Instrument cluster harness pins - electrical question

[Gibson]

I may know what causes this - but wanted to check with you guys and make sure.

So you know how a lot of the components in the instrument cluster share a common ground? (like all the illumination bulbs all share a ground) Well, I was mapping out the circuit on the back of the cluster cause I'm about to do some modifications - and I noticed something weird. I was using my multimeter on the Highbeam bulb trying to figure out which of the leads was the ground. So I tested for continuity with the chassis thinking "Whichever one has continuity with he chassis will be the ground"

But BOTH pin leads in the harness clip have continuity with the chassis! Is this because it is finding continuity back through its positive pin, then through a splice somewhere, then through a bulb somewhere to that bulb's negative side, and then to the ground/chassis?

I started testing the other pins in the harness and noticed a vast majority short out to the chassis (apparently).

If so, is there a simple way to figure out which of these lead are actually grounds, and which ones are just working their way back through the wiring somewhere?



Thanks!

[95 S_Trucker]

were you just using an audible continuity tester?

if you were, the meter was going through the bulb as well.



use an ohm meter and whichever lead has the lowest resistance to ground would be ground.

[Gibson]

Ah - gotcha. That works! Thanks!

[glock35ipsc]

On the highbeam bulb, only one lead will map directly to the harness connector without stopping off anywhere else. But the ground will likely be a ground for many other bulbs and possibly a few gauges as well on its way to the harness connector.

[95 S_Trucker]

it sounds like you got it figured out, but if you are still having issues you could pull all the bulbs out and then test

[Gibson]

Originally Posted by 95 S_Trucker

it sounds like you got it figured out, but if you are still having issues you could pull all the bulbs out and then test

Yeah - it worked a trick - resistance was the correct way to go. And I also will try the "remove the other bulbs" thing if it gives me additional trouble. Thanks guys!