The gas bars, does this happen to anyone else?

[Ilovemyyaris]

Does anyone else ever witness a gas bar disappear while you don't have the car on?

Okay so tonight I was sitting in my Yaris cleaning the inside. I did NOT have the engine running but I did have the radio and lights on. Well I had a full tank of gas "all 8 bars" and when I was done cleaning/vacuuming I just sat in the front seat let it back and relaxed a little. I sat there for about 5 minutes and I was about to leave when I noticed one of the bars was missing.

It's done this once before, then the bar came back when I drove a little before actually disappearing. The last time it happened the same situation, I was sitting inside without the engine running and a bar disappeared.

Is this normal? This is the first car I've actually ever owned, so it might be normal for all cars idk. It's a 2011 model 5 door hatchback. It's a minor problem, I just want to know is it normal or just happens with mine?

[Altitude]

Here's a possibility:

Minor fluctuations in the voltage may cause the value being read from the sensor to change. Since you were running your battery without the motor on, this likely caused enough of a voltage drop to affect the reading.

[CTScott]

That's exactly correct. The fuel level sender uses the unregulated battery voltage, so the change from 14.x when the alternator is whizzing to 12.x when you're sitting there cranking the tunes with the engine off makes a difference of up to a full bar.

[Ilovemyyaris]

Okay thanks.

[MadMax]

Yep, happens a lot to me at work. I park my Yaris with the fuel gauge reading one level, then I come back in the afternoon and it's a bar lower. I always figured it might have something to do with the heat and pressure inside the tank; but the voltage fluctuation makes sense as well...

[mazilla]

Originally Posted by CTScott

That's exactly correct. The fuel level sender uses the unregulated battery voltage, so the change from 14.x when the alternator is whizzing to 12.x when you're sitting there cranking the tunes with the engine off makes a difference of up to a full bar.

Same question, different thread...can we regulate that voltage somehow? I don't like how much it bounces around my gauge.

[CTScott]

Originally Posted by mazilla

Same question, different thread...can we regulate that voltage somehow? I don't like how much it bounces around my gauge.

Yes. You would have to add two 12 volt regulators. One for the ECU-B and one for the MET feed to the cluster.

[mazilla]

Originally Posted by CTScott

Yes. You would have to add two 12 volt regulators. One for the ECU-B and one for the MET feed to the cluster.

My gauges sometimes show 15.5-16.5 at the battery, I'd like to stabilize it @ 14 if I can. Could you drop an example link on the part I would need?


Thank you for all the

[CTScott]

Originally Posted by mazilla

My gauges sometimes show 15.5-16.5 at the battery, I'd like to stabilize it @ 14 if I can. Could you drop an example link on the part I would need?


Thank you for all the

You need to stabilize it low, not high. A regulator doesn't bring the voltage up, it will just take a higher voltage and bring it to a lower stable voltage. The part you want is a simple LM7812 voltage regulator (radio shack usually stocks them). It is a 3 pin device with in, ground and out. Normally you would add two capacitors when using one, but in this case, because you are just regulating a supply that really doesn't need to be regulated you can skip the caps.