Amazon: Smiths Rev Counter/Tachometer Issues

[Carlsson 986]

Hi Y'all,

I have a Smiths RVI 5000/00B rev counter/tacho in my 1967 122S, very similar to 123GT pod tachos, but it has developed some issues as follows.

If the unit is hot/been running, or, it's a hot day/exposed to the sun, the needle peaks to 8000rpm before the engine is started. In fact, it can read this before the key is inserted! So I think there is an associated wiring issue here.

When it does operate, the rpm readout is low in comparison with the engine speed, as I have checked this with a multimeter. So again, something is amiss.

I have scoured the internet as one does in search of wiring details for this particular unit to little or no avail, so could you electrical boffins out there please put me right on the wiring. It is a 6-wire unit:

2 x white to coil & distributor (contact points as standard)
1 x red/white dial illumination
1 x black deemed earth
1 x green deemed switched live feed (via ignition sw)
1 x red deemed unswitched live feed (via fuse box)

NB: these last two MAY be the other way round, I haven't checked recently.

I've taken the unit apart as far as I dare, to confirm the wiring internally and you'll be able to follow these if the photos load. There are lots of web items on RVC tachos but none of these are applicable.

Would this unit 00B have been for a positive earth vehicle originally given its age, and if so would that produce the effects above? Any and all assistance would be very gratefully received.

See you at BKV!

Ric
Cannot upload photos for some reason - admin advised.

[Carlsson 986]

Photos now attached - size issue!

[Carlsson 986]

Ok I believe I've managed to resolve the wiring issue as follows for the six-wire pod mounted Smiths unit similar to the Volvo 123GT units:

2 x white to coil & distributor (contact points as standard)
1 x red/white dial illumination
1 x black earth
1 x green earth also
1 x red switched live feed (via ignition)

This is now working in my car but I did have to swap the white wires around initially to get a reading that matched the revs. Hope this helps others in this situation but remember it only applies to non-electronic set ups.

Ric

[Carlsson 986]

Ok I believe I've managed to resolve the wiring issue as follows for the six-wire pod mounted Smiths unit similar to the Volvo 123GT units:

2 x white to coil & distributor (contact points as standard)
1 x red/white trace - dial illumination
1 x black earth/ground
1 x green earth/ground also
1 x red switched live feed (via ignition)

This is now working in my car but I did have to swap the white wires around initially to get a reading that matched the revs. Hope this helps others in this situation but remember it only applies to non-electronic set ups.

Ric

[jamie]

Sorry what does that mean only applies to non electronic
You are wiring it so it must be electronic....I am sure the answer is obvious and I am misunderstanding something???
Jamie

[Carlsson 986]

Jamie,

It means the electrical wiring is only for distributors that have contact points and condensers and not the likes of Accuspark, Lumenition or 123 Distributors or similar all of which rely on the dark art of electronics.

Cheers Ric