The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Morrison Fabrications
Please Support ExtremePSI

2G Voltage drop

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Thanks for that update. Until hearing this I had no idea your car had this problem since last summer and was a winter's build. We ONLY know what you tell us and people not telling us everything is ALWAYS the biggest problem. So we have to assume that whatever you tell us is accurate and what you don't tell us must be working fine. And when people tell us about electrical problems we have to assume they understand electricity and know what they are talking about (what else can we do?). So I've been telling you advanced techniques because of this (which are probably beyond your ability and understanding). Your admission of your lack of electricity knowledge helps us, thank you. [Here's a primer about using a multi-meter which will also give you some electrical knowledge (like how electricity is like water flowing through a pipe): https://www.dsmtuners.com/threads/multi-meter-usage-primer.404574/ ]

I wish you had told us about the dimming right away. Instead we got mislead with all the incorrect talk (and assumptions) about blown fuses and voltage drops (and voltage drops is something most people really don't understand). Now it's sounding more and more like you may just have a bad/weak battery (due to the dimming statement). A battery that is losing it's capacity (eg. old or weak) will cause nearly all the problems you describe. So install that new battery from your basement (charge it up first) and then get back to us.
 
Last edited:
Thanks for that update. Until hearing this I had no idea your car had this problem since last summer and was a winter's build. We ONLY know what you tell us and people not telling us everything is ALWAYS the biggest problem. So we have to assume that whatever you tell us is accurate and what you don't tell us must be working fine. And when people tell us about electrical problems we have to assume they understand electricity and know what they are talking about (what else can we do?). So I've been telling you advanced techniques because of this (which are probably beyond your ability and understanding). Your admission of your lack of electricity knowledge helps us, thank you. [Here's a primer about using a multi-meter which will also give you some electrical knowledge (like how electricity is like water flowing through a pipe): https://www.dsmtuners.com/threads/multi-meter-usage-primer.404574/ ]

I wish you had told us about the dimming right away. Instead we got mislead with all the incorrect talk (and assumptions) about blown fuses and voltage drops (and voltage drops is something most people really don't understand). Now it's sounding more and more like you may just have a bad/weak battery (due to the dimming statement). A battery that is losing it's capacity (eg. old or weak) will cause nearly all the problems you describe. So install that new battery from your basement (charge it up first) and then get back to us.
I will do so. I apologize to yall for the misdirection caused by a bit of ignorance.
 
Just to clear one thing up for you for the future, a voltage "drop" would mean that you have normal voltage on one side of a wire or connection and low voltage on the other side. Usually from excessive resistance caused by corrosion or a damaged wire. So for instance if you had 12.6 at the battery and 8 volts at the fuse box you would have a voltage drop.

What you have is a voltage dip. Meaning something is pulling more amps than your battery can keep up with causing the voltage to dip down on the battery itself.
 
Sidenote: I hope you do this for a living because if you don't then you should LOL.
Ha, ha. I have an electrical engineering degree (in electronics) but am retired now (I'm 70 yrs old). I worked for Control Data's Magnetic Peripherals and then Seagate writing the internal microcode to operate disk drive hardware and electronics. Driving cars in rallying and fixing them has always been my hobby so I have a lot of experience with both. I'm the original owner of my 99 GST (DD and which I also rally), do ALL my own maintenance (no matter how hard it is), and it's been my only car for 22 yrs (wife only has an 18 yr old Corolla which I also keep running).
 
Last edited:
it's been my only car for 22 yrs
This is impressive in its own right. I have had mine for almost 7 years now. Love every second of it and will never sell. Found it in a junkyard for 200 bucks and had no idea what I was buying but wanted something to tinker on. Back then, I didn't even know how to change spark plugs.
But in reality I think that's a culture change thing. I'm 26. Your generation took pride in owning and maintaining a car. Mine takes pride in buying the next new one and trading in the old.

But ether way, I will change out the battery tomorrow as it's a little late already and a post work beer is calling my name more than the car. I will post an update tomorrow. Thanks guys!
 
If you mean by putting in a new battery and the voltage still drops, the only thing would typically be a short (or connecting way too many things that draw more amps than the battery can deliver). All batteries have a very small internal resistance (which increases with age and inability to hold a charge) so too large a current draw causes an internal battery voltage drop [voltage drop = current x resistance] which leaves less voltage at the battery terminals (which is why the battery voltage starts decreasing with higher current draws). When the engine is running the alternator takes over so the voltage is maintained or even higher to charge the battery and run things (normal charged battery voltage = 12.6V, normal alternator voltage = 14.4V).
 
All batteries have a very small internal resistance (which increases with age and inability to hold a charge)
Does this also increase with years of cycling the same battery between empty and charged?
Because I'm guilty of liking to work on this car more than driving it and I definatly have had more "first starts" then the average person hahaha
 
Running a battery completely empty too many times is not good but you'll have to ask a chemical engineer as to the reason. Running it down just a little is fine as that is what happens when you engage the starter or use electrical devices with the engine off. The battery is designed to be charged thousands of times as that is what the alternator does. When storing or not using a car battery for a long time, it's best to have it fully charged with a trickle/maintainer (like a "Battery Tender") charger on it. I keep one on my motorcycle and riding lawn mower batteries over winter. Back on the internal battery resistance: It is very very small, like typically less than 0.03 ohms on a new battery fully charged.
 
Last edited:
I would think of it this way, if you had a fully charged brand new battery there is no fuse in the car that has an amp rating high enough to withstand if you short a positive wire to ground. So I don't want to confuse you with all the 1 in a million chance things that could possibly happen but 99% if you put the new battery in and there is a problem somewhere the voltage won't dip you will just pop the fuse for the problem circuit.
 
Pb(s) + HSO4(aq) → PbSO4(s) + H+(aq) + 2e−

By discharging the battery, you are changing the chemistry inside it. For the most part the reaction is reversible, hence why you can charge and discharge the battery, but a small amount of the lead sulfate on the surface of the lead plates will form a hard crystalline structure that will not revert back to lead and sulfuric acid when charged. Under normal operation this leads to a degradation in overall capacity over 5 years or so, but if the battery is allowed to discharge completely, the crystalline buildup from one cycle might be thick enough to prevent the battery from holding any charge at all. Many deep cycle/marine batteries get around this by having more surface area on thicker lead plates so that they can handle more discharge cycles before being unable to function. But this is why trickle chargers are a thing. As long as the battery stays charged enough to be able to start a car it should be just fine for years.

Have you checked your alternator? A faulty or inadequate voltage regulator will prevent the battery from charging properly, and over time could lead to premature death of a battery even if it is still able to start your car every time.
 
Have you checked your alternator? A faulty or inadequate voltage regulator will prevent the battery from charging properly, and over time could lead to premature death of a battery even if it is still able to start your car every time
***chemical engineer has entered the chat*** LOL LOL LOL

Thank you for that. Always curious and you hit it out of the ballpark

As for the alternator, I have replaced I this last winter but keep in mind, the issue I am having has gone on prior to the replacement of the alternator.

I have since replaced it with an OE galant 90amp and relocated it to the back but the old alternator had seen better days. It was OEM, and I had no reason to believe that it wasn't the origonal one (Prior owner had an addiction to autozone).
But all and all it could have been that. Although it was still charging, it was in really rough shape. Definatly spent most of its life prior to me being leaked on by the power steering pump.
 
Well. I guess it's fixed. Idk what it was. New battery and had unplugged everything and plugged it back it. If it comes back yall will be the first to know. Thanks dudes!

You must be logged in to view this image or video.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top