Speedo issues

[Mickyfinn121]

Hi guys my 1991 940 speedo isnt working. Ive checked and tightened all the screws on the back checked all the plugs. Everything else works apart from the speedo. I was told from the original owner that he had the sensor tested under the car and that was fine. Its got me completly stumped cheers.

[Jebus]

Since you have a 91 car, like has a damaged speed circuit board, there is in brilliant guide in the FAQ that explains everything, but short story is the capacitors leak and cause issues, but you are lucky can change them and clean it up

[bob12]

Your cluster and speedo will be OEM Yazaki so odds on it's the pcb within the speedo itself with blown capacitors.

[Laird Scooby]

Does your car have ABS and if so, does the ABS warning light behave as it should? In other words, come on for a few seconds when the ignition is first switched on then go off and stay off?

If not, the fault could be somewhere in the ABS system as that is fed by the same sensor on the back axle.

Also do your odometer and trip meter still work? If so it's almost certainly the capacitors in the speedo head.

[WUMPSTER]

There is a company that repairs them link here https://www.autotronics.co.uk/volvo-...er-repair.html

[Mickyfinn121]

Originally Posted by Laird Scooby

Does your car have ABS and if so, does the ABS warning light behave as it should? In other words, come on for a few seconds when the ignition is first switched on then go off and stay off?

If not, the fault could be somewhere in the ABS system as that is fed by the same sensor on the back axle.

Also do your odometer and trip meter still work? If so it's almost certainly the capacitors in the speedo head.

No abs light and everything else work apart from the speedo it still recors miles and things

[Laird Scooby]

Originally Posted by Mickyfinn121

No abs light and everything else work apart from the speedo it still recors miles and things

Then the fault lies in your speedo head. What are you like at electronics?

[Ian21401]

Have a look at these:

http://www.brickboard.com/FAQ/700-90...sterRemovalAll and

http://www.brickboard.com/FAQ/700-90...eterRepair.htm and

the threads I started: Intermittent Speedo/Odometer Fault and
Help Please re Speedometer Fault.

My brother has spent most of his working life fixing PCBs and the stuff that is soldered to them so I obtained the capacitors and he replaced them for me.

[XCR]

Useful info as I'm having some issues with mine too.

Whats the likely issue with mine ? Diff sensor or PCB/Capacitor ?
Its a '91 940 (so the Yakuzi unit) with the following symptoms.....
Sometimes sticks at 36mph (or 46 depending on how its feeling) and the odometer and mileage stop dead BUT on occasion the numbers race round (a mile every 100 yards or so !) and it all catches up....sometimes all reads normal...
Today the miles are being counted as normal and speedo is at 0....
Where do I go from here ?
I'm using a Garmin as a speedo but I'd like to sort this....

[Laird Scooby]

Originally Posted by XCR

Useful info as I'm having some issues with mine too.

Whats the likely issue with mine ? Diff sensor or PCB/Capacitor ?
Its a '91 940 (so the Yakuzi unit) with the following symptoms.....
Sometimes sticks at 36mph (or 46 depending on how its feeling) and the odometer and mileage stop dead BUT on occasion the numbers race round (a mile every 100 yards or so !) and it all catches up....sometimes all reads normal...
Today the miles are being counted as normal and speedo is at 0....
Where do I go from here ?
I'm using a Garmin as a speedo but I'd like to sort this....

Does the ABS warning light come on when the speedo plays up? No? Then it's not the diff sensor.

It sounds very like a mechanical problem within the Yazaki speedo head, almost as if the drive motor is winding something up that is twisting until it pings out of whatever is preventing normal movement and then it adds the miles on faster and shows faster than you're really going.

I'd say even if you changed the caps in it, you'd still have a problem, easiest way to fix it is buy a secondhand instrument cluster on fleabay or similar. Take before and after photos of the new and old togeher, new one sat on top of the dash showing the mileage and the old one in the dash showing the mileage.

Change the clusters, put the old cluster on top and take another photo so the mileages can be seen. Then you can prove to whoever it wasn't done as a fraudulent way of reducing the mileage.