66 6F HCS

Just replaced my speedo cable and housing last week since the original had rubbed against the headers and melted/frayed until the cable was exposed. The new one was about 1' longer than the original and was bought at Napa.

The speedo bounced a lot at first even though the cable was lubed correctly. Then a few days later, the speedo just kept turning around and around slowly as I drove. Steady 3000rpm on my tach; flat highway, but the speedo slowly turned continuously ALL the way around in a circle. When I stopped, the speedo wouldn't go back to zero, it just stopped turning. WTF! Is my speedo head hosed now? Do I go back to Napa and demand they rebuild or replace my speedo?
I called the ONLY speedo rebuilder here in Denver and they said that it might be that the amount of cable sticking into the back of the speedo may have been too long and gone too far into the head, thus destroying it. HUH?? They're quoting $130 to rebuild the speedo and ensure the cable is the correct length. I also called Colorado Mustang who will sell me a good used speedo for $75.

I haven't had the chance to yank out the entire dash AGAIN to figure out the problem "exactly", but now the speedo is acting different than before with the funky spinning thing.

Now it's set at 110mph when I'm stopped and -20mph when I'm probably going 40mph. The needle bounces ALOT, even though it was prelubed by the manufacturer, which I confirmed by pulling the entire cable to make sure before installation. No kinks or really tight bends in the cable housing.

I'm REALLLLLLLY not looking forward to yanking this thing apart for the THIRD time, but at least I know how it all goes together and can do it more quickly than before. Somehow this wasn't one of the things I wanted to have a lot of experience with. :(

--
Scott W.
'66 HCS Mustang 289
'68 Ranchero 500 302
'69 Mustang Sportsroof 351W
ThunderSnake #57
http://home.comcast.net/~vanguard92/

 

Big Al

"66 6F HCS" <69ta_mustang@comcast.net> wrote in message
news:tuidnQ7tfpJUx3XfRVn-hw@comcast.com...
Just replaced my speedo cable and housing last week since the original had
rubbed against the headers and melted/frayed until the cable was exposed.
The new one was about 1' longer than the original and was bought at Napa.

The speedo bounced a lot at first even though the cable was lubed correctly.
Then a few days later, the speedo just kept turning around and around slowly
as I drove. Steady 3000rpm on my tach; flat highway, but the speedo slowly
turned continuously ALL the way around in a circle. When I stopped, the
speedo wouldn't go back to zero, it just stopped turning. WTF! Is my speedo
head hosed now? Do I go back to Napa and demand they rebuild or replace my
speedo?
I called the ONLY speedo rebuilder here in Denver and they said that it
might be that the amount of cable sticking into the back of the speedo may
have been too long and gone too far into the head, thus destroying it. HUH??
They're quoting $130 to rebuild the speedo and ensure the cable is the
correct length. I also called Colorado Mustang who will sell me a good used
speedo for $75.


Hate to say this but I think the speedo shop is right. You pushed the driven
part into the housing and it's causing the magnetic to rub. That speedometer
works on eddy currents. A spinning magnetic "influences" an Aluminum disk
that drives the needle with a hairspring providing the resistance. In your
case the magnet actually rubs the disk.

Another thing, 1000 RPM equals 60 MPH on almost all cars with a old
mechanical speedometer..

Here are some articles to put you to sleep:)

http://www.alfaclub.org/techstff/speed.htm

http://www.exploratorium.edu/xref/ex...eedometer.html

Al # 35