tach wiring

[siii8873]

I have a defender tach that I want to install in SIII. Anyone have a wiring diagram for the tach?

[knac1234]

Don't suppose it's as simple as connecting it to the pos and neg on the coil? Did that when adding a tach to my Imp and the Rover.

But both of my tachs had a switch for 4, 6, or 8 cylinder engines. Not familiar with the Defender one though.

Regards,
Julian

[siii8873]

Looked closer at tach there are 3 connectors (G,+,-), I assume??
G to Ground
- to Negitive side of coil
+ to Positive side of coil

[Apis Mellifera]

You can go it that way. I wired an MG Midget tach in my SIII that way. Basically you want a ground, switched power, and the signal from the negative side of the coil.

[Terrys]

Defender tach gets it's pulse from the W terminal of the alternator. If you're running a late alternator, it should have the W terminal, early ones do not.

That's a VDOtach btw, for anyone who wants to run a tach, they are available for about $70

[Andrew IIA]

Series Rovers shouldn't have a tach. There, I said it.

[Terrys]

Series Rovers shouldn't have a tach. There, I said it.

Stop beating around the bush and tell us how you really feel.

[siii8873]

OK I see two hookups here, not sure which is correct. How can I tell which way to hook this up? Again three connections are marked G,+,-
Sort of agree about the series tach comment but it came free with some parts so what the heck. Would be handy for tuning ect.

[Apis Mellifera]

Basically you want a ground, switched power, and the signal from the negative side of the coil.

The above should do it. G to ground, - to - on coil and + to + either on the coil or some other source.

[Terrys]

The above should do it. G to ground, - to - on coil and + to + either on the coil or some other source.

But it won't.

siii8873 stated in the first post that he had a Defender tach. First off, The Defender tach (VDO) gets it's signal input from the W terminal of the alternator, an AC signal. Refer to the attached schematic from the Defender manual.
VDO makes all sorts of electronic 2 1/8" tachs that look alike, but differ in how they get and interpret the input. The Defender tach has no provision for setting the number of engine cyliners, as would be necessary in a DC pulsed input. With a generic VDO Programmable, you must set dip switches on the back for 4,6, or 8 cylinders. Another dip switch is toggled for DC input (coil connected) or AC input (tapped from the alternator, one corner of the three phase AC winding, before the bridge.
The Defender tach has no provision for programming AC, DC, or inductive input.
Go to egauges.com for various VDO tach wiring diagrams (as well as other manufacturers)

[SalemRover]

The W terminal is a just plug that runs to the Stator. What Terrys said is spot on, you wont be able to calibrate your D90 tach to your series. Check this link for some ideas on hooking up a vdo tach to an alternator.

http://siteground237.com/~gunsandr/showthread.php?333-Simple-Mechanical-Diesel-Tachometer

[Terrys]

I found these while hunting up a VDO tach for my boat. They can be connected W (alternator) Inductive pulse (optional transducer) or coil. It retails over $175, so this is a pretty good deal ( I actually bought two). Perfect for the 2 cyl diesel in my launch, whose engine harness was pre-wired with a lead from the W terminal. The Hour meter is good in the boat, but handy for service schedules on our trucks that make lots of short trips. I don't know about others, but I doubt I ever rev my s3 over 4000 rpm, and the boat engine will never see 3500. Too bad they aren't the 52mm version.

http://cgi.ebay.com/ebaymotors/VDO-TACHOMETER-GAUGE-0-4000RPM-BLACK-FACE-GREAT-PRICE-_W0QQcmdZViewItemQQ_trkparmsZalgoQ3dLVIQ26ituQ3dUCIQ26otnQ3d2Q26poQ3dLVIQ26psQ3d63Q26clkidQ3d2784615638376378907QQ_trksidZp5197Q2em7QQitemZ170665238026

[Apis Mellifera]

I guess I was assuming it would be as simple as an RVC tach. Since it's not and won't work, if you still want a tach, I'd suggest a Smiths from an MG Midget, MGB, etc. You can get them for $20 and they look like they belong in a Series.

I rev limited by ear prior to fitting the tach. I've since found that means around 3000, which is ~60mph with OD on. 4000 is 70ish.

[Andrew IIA]

Series Rovers shouldn't have a tach. There, I said it.

Terrys Quote:
Originally Posted by Apis Mellifera
The above should do it. G to ground, - to - on coil and + to + either on the coil or some other source.

But it won't.

I am not going to say ..... ITYS ....







[kidding kidding. do what you want with/to your Rover and enjoy ]