1990 740 speedo problem

  • Thread starter Thread starter Richard Setford
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Richard Setford

Hello again,

been a while since my last posting but have been keeping up with
everything (pretty much anyway).

I've got a issue with my 1990 740's speedo. When traveling along at any
speed over any surface it will just drop to zero. A well placed tap on
the top of the dash brings the speedo back to life.

Some days it won't do it at all, others it won't work for miles and then
bring itself back to life. I've had a feel around behind the speed (it's
quite easy to access from underneath the dash) and can't feel anything
that's come loose at all so I'm guessing that it's a dry joint somewhere.

Any suggestions as to what I should do? If possible, I'd like to avoid
taking the dash apart but if needs must then so be it.

Thanks and regards,

Richard
 
Richard Setford said:
Hello again,

been a while since my last posting but have been keeping up with
everything (pretty much anyway).

I've got a issue with my 1990 740's speedo. When traveling along at any
speed over any surface it will just drop to zero. A well placed tap on the
top of the dash brings the speedo back to life.

Some days it won't do it at all, others it won't work for miles and then
bring itself back to life. I've had a feel around behind the speed (it's
quite easy to access from underneath the dash) and can't feel anything
that's come loose at all so I'm guessing that it's a dry joint somewhere.

Any suggestions as to what I should do? If possible, I'd like to avoid
taking the dash apart but if needs must then so be it.

Thanks and regards,

Richard
Click to expand...

Solder joints on the instrument cluster PC board are the usual culprits.

Unless yours is very different from our 85 model (I don't think it is)
getting the instrument cluster out and back in is very easy. Once the screws
are removed from the front the cluster can be pulled far enough out to
unfasten the connectors and voila! you have it. The connectors are unique,
so there is no need to mark which goes where. Just note any connectors that
are vacant on the cluster, and maybe tie a string to the connectors before
you remove them so they don't try to lose themselves behind the dash (not
really a problem). The cluster goes back in the reverse of the way it came
out; slide the top in first.

Mike
 
Michael Pardee said:
Solder joints on the instrument cluster PC board are the usual culprits.

Unless yours is very different from our 85 model (I don't think it is)
getting the instrument cluster out and back in is very easy. Once the screws
are removed from the front the cluster can be pulled far enough out to
unfasten the connectors and voila! you have it. The connectors are unique,
so there is no need to mark which goes where. Just note any connectors that
are vacant on the cluster, and maybe tie a string to the connectors before
you remove them so they don't try to lose themselves behind the dash (not
really a problem). The cluster goes back in the reverse of the way it came
out; slide the top in first.
Click to expand...

Yes- easy to remove.
Also, I found that my octal connectors(?) were pretty dirty and needed
cleaning as well. Also a good time to replace bulbs where necessary
(look for darkened bulbs, and removing and replacing them also helps
maintain a good connection. And i took the opportunity to remove the
instruments and clean out the inside of the cluster as well.





__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
Randy G. said:
Yes- easy to remove.
Also, I found that my octal connectors(?) were pretty dirty and needed
cleaning as well. Also a good time to replace bulbs where necessary
(look for darkened bulbs, and removing and replacing them also helps
maintain a good connection. And i took the opportunity to remove the
instruments and clean out the inside of the cluster as well.
Click to expand...

Doesn't the '90 use the newer instrument panel like the 940s have? I think
it's a little different to remove, but still quite easy.
 
James Sweet said:
Doesn't the '90 use the newer instrument panel like the 940s have? I think
it's a little different to remove, but still quite easy.
Click to expand...
Very easy (from memory):
-have container handy to hold hardware as it is removed.
-Disconnect battery
-Pry out horizontal trim strip below headlight switch panel (it pulls
out back towards the driver)
-Remove the headlight and dimmer knobs (pull off)
-Pry out panel that holds rear fog light switch
-Pry out two dummy instrument covers (or instrument bezels if so
installed) to the right of the instrument panel (between instruments
and radio area).
-Remove 4 screws- two along the left edge and two on the right edge)
of the instrument panel.
-Remove the metal shaft locator for the light switches.
-Center steering wheel and pull entire cluster out.
-Disconnect wires from back of cluster and remove cluster from car.


__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
The problem is that 740s continued to use the old VDO instrumentation as
well as the Yazaki setup, whereas the 760s got the all-Yazaki
instrumentation. I have a guy (UK) with just such a problem with a
customer's 1990 740, where the instrument circuitry is quite different from
the Yazaki layout. His problem seems to be the regulator has burnt out
causing fuel and temp gauge problems and his VDO speedo became intermittent
and has now stopped reading Trip and Odometer. This has a similar origin to
the Yazaki instrument in that a small nylon drive gear wheel splits and no
longer makes a good tight fit on the shaft.

All the best, Peter.
 
Hello again,

been a while since my last posting but have been keeping up with
everything (pretty much anyway).

I've got a issue with my 1990 740's speedo. When traveling along at any
speed over any surface it will just drop to zero. A well placed tap on
the top of the dash brings the speedo back to life.

Some days it won't do it at all, others it won't work for miles and then
bring itself back to life. I've had a feel around behind the speed (it's
quite easy to access from underneath the dash) and can't feel anything
that's come loose at all so I'm guessing that it's a dry joint somewhere.

Any suggestions as to what I should do? If possible, I'd like to avoid
taking the dash apart but if needs must then so be it.

Thanks and regards,

Richard
Click to expand...
More often than not the speedo is losing signal from the sensor in the
diff. The wiring is not very stout and tends to break inside the
insulation, due to excessive clamp force on the wire when the waterproof
sleeves were molded over the connector.

Before you remove the wire seal on the sensor pull on the wires and see
if they stretch easily. If they do you will have to replace the two
wires in the connector with Volvo p/n 3523813. These are the wires for
converting the early style 240 washer pump harness to the later
connector on the pump motor. The wires in the harness are a twisted pair
so take care to maintain the twist when splicing in the new wires.

Bob
 
Thanks for all the suggestions guys, A job for next weekend me thinks.

I'll let you know how I get on.

Richard
 
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