740 Speedo Problem

Speedometer does NOT work. Does anyone know where I can begin to look for my
speedometer problem? Are there any "recurring" problems with these things?
TIA

 

What year car?

Couple questions - do the odometer and/or trip meter work?

I have a 1987 740 - everything on the dash works except the speedo.
Here's the most common problem:
Jack up the rear of your car and look at the rear differential. There
will be 2 wires with a snap on connector. There is a magnet inside of
the diff that sends a signal through these wires to your speedo on the
dash. If everything on the dash is dead - tach, speedo, mileage,
chances are these wires have worn out, maybe shorting, etc. Often a
repair of these wires will get you back in business. Unsnap the
connectors and inspect. No need to take out the diff unit - VERY rare
to fail.

If everything on the dash is working BUT the speedo - that's another
issue. I just took apart my cluster and it was not fun - tons of
little screws and when I pulled the speedo apart - coils of wires
inside. From here you have two choices - replacement speedo from the
boneyard or ship it off and pay the $100 or so they want.

Option three is find someone with instructions on repair. All I could
find was for a 200 dash and the speedo is different I think.

jamie

 

Jamie, thanks for the reply. Mine is a '91 740. The odometer nor the trip
meter work. Every once in a while the speedo jumps up to about 75mph and
stays there for a couple of seconds then dies again. I'm usually cruising
about 35-55mph when this happens.

 

You have two separate faults.

The odometer is as broken as they all are. The tiny plastic drive gear
inside the odometer is stripped. There's a guy somewhere on the web who
was selling spare gears, otherwise it's a squillion bucks for a new
speedo from Volvo. Or else just live with it, like the rest of us. You
can't get a scrapyard one because that will have the same fault too.

The intermittently dying electrical gauge (any gauge, take your pick) is
caused by bad contacts through the dashboard plugs. Strip, clean,
re-assemble. They all do that too.

It's unlikely to be the back end. If that fails then it's permanent
rather than intermittent (rare, but it happens, and its usually just the
wiring not the sender).

 

Mine has never broken (knock on wood) and I've picked up several good spares
from scrapyards. Perhaps climate has an effect on this? I just don't see
many broken odometers in 740s.