92 Volvo 940

[Kim Slyns]

My speedometer/odometer was intermittent for quite a while but has now
stopped working altogether. Repair is estimated at A$350 so I would like to
see if I can fix it myself.
Any ideas anyone?

 

[James Sweet]

My speedometer/odometer was intermittent for quite a while but has now
stopped working altogether. Repair is estimated at A$350 so I would like to
see if I can fix it myself.
Any ideas anyone?

It's almost always solder joints on the circuit board in the speedometer.

 

[Telespalla Bob]

James Sweet ha scritto:

It's almost always solder joints on the circuit board in the speedometer.

Is also probably that electrolytic condenser leakage make problems in
printed circuit board.
Clean PCB, eventually repair interrupted PCB wires and replace
condenser, preferably with tantalum capacitor.
this is what I have done in my '91 940 speedometer

bye.

 

[don b.]

It's almost always solder joints on the circuit board in the speedometer.

I wish I had better news for you but, I've been dealing with the exact same
issue for a year. What repair business said they could fix it for 350? Be
cautious of there claims. There are a couple of things that go bad on the 1992
940 speedometer boards. Soldier is one but, this comes from the biggest issue. A
capacitor. It goes bad and leaks on to the board. Once that happens the chances
of repair drop. Still worth letting them try but get a guarantee! I've sent mine
back three times. Each time they SWEAR it works on the "bench". However, after
putting it back in the car it was the same. They have had it for months now
"trying" to get a replacement from a savage yard and put something together that
I can use. Good luck!

 

[James Sweet]

I wish I had better news for you but, I've been dealing with the exact same
issue for a year. What repair business said they could fix it for 350? Be
cautious of there claims. There are a couple of things that go bad on the 1992
940 speedometer boards. Soldier is one but, this comes from the biggest issue. A
capacitor. It goes bad and leaks on to the board. Once that happens the chances
of repair drop. Still worth letting them try but get a guarantee! I've sent mine
back three times. Each time they SWEAR it works on the "bench". However, after
putting it back in the car it was the same. They have had it for months now
"trying" to get a replacement from a savage yard and put something together that
I can use. Good luck!

Should have thought to mention that too, I haven't had the capacitor
problem on 700s, but I have had it with the analog clocks in 240s.

It's worth replacing all the electrolytic capacitors in things like
that, they're cheap and most of them fail eventually. Tantalum is an
option, under most circumstances they last a very long time and do not
degrade over time or become temperature sensitive, but they are not
immune to failure either, and when they do, it tends to be spectacular.
The usual failure mode for a tantalum capacitor is they short circuit,
and if there's enough current capacity behind them (car electrical
system for example), they will usually catch fire.

 

[Tony]

Should have thought to mention that too, I haven't had the capacitor
problem on 700s, but I have had it with the analog clocks in 240s.

It's worth replacing all the electrolytic capacitors in things like
that, they're cheap and most of them fail eventually. Tantalum is an
option, under most circumstances they last a very long time and do not
degrade over time or become temperature sensitive, but they are not
immune to failure either, and when they do, it tends to be spectacular.
The usual failure mode for a tantalum capacitor is they short circuit,
and if there's enough current capacity behind them (car electrical
system for example), they will usually catch fire.

Tantalums are high density high performance caps with good electrical
characteristics. At the end of the day capacitors are hard to make and
they are many many choices which trade off different characteristics. I
doubt these need to have any special characteristics so the thing to go
for is life time (Aluminium electrolitic). It can he hard to find this
in the cataglogue but you want the highest temperature rating with the
longest life. eg 125C at 5000hrs (105C at 2000hrs is also not bad but
much more common). Also go for the large parts variants. I have also
seen solid polymer Electrolitics recently, but are much more expensive.
Also of course go for a high quality brand (usually Japanese).

These circuits are not espeically high density and should be repairable
even it looks a bit messey with extra wire and glue.