Grounding questions.
Grounding questions. I have some issues. My fuel pressure gauge acts wierd when I turn my wipers on. They are not getting power from the same source however, they might be grounded on the same area (firewall). The gauge is fine but when I turn on the wipers thats when weird things happen. once the wipers have started then when the turn signals are used they effect the gauge in sync. It pulsates with the turn signal.
Could this be because they are both grounded to the firewall? I'm going to move my gauges ground over to the fender tommarow just wonderd if anyone could help. Thanks.
Could this be because they are both grounded to the firewall? I'm going to move my gauges ground over to the fender tommarow just wonderd if anyone could help. Thanks.
Joined: Nov 2003
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From: Jacksonville, FL (originally from Toronto Canada)
No, grounding to the same location won't cause problems unless the location isn't really a good ground. Make sure there is no paint, grease, etc. that might be preventing a good ground but there is no reason to separate them.
well ya its not a grounding issue with the gauge, I'm not sure what to do now. I guess just see where its getting power from, try another source. If its still F'd I'll just get another one, It doesnt change color like it should anyway.
EDIT: just tried different sources. I dont get it. Either the gauge is F'd which seems possible since it doesent change color like it should. or the sender is screwed, possible, or the electronics in my car are shitty and that actually does affect the fuel pump and it does drop in pressure.
EDIT: just tried different sources. I dont get it. Either the gauge is F'd which seems possible since it doesent change color like it should. or the sender is screwed, possible, or the electronics in my car are shitty and that actually does affect the fuel pump and it does drop in pressure.
Last edited by cherryelky305; Oct 24, 2007 at 10:17 PM.
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it is not a grounding issue, as all grounds are just simply the path to the negative side of the battery terminal. The firewall is not a bad ground at all, so it could be because the 12V + accessory wire is grabbing power from the relay that controls the blinkers, and that is why it is fluxuating. I do car electronics and custom audi at a very high end shop, so i know what i am talking about. Also, it could just be a bad guage, but i would make sure that the power source is good ( in the GM's the constant 12 v is a think red wire in the ignition harness, the accessory is a brown wire, and the ignition wire is a pink wire, also thick). Now, dont take my word for this and just hook it up, make sure to test the wires witha METER, not a light or power probe. Also, make sure that the ground has, bare metal contact, as just drilling the hole does not provide enough contact with Bare Metal.
Joined: Nov 2003
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From: Jacksonville, FL (originally from Toronto Canada)
I've often wondered why so many people discount the usefulness of a test light. Meters have their place when voltage differences are important but when you're just trying to identify power and ground, a test light is a very useful tool that is quicker and easier to use (because the tip is sharp enough to penetrate the wire's insulation and you just want to see the light on or off rather than looking at the meter). I keep a test light right at the top of my tool kit.
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Joined: Apr 2002
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From: Eastern MA
I've often wondered why so many people discount the usefulness of a test light. Meters have their place when voltage differences are important but when you're just trying to identify power and ground, a test light is a very useful tool that is quicker and easier to use (because the tip is sharp enough to penetrate the wire's insulation and you just want to see the light on or off rather than looking at the meter). I keep a test light right at the top of my tool kit.
Also, instead of damaging insulation, you can use a clamp meter that detects current through induction instead of physical contact (I don't have one and my knowledge of them only extends to their existence and basic theory). A better bet is to try and trace the wire to a connection and touch the meter or test light to its pin in that connector.
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Joined: Nov 2003
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From: Jacksonville, FL (originally from Toronto Canada)
Oh, I have several meters and I use them when necessary but a test light is still a useful tool. In this case, determining which of the power wires at the steering column is ignition switch controlled certainly doesn't require a meter.
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Joined: Apr 2002
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From: Eastern MA
I think it would be useful in this case. It may tell him if the power going to the gauge is fluctuating or if its giving an accurate reading. Which would mean that there is a problem with the pump or sender.
I ordered a mechanical fuel pressure gauge for my rail to compare since i still want a gauge in the car. I also sent an email to the company I got the gauge from, hopfully they will take care of me but I think not and I will just have to scrounge up another $46.
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A test light can BLOW AIRBAGS AND DESTROY COMPUTERS, if accidently probed into the wrong wire, as they CAUSE CONTINUITY TO GROUND TO COMPLETE THE CIRCUT. A meter is 100% safe! I will say, that in older cars, a test light is absolutely fine, but once you start to get into the years with airbags, and computers...using a test light is FOOLISH! If you probe the wrong wire, you could have thousand of dollars worth of damage.... so use the meter and avoid any possibilities. A test light also cannot test the resistance of the Ground!
Joined: Nov 2003
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From: Jacksonville, FL (originally from Toronto Canada)
The original statement was to use a meter to determine the ignition and constant power wires at the steering column. These wires are thicker and carry power only so a test light is quite sufficient for determining which is which. The airbag wires are in a special sheath to avoid people messing with them and the power wires have nothing to do with the PCM, BCM or any other computer. Granted, you should have a good idea what you're doing with a test light but an improperly used meter can blow computer circuits just as easily (for example, using an ohmmeter to determine resistance to ground on some solid state circuits). It's a case of using the right tool for the job.
I got a mechanical gauge and it reads 58 psi all day long, so at least i know theres nothing else fishy going on just a case of a bad gauge i think. its still possible that its not getting a good power source though. I think I will eventually get a new gauge, better brand or something. POS glowshit products. Anyone know of a good cabin mounted gauge thats 2" around for my mount place?