Wonky speedometer on 2000 OBW

[Yousuf Khan]

Well, my OBW's speedometer started acting wonky as of today. As I'm
moving along, the speedo goes to rest at zero for a few seconds, and
then it immediately races back up to show the proper speed for a second
before going to rest again. The tach is still working normally, so I can
estimate the real speed by looking at that. Also I can check the GPS to
see my real speed if necessary.

Not a big deal, just very distracting watching the speedo flop around
like that. What are behind speedos these days? Is it a cable and a
magnet like the old days, or is it some kind of electronic thing? If
it's electronic, is there a fuse or something that I can change?

Yousuf Khan

 

[Carl 1 Lucky Texan]

Well, my OBW's speedometer started acting wonky as of today. As I'm
moving along, the speedo goes to rest at zero for a few seconds, and
then it immediately races back up to show the proper speed for a second
before going to rest again. The tach is still working normally, so I can
estimate the real speed by looking at that. Also I can check the GPS to
see my real speed if necessary.

Not a big deal, just very distracting watching the speedo flop around
like that. What are behind speedos these days? Is it a cable and a
magnet like the old days, or is it some kind of electronic thing? If
it's electronic, is there a fuse or something that I can change?

Yousuf Khan

That behavior does seem like an electronic intermittent connection.
maybe a bad ground or other connection on a PC board?

I dunno


Carl

 

[YKhan]

That behavior does seem like an electronic intermittent connection.
maybe a bad ground or other connection on a PC board?

Yeah, that may be because it's all gone now, it's working normally
again. That day was a somewhat cold night, which had followed a really
heavy snow day. Maybe some moisture freezing up?

Or it could've been just the ghost that inhabits the body of my
car?

Yousuf Khan

 

[X-Eliminator]

That problem will be back if not sooner than later. I had to replace
the speedo cluster to make that intermittent problem go away in my
late 99 Subaru Legacy 30 Ed. It probably not a sending unit problem as
I did a full year of chasing various electrical theories of loose
wires, shorts, intermittent sending unit bla bla bla. In the end it
will problably be the speedo cluster. The good thing is that all you
need is a phillips screwdriver and about 30 minutes to repace it.

 

[MM]

Well, my OBW's speedometer started acting wonky as of today. As I'm moving
along, the speedo goes to rest at zero for a few seconds, and then it
immediately races back up to show the proper speed for a second before
going to rest again. The tach is still working normally,

This seems to be a typical problem on many Subaru cars. I just bought a '99
Legacy and it has the same problem except for the speedo goes dead for
longer periods. I have done a lot of research on the net and I believe the
problem has nothing to do with either the speedometer itself or the speed
sensor(s). A lot of people spent tons of money replacing these parts
sometimes several times with varied success. In many cases the problem would
come back in a few years after the whole instrument cluster or speedometer
was replaced. I believe the real problem is the bad ground connection (due
to a design flaw) of the speedometer as have been pointed out by at least
two people:

http://www.automotiveforums.com/vbulletin/showpost.php?p=5679652&postcount=25
http://www.automotiveforums.com/vbulletin/showpost.php?p=5798464&postcount=26

I am yet to prove that this is indeed the root of the problem in my case,
but being an electronics engineer myself I am pretty confident that the
problem must be bad ground.

/MM

 

[YKhan]

This seems to be a typical problem on many Subaru cars. I just bought a '99
Legacy and it has the same problem except for the speedo goes dead for
longer periods. I have done a lot of research on the net and I believe the
problem has nothing to do with either the speedometer itself or the speed
sensor(s).  A lot of people spent tons of money replacing these parts
sometimes several times with varied success. In many cases the problem would
come back in a few years after the whole instrument cluster or speedometer
was replaced. I believe the real problem is the bad ground connection (due
to a design flaw) of the speedometer as have been pointed out by at least
two people:

http://www.automotiveforums.com/vbu...ums.com/vbulletin/showpost.php?p=5798464&post...

I am yet to prove that this is indeed the root of the problem in my case,
but being an electronics engineer myself I am pretty confident that the
problem must be bad ground.

I've had quite a few weird little electrical or electronic problems on
this car, that come and go. Sometimes they will not reoccur for
several years. I once had a problem with one of the turn signals on
one side of the car, but not the other. It fixed itself up, and has
never occurred since the first days I owned the car.

The bad grounding seems to be a plausible answer.

Yousuf Khan