Gas Gauge Wonders

[YotaFun]

I have a 97' SR5 Auto 4WD
This past winter, right about February,
I started to have issues with my gas gauge.

However recently I have come to find out that it is not the sending unit in the tank...

Somehow my fog lights are messing up the gas gauge.

When my fog lights are on, the gas gauge reads 1/4 below what it is really at.

When the fogs are off, it is normal.

At first I thought this might have been a ground issue with the fog lights.

But after grounding the fogs right to the frame.

I still have the same issue as when the fogs were grounded to the bumper.

Can anyone give me any input on this?

Because I would like to be able to drive with the fogs on, without having to remind myself every time that the gas gauge is reading a 1/4 below what it is.

I will get some video footage in a bit.

Thanks for the help.
~Avy

Here is the video to show what I mean.

[Robinhood4x4]

Are these aftermarket fog lights? If so, where did you tap the power from?

[YotaFun]

They are aftermarket,
However, they retain the exact same wiring as the stock ones that came on the truck.
Same relay, same power and ground tap, same tap on the headlights wire so that when the high beams are on, they go off.
I even have the factory fog switch.

[YotaFun]

Bump...

[MTL_4runner]

The only reason you'd see something like that was if you were dropping the operating voltage on the battery. Did you test the system to see what the charged voltage is on the battery? Is the alternator charging properly? You might also have the battery load tested just to be sure that system is ok. If all checks out then you may need to redo the wiring for the fog lights, using the realy and wiring them directly to the battery instead. They may just take more juice than the factory fogs.....not sure on that.

[YotaFun]

The only reason you'd see something like that was if you were dropping the operating voltage on the battery. Did you test the system to see what the charged voltage is on the battery? Is the alternator charging properly? You might also have the battery load tested just to be sure that system is ok. If all checks out then you may need to redo the wiring for the fog lights, using the realy and wiring them directly to the battery instead. They may just take more juice than the factory fogs.....not sure on that.

Recently I have been also having some starting issues which I am chalking up to a bad battery.
The reason I say bad battery, I was with a friend of mine who works for AAA and asked him to test my bat.
And test did prove that the battery should be replaced.
Should I start there and then worry about the alternator and such?

Just going to go off topic quickly.
I plan on running a lot of aux lights on Tess, is there a beefier alternator I should be looking into?

[YotaFun]

Well the issue has been solved!
But I have a few more questions lol!

First off, to solve the issue I ran the grounds for the lights straight back to the negative terminal on the battery.
1) This made the gas gauge issue go away.
2) The lights are actually shinning nice and bright like they should.

Now my question is.
Why is it like that?
Am I going to have to run a negative line for all my aux lights when I put them on back to the negative terminal?

Or is this a sign that my alternator is going, cause I had the battery checked and its good.
How can I test my alt voltage to make sure its good?
Cause I did notice after I got the job done that when ever I turn on the lights or even use the power window it sounds like the alt is starting to strain or the belt might be starting to loose its grip.

[Seanz0rz]

im guessing your chassis ground on the battery is under sized. i plan on beefing up mine very soon.

[Tanto]

Replacing the battery seems the most prudent thing to do since that is an important issue anyways.

And if it doesn't fix everything, at least you know that you have a reliable battery.

[YotaFun]

Would a battery going cause a strain on the alternator though?
Though I don't have a dimming of the lights when I use any power accessory so.
When the truck come back from the shop after my rear end issues is figured out I will take it to Autozone and check both the alternator and then battery.