Low Running Voltage (searched)

[EskyDSM]

Hey everyone,

Three times in the last 3 months I've had my car out this year, I've had my battery and brake light turn on when I first start my car. They stay on for a little while. I check my voltage at my turbo timer and with a multimeter at the battery and the highest it reads is about 12.2v, but seems to cycle around 11.9v. I would start driving, and all of the sudden the lights would go out, and the voltage would jump up to mid 13s (which is still not where it was since I bought the car, 14.4v). I've had issues in the past where my factory cluster will not respond when I first start the car, then out of the blue, all the needles and lights jump and everything works fine.

Then, two days ago, it when through this cycle of low voltage, but stayed there. The battery and brake lights did not stay on, and currently are not on, but my voltage has not recovered. It teeters at mid to high 11s. If I turn on my head lights and some accessories, my voltage typically drops another.5 volts or so.

The car is 155k old, and I'm sure the alternator is original, so I thought the voltage regulator was taking a dump and it was time for a replacement.

Yesterday, I installed a brand new alternator, and while I was at it, made sure all my connections were corrosion free, and they all look great. I scuffed them up a little bit just to be sure. I still only have high 11v while idling, and mid to high 11s while driving.

My battery is brand new, my main ground is brand new, my connections/terminals are corrosion free. What else can I check that would cause this low voltage issue on an apparently fully functional old alternator and a brand new one?

 

[shadow_FIX910]

This is strange. If the alternator is clearly good, and the battery is good, and the terminals are clean and tight, (they are, right?) then it sounds like something must be going on somewhere else in your wiring. What aftermarket items do you have hooked up (like cd player, gauges, etc.)? My first guess would be start checking those to see if there's anything wrong there.

 

[EskyDSM]

I have 4 gauges (boost, WB, oil press, and EGT) which are body grounded and fed by the cigarette lighter circuit (switched by the circuit). I have a Panasonic headunit which I never have on. And I have my HKS turbo timer, which is always on. I also have HIDs installed with a dual relay wiring harness, built by my good friend. That's pretty much it. They all work flawlessly, but I guess I could start trying to unplug them all and see if there is a change. They've all worked fine since the get go, the head unit was installed by Best Buy (before I purchased), the gauges were installed by me, and I used brand new wire, no chinsy splicing, all taped, and tucked. The HKS timer is connected with the GReddy wiring harness. The HID harness was a work of art. It really is amazing how better than professional it looks. It was also tested on an external power supply for continuity, draw, and switching, and it was perfect.

Tell me if this sounds strange:

When I brought my car in and had them test the alternator (original) while it was still in the car, it said it was putting out a peak 12.0v and 166 amps. 166!? She checked it again, and the same deal...

How does that happen?

I'm going to bring my car in again tomorrow and have them do another test on the new one and see what kind of readings I get. I wonder if I got a POS outta the box...

Ok, so I had my new alternator and battery checked at Autozone (again, how much can I trust their tests?) and after three tests, the battery came back "bad." I don't believe it, but what the hell, I'll get a new one anyway. It's covered.

Put the new one in...no change. They told me the 166 amp reading is the machine putting load on the system, not amperage that the charging system is putting out. Ok fine, so their test shows 12.0ish volts, which is basically just a reading from the battery...the alternator is not charging the system (supposedly). Yet my battery is not draining, either.

What else is in this charging system I could check? The guy said something about the ECU may not be telling the voltage regulator to bump up the voltage, or maybe a relay is bad. Do our cars have these issues as possibilities? If it were one of these, wouldn't I have a completely non functioning alternator?

 

[1slo1g]

this happened to me turned out being the voltage regulator inside the alternator swap the alternator out and check to see if that works.

 

[EskyDSM]

Yes, as stated above, I have replaced the whole alternator with a brand new one (which includes the regulator), and I will be installing another brand new alternator tomorrow to see if anything changes.

I am wondering if there is anything else that could be causing the low voltage output? Even with the low output, I drove 30+ miles with little, if any, voltage drain from the battery, yet the alternator is not putting out the normal high 13/mid 14 volts it should be.

The car also sat for 10 hrs, and I went and multimetered the battery and it was sitting pretty at 12.5 volts, so there can't be a very large drain.

Is there anything else, relay, ECU, whatever, that could be the culprit for low voltage output, besides the alternator itself?

 

[TOONAH]

An alternator should output a minimum of 13.6V under normal load conditions. If you have installed some fancy ultra blue headlights you should know that they draw double the current of stock headlights.
It is impossible to troubleshoot an electrical problem using voltage tests alone. A DC current clamp can be purchased for most multimeters for under a $100.
The clamp can be used to isolate the circuit that is drawing excessive current. Some component in your car is drawing too much current. It could be a partial short to ground or something like the headlights.
When you spec out a component, be sure you look at the current draw. If your alternator is OK, then something is drawing excessive current from the battery and alternator. It is called voltage drop. If where you measure the voltage it is 12V, disconnect it and then measure the voltage at the +12V battery terminal. If it reads 12.1-13.6V then you are on the right track.
One last thing, stock alternators for the 4G63 do not output 166 amps. I believe they are rated at 90 amps. So if 166 amps was measured, KA BING KA BOOM!!! the alternator was overloaded and naturally the voltage drops. Ohm's Law. Find the circuit drawing excessive current before your wiring harness catches on fire, because another way to find the problem is an infra red temperature sensor.
A component drawing 166 amps through a 16 gauge wire is going to get very hot. The wire is going to get hot too.

 

[evileagleawd]

hey not to ask any stupid question but is the alternator fuse good? Because i have seen some tricky things happen with dsm electrical systems when that fuse blows.

 

[EskyDSM]

Yes, as stated above, I understand what an alternator should be putting out (hence why I see there is a problem). Also stated above, it was pointed out that the 166amp reading the machine was giving them was not what the alternator was putting out. When they told me that to begin with, I asked them, "How is that even possible? It's not rated to put out nearly that much, and if it was, I'm sure I would have bigger problems than low voltage." My car's setup has not changed in the last three months to warrant anything newly installed causing a draw situation like this.

I did a lot of research on HIDs before I put them in, and I know how they work. It should also be pointed out that HID systems only use double the watts (factors in current) of standard halogen lamps upon ignition/warm up. This lasts 30 seconds or so. After which, the HID system uses less watts than the standard halogen system. Also to be noted, they only use power when they are on (unless there is a short). My HIDs are running on a home made (very meticulous and correct) dual relay, fused, heat shrunk, and isolated wiring harness, not the factory wiring.

This power issue was partially present before I put in the HIDs, and I disconnected them and tested to rule them out. I reran all my gauges with new wire and wrapped them to make sure nothing was grounding out. They are powered by a switched circuit.

A short could definitely cause a problem, but if there was a short of this magnitude, shouldn't my battery be draining while it sits? The car sat for 10 days while I was on vacation without being started, and when I got back, it strongly fired up first shot.

As far as the alternator fuse, I guess I was under the impression that if that was out, my alternator would cease functioning at all, which would have appeared as a non starting/running car. If the circuit continues to "work" (depending on how you look at it) with the blown fuse...why is the fuse there? I've driven the car over 200 miles since this issue really popped out, and the battery has held a steady 12+ volt charge, which tells me the alternator must be doing something. Maybe I'll throw a new fuse in there just to be sure. Is there a relay that might need replacing somewhere?

I appreciate the responses.

 

[1983gsp]

check the voltage at the "b" terminal on the alt with the wire connected, it should be batt voltage. if not there is a break in the wire. if "b" terminal wire checks good, remove "b" terminal wire from alternator. we're about to check the voltage regulator.

insert voltmeter "+"lead into the "s" terminal wire. ground the "-" lead to frame or good ground. turn ignition switch to run position and check voltage at "s" terminal wire. if its 0 volts, check for short or open circuit.

connect an ammeter in line from the "b" terminal lug on alternator to the "b" terminal wire that you removed. start car and keep all accessories off. idle engine up to 2500 rpm. when amperage on "b" terminal wire drops below 10 amps, read voltmeter attached to "s"terminal wire. depending on temp of alt, it should be between 13.1v and 14.9v at 2500 rpms.

if voltages are not satisfactory, voltage regulator is faulty. replace the regulator or alternator assembly. hope this helps.

 

[EskyDSM]

Thank you for the response. I'll jump into that hopefully tomorrow too and see where I get.

 

[DSM1G90]

I believe they are rated at 90 amps

..if you're in Canada .. we use 75 amps down here.

This is what I just HATE about people heading to "AutoCrapZone" (no offense, of course): They take what they say as gospel instead of HEADING TO NAPA, or SOMEWHERE PROFESSIONAL for a second, third, et.al. opinion on any sort of issue!

I bet you got WAY too much high drawing equipment attached to your system and it's frying up the alternator.

What I would do for a simple test is: to disconnect all the extra that is attached to your system, then do the voltage reading across the battery with the car idling. See if it can read close to 13.6VDC. If you do, then one by one, reattach all what is added on your system and see if the voltage begins to drop across the battery at engine idle.

If something suddenly causes the voltmeter to drop, then you got something that is a power hog.

Also, you must know that there are two grounds: chassis and battery ground. Reading that you have some devices attached to chassis ground - wonder if you should place those to battery ground since chassis is more resistive than a direct connection to battery.

Good luck in your find and happy motoring .. - DSM

 

[EskyDSM]

I don't have any heavy drawing equipment in my car. The only things I have are the 4 gauges, a head unit, turbo timer, and my HIDs. The head unit and HIDs are not usually on, and as I stated before, the issue has been present before installing the HIDs, which I would guess is the most drawing of the stuff I have.

The alternator is brand new, and never put out the correct voltage, not even for a little bit, and I didn't load it down with anything when I first tested it out. As far as cars go, I think mine is pretty simple. All geared for performance, no amps, no caps, no junk. I'd tear the headunit out if I had something to put in its place. I live in the country, so the HIDs are a God send at night.

I buy from Autozone here because we only have a couple small parts stores here, and Autozone is the only place that even carries things I need. But really, what would you say is the problem when you can watch your voltage bounce between 10ish volts and high 13s volts? Voltage regulator, which is what Autozone told me, which is what I assumed anyway. I had them test it just because it didn't cost anything, and was supposed to confirm what I already thought anyway. But, now, instead of having a bouncing voltage, I have a very stable, pretty low voltage.

I already started disconnecting things without any change...I'll report more later.

Update:

I disconnected every aftermarket electrical device in the car. This includes my HIDs, head unit, gauges, turbo timer, and Sirius box. No change. Still low voltage. I rechecked my connections/terminals...all tight and corrosion free.

I also checked my alternator fuse. It looks perfect. It's shiny, unburned, unbroken. I will have to go into town to buy another 100amp fuse, but I'm thinking it's just fine.

I rerouted my grounds and positives just to be sure of proper connection. No change.

 

[DSM1G90]

(REVIEW) ?..and you're doing the voltage check with the VOM across the battery with the car idling..?

What about voltage checks where you have your appliances attached at - showing what is coming out of the alternator, or a drop in this area?

..trying to help you out.... - DSM

 

[EskyDSM]

I checked the voltage with my multimeter across the battery with the car off, with the car idling, with the car revving. I did a number of tests tonight. I don't have an ammeter, so I did what I could.

With Car off
Positive to negative: 12.4v
Positive to ground: 12.4v
Checked for continuity between battery and alternator side of fuse: Good
Checked for continuity between alternator side of fuse to eye connector on alternator: Good
Checked for continuity between eye connector on alternator and battery: Good
On battery side of alternator fuse: 12.4v
On alternator side of alternator fuse: 12.4v
On alternator side of alternator fuse to eye connector on alternator: 12.4v

Disconnected the eye connector from the alternator, and checked power from the alternator terminal to ground: 12.4v

With Car running
Positive to negative: 12.36v
Positive to ground: 12.36v
Checked for continuity between battery and alternator side of fuse: Good
Checked for continuity between alternator side of fuse to eye connector on alternator: Good
Checked for continuity between eye connector on alternator and battery: Good
On battery side of alternator fuse: 12.36v
On alternator side of alternator fuse: 12.36v
On alternator side of alternator fuse to eye connector on alternator: 12.36v

Just for the hell of it, I checked power at the starter, 12.36v.

One thing I didn't do because I wasn't sure if I should, was disconnect the power from the alternator, and start the car, then read the terminal on the alternator to ground. Can I do that?

Also, what would happen if I had everything hooked up, except for the 4 pin connector that plugs into the alternator? One thing I haven't really seen anyone say in my searches is if the ECU is what tells the voltage regulator to kick up the voltage to 14ish. If I disconnect the 4 pin, what will happen? I can't seem to find a diagram on what the 4 pins even are, though I assume there is at least a power, a ground, and an ECU wire in there.

 

[kergilman]

With Car running
Positive to negative: 12.36v
Positive to ground: 12.36v
Checked for continuity between battery and alternator side of fuse: Good
Checked for continuity between alternator side of fuse to eye connector on alternator: Good
Checked for continuity between eye connector on alternator and battery: Good
On battery side of alternator fuse: 12.36v
On alternator side of alternator fuse: 12.36v
On alternator side of alternator fuse to eye connector on alternator: 12.36v

Just for the hell of it, I checked power at the starter, 12.36v.

Also, what would happen if I had everything hooked up, except for the 4 pin connector that plugs into the alternator? One thing I haven't really seen anyone say in my searches is if the ECU is what tells the voltage regulator to kick up the voltage to 14ish. If I disconnect the 4 pin, what will happen? I can't seem to find a diagram on what the 4 pins even are, though I assume there is at least a power, a ground, and an ECU wire in there.

With the vehicle running, you should have seen around 13.5v at all of those points so you have a current draining problem or the regulator is not functioning correctly (which is unlikely since you installed a new one). The N/T's alternators are regulated via the ECU. The turboed models use regulators within the alternators.

 

[One Equals Two]

What happened here? Any solutions? This sounds exactly what is happening to me!! If you figured it out, please let me know....

 

[EskyDSM]

Yep, just figured it out yesterday.

My problem is the ECU. The one thing no one would say was the problem, and the one thing I didn't want to believe but was expecting more and more.

I swapped another ECU in and the problem vanished...swapped my ECU in, and the problem was back immediately.

I'm going to get with the ECMLink guys and see if they can fix it. Since it is the only problem the ECU is having, they're guessing it is just an output problem and they should be able to nail it down.

 

[D3adch1ld]

I have similar problems on 97 gsx, but my voltage actually is running 11.7. I already know is the alternator, but here's the thing: I have replaced the alternator multiple times, with HO and rebuild oem spec ones. Some didnt work from the beginning, but some actually solved the issue for a few weeks then came back. I replaced the alt-battery cable with a 4 gauge wire and bypassed the alt fuse, as recommended by alterstar, and took it even further by changing the grounds all around, tested the individal wires going to the VR, even swapped the ecu with a spare I have, but it happens without warning. Also, some of the alternators break undercharging or overcharging, so be on the look out because I almost burned my electronics. If the ecu swap really worked for you thats great, for those other guys with similar issues to me. We have other threads going on about this and are looking for some help as well.

 

[One Equals Two]

Crap, I sure hope it's not the ECU. I have DSM link which I think replaces the stock ECU with a flashable chip if I remember correctly. That's dam expensive so, I don't want it to be that. Anyway, I think I'll try a new chip.

 

[KB90TSIAWD]

Sorry for digging up an old thread...

I have a 90 talon. Just rebuild the motor everything is a go and fired it up with a jump (sitting battery) fires up but voltage wont hold. with key on it sits at 11 if im lucky any time an accessory is used it drops, Everything that ive rewired is unplugged. New 90 amp alt. my 2nd, and new battery the 2nd also. new alt fuse. It runs but wont last long before it wiggs out. My temp gauge will shoot to the overheating side, car wont start for a while then will sometimes. Under the hood smells almost like burnt coolant. But I know its not overheating when link is telling me 160 deg.

Its odd because sometimes it will show 13ish volts and seem then will drop after a while and never go back up Im at a loss for what to do

 

[Ghost_92TSi]

I don't know why you revived this old thread, and shortly after posted a new one.

I would think replies would best be directed here:
http://www.dsmtuners.com/forums/newbie-forum/471872-running-very-low-voltage.html