I have a 123GT tach that I want to mount on the dash when the new 123GT dash pad arrives. It has 5 wires on it - 2 black wires and 3 white wires, (2 of the 3 white wires are longer with a bit of harness wrap on it, which I assume end up in the engine bay somehow).

Does ANYONE know how to hook this thing up? I'd like to start using it.

Thanks!

I have just posted photographs of wiring to coil & distributor as well as engine bay.
Hope these help out.

Cheers
Bilo

Quick question Bilo (or anyone else):

When I saw your pictures I noticed that the wire that I've got running directly from the coil negative to the distributor would be replaced by the wires on the tach. Can I safely run BOTH wires, the original AND the tach wires without there being much of an issue?

I ask because when I replaced that single wire with the 2 ends of the tach wire, the car seemed to run a little irratic, like maybe there might be some sort of issue with the wires to the tach, but when I ran the wires to the tach AND connected the single wire from the coil direct to the distributor, the problem lessened and it seemed to run smoothly as well as the tach working.

Please let me know if you foresee any potential problems.

Thanks!

OH!!!! When I saw that on my car I had no idea that I'd be replacing the wire that runs from my coil to the distributor with leads of the tach instead. NICE! Thank you!

I have just posted photographs of wiring to coil & distributor as well as engine bay.
Hope these help out.

Cheers
Bilo

Sorry but these wires are the original colours from the 67 GT tacho and agree with the wiring diagram for the GT from the user manual.
There are several versions of tacho depending on year and whether they came out of
a genuine GT or were a tacho included as an option on the 122.
My tacho has RPM X 100,a red needle and rectangle shaped foot. 68 model changed to RPM X 1000 and a white needle. The optional tacho for 122 had a round foot as far as I am aware.
I think your tacho may have come from the optional version because of the wire colours. Yes disassemble but be very careful with the internal wiring as it is extremely delicate. Hope it all goes well.

www.classicvolvoshop.com used to have a photo of all the variations but I notice the website has just been updated so you may be able to find some helpful info there. I have not had a chance to check out the site myself yet.

Cheers

Hey Bilo you may be right about the "optional" tach for 122, as mine has a round foot as you described and I'm finding the GT tachs to have the longer narrow rectangular foot w/ red needle, and mine has the white needle, RPM x1000 and round foot.

I disassembled it and found that the 2 black wires are positive and negative. I followed the leads to the circuit board and one lead on the board looked like it would have grounded the bulb. Verified it by attaching the white wire for the bulb to a positive feed and then touching the end of the black wire in question to the ground until it lit.

The 2 longer white wires are to the coil/distributor. The shorter white wire is the positive lead for the bulb.

So, question: The car is a '65 w/ a B20 but looks to be using the original 1.8L distributor. Where will my 2 leads go? I know one goes on the distributor somewhere, and the other goes on the coil somewhere. Any suggestions? Those are my last 2 puzzles. Thanks!

All I can add is that the coil has a connector on the side and distributor also has a connector. If you are stuck I can email photos.

Cheers Bilo

I am very stuck. Please post pics.

BR;

If the two white wires use the non-contact/inductive coupling technique as the 1800 tachs did (verify by following to the end...do they just make a loop around a component without actually connecting to it?...if yes, that would be the coupling transformer), then one side goes to points, other goes to coil neg. ..if it doesn't work circuit may be polarity sensitive...reverse and check again...

While you have tach open, is it possible to take some detailed pix and send them to me? I'd like to add them to my reference article: http://sw-em.com/Smith's%20Tachometer.htm

Cheers

Yes I can pull the D80 out and take some detailed pics for you right now.

The white leads look like they go around something that's got copper wire wrapped around it...

Hi

I thought someone would have replied by now - have just checked my 67GT.

White - Coil
White - Distributer
Black - Earth on engine bay firewall
Red - Fuse box
Red - headlight/parker switch on dash

You may have to track the wiring for the small internal light bulb to light
switch so other red obviously goes to fuse box.

This only leaves 2 whites which you can alternate to get right.

My car goes nowhere without the tacho being correctly connected.

Cheers
Bilo

I have no red wires, just 3 white and 2 black?

I think I will have to crack the case and see where they go...

Nobody?

Bilo and Boost-


I just wired up a tach in my gt. I found this page on the tach's. http://hem.bredband.net/b215872/amazon/downloads/Tachometer%20in%20Volvo%20Amazon.pdf

The one I have has the 2 whites, 2 reds and a black, black being ground, 1 red going to the fuse box, the other being tapped into the dash light harness and one white going to the coil the other going to the distributor. I did find that when I first hooked it up, it did not work, switched the white wires and it did. I have a spare tach that also came from a GT, however, it is wired like Bilo's, with 1 red and two white and have not found any info on the wiring on this one.

cheers,

M