as title really, what 'feeds' them to make them move?

do they have a switched live to them and just get a -ve from the coil, every time it fires?

using an old style coil set up as an example


thanks.
P

 

cable running from the gearbox,

ignore me - i thought u said Speedo

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the rev counter runs off a wire which is receiving an electronic current from the coil

 

thats the speedo mate.

 

its black magic you turn the key & they work unless you run coil packs then the read double or not at all

 

The ford ones rely on the collapse of the coil generating back EMF to drive them I believe, so arent a simple example.

most work how you described though

 

I am now running coil pack, and different ECU.. and have a tacho driver from the ecu to the rev counter...

just basically wondering what i should be seeing at the wire that feeds the rev counter!?

ive got about 6v at idle... but i was kinda expecting it to be a pulsed -ve LOL doh.

 

It will be a pulsed output, but you won't see the pulses on an LCD volt (multi) meter they don't react fast enough.

.

 

something is definitly wrong then lol
hmmm

 

Depending on what type of signal the tacho is looking for you may or may not need a tacho driver, the std sierra one will with coilpack, the emerald ecu for example can be CALIBRATED as well to the tacho to make it accurate at all times, as ecu output can be massaged.
tabetha