Tacho and vacuum gauge

[disco2hse]

I am thinking about putting a tachometer and vacuum gauge into George (for those who don't know, Stage 1 3.5L 24V).

Any recommendations for brand, fitting place -- you know, that kind of thing? Also, any advice on where to put things, like would I take the +ve lead from the voltage stabiliser, etc?

[JohnR]

Not sure who to go to over there in NZ but VDO and Stewart Warner both make excellent gauges that can deal with 24v at a reasonible price. As for how to connect them most good auto electricians can help you with that. But if you want to do it yourself, are you running electronic ignition? It should have a tacho output if not and you still have a coil then you can get a pulse off the negative side of it. Then all you need is ignition +24v and a good earth.

I hope this helps,

Cheers,

[disco2hse]

Thanks John. I have a price for a VDO one here but it's $340 :eek:

Seems the problem is that most 24V tachos are designed for diesels and only go up to 3-4000rpm :(

On the bight side I should be able to get matched tacho and vacuum gauge.

I'll check out the Stewart Warner agents here and see what we can do there.

[LRHybrid100]

have you tried Speco? - Taiwanese made VDO at much cheaper prices

HTH

LRH

[disco2hse]

I've just spoken to the Speco agent and he is going to see if they can do a 24V version of the tacho and vacuum gauge. There is a 24V illumination conversion at least.

[Dougal]

You can use resistors to drop the voltage to safe levels.

[disco2hse]

You can use resistors to drop the voltage to safe levels.

Really? Where do they go and what resistance?

[Dougal]

Really? Where do they go and what resistance?

They go between the power lead and the power terminal on the gauges. But it needs some work to figure out the best resistance.

My method is running them on a known voltage (like 12v) and measuring the current. Then the resistance of the gauge is R=V/I. Once you know the gauge resistance then for 24v this is the same value for the dropping resistor.

This is of course only needed for powered gauges. If the gauges only have lights in them, then it's best just to swap them for 24v versions the same size.

[Aaron IIA]

Use a 12V tacho. Visit your local Dicksmith or Jaycar shops (or website) and get a kit that will drop the voltage to get a steady 12V or 14V or what ever you like. It may be advertised as a kit to drop 12V to lower levels to operate 9V, 6V, 4V or what ever voltage appliances, but will also drop from 24V to 12V when set up slightly differently.They use a chip called a voltage regulator, and come in preset values, or they can be adjusted. This way you have a stable voltage that does not change with differing current usage.
Aaron.

[disco2hse]

I'll check them out :)

[Blknight.aus]

an easier way than resistors is to simply put a 1 or 2 watt 12v light in series with the gauge.