Speedometer problems with my 1992 940 GL

When I bought the car the speedometer didn't work. I sent it in for repair.
Speedometer Service Co. fixed it but after installation it will work
correctly for a few seconds, then peg the needle, then settle back to no
reading at all. The odometer works fine as does the tripmeter. So I don't
think it's the sending unit. I sent it back to be checked and have been
told it works fine on the bench.

I'm not the one taking it in and out of my car. That's done by a local
Volvo GOD (IMHO)! So it's not my fumble fingered installation!

A little unimportant background info. From my understanding. For a few years
('91-'93 I think) a division of Honda made the 940 speedometers. These are
known for failing... Later improved models are not interchangeable.
The "good" news is you can get a fresh new one from Volvo for $730 US!

Anyone have any similar experience or ideas

Thanks

 

Send it back to the place that fixed it, if the odo works then the speedo is
still broken.

 

It's there now. I'm told it has 100 miles on the bench with no problems.
It's being rechecked for the second time.

 

there are two electrolytic capacitors on the circuit board for the
speedometer... When mine stopped working about a year ago, I unsoldered them
and replaced them with some from my junk box (new ones might cost a dollar
or so)... worked fine since then! ('89 240 wagon)...

 

I fixed the problem with my wifes speedo I set it so it looks like shes
doing more than she is had only one ticket since .I run just under the
speed limit so the cops cant get me but they have still tried .Once I tell
them I won the first case against a radar cop in Australia they seem to lose
interest as well I always carry a tape recorder .Less than 2 miles an hour
over the limit is a large fine 3klms and hour here as well they put up road
spped indicators which are under the true speed catching many out .The
latest is speed cameras in Rubbish bins .

 

That's weird, 10 years of driving Volvos and I've been pulled over exactly
once in my life, and it was for a burned out license plate light in a rural
area. I swear they're invisible to cops in the US, I don't drive
particularly slow either.

 

I ended up with a new speedo in my 91 240 and it cost ~ $700 + taxes.
Fortunately, I didn't pay for it, the garage who damaged the speedo
while working on it had to order and pay for a new one.

 

Speaking of speed cameras, the other day I saw a M-B with a sort of
transparent plastic over the rear licence plate. It worked
flawlessly. From 0-10 feet from the plate, everything was clear and
readable, but as soon as you went further then 10 feet, it gradually
and quickly became invisible (the numbers on the plate, that is).

I wish I could have stopped him and asked him where he got it. I've
never seen another car with such an effective plastic to hide your
plate.

If anyone knows, please let us know.

 

I'm not sure everyone has seen the TV show Myth busters but they did one on
all these methods of obscuring a tag. Not one of them worked against the
camera. The number was clear on every photo. Perhaps because the camera uses
a strobe...

 

By the way. My speedometer problem on my '92 944 (that this
post was originally about) is as bad as ever.

To date I have had the speedometer in the repair facility
twice. They assure me it's done 100 simulated miles on the bench
without a tick.

I have tried a new replacement sensor on the differential
with no change in performance. Still wildly erratic.

I've rewired the last 16 inches of the connecting wiring harness
to the speedometer sensor. Since it's a known problem with the
insulation going bad from exposure.

No change.
don

 

That's so weird, there's really nothing to the speedo wiring, just a
pair of wires going back to the sender, one pin on the speedo is power
from the fuse box, one is ground, and the other goes to the sensor.
Makes me wonder if the speedo is picking up electrical noise. Can you
get a junkyard speedo just to see if it works?

 

had speedometer problem in my '89 240 a year or so ago... from the circuit
diagram, I noticed there are two electrolytic capacitors on the board. One
is across the + and - power lines, so acts as a noise filter. The other
apparently "integrates" the pulses from the differential. I simply replaced
both of them with same-value caps and no more problem!

even at RadioShack, the caps shouldn't be more than a couple bucks...

 

sounds like time for a visit to the junkyard....

 

Good old Victoria..the most overgoverned overtaxed overrated state in
Australia (yet with inept police), and only just behind NSW for having
the most incompetent government (well actually behind NSW and Kevin
Dud). I share your pain John .

John