Speedometer Dead

[MrAl]

If I recall th3 -98 operates differently to the 99- cars in terms of ABS signals. It could still be the ABS module or a speed signal issue. It may not have run long enough to throw a code yet is another possibility. Realistically as xanathin says some form of diagnostic is the easiest way forward with this issue.

A simple thing you could try, that I have seen done in the past, is to check the connectors on the ABS module that they are seated correctly and not corroded. The main ABS module connector can be a challenge to undo if it has not been removed before. It kind of flips up and as it does it pulls a lock mechanism to the left as you look at it from the front of the car. Clean the contacts on that and the power connector cable.

Actually there is a simple test you could do even before that. Try to wedge a piece of cardboard between the connectors and the ABS module body. Don't get all crazy, but it needs a positive force pushing outwards on the connectors. What this does is it may force any broken contacts against the other part and if it works then you know you have an ABS module issue. One of my buddies ran his car like that for years. I don't recommend it, but he was ok with that.

ABS signal issues from the wheels I would expect to throw a ABS code, so while like anything on an old car is possible, I think for now that can be ignored.

Neil.

Hi Neil and thanks for the reply.

Is there an ABS module on every wheel?
If so, can just one ABS module cause the speedometer to not register anything at all? Doesnt move a hair.

I am not entirely sure how to test the speed using the OBDII reader.

[scot850]

Sorry, for clarity, there is and ABS SENSOR on each wheel. The wires can get chafed or broken near the wheel. The 4 wheel sensors feed back to the ABS Module which is attached to the underside of the ABS pump. The wires are on the front of the pump nearest the LH headlight.

Here is Roberts video on swapping an ABS module.



This write-up covers what I mentioned about a spacer to help the module work:

https://www.carinstructions.com/volvo-s ... bs-module/

Then finally, Matty Moo's (Mid-West ABS repairs) trouble shooting guide. This is excellent:

https://midwest-abs.com/troubleshooting

Neil

[wizechatmgr]

Check front driver's ABS sensor. MattyMoo can likely tell you what has to be right for you to get a signal to the speedo.

[MrAl]

Sorry, for clarity, there is and ABS SENSOR on each wheel. The wires can get chafed or broken near the wheel. The 4 wheel sensors feed back to the ABS Module which is attached to the underside of the ABS pump. The wires are on the front of the pump nearest the LH headlight.

Here is Roberts video on swapping an ABS module.



This write-up covers what I mentioned about a spacer to help the module work:

https://www.carinstructions.com/volvo-s ... bs-module/

Then finally, Matty Moo's (Mid-West ABS repairs) trouble shooting guide. This is excellent:

https://midwest-abs.com/troubleshooting

Neil

Hi again Neil,

Oh thanks very much for that info that can help a lot, a real lot.
I also found out what ABS means, it means "Automatic Braking System", am i right on that?
I had totally forgotten about that because i don't think any of my other cars in the 50 years before this Volvo ever had that, so i forgot that cars started to have that at some point.

Just a quick note on Roberts Videos. I noticed sometimes he doesn't indicate WHERE the stuff is on the car, like in the engine compartment. The detail is really great though, once you find out where the part is. I was looking for the ABS module, and i had no idea where it was on my car even after watching Roberts video. What i did see though was the shape of that aluminum box with the four pipes coming out of it and now i know those are the brake lines, in that video. I was lucky to have a snapshot of my engine compartment at just the right angle to see that box and the pipes and in the pic i could see it was under one of the fuse boxes and the brake fluid reservoir.

I did some reading and i don't think it is the ABS module, that's all i know so far, but do you think just ONE of those ABS wheel modules could cause the speedometer to completely stop working, with the needle resting on zero even when driving? That would not make any sense to me, but then this whole car does not make any sense to me, and i have to admit i am a complete dummy when it comes to almost everything on this car (ha ha, but it's true unfortunately). I know more than when i just bought the car, but only certain things, so when you tell me about something just imagine you are talking to a complete dumb bell about cars, and that would be just about right.

I will be doing some more testing hopefully tomorrow or the next day and see what i can find out, but i really appreciate all that you have explained so far and if you can think of anything even something little please don't hesitate to mention it.

Thanks again,
AL

Oh BTW, if you think i can help with anything electrical (like general stuff) i would be happy to help, that's my area. Unfortunately, i dont know that much about the Volvo electrical system, only what schematics i can find around. I used to have the complete system for this car (1998 v70) but not sure what happened to it.

[MrAl]

Check front driver's ABS sensor. MattyMoo can likely tell you what has to be right for you to get a signal to the speedo.

Well thank you, but i have a big problem. My scanner is too basic i think and does not show ABS stuff, i don't think because i don't remember ever seeing that. It shows some trouble codes like with the SAS and it also has that little "service light" that is supposed to tell yu when the car needs an oil change or something. That reminds me, that service light came on for the first time in months HOWEVER i did very little driving in the past few months, and i KNOW it was nowhere near 3000 miles, i know it was every less than 1000 miles, much less, probably 500 miles tops, so the service light should have not come on i think. It does go out after 2 minutes as usual. I wonder if it misread the odometer which is also dead. Nothing else seems to be dead though. Gas gauge ok, RPM thing ok, etc.

Do you know if there is a connector on the back of the gauge cluster that plugs into it that could be the cause of a dead speedometer?

Thanks much.

[Chuck W]

.. or if have PC and ELM327 with full V1.4b compatible device then https://jonesrh.info/volvo850/volvo850diag.html Volvo850diag is very good call.

If have Android device and ELM327 with full V1.4b compatible device then one way is use an App "850 OBD-II" to read directly ABS module data. *Disclaimer i am guilty of this then.

This, right here, is the post to follow and use for the diagnostics/code reading.

Pick up a BlueTooth ELM327 device and either use the app (if you have an Android phone) or a PC.

This will get you the DTCs and a direction. If you want to fire the parts cannon at it, then start with the driver side front wheel sensor, but I would recommend getting codes first.

The "850 OBD-II" app is great and I highly recommend it. You can even do a "Gauge Test" and it will get codes for pretty much any system that OBD-II is connected to in the car. (It even picks up DTCs for the power driver seat in my wife's car...)

(You can also change the "Service" light interval, which you cannot do with most scanners)

[scot850]

If you read Matty Moo's diagnostic chart you can usually find the issue without all the fancy stuff. The problem is why their is no warning light coming on on the speedo unit?

In Matty's diagnostic it gives info on resistance checks for the ABS (Anti-Lock Braking System) to identify or eliminate a sensor issue.

The service light is a time based and not distance based reminder.

Appreciate the electrical help offer! I am hopefully going to reinstall the repaired dashboard today, or more likely tomorrow. But first I have to refit all the aftermarket Viper alarm and immobilizer system I removed to try to figure out where the hard wire the installers had soldered into the removable site of the harness for the dash! The guys had used many roles of tape to tidy the many small wiring harness for the system up to the point you could not see what went where will upside down under the dash. I am seriously not looking forward to that and the more than 100% likely the car will never start again!!

Neil.

[Matty Moo]

Do the abs/tracs off lights illuminate for a few seconds when you start the car? Yes/no

Have the abs/TRACS off lights been on, if so how long?

Does the "SERVICE" currently blink continously or has it at any recent time?

[MrAl]

.. or if have PC and ELM327 with full V1.4b compatible device then https://jonesrh.info/volvo850/volvo850diag.html Volvo850diag is very good call.

If have Android device and ELM327 with full V1.4b compatible device then one way is use an App "850 OBD-II" to read directly ABS module data. *Disclaimer i am guilty of this then.

This, right here, is the post to follow and use for the diagnostics/code reading.

Pick up a BlueTooth ELM327 device and either use the app (if you have an Android phone) or a PC.

This will get you the DTCs and a direction. If you want to fire the parts cannon at it, then start with the driver side front wheel sensor, but I would recommend getting codes first.

The "850 OBD-II" app is great and I highly recommend it. You can even do a "Gauge Test" and it will get codes for pretty much any system that OBD-II is connected to in the car. (It even picks up DTCs for the power driver seat in my wife's car...)

(You can also change the "Service" light interval, which you cannot do with most scanners)

Sounds good i will look into that device, thank you very much.

[MrAl]

If you read Matty Moo's diagnostic chart you can usually find the issue without all the fancy stuff. The problem is why their is no warning light coming on on the speedo unit?

In Matty's diagnostic it gives info on resistance checks for the ABS (Anti-Lock Braking System) to identify or eliminate a sensor issue.

The service light is a time based and not distance based reminder.

Appreciate the electrical help offer! I am hopefully going to reinstall the repaired dashboard today, or more likely tomorrow. But first I have to refit all the aftermarket Viper alarm and immobilizer system I removed to try to figure out where the hard wire the installers had soldered into the removable site of the harness for the dash! The guys had used many roles of tape to tidy the many small wiring harness for the system up to the point you could not see what went where will upside down under the dash. I am seriously not looking forward to that and the more than 100% likely the car will never start again!!

Neil.

Hi Neil,

Warning light? I am not familiar with that. Would that come up in the instrument cluster like the 'service' light?

Thanks for the info on the service light. That solves that little mystery. So it's not as sophisticated as i thought.

Good luck with your upgrading too, it sounds like you really really have your hands full.