I have a 1997 850 GLT. The speedometer works erratically. Occasionally it works just fine, but most of the time – nothing. The odometer stops when the speedometer stops. I tried replacing the speedometer, and the sensor on the transmission. Neither changed its erratic ways. I also tried unplugging and plugging the connectors under the dash, below the fuse block. I even tried jacking it up, putting in gear and watching the speedometer while I moved and shook wires. Nothing made a difference. Any ideas? Where could I get a schematic or drawing to show me exactly how the wiring runs from the sensor to the speedometer? I may need to trace out every inch of wiring. Any help would be appreciated.

 

I just purchased a 96 850GLT on friday. Yesterday mine did the same thing. The odometer doesn't work. Most of the day the speedometer worked, but sometimes it would NOT. I plan on replacing the odometer gears as already stated in another thread. Should I do anything else before undertaking this task?

 

While at this point I have no ideas on how to fix this issue, I find it interesting that two different 1996 vehicles apparently have the same problem. Please keep us posted on how the repair progresses.


Glenn

 

See attached for some info. Also note, that the speedo receives some signals from the ABS module.

There are 2 different instrument mfgs; VDO (German) and Yasaki (Japanese). The electrical circuit seems different on those clusters.

If nothing else helps, wait to see if you can receive a reply from the top-dog of the forum named Moderator Tech.

Good luck,


JPN

 

.

 

.

 

.

 

.

 

Thanks! I bought a Haynes book, but I couldn’t find any diagrams showing the speedometer. It listed speedometer in a section listing all items, but no speedometer on any diagrams (that I could find anyway). This info from you is helpful. Mine is a VDO type. I saved all of this info from you, and will run these checks. Thanks again!

 

I saved the pix as well, thanks!

 

My pleasure.

I wish you luck solving the problem.


JPN

 

Tried the suggestions, and the info doesn't seem to apply to mine. It seemed to show a speed sensor on the bottom of the transmission, and mine is on the top. I did try swapping the sensor with one from another 850 I have, and it didn't change anything. The speedo (VDO type) just works sporadically still. The one I removed from this troubled car works fine in the other 850. I noted comments about the odometer. The odometer works fine all the time. There’s nothing wrong with it. It’s just the speedometer, and about 10% of the time, it works ok. When it works, it works well. Then, it’s like someone turns off a switch – nothing. Since I replaced the sensor, and replaced the speedo, and nothing changed, it just about has to be in the wiring, right? Any held on tracing that out? I could just run new wires if I knew where it went. Does it go directly to the speedo, or to a computer, then to the speedo, or????

 

850 Man, I have another issue I was hoping you could assist. I believe you stated that you disconnected the speedo from the top of the tranny, and the car still ran fine? (I am swapping a 96+ trans into a 95 and I might have to jerry rig the speedo, but I was not sure if the car would operate correctly with 'missing speedo (Vehicle Speed) sensor). Can you confirm the car drove and shifted fine? =D

 

It drives fine without the speedo apparently working (it registers 0 mph), but I don’t think I actually drove it without the speedo connected, or without the speed sensor. So, I’m sorry, but I can’t really say what it would do without it. I can say that I have a 94, a 96, and a 97, and from what I can tell, the sensor and speedo parts seem to be interchangeable for those years.

 

850man, please see http://www.matthewsvolvosite.com/cha...ic.php?t=12962 and tell me what you think... sensor is in different spots and the clip is different... (still two posts though). Thoughts?

 

I just wanted to let everyone know that I finally figured out what was wrong with my 850’s speedometer (working sometimes and not working other times). A very smart Volvo mechanic finally told me it was the ABS unit. I thought he was pulling my leg, but I contacted WWW.AUTOECU.COM, and they verified that the ABS unit would definitely cause the speedometer to work erratically (speedometer sensor wiring runs through the ABS module). I removed the electronics portion of the ABS (also found out you can take this part off and drive fine – no brake fluid loss or anything – brakes still work, just no ABS – until it’s reinstalled) and sent it to WWW.AUTOECU.COM. They rebuilt the module, updated it, and fixed any potential problems. They were great. I had it back in a few days, and it fixed the problem just like they said it would. BTW – the electronics part of the ABS isn’t so bad to take off, but you do need a small reverse Torx socket to take out the 4 screw/bolts. The wiring just unplugs. If the screws were easier to get to it would be super easy. I did have to remove the air filter to get to these 4 module mounting screws. Anyway, just wanted to let anyone know that’s having erratic speedometer problems, it could be your ABS – especially on a 1997 Volvo 850. I searched for months, replaced parts, and couldn’t find any info on it anywhere on-line – certainly not this solution. Just thought someone should share the info!

 

Good man posting the followup. Always nice to follow through

 

Very well done!


JPN

 

Somehow I missed this post otherwise I would have told you ABS module from the start.

 

My sister's 850 does the same thing. I was going to order a new speed sensor tonight, but after reading this thread decided not to. Turning the ignition key off, and back on while driving will sometimes get the speedometer to work again. Have either of you found this to work?

-josh