My good buddy/roommate has just joined the brick world with his purchase of a 1994 940 Turbo. Everything seems to be great on it. It needs a few things here & there but overall a decent little car for the price. The issues we are having is the Odometer, Trip & Speedo are not functioning. Also, it is stuck in Overdrive off, so it will not shift into 4th. Please help!! I'm not really sure how to proceed. I'm going to change the relay for the OD & see if that fixes it. Thanks in advance!

 

The odo is a common problem on the X40 series.

Edit: See Lev's post below. This was irrelevant

 

take a look ad the OD relay, is it clicking when you press the button? is the orange arrow on your dash?

do you want to be able to toggle it? because you can easily and cheaply bypass it so that 4th gear is always automatically selectable

Volvo Automatic Over-Drive Solenoid Bypass Kit IPD 110397 1239928 1239679

 

Change the relay first, in most cases that is the issue for the O/D.

The speedo of the 900 is nothing like the 240, no "little plastic gear" to break. Most likely the capacitors in the back of the speedo head are bad--but check the pick up connector/wires at the differential just in case.

 

Thanks for letting me know. I appreciate your posts here.

 

Good to know Lev. Thanks to everyone for the help! We got the OD fixed. The relay was faulty. I'll have to take a look at the pick up today & see if there's any issues there.

 

Great! good to hear

and Lev is correct, the speed is all electronic. The solder connections and grounds are a known issue at this point in their lives. I have been very successful fixing the fuel and temp gauge issues but have never had a speedo issue on the electronic ones.

basically remove the screws and clean off any corrosion (get some electric grease too on those)

check for cracked solder points and simply reflow the solder. The printed circuits are on super thin plastic and it melts easy so get a really hot soldering iron and don't linger! (hot will flow the solder without letting the heat spread too far, I know it sounds contradictory)

also check the printed fuses (there are a few and they are designated by a squiggly line) if they are popped you can replace them by jumping it with a thin wire (you won't be fused anymore but it'll work again)

 

wait, if the speedo is dead, before even pulling the instrument panel, check the wiring of the sensor on the rear axle... the speed sensor is on the upper 1/3rd of the back plate cover on the differential, and the wire can get damaged by road debris, etc. the sensor itself is a rugged simple magnetic coil thing that reads holes on a 'tone ring', and generates small signal electric pulses, which the speedo counts, so many pulses per second == X miles per hour

note its a shielded twisted pair wire, not just a simple conductor.

 

The speedometer in our '93 940 stopped working not long after we resurrected it, after it sat a year and a half due to the previous owner melting all the fuel pump wiring.

I popped the sensor out of the rear diff, and cleaned all the black crap off it. Also checked the connection there for corrosion - seal was pretty good on the weathertight connector. Re-installed it, and the speedo worked for about a week, then croaked again. Then without doing anything, it started working again, and has been for over 11k miles now. Go figure!

 

that suggests to me intermittent wiring.

 

Yeah, that's what I figured. I think I threw some dielectric grease on the rubber in the connector last time I pulled it apart. Probably just unplugging, and plugging it back in cleaned up the contacts. Now nothing should be able to get in there. We'll see.

 

The wire coating on mine had degraded to a point where bare copper from the (2) wires was rubbing together. Check that as well.

 

Thanks for the info. If I have any more issues with it, that's what I'll look for first.

 

The wires on my buddy's car were cut completely. We spliced them back together, red wire on the driver's of the plug & green on the passenger side. Thanks for the help!