I have one of those pod-mounted (Smiths, I believe) accessory tachometers that Volvo sold back in the day... I'm running electronic ignition (sourced from a 240 engine) and dual SU's. I've read that the old style tachometers won't give an accurate reading with electronic ignition and that age itself can render them inaccurate.

I verified that the tachometer works; ie. I hooked it up temporarily in the engine bay and it gives readings and responds to revs. Since the engine seems to 'rev' only to about 2000 RPMs or so, I do believe that it's off by more than a little bit!

I'd like to get it 'converted/rebuilt' to working with my setup. Absolute accuracy not required but ballpark accuracy would be nice...

Any suggestions?

Thank you.

KaiS
'67 Duett

If anyone is interested I have a schematic of the Smith inductive tach with a parts list. Armed with this ( less than $10 in parts to fix all 3) I have salvaged 3 Smith tachs for my own use.

Also there is an electronic device called tachmatch which can be used to reconfigure tach signals such as a 6 cyl tach in a 4 cly car etc. It also works in the reverse as in a 4 cyl tach in an 8 cyl car. www.technoversions.com in Washington state

Also Mark Olson at accutach www.accutach.com is in the business of repairing these old tachs and calibrating them very reasonably. I believe Mark is in California
Steve in Canada

In addition to the tach repair I would like to add that I have recently added a 123 ignition distributor to my car and that I was able to make it work with the old Smith, contrary to everything I have read about solid state ignition not working with the old inductive tach's. Worth knowing for someone holding out or considering having theirs modified because of this concern I know I was.
Steve in Canada

I have a Volvo 123GT tach (RPM x 100) on my '67 4dr. Amazon. I also have the '75 240 electronic ignition. I had the tach calibrated many years ago in 1995 by;
Palo Alto Speedometer Inc,
718 Emerson St.
Palo Alto, CA 94301
(I have no idea if they are still in business).
In any case, the tach still works fine after all these years

Fred;

I think this is encouraging news, and just the info which Kai needs! ...please give details on how you have your GT Tach connected into ignition circuit with a 240 Ign Amp.

Cheers

I followed the instructions from the article in VClassics Archives, Bosch Breakerless Ignition Conversion by Cameron Lovre
The 2/two white wires from the 123GT tach are connected to the coil and the black box. Please see below;

http://vclassics.com/archive/breakerless.htm

They are adjustable.




They also have a weird wiring setup. I know I had one working fine on a '75 240 electronic ignition system in a 122. From what I remember, the tach ran on the slow side, but adjusted using a cheap aftermarket digital tach, and it matched up fine.

Paul

Here's a description on the wiring. I know the color was different on mine. If you need more info, let me know and I can figure out how it's setup on mine. (Mine has 3 white and 2 black wires coming out of the tach, and has the complete wiring harness intact).

https://www.brickboard.com/RWD/volvo/1426810/120-130/123gt_smith_tach_wiring.html

The 1967 123GT came with a tachometer which had P/N281046 manufactured by Smiths for Volvo. The 123GT tach differs somewhat from the Smiths tach that was later sold as an accessory in that it has a chrome ring and a 10 x 100RPM grading. The accessory tach had a matte ring and a 1 x 1000RPM grading. Both had the same part number. It had 5 wires, one black, two red and two white. Wired as follows;
Black wire to ground
One red wire to instrument lighting
One red wire to the 25A fuse
One white wire is connected on the coil iso the black which is removed.
One white wire is connected to the distributor (where the just removed black wire was).
If the tach doesn't work, switch the two white wires.

Suggest and look inside the tach to see if the black wires replaced the red wires and if the single white wire replaced the black ground wire.
Hope this helps.

Yes the white wires from the tach replaces, puts it in series with the wire that goes normally from the coil to the distributor, so coil to tach to distributor, and as said reverse the coil and distributor connections if it doesn't work. You can add a couple wires to the coil and dizzy to mock it up first if you like which keeps the tach wires at max length so you can tuck them away neatly after you've found which way they go.

Honestly , I gave up on mine years ago and installed an Autometer tach. Working great for many years.

Yes, but for me, an iconic part of the car. I'd like to keep the one I have, thanks.

Does your 240 system have an ignition amplifier? I believe that there is a rev counter output connection on those.

Derek;

I don't believe that rev counter connection on a 240 ignition amplifier will work with the GT Tach because it is probably a (single wire) voltage pulse intended to work with later voltage sensing Tach circuits.

Kai;

...but a GT Tach might still be made to function with a 240 ignition amp...the GT Tach uses the same Smiths, current sensing, magnetic coupling ONLY, circuit as the 1800, so its' two white wires must be in series with Ignition Coil primary (and in the correct polarity...direction of current-flow matters!) I would advise to wire it in series with Ign Coil primary and try it (in both directions).

Cheers