This is a condensed and up-dated version
of an article published in the April 2012 Issue of the UK VOC magazine
‘Driver’, and also here on Dave’s website, about the repair of a VDO
speedo odometer on a 1990 UK Model 745 (Wagon).
You can no longer obtain a replacement speedo from Volvo UK as it is a
discontinued part. It’s also now getting difficult to find a used
and fully functioning speedo on the second hand market.
As the speedo needle was working faultlessly I decided to try and find
out as much as I could about the speedo unit before I extricated it in
an attempt to fix the problem. As the speedo needle was clearly
fragile I was worried about its removal without damaging it.
clusters were manufactured by either the
German company, VDO,
Without removing the cluster the two can be differentiated by looking
at the speedo faceplate. On the
unit there is only one ‘blank’ on the speedo
faceplate between the hundreds and tenth of a mile on the trip
whereas each mile and tenth is divided on the Yazaki (PHOTO
should stress that VDO
clusters are not
Over the years the design of the VDO
speedo had progressed from cable
driven metal cased to the more ‘plastic’ framed versions of the
mid-1980/90’s as fitted across some 200/700 and 900 Series (as well as
other models and car makers). The basic design of the speedo
remained little changed except for the gradual introduction of more
electronics. In consequence similar faults arose across model
ranges fitted with VDO clusters.
In the case of the VDO odometer one (of two) of its primary faults
after time is the failure of teeth on a very small (about 10.5 mm
diameter) plastic gear wheel linked to a small stepping motor in the
train that finally drives the odometer cogs around. One or two
teeth fail and consequently the odometer ceases to turn. What is
it they say … “something is only as strong as its weakest link”, and
this little insignificant gear wheel is just that.
Some say the failure of the gear wheel teeth is attributable to
resetting the trip odometer when the car is moving and the odometer
turning. This seems logical, but whether or not it is true, or
the plastic of the gear wheel just becomes brittle with age; I have no
idea. Whatever, I shall not be trying to re-set the odometer
whilst the car is moving, but it’s very difficult to break the habit of
Before I started I was lucky to obtain a complete identical VDO cluster
(with one exception) from a 1989 745 base model so I had the luxury of
not worrying if I ‘messed up’ the original speedo. All I had to
do to the replacement (other than trusting the assurance I had been
given that everything worked) was to swap it over after changing the
two tell-tale plastic warning light strips at the inside bottom of the
cluster for the ones from my original cluster.
The warning light sequence is different between models versions, but
the VDO cluster appears to be the same with the same multi-plug
connectors etc on the back of the cluster. Volvo used different
wiring looms with multi-plug connectors wired to suit model versions so
there is no problem as long as you have the right warning light
sequence set up on the two plastic tell-tale inserts across the bottom
of the cluster. Having changed the strips over it really was a
matter of ‘plug and play’ and everything worked well.
In fact, after some years of going around with dodgy (intermittent)
cluster; radio/heater control and switch illumination these lights now
worked perfectly. Before the change over the lights had also only
worked when they felt like it. Now they all work perfectly.
In my searches for information I found an article in Dutch on the
Nederlands Volvo Forum website followed shortly thereafter by one on
the VOC Forum website. Unfortunately, although the VDO speedo
units looked more or less the same the method of removing the needle
was different in each. I was unable to resolve the issue so I had
to proceed with care.
Several American firms offer replacement gears. After reviewing
them I sent an email, together with some photos, to Dave Barton who
replied more or less by return.
We concluded that there did not seem to be any material difference
between what I had ascertained by this time to be my ‘dead’ 25 tooth
gear wheel and those Dave had in stock for the 200 Series VDO speedo.
In the States I understand that VDO speedos fitted to 740’s are likely
to have 26 toothed gear wheels. This is not the case with UK
models. To date I have not yet heard of one in the UK fitted with
anything other than a 25 toothed gear wheel. So, depending upon
where you live beware and ensure you get the right replacement. I
assume it is something to do with different rear differential ratios
between the two markets.
Dave Barton’s cost was competitive, and as his help could not be
faulted, I ordered and paid for a couple of gears via his secure
website which he despatched the same day I ordered. The ordering
process was easy and professional with the usual acknowledgements of
payment and despatch.
The delivery time to the UK was a little longer than anticipated at
something just over two weeks, but the gears duly popped through the
letter box neatly packaged and wrapped. The gear wheel appeared
to be a perfect replacement part. In fact it looked better made
than the original. All I had to do now was to fit the gear and
re-assemble the speedo.
The main parts of the odometer fix sequence are illustrated below,
together with comment. If you are unsure how to extract the
cluster and separate its two component halves that is dealt with
briefly at the beginning, but to start with a quick recap on the speedo
The VDO speedo and the odometer are driven off a sensor on the rear
differential. The input signal derived from the sensor is fed via
the wiring loom (and connectors) to one of the multi-plugs on the back
of the cluster where it is linked to the ‘blue’ plastic circuit
attached to the white plastic backboard. From there it is routed
via a multi-connector fixed to the white plastic backboard to the
speedo connection by either four tags on a wing, or five metal pins,
off the speedo unit printed circuit board (PCB) depending on age and
design. The signal then goes via circuitry to an integrated
circuit on the PCB where it is split to drive a galvanometer (the
speedo), and a stepping motor that drives the cogs of the odometer
around. Should you just happen to have a taxi there is also a
take-off for a taximeter!
1.0 to 1.2 – Remove the cluster module from the car – 2 screws at the
base of the cluster left and right underneath plastic ‘pop-off’ blanks
adjacent to the rheostat and clock set buttons.