EGT hotwire location

[Rabbit TD]

Ever since I put the TD engine in the Rabbit last winter and hooked up my Autometer Boost and EGT gauges {Spruce thermocouple also} I have noticed that whenever I have my headlights on the EGT gauge's needle will start fluctuating like crazy after a minuet or 2.  When it is doing this if you put another load on the electrical system like the wipers or the heater blower it seemsto stabilize for a little then starts acting up again.  It acts perfectly until I use the headlights.  I have the EGT, Boost and Water Temp gauges in a 3 hole pod on top the dash with the hot wires from the EGT and Water Temp spliced together but I can't remember for the life of me what I tied them into under the dash.  I used a circit tester to find out which wires were hot under the dash when the key was on but I don't remember off-hand what I actualy tied it into other than it was a reasonably heavy wire at least 16 ga.  Is there a recomended place to splice this too?  I also spliced the 2 grounds from the 2 gauges together with a separate wire to the firewall for ground.  Or is this a common problem having to do with alternator noise or something on those lines. I've never had  any electrical or charging problems of any kind other than this annoying situation when the headlights are on.  I have a feeling I tapped into a wire on the light switch that becomes hot when the key is on even though the actual lights are not.  Do you think  this could be the problem and where is the recomended place to splice into?

[macka]

I'd wire in a line from something you don't use much, like if you don't smoke, a lighter plug. Just run a jumper up to the hotwires from the lighter hot wire, use an oddball colour if possible.

[92EcoDiesel Jetta]

You may have a ground loop problem. Try connecting the grounds of the EGTgauge to one point at the battery negative terminal instead of the fire wall.

[rabbitman]

I kinda have that problem only it doesn't affect the pyrometer. It used to only do it if I had the rear window defroster on then the dashlights dim and brighten, not a lot but enough to make me think somethins wrong. Now I think it does it anytime the dashlights are on.

[Rabbit TD]

I kinda have that problem only it doesn't affect the pyrometer. It used to only do it if I had the rear window defroster on then the dashlights dim and brighten, not a lot but enough to make me think somethins wrong. Now I think it does it anytime the dashlights are on.

I think we're gonna need a Pimp Your Pyrometer thread, it seemed to help the glow plug issues a lot.  I've been thinking about the ground situation too.  I know it's gonna be a pain to get at those wires on the gauges as they are in a 3 hole pod on the dash.  It actualy fit right over the place where the padding had a lot of cracks in it and the pod covered it completely.   

[rabbitman]

Don't know if this is still an issue or not but my pulsing lights got bad enough that I could see the headlights pulsing too........that'll about drive a guy crazy!!!

One day the pyrometer started bouncing around, it would climb if I pushed the brake and drop when I let off. I swapped the alt out for a used bosch unit and it fixed everything, except now I have to rev to 1700 to get the charge light out.