Aftermarket Gauges acting all funny

[Patryn]

I just relocated my battery to the trunk last weekend. It is connected via a 2 gauge power wire and a 2 gauge ground wire grounded to the frame. I'm using a distribution block near where the original battery was. However the car had a weak start which I tracked down one of the original grounds that I relocated on the firewall. I sanded the paint away near that connection and starting was much stronger.

However after doing that I noticed both my prosport guages are being rather erratic. As in the needles are dancing all over the place when the car is in motion. When idling for instance the boost gauge just stays pegged at the bottom or the top.

The way I have the gauges setup is they are on their own circuit. I ran a 10 gauge from the distribution block, formerly from the battery to a 5 amp fused switch. The switch powers my AEM A/F Gauge and the two prosport gauges, which are located in the A-Pillar. Everything that needed a ground I ran them all back to a single location on the passenger side of the center console and just grounded them to that via a bolt. The Oil guage however I grounded near where the sensor is on the oil adapter plate to the frame again via a bolt.

Any ideas on what could be causing the gauges to jump around or if there is a better way of doing the grounds or power wires for that matter?

[tachyon_ftl]

Well, it definitely sounds like a grounding issue.

- Is the new battery ground solid? Do like you did on the firewall and scrape off the paint, then make sure that the ground lead is solid in it's terminals and bolted well at both ends.

- Test the gauge ground by getting a battery jumper cable, and putting one end on the battery the other on the gauge grounds (remove them from the car first). Fire up the car. If the gauges behave normally, then move the gauge ground from the console to the frame, either directly in the cockpit or with another D-block in the cockpit that you ground to the frame elsewhere.

- The size of the grounding conductor for the gauges won't matter, but making sure that the gauge ground and the battery ground are at the same potential does. If you have a multimeter, you could check to see if there's a potential between the gauge ground point and the battery negative post with the car running - I'll bet there is.

- Is the engine now well-grounded to the frame? Since you moved battery, all the stuff that used to be on the battery post is now on the "frame" someplace, but are they all on the unibody (firewall, say) and are they all well grounded - no paint, good leads, tight screws, etc.

I hate ground loops. They are a complete PITA. But you have some after the battery move. So, I'd check all the grounds that you moved in the engine compartment and the ones for the gauges in the cockpit. Someplace, they are not as good as they could be is my guess.

Also, make sure you have a grommet around the #2 conductor where it goes through the firewall (or any other structure if it goes thru anything else). Friend of mine moved his battery a few years ago and set the car on fire when the insulation on the cable abraded and the battery then grounded out where it went thru the wall!

[mike92stealthtt]

I'd move your ground for the gauges to the bolt behind the plenum where the engine also grounds.