Need electrical help: Battery Volts only read 12v
09-10-11, 01:06 PM
#1
Need electrical help: Battery Volts only read 12v
I've been holding off posting this but I've reached the point where I'm all out of ideas.
So this issue started 2 weeks ago. I was sitting in the car while it was idling writing down all the inj corrections (took foreverrrr) and after about the 20 minutes of the car idling it just died. I was lazy so I left it alone. the next day I jumped it and it died shortly after. The volts would slowly decline and die out. I thought it was the alternator although none of the lights flashed (air bags, battery, etc)
Since I have a few alternators I swapped them out to not avail. I assumed they were all bad so I ended up getting another one (Thanks moosejaw!!) swapped that in it wouldnt even turn on. looked at that battery and it was reading 9-10 volts. So I went to charge the battery at autozone, and it had a bad cell. They gave it back and the car fired up right way. BUT on the commander, it was only reading 12.0 volts, battery read 12.3x. warmed the car up and slowly volts began reading 11.8-11.9. after 5 miles of driving the volts read 11.6. I thought it was the battery since it had a dead cell so I went back and luckily got them to replace it under warranty. fired right up, but still reading only 12.0 volts. I drove it about 2 miles and went down to 11.9 but seemed okay.
Now my question is why is it only peaking at 12.0 volts? with the multimeter on dcv? 200, the alt reads around 32.x. shouldn't the volts be reading 13.5+ on the commander while I drive...?
I've ruled out the alternator and battery. I looked over the grounds and they dont seem to be an issue. Any other ideas? I need practical things to check first before throwing out the one in a million chances, last time I did that I went crazy undoing everything and adding a ton of work and stress.
So this issue started 2 weeks ago. I was sitting in the car while it was idling writing down all the inj corrections (took foreverrrr) and after about the 20 minutes of the car idling it just died. I was lazy so I left it alone. the next day I jumped it and it died shortly after. The volts would slowly decline and die out. I thought it was the alternator although none of the lights flashed (air bags, battery, etc)
Since I have a few alternators I swapped them out to not avail. I assumed they were all bad so I ended up getting another one (Thanks moosejaw!!) swapped that in it wouldnt even turn on. looked at that battery and it was reading 9-10 volts. So I went to charge the battery at autozone, and it had a bad cell. They gave it back and the car fired up right way. BUT on the commander, it was only reading 12.0 volts, battery read 12.3x. warmed the car up and slowly volts began reading 11.8-11.9. after 5 miles of driving the volts read 11.6. I thought it was the battery since it had a dead cell so I went back and luckily got them to replace it under warranty. fired right up, but still reading only 12.0 volts. I drove it about 2 miles and went down to 11.9 but seemed okay.
Now my question is why is it only peaking at 12.0 volts? with the multimeter on dcv? 200, the alt reads around 32.x. shouldn't the volts be reading 13.5+ on the commander while I drive...?
I've ruled out the alternator and battery. I looked over the grounds and they dont seem to be an issue. Any other ideas? I need practical things to check first before throwing out the one in a million chances, last time I did that I went crazy undoing everything and adding a ton of work and stress.
09-10-11, 01:16 PM
#2
Are you looking at it while idling? Most alternators don't put out 13 volts at idle but they will once you get up to around 1500-2000 rpms. Try reading the battery with a meter while someone holds the car around 1500-2000rpm. But if it never shows over 12 volts there might be a problem with the commander or the pfc. And you should set your meter to VDC 20 to read the volts right.
09-10-11, 01:37 PM
#3
i idle at about 1400... the battery with a multi meter reads 12.54 so i know the battery is good.
i only put it to the 200 setting to read the alternator because at the 20 setting, it will blink anywhere from 16.x to 19.x and then nothing will show up
i only put it to the 200 setting to read the alternator because at the 20 setting, it will blink anywhere from 16.x to 19.x and then nothing will show up
09-10-11, 02:07 PM
#5
Well if the alternator is putting out that kind of voltage that's too much. But what I was wondering is how much voltage you have at the battery at idle. That will tell how much the alternator is putting out to the battery. Also I was just looking through the wiring diagram and it looks like the ecu gets the voltage signal from the 15A engine fuse (I think this is in the car) read for voltage there and see if that reads more than 12 if it does then there is something wrong with the PFC for reading voltage.
09-10-11, 04:34 PM
#6
Battery is relocated, ground wires look good, ill have to double check the power wires. (ran under car)
Pulleys are believed to be greddy
Charge harness is new 4 gauge wire (stinger)
Alt- It was said to be working before i got it, ive swapped out 3 other ones, so i've ruled it out...
Well if the alternator is putting out that kind of voltage that's too much. But what I was wondering is how much voltage you have at the battery at idle. That will tell how much the alternator is putting out to the battery. Also I was just looking through the wiring diagram and it looks like the ecu gets the voltage signal from the 15A engine fuse (I think this is in the car) read for voltage there and see if that reads more than 12 if it does then there is something wrong with the PFC for reading voltage.
thanks for the help
09-10-11, 05:06 PM
#7
You shouldn't be running a lead-acid battery inside the car. It vents toxic fumes and can spill on you in the event of an accident.
You still haven't tested the alternator so you are going on asumption.
Do you have a smaller crank pulley too? Underdriving the alternator is not good.
You still haven't tested the alternator so you are going on asumption.
Do you have a smaller crank pulley too? Underdriving the alternator is not good.
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09-10-11, 06:33 PM
#8
Where are you grounding the battery? I've found that running two grounds is best. Also make sure you are running at least 4 gauge battery cable. 2 gauge is better. The ends should be both crimped and soldered. Also, run a 6 or 8 gauge cable from the alternator post to the bus bar in the fuse box. You can unbolt one of the m6 bolts that hold in the main fuse and secure it there. This will provide an alternate path of current from the alternator in case the charging harness is suspect. Also might be a good idea to check the actual connector to the alternator. Those wires become brittle with age.
Last edited by IRPerformance; 09-10-11 at 06:36 PM.
09-10-11, 06:55 PM
#9
RX-7 Bad Ass
iTrader: (55)
This is part of the reason I don't like battery relocations. More often than not there's goofed up problems like this.
That said, you need to be looking at the voltage the alternator is putting out. Put the negative terminal of the meter on a ground and the positive terminal on the main output post of the alternator. At idle I see 13.5-14v on my car, that's where it should be.
The alternator is a simple device - if you spin the alternator, it produces current. The voltage regulator (the two smaller wires going to the alternator) keeps the voltage at a reasonable level, otherwise the faster you turn the alternator the more voltage it would produce.
So, if the alternator is producing proper voltage, it could be something with the main power wire from the alternator to the positive terminal of the battery.
Get out the stock wiring diagrams and find out how it's all wired up stock and make sure you have the same connections with the relocation. Also, make sure you don't have some weird blown fuse somewhere, I THINK the feed to the alternator is a fused circuit.
Dale
That said, you need to be looking at the voltage the alternator is putting out. Put the negative terminal of the meter on a ground and the positive terminal on the main output post of the alternator. At idle I see 13.5-14v on my car, that's where it should be.
The alternator is a simple device - if you spin the alternator, it produces current. The voltage regulator (the two smaller wires going to the alternator) keeps the voltage at a reasonable level, otherwise the faster you turn the alternator the more voltage it would produce.
So, if the alternator is producing proper voltage, it could be something with the main power wire from the alternator to the positive terminal of the battery.
Get out the stock wiring diagrams and find out how it's all wired up stock and make sure you have the same connections with the relocation. Also, make sure you don't have some weird blown fuse somewhere, I THINK the feed to the alternator is a fused circuit.
Dale
09-12-11, 09:50 AM
#10
sooo, it turned out to be the power cable that connects to the altenator... i tried these "solder plugs" from del city.com and well the suck. i found out today that the wire fell out of the plug as the "solder plug" lost its connection and was only held on by the electrical tape that was used to wrap the wire...
on a side note, now my battery reads 15.0v lol.. is that bad? i have the alt power wire running straight to the battery. is that okay? (my fuse boxes are relocated to the rear bin)
on a side note, now my battery reads 15.0v lol.. is that bad? i have the alt power wire running straight to the battery. is that okay? (my fuse boxes are relocated to the rear bin)
09-12-11, 07:11 PM
#14
sooo, it turned out to be the power cable that connects to the altenator... i tried these "solder plugs" from del city.com and well the suck. i found out today that the wire fell out of the plug as the "solder plug" lost its connection and was only held on by the electrical tape that was used to wrap the wire...
on a side note, now my battery reads 15.0v lol.. is that bad? i have the alt power wire running straight to the battery. is that okay? (my fuse boxes are relocated to the rear bin)
on a side note, now my battery reads 15.0v lol.. is that bad? i have the alt power wire running straight to the battery. is that okay? (my fuse boxes are relocated to the rear bin)
15v is too high. Sounds like you have a bad regulator. It is replaced in my 140 amp upgrade.
DO NOT run a power cable from the alternator straight tot he battery. Run it through the main fuse.
09-28-11, 09:53 PM
#15
soo just to clarify, at start up it peaks at 15.0-15.1
i got a bit nervous and did some more research and it seems normal for the volts to peak at 15 when its cold and normal at around 14.5 volts...
http://www.race-dezert.com/forum/sho...at-15-volts-ok
thoughts?
i got a bit nervous and did some more research and it seems normal for the volts to peak at 15 when its cold and normal at around 14.5 volts...
http://www.race-dezert.com/forum/sho...at-15-volts-ok
thoughts?
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