Heads-Up through stereo?

[Florida240]

Ok, check this out - I've posted a few times asking about problems with my Heads-Up Display on a 92 240sx, I've checked every fuse and wiring harness I could find without any luck getting either the HUD or the digital speedo to work.

This week I put the factory stereo back in and hooked everything up (had no stereo before because the kid I bought it off took his aftermarket one out) and now it works!

Well, it works if I have the headlights or parking lights turned on. Turn them off and both the HUD and Speedo go out. Does the wiring for the speedo/HUD go through the stereo?! Anyone else run into anything like this? I'm thinking about just taking the car up to Best Buy or Circuit City and having them do an install on a new CD player - if it runs through the stereo then they must have the schematics or instructions on how to set things up correctly, right?

[1dollar240]

I doubt it runs through the stereo but there are issues with dimmer switch wire- the wire that dims the lights on the radio when the headlights turn on. My stereo used to be wired incorrectly ( i think it was grounded to the dimmer wire, not really sure) and it would only work if the headlights were off. Here is my advice- Unhook your stereo, make sure ALL fuses are ok, get a voltmeter and test every wire in the stereo compartment with the ignition on and off and label them- you should be able to find the 2 power wires (1-constant, 1- switched by ignition), then run a new ground wire to any substantial metal you can find. This will isolate the stereo from the HUD system, then you check the ground wires for the HUD/speedo because it sounds like you are ground the HUD/speedo through the stereo somehow- not a good thing. . .

[Florida240]

I've gone through the fuse boxes numerous times, they're all fine. I hooked up a new CD player this weekend, verified grounds and power wires - still the only way I get a display on either the speedo or the HUD is to turn the lights on. Any other ideas?