wires get spliced together, since the 1259750 relay provides power to both the "5" light and the solenoid through one terminal. Main reason for doing so was due to our other M46 240s using the older relay - one was an '83 245Ti, the other was an '84 245GL that was built just before the upshift light was introduced, so it had the speed sensor in the diff, but no wiring. Didn't want to be stocking two different M46 overdrive relays. In retrospect, I could've replaced the blue relays with the red 1347768 relay used on the later cars, since it can be used with the earlier wiring. Just have to tape off the extra terminals that won't be used. Both of my current cars use the 1979-80 overdrive wiring setup without the relay. 245 was wired that way when I originally converted it from an Aw71 to a M46, and I wanted both cars to be identical.

As an aside, I have come across a few 1985 240T cars with Aw71 that came from the factory with the 1307793 orange relay, instead of the white one. Install the white relay, and it will cause the od off arrow to light up when the overdrive is in the default on position.
 
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