Hi All, I'm new to the forum and I'm having a problem with my '91 740 sedan. The speedometer works only some of the time, and then it works improperly. It never goes above 45 mph. Sometimes it works and then suddenly, the needle drops straight to zero, and when that happens the odometer doesn't function either.

TIA, Scott

 

2 things it could be
1. The ABS sensor in the Rear end of the car.
2. The speedo itself.

 

Does ABS = anti-lock brake sensor? How would that affect the speedometer, and how do I determine if that's the problem? From what I've read, it seems it's the speedo, the trans gear, the differential sensor, or the wiring connecting it all together.

If it's the speedometer, do I pull it apart and look for broken gear teeth?

TIA, Scott

 

The ABS sensor is the Diff. sensor. Thats how the car gets the signal for the ABS and the Speedo.
Yes there is problems with the wiring as well check everything good.
There is a way to OHM the sensor and run it on a lift or Jack stands but I don't have the Spec's.

There is no sensor on the Trans.

If it is the speedo you are Screwed and need a New one. Or used one.

 

Thanks and ..... Ooops, i meant the little gear inside the differential, not the trans. Sorry I got a little confused, I've read so many posts on speedometers and some refer to models where the speedo goes into the trans, I assume there's one in the differential too. I've also seen links leading to replacement internal gear parts for some speedometers, that's why I brought it up. I doubt I'll be able to ohm test the ABS. I will carefully consider everything you said. Appreciate your time, Scott

 

Is there anyway I can TEST the speedometer to eliminate it as a potential problem?

Scott

 

Im not sure how to test the Speedo itself.
You might be able to find a speedo repair shop and see if they know how to test it.

We never get that involved. People usually either just buy a New one or a used one.

 

Well Tech, now that the 850 issue is reaching resolution, I'm looking into THIS one a little further. When I look at the differential I see a metal piece that is bolted on and it looks like it holds a plastic sensor. Do I just need that plastic sensor or do I need the metal piece too? I think I can get it from the junkyard. Should I just snip the wires and pop the plastic piece out? I know I can go under the car and actually remove the metal bracket and I might be able to better determine exactly which piece(s) I need, but I thought I'd be lazy and ask you first.

 

You need the little sensor located in the metal cover.
1 allen screw holds the sensor in.

Make sure you get one from the exact year and they look exactly the same.

 

I saw 3 vehicles in the junkyard that looked like they had the exact same metal bracket as mine, tho none of them were the exact same model and year, they were all early 90's. I saw that allen screw, so I know exactly what you're talking about.

So, how many inches of wire should I snip, and will regular electrical crimp style connectors work to reattach the wires?

 

Keep as much wire as you can get. To much never hurts you can always trim.
Yes the Butt connectors will work fine. Maybe shrink wrap to to be safe.

 

OK, most of the instrument clusters were already gone. There was one similar one, but I don't think it will work. Is a $25 a good price for a used cluster?

 

Yes it is a good price JUMP ON IT!!

 

Hi Tech, good to see ya back, hope you had a good time!

I did get it. It was from a '93 940 and everything works except the gas gauge. I have one plug with a green and a red wire hanging from my '91 that has no place to go on the '93 cluster. I suspect this is the gas gauge connection. I'm hoping I can cut the plug off and somehow connect these wires to the correct spot on the '93 cluster. I just can't figure out where to connect them.

Scott

 

I will see what I can find.

 

I appreciate that tech!

Just to be clear....on the old cluster the fuel wires appear to be on a single isolated connector. On the new cluster, it would seem that they must belong on one of the multi-connectors. I need to know which multi-connector and where on that connector.

TIA, Scott

 

See if this wiring diagram site can help you.
Not sure if it has a 1993 940 diagram.
http://www.volvotechinfo.com/WD123/

 

Thanks Tech, I'm going to take a look at it. In the mean time, I've posted pics here...

http://volvospeed.com/vs_forum/index...0&#entry670440

and been getting some other help here...

http://forums.turbobricks.com/showthread.php?t=69888

 

Yes, it was a good diagram. At this point, I'm about 99% sure that the cluster I grabbed has a broken gas guage. Still can't figure out what the green and red wires on the extra connector go to.

 

Any way those two wires could be for the sterio? Mine had a green power wire and a red accessory wire.....just a thought