Electrical Experts ### help

[twinkiemobile]

Ok, so i was trying to fix the wiring for my after market gauges that were installed on my car by the previous owner. however, after everything was said and done, i was trying to turn on my car, and it was ok, but it seems like the gauge cluster was getting the power sucked out of it.. it was very dim, the headlights would turn on but won't turn off.. radio/power seats/windows/locks/mirrors won't work.. but the sunroof will. does anyone know what wire i could have tripped to cause these problems. thanks for any advise

- JOse

 

[luv2rallye]

I AM an expert on electrical so read carefully. Your gauges power is not hooked up to a true +12V power wire. Instead it is connected to the "switched to ground side" of a device (probably the headlight relay coil). Example: your headlight relay coil always has +12V on one side. The other side is switched to ground by the headlight switch (ie. applying ground to that side activates the relay). Your gauges are probably connected to that side. So when your gauges are on (and headlight switch off) half the voltage is dropped across the relay coil leaving only half for the gauges (result: dim). In addition, the gauges are providing a path to ground for the relay coil so current flows and keeps the headlight relay activated (result: headlights on).

This is a very common mistake by installers. You can't just test for +12V and assume it's a true power wire. The "switched to ground side" of any device that has +12V on the other side will always have +12V on this side too if it is not switched or connected to anything on this side (so it's not turned on). But it is not a true power wire since any current has to go through the device first which will drop voltage.

I'm not sure how your gauges are connected or which way they operate or what you're trying to do. If you are trying to hook up the gauge's dial lights to go on with the headlights and one side of them is already connected to ground (so you just need a "switched on with headlights" true +12V power wire), then connect the + dial light wire to the contact side of the headlight relay that goes to the headlights (this is the contact side, not the coil side). Most people however, want the dial lights to go on with the taillights the same way your dash lights go on. So just hook the + dial light wire to the same wire (green/white) that goes to your dash instrument lights (this goes to the contact side of the taillight relay). If you have some other arrangement pm me and I'll help you.