I am trying to install my Greddy 52mm gauges and I am having trouble with the wiring. I chose to tap the wires from the stereo harness since it has everything I needed. I hooked up everything as per the instructions, but the gauge isn't working as expected.

The Greddy gauges require a constant 12V as well as a switched 12V, which I correctly hooked up. When I turned on the car to try out the gauges, I noticed that there was no start up display (it should sweep all the way right then back to 0). However it DID show the start up display if I unplugged then replugged in the gauge. So I thought I just merely switched the constant 12V and switched 12V, but that wasn't the case. It was actually hooked up correctly, but for some reason the gauge was just ALWAYS on using the constant 12V (even if the car was off) and ignoring the switched 12V.

If I swapped the constant 12V and switched 12V wires on purpose, then the start up display works fine when I turn on the car, but after some thought I realized that if I hooked it up that way then that meant that the constant 12V wire wasn't doing anything. So I unplugged the constant 12V and yup, no difference. Should I just leave it installed this way without the constant 12V hooked up?

The other problem is that I am using the ashtray light as the dimmer light source, however that gives me inverted dimming! Ie. The gauge would glow brighter as I turned DOWN the dimmer switch. If I used the other wire on the ash tray light instead, it would just stay on with no adjustable dimming. The greddy gauges just has 1 input for the dimmer, so I can't hookup the dimmer to both ashtray wires like the Autometer gauges.

Does anyone else have Greddy gauges that can give me some advice?
Note: I am not using the SM Integrate ones with the link box, these are the normal stand alone ones.

 

When you unhooked the constant 12V does it do the shut off display? The reason for the constant 12V is to be able to keep data after shut off. Most likely you lost this feature without knowing it when you unhooked the constant 12V.

 

I didn't install the illum wire at all. I got a constant power source from the ACC wiring in the steering column, ignition II from the turn signal tree, and ground from the ground circuit for the cluster illumination. Since the FD uses a modulating ground signal to affect dim, there is no use for the separate illumination wire.