I installed a Volt Meter following the manufacturer instructions; yellow wire to the positive post of battery, black to ground which I connected to a place where I have my tachometer ground connected to. The orange wire connected to the illumination source.... used the same spot that I used to connect the tachometer.. I used the panel dimmer switch. Coneccted the purple wire to the fuse box. I used an "add fuse circuit" connector for this connection.
Prior to finalizing all connections I disconnected the ground wire from the battery, and connected the voltmeter's "battery" wire to the positive post. Connected all other voltmeter's connections, fuse box, illumination and ground and reconncted the negative battery wire.
As I started the car I saw that the voltmeter was not registering. It illuminated but no voltage reading. Turned car off and came back to work on it after several hours. Turned the car on to warm it up and left it idiling. After 10-15 minutes came back to the car only to find that the stock tachomter was not registering at all and the motor was hesitating. The hesitation disappeared when the headlights were on. The rpms stabilized around 500/600. Turned the AC on the car stalled.
Decided to disconnecct all of voltmeter connections to bring car to the "before"/original position. After reconnecting every thing back re-started the car and found the same problem. Took the car for short drive and noticed that the gauge cluster illuminations was very dim. The head lights were ok, the tach. registered rpms but hesistation was still present. Turned car off and disconnected battery ground wire to reset computer. Restarted car and everything seems and sounds ok...except it is idling at around 200, when the A/C is on it goes to 400.

I need mad help here, I have to drive out of state tonight!!!