Voltage Gauge bounces when my foot is on the brake or accelerator
09-09-2016, 03:16 AM
#1
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Voltage Gauge bounces when my foot is on the brake or accelerator Just noticed this today, but the needle will bounce around when my foot is on either pedal. If I let the car coast it will become stable though. In park it seems mostly stable but still bounces slightly. Not sure what it could be considering I haven't notice any other problems yet.
09-11-2016, 08:17 PM
#5
So what's the attachment to the brake pedal, or is there none? Is the problem only there when the RPM's are above idle? If so, the first think I would check for is belt slippage. (There are three marks on the tensioner. Two marks on one side and one on the other. The one mark should be between the two.)
09-11-2016, 08:56 PM
#6
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No I'm just trying to be descriptive, the only time the needle settles is when I am coasting at 35 mph or below without my foot on either pedal. Even when I am sitting in park and idling it bounces slightly...if the headlights are on I believe it fluxuates a little more.
Just noticed something else as well. When I'm driving at night and turn on my dome light or lights on the rear view mirror they flicker if you watch closely...when I turn off the car and turn them on it stops.
Just noticed something else as well. When I'm driving at night and turn on my dome light or lights on the rear view mirror they flicker if you watch closely...when I turn off the car and turn them on it stops.
Last edited by Dyson350; 09-12-2016 at 06:10 AM.
09-12-2016, 06:16 AM
#7
you are measuring voltage from two spots, 12V and Ground signal right
When the needle moves, it is because some resistance on either side of those two wires changes. In other words, you arn't looking at the battery's voltage (you didn't wire it to the battery directly) you are looking at fluctuations in your sub-harness(es) where the gauge is wired. If you want it to sit still, you have to eliminate changes in resistance, or reference a stable ground at least; which means you need to basically wire the gauge directly to something that supplies a consistent reference with the other electronics i.e. the ECU.
If you ever pull up an FSM (factory manual for the engine) and trace signal wires grounds for sensors, you will see they ground back at the ECU as their reference. If you happened to wire an IAT for example, to something besides the ECU, the resistance to that spot could change and throw the IAT reading off while you are driving (the ECU has no idea the ground reference changed). That is why there are special "signal wire grounds" that always lead back the computer.
When the needle moves, it is because some resistance on either side of those two wires changes. In other words, you arn't looking at the battery's voltage (you didn't wire it to the battery directly) you are looking at fluctuations in your sub-harness(es) where the gauge is wired. If you want it to sit still, you have to eliminate changes in resistance, or reference a stable ground at least; which means you need to basically wire the gauge directly to something that supplies a consistent reference with the other electronics i.e. the ECU.
If you ever pull up an FSM (factory manual for the engine) and trace signal wires grounds for sensors, you will see they ground back at the ECU as their reference. If you happened to wire an IAT for example, to something besides the ECU, the resistance to that spot could change and throw the IAT reading off while you are driving (the ECU has no idea the ground reference changed). That is why there are special "signal wire grounds" that always lead back the computer.
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09-12-2016, 02:51 PM
#9
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161,000 roughly, I just replaced the battery because it was old and needed replaced anyway and aso has the alternator checked and it was good. New battery didn't make any difference
Also I noticed the headlight and turn signal lights seem to flicker faintly as well
Also I noticed the headlight and turn signal lights seem to flicker faintly as well
Last edited by Dyson350; 09-12-2016 at 09:13 PM.
09-12-2016, 05:01 PM
#10
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Checked to see if your pedals have any wires wrapped around them?
09-13-2016, 04:07 PM
#11
That's wayyyyyyyy old for a belt. Mine have stretched beyond spec reliably after 75K miles. If you really have 160K on your belt, I can guarantee its shot, even if it isn't the source of this problem. I'd replace your belts next and see what happens. You can check the note in post #5 and see the process for looking at the stretch on the belt tensioner to confirm if your's is out of spec and could be slipping.
09-13-2016, 08:03 PM
#12
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That's wayyyyyyyy old for a belt. Mine have stretched beyond spec reliably after 75K miles. If you really have 160K on your belt, I can guarantee its shot, even if it isn't the source of this problem. I'd replace your belts next and see what happens. You can check the note in post #5 and see the process for looking at the stretch on the belt tensioner to confirm if your's is out of spec and could be slipping.
I thought you just asked regarding the car in general. The belt was replaced a couple years ago so its it good shape. Not sure if its lose or not but I also wonder if its the throttle body.
09-14-2016, 08:08 AM
#13
The first step would be to check the marks on your belt tensioner. 2 seconds - and that will confirm if your belt is still in-spec. If it's good, I'd look for loose or corroded power/ground wires next - including your exciter wire.
09-14-2016, 04:39 PM
#14
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It's not the throttle body. It's either a loose belt, the alternator, (even if it "tests" good...) or a wiring issue.
The first step would be to check the marks on your belt tensioner. 2 seconds - and that will confirm if your belt is still in-spec. If it's good, I'd look for loose or corroded power/ground wires next - including your exciter wire.
The first step would be to check the marks on your belt tensioner. 2 seconds - and that will confirm if your belt is still in-spec. If it's good, I'd look for loose or corroded power/ground wires next - including your exciter wire.
09-19-2016, 12:47 PM
#15
Right. I'd expect this to be related to RPM. If you can relate it directly to readings on your RPM gauge (those readings may be different accelerating and decelerating), that would limit the problem to your belt, exciter wire, or alternator.