Mason Edmison

Wiring diagram
Hi all,

Just installed a Tachometer on my 94 pick up with 22re and am doing the oil pressure gauge tomorrow.

For my tach, I spliced into the red/blk wire going to the dimmer hoping that I could dim it but it seems the dimmer switch has the opposite effect on the light on the tach (full bright all the way off and off when the dash lights are fully on) so, not sure whats going on there.

So I was wondering would it be better to splice into the light switch? From best I can tell the white/blk wire would only send power to the light when it is on? can someone verify this? One day I will be literate in automotive wiring diagrams...

Interior light wiring diagram attached.

wyoming9

iTrader: (1)

Do you have a schematic that came with your tach??

That might shed more light on why it does not dim .

scope103

The rheostat is on the "low" side. So you connect one of your lighting wires to +12v, and the other to the Red/Blk to the rheostat.

If you have LED lighting, you have to mind the polarity.

And, if you have ONE "ground" wire, one "power" wire, a pickup wire (to the IGN output), and finally ONE "lighting" wire (like this one https://www.autometer.com/media/manual/2650-468X.pdf), well, you're out of luck. The tach requires +12v on the power wire and -0v on the ground wire, and you don't have access to the "two" wires that power the light. You can't connect the tach ground to 12v without damaging the tach.

Which brings you right back to wyoming9; where's your schematic for the gauge?

Mason Edmison

Hey all,

So the schematic basically said to run red (power) to a 12 v source thats only on when the car is on - I went to the ignition fuse, one ground, one to the negative side of the coil, and last but not least, one to the "dimmer" switch. I did run to the red/black of the dimmer and it looks if I put the dimmer switch about in the middle I can get both the dash lights and the tach light. I guess my only other option would be to tag on to a wire on the actual light switch.

wyoming9

iTrader: (1)

The tach signal is pin 4 of the igniter plug

scope103

Assuming you mean the light switch on the steering column stalk, no, that wouldn't work either. It too is on the "low" side.

But the stalk switch just switches the Taillight relay, which powers the Tail fuse, which is in the high side. The Green wire from the fuse is 12v with lights on.

You CAN pick up the tach signal from pin 4 of the igniter, but the usual place to pick up the tach signal (on a '94) would be at the "tach" pin on the diagnostic connector.