Speedo not working.......help fault finding
OK, after 3 penalty point speeding because my speedo doesnt work, I took the plunge & bought a replacement dash pod (as my tacho was faulty too).
Tacho is fixed................ but......
Speedo still doesnt work.
So conclusion is;
a) I have 2 dash pods & the speedo works in neither or
b) I have a fault somewhere further down the line.
I think it is option b.
I have checked the rotating cable, all ok.
I put a multimeter on the output from the pulse generator & found the following;
1 cable has 12v
1 cable is earth
1 cable has a constant 6.7 volts, irrelivant of speed.
now I know that the pulse generator gives out a oulse signal, so the 6.7 volts is probably that signal, but how do I check the "pulse" it is giving with a standard multi meter ?
secondly, I cant seem to locate the wires after they dissappear behind the bulkhead / firewall.
before the firewall, I have a black cable, a pink & white cable, & a white cable.
I look at the 4 connector blocks that go into the dashpod, & there is no pink & white cable. I cant find out which black cable is the one from the pulse generator, as at the pin they are twinned up & always arc to earth.
which cables on the 4 connector blocks belong to the speedo ?
Can anyone help ?
I dont really want to take the dash apart again, untill I know which cables I need to look at.
1989 Alfa 75 3.0V6 & 1971 Alfa Giulia GT1300 Junior