Roof lights on and can watch the fuel gauge go down? WTF!

[Farva]

gday guys

im in a bit of a pickle here and fuk knows why its doing it. ive wired up 4 extra spotties on me ute. making it a total of 4 XGT's and 2 170's. problem is when i go out for a drive with all the lights on the fuel gauge goes down. you can actually watch it moving down. when i turn the spotties on the roof off the fuel gauge starts to go back up. anyone got any ideas here?

ive wired them uplike you would normal for a set of spotlights but instead, ive biggybacked the high beam trigger wire at the relays to make it cleaner etc. and made it so that all 4 on the roof run off the one switch so ive piggybacked it there as well.

im driving an 04 GU ST ute. running a red top optima thats probably all you need to know to help me out. anyone got any ideas?


cheers

adam

[Gwagensteve]

6 spotties on is 50 amps, + the rest of the car - I reckon your getting volt drop because the alternator can't keep up and that's making the gauge inaccurate.

I vote you need more alternator.

Steve

[Farva]

gday steve

mate i was actually thinking that after i posted, im putting me multimeter on it today to see how she goes.

cheers

[rapid80]

Mate I reckon if you ever needed an excuse to go hid you just found one.
I've got a similar setup to you but have 2 ipf xs with the 65w globes and converted 2 rallye 4000 compacts to hid. I've still got 2 lf 170 in halogen 100w but haven't had a problem with voltage using 100amp alt.Wired up the same as yours with 1 switch and 2 relays for the roof lights and a seperate switch and relay for the bullbar mounted.
Do you know what amperage your alternator is ?
I reckon it might end up cheaper to convert the lights than replace the alternator as well as getting the visual benefits of hid. I picked up a cheapie hid kit for $135 and so far so good.

[GeneralFubashi]

I had the same problem, its a grounding issue with the body of the car, im pretty sure the guage is quite sensitive to voltage drop. You can make it a bit better by running some ground wires from the bat to the body, body to chassis/engine etc, and making sure the spotlights are grounded directly back to the battery, not through the body or chassis.

I still notice movement, but not nearly so bad now.

Sam

[Shadow]

I had the same problem, its a grounding issue with the body of the car, im pretty sure the guage is quite sensitive to voltage drop. You can make it a bit better by running some ground wires from the bat to the body, body to chassis/engine etc, and making sure the spotlights are grounded directly back to the battery, not through the body or chassis.

I still notice movement, but not nearly so bad now.

Sam

Fubashi is spot on

you have a ground problem, the in creased current of your spotlights has made the ground from battery to body (chassis) too small.

Beef up the ground lead and also clean the connection points on the body and chassis, bare metal, then bolt the terminal down, then a touch of zinc paint to stiop the rust.