I'm still a novice at this, but I looked at Volvo's green manual and you're right about 4 wires to the speedo, although the book shows the ground wire (BN-GR) on a separate plug. The only component on the board is a fuse (mounted at the top of the board just left of a "notch" on the upper edge (looking at the boatd from the back). It gets 12 volts from pin 15R on the ignition switch and goes directly (no connector/plugs) to the cluster (wire color BL-R). Its routed through the speedo and (wire GN-W) goes to the sensor. If there was a break in the ground from the sensor (wire BN-W), it would still read 12 volts at the plug at the dash. After all this rambling, I'd check continuity of the ground wire between the dash plug and the sensor. The only connector, BTW, is at the left end of the dash. Hope this helps, although, remember, I'm just a novice with a book. I can eMail a copy of these pages if you want - jwsocw@earthlink.net.

Jim Weiss
83 245T/M46, 90 744T/M46, 90 760T, 93 945T, want more ...



I just looked at Spook's response (I was writing at the same time.) I like his answer - he says it better - but let us know.

Dear Yaofeng,

May this find you well. I recall reading a post - or possibly in the FAQs (under FEATURES, above) - that corrosion under the screws that attach the flexible circuit card to the instrument cluster chassis, can produce erratic instrument operation, or total failure to operate.

However, getting two clusters, neither of which work, seems improbable.

I suspect a faulty ground. The ground wire for the speedometer runs to a connector (C-1) which is located at the base (bottom) of the driver'side windshield support column (A column). From there, the wire runs to a position just in front of the lower, driver's side (in the US/Canada) door hinge.

To access this ground point, the outer kick panel will have to be removed. To do that:
(a) Remove the plastic end cap at the front outer edge of the driver's seat track. It is secured by a single torx screw. Be gentle, when disengaging the tabs
(b) Remove the plastic door threshhold strip. It is secured by three torx screws, under the rectangular plastic caps. Pry-up the plastic caps with a blunt-edged putty knife.
(c) Remove the kick panel. It is secured by a single torx screw. You'll need to ease the panel out from under the one above it. Be gentle.

The ground wire - brown/green - according to the wiring diagram, is the only wire grounded there.

It is also possible that the ground wire from the diff pick-up is broken. It is a brown-white wire. This wire runs along the rocker panel on the driver's side of the car (US/Canada), and to Connector 1 (see above). It is spliced to the speedometer ground wire near the instrument cluster (the diagram does not show the actual connection).

I'd check the ground near the door. Clean it. If that does not restore function, then I'd check each section of ground wiring, looking for a break.

Hope some of this helps.

Yours faithfully,

spook