Gauge problem

[scoobyimprza]

The Problem:
The gauges will work when the power is on but when I turn the engine on, the gauges don't work or they flicker violently.

What I've done so far:
Checked for bare wire and taped it up. I checked the ground and ignition wire for power at different points. They are good. I cut the ignition wire from the gauges and connected it to a different wire.

I'm at a loss here. The gauges are EGT and A/F ratio. All the power is there.

Brent

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[Sparks]

Brent,

What brand gauges?

Where do you have then wired? Power, Ground, Lighting?

[scoobyimprza]

They are Autometer. I can't remember when the problem started. I have gauges grounded to some metal around the steering column and the power is coming right from ignition coming off the key coil. Lighting is coming from a wire on the defrost button near the gauges.

All the power is there, I have tested that with my little light thingy. So that is the strange thing...

[Sparks]

Wow, you made it hard on your self.

On the back of your radio harness is a small plug tapped to the harness. Those 2 wires are for lighting of the stock turbo gauge. Use them for lighting.

While you're at the radio harness, you can tap power and ground if you'd like. Some also use the clock wires for a reliable ground and power input.

When ever possible avoid using chassis ground for gauges. Almost every sensor in our cars have a seperate ground input.

Another caution is never use anything "lighting" for a ground, Subaru uses a reverse positive voltage for lighting.

Hope it helps,

Shaun

[scoobyimprza]

Thanks for some instruction. My car is a 93, btw. I'm getting power and my grounds are fine, that's why I think this is strange.

[Sparks]

You could have a short in the EGT line. Check the resistance of the EGT wires when cold, then start, and see what happens to the R value

[WhatleyWRX]

Originally posted by Sparks
Another caution is never use anything "lighting" for a ground, Subaru uses a reverse positive voltage for lighting.

Shaun

Its called a hot reference, and its a pretty common practice. I doubt subaru is the only car manufacturer to do it.

I would just run illumination from a ignition (ACC) power source. This may be your problem, may not.