Charging System/Voltmeter Information Needed
04-05-07, 07:47 AM
#1
Charging System/Voltmeter Information Needed
Cliffnotes
My voltmeter always sits at 12.4 constantly. New alternator with a bad internal regulator fluctuated the gauge from 12.0v to 16.0v. Why is the gauge just now reading right?
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For the last 4 years my voltmeter has sat at ~12.0v to ~12.4v consistently. With a DMM my alternator always tested out higher (usually 13.5v or above, although I did have to replace an alternator). So basically my gauge is too low. Annoying, but not a debilitating problem. The only other time it read higher, up to ~14.0, so basically actually voltage, (see below for context to "other time") was when I was having connection issues with my battery (bad terminal, infamous click click when starting).
This morning I got in and it started fine (2 tries just to check) but my voltmeter was anywhere from 12.0v to ~16.0v, depending on engine speed. I promptly shut the car down because I didn't want to blow anything out. I didn't have a DMM with me and had to go to work so I couldn't test it. However, from how bright my lights were (it was actually kind of nice) I'm assuming my voltmeter was correct.
From my searching, my alternator apparently has a bad internal regulator. I got the alternator last weekend (reman), so... yeah... lets hear it for Advance.
Question: Why, just now, does my gauge actually read higher than 12.4v when the alternator has been putting out more than 12.4v for years?
This is how it looked for about 4 years.
P.S. to NZConvertible: Yes, I did get gas shortly after this pic was taken.
My voltmeter always sits at 12.4 constantly. New alternator with a bad internal regulator fluctuated the gauge from 12.0v to 16.0v. Why is the gauge just now reading right?
Full Story
For the last 4 years my voltmeter has sat at ~12.0v to ~12.4v consistently. With a DMM my alternator always tested out higher (usually 13.5v or above, although I did have to replace an alternator). So basically my gauge is too low. Annoying, but not a debilitating problem. The only other time it read higher, up to ~14.0, so basically actually voltage, (see below for context to "other time") was when I was having connection issues with my battery (bad terminal, infamous click click when starting).
This morning I got in and it started fine (2 tries just to check) but my voltmeter was anywhere from 12.0v to ~16.0v, depending on engine speed. I promptly shut the car down because I didn't want to blow anything out. I didn't have a DMM with me and had to go to work so I couldn't test it. However, from how bright my lights were (it was actually kind of nice) I'm assuming my voltmeter was correct.
From my searching, my alternator apparently has a bad internal regulator. I got the alternator last weekend (reman), so... yeah... lets hear it for Advance.
Question: Why, just now, does my gauge actually read higher than 12.4v when the alternator has been putting out more than 12.4v for years?
This is how it looked for about 4 years.
P.S. to NZConvertible: Yes, I did get gas shortly after this pic was taken.
04-06-07, 07:52 PM
#3
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Your gauge should be at or near the line right above 12v. The gauge may be wrong. You will see a difference when testing the voltage at the battery compaired to at the ECU or gauges. You could see up to a 1.5v difference. So if your battery is at 13.5v, then inside you may only have 12.8-13v.
Its just like when you test the voltage at the alternator, you will or should see 14.5v, but at the battery you will see 13.5+ and inside the car even lower.
ITs all about the resistance in the wires and how many items require power from one specific wire which wil lower the amount of total voltage. You will never get the same voltage inside as you do at the battery or alternator. At the battery will always be higher then inside the car.
You can check the voltage inside at the fuse box or at the cig lighter plug to see what the voltage is inside.
Its just like when you test the voltage at the alternator, you will or should see 14.5v, but at the battery you will see 13.5+ and inside the car even lower.
ITs all about the resistance in the wires and how many items require power from one specific wire which wil lower the amount of total voltage. You will never get the same voltage inside as you do at the battery or alternator. At the battery will always be higher then inside the car.
You can check the voltage inside at the fuse box or at the cig lighter plug to see what the voltage is inside.
04-06-07, 10:22 PM
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i'm a lil curious now. I have a electrical problem in my car.
My battery was dead and alternator was bad so i replaced them 2 days ago, and now my battery is dead...Nothing was left on to my knowledge.
Any ideas or comments?
My battery was dead and alternator was bad so i replaced them 2 days ago, and now my battery is dead...Nothing was left on to my knowledge.
Any ideas or comments?
04-07-07, 05:50 AM
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This is something you will have to troubleshoot. You may have a short some where. Did you replace the alt with a factory unit? One that fits your car or an upgraded one?
Use a DMM and use the Ammeter portion. Disconnect the negetive cable of the battery while the key is in the off position and out of the ignition. Connect one of the leads to the neg terminal on the batt and the other lead to the neg cable. This will tell you if youhave any large current draw.
Here is a thread with more information, disregaurd the arguing in it though
Battery Drain Issue - https://www.rx7club.com/2nd-generation-specific-1986-1992-17/battery-drain-issue-628141/
Use a DMM and use the Ammeter portion. Disconnect the negetive cable of the battery while the key is in the off position and out of the ignition. Connect one of the leads to the neg terminal on the batt and the other lead to the neg cable. This will tell you if youhave any large current draw.
Here is a thread with more information, disregaurd the arguing in it though
Battery Drain Issue - https://www.rx7club.com/2nd-generation-specific-1986-1992-17/battery-drain-issue-628141/
04-07-07, 08:05 AM
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Originally Posted by RotaMan99
This is something you will have to troubleshoot. You may have a short some where. Did you replace the alt with a factory unit? One that fits your car or an upgraded one?
Use a DMM and use the Ammeter portion. Disconnect the negetive cable of the battery while the key is in the off position and out of the ignition. Connect one of the leads to the neg terminal on the batt and the other lead to the neg cable. This will tell you if youhave any large current draw.
Here is a thread with more information, disregaurd the arguing in it though
Battery Drain Issue - https://www.rx7club.com/showthread.php?t=628141
Use a DMM and use the Ammeter portion. Disconnect the negetive cable of the battery while the key is in the off position and out of the ignition. Connect one of the leads to the neg terminal on the batt and the other lead to the neg cable. This will tell you if youhave any large current draw.
Here is a thread with more information, disregaurd the arguing in it though
Battery Drain Issue - https://www.rx7club.com/showthread.php?t=628141
Ok thanks!
Yea i replaced it with the factory one, because i wanted it working right before i make any mods to it
04-08-07, 02:19 AM
#7
RX-spec7
dont always count on the dash volt meter, if you test the circuits under the hood and the numbers are good then just leave it be. like Rotaman99 said there is probably voltage drops in the wires and i wouldnt worry about the guage.
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04-08-07, 10:18 AM
#9
Originally Posted by RX-Spec7
dont always count on the dash volt meter, if you test the circuits under the hood and the numbers are good then just leave it be. like Rotaman99 said there is probably voltage drops in the wires and i wouldnt worry about the guage.
04-08-07, 10:34 AM
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Take the gauges out and messure how much voltage is at the gauge. It may be right. If you would like it to read higher, try running a wire from a location where there is more voltage.
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