87 IROC CAMARO 350TPI

ok i have stated before that my batt and alt are good, there is no draw that i have tested for and found (when car is off), and yet my batt drains when the car is on.
ive noticed that after a decent charging of my batt, the car can hold that charge when it is on although i have not had it on for long enough to see if it holds up forever. usually on hot days, i turn my car on and after a minut it will noticeably drain my batt. WHY COULD THIS BE HAPPENING? like i have stated before, in accessory mode my batt is at 12 volts and when i turn on the car it is at 10 volts????whats up with that?

 

your alt is no good, or you got a bad connection from that to the battery, you only have 10 volts cause the battery is powering everything when the alternator should, test at the back of the alternator the red wire to the battery and see if you get 14v while running

 

Could easily be a bad battery too if it's really going down to 10 volts. Although there is no way it would restart if it went that low so i have a feeling he is using the dash guage which is nothing like reality. But a good battery can run an engine for a long time with minimal accessories. I once drove my TPI convertible almost 2 hours on a dead alternator and it barely dented my 5 year old battery.

But the dash guage middline line ( 10 ) is actually more like 12, and i think our friend is just driving on the battery, which naturally hovers higher when off due to a charge buildup. That range of the factory guage is pretty sensitive.

mid 80s GM cars have lots of quirks that make debugging easier when you know them.

 

the batt gauge is reading around where 10 volts would be, but i also had a multimeter to test with car on/off and thats where i got the 10.so&so volts when on and 12.so&so when the car is off. i recently put a thicker guage wire from the alt to the bat and that made no difference.

my alt and batt have both been tested at 2 diff places and they checked to be good.

still any ideas?

86Z:test at the back of the alternator the red wire to the battery and see if you get 14v while running

how exactly would i go about doing this? use a multimeter and attach the positive/negative leads where? im pretty sure ive done it right befor and still got 10 volts or so.

 

best way to check your alternator:

Start the car, take off the Negative battery cable. If the car dies, alt is bad. if it stays running, then probably the battery or somethin else....



oh and just make sure all wires/cables are secure. especially, batt cables and the lil wire on the back of the alt.

 

yes thats the easiest way but i hear all too much about the chance on frying my computer and i am not willing to take the chance. im not sure if this is the same results but when my batt completely drains my car stays running but at higher RPM like around 2K+?

 

never heard of that....ive done it alot. to alot of different cars.

 

yes there is a chance you can blow the computer doing that, do not disconnect the battery while it is running.

use a multi meter and put the red lead on the wire on the back of the alternator usually covered by a rubber boot then the black lead to an engine ground, that alternator should be putting out 14v right then when it's running, if not, its no good, if it is, you have a bad ground/connection

i just had the same problem with my beretta all the sudden the gauge is reading 10v, replaced the alternator and it's fine

 

ok thanks very much for that info, ill try that as soon as i get the chance. ill post my results then.

 

ok so that may solve my lack of voltage when car is running fine (for the few minutes it holds the charge), now if theres anyone with any ideas on my severe draining when the car is running feel free to post, i could use the help as i do not want to bring it to a mechanic and later have the same problem as they say they "fixed" it.

 

did you check the voltage at the alternator yet?

 

no i havnt yet, i need to recharge the batt which will take a while. as soon as thats done i will check and post a reply

 

hey check out this thread https://www.thirdgen.org/techbb2/sho...hreadid=188718

 

alright, i read that thread and i was wondering how many amps the fuse for the fans should be?my fuse box is very faded and i had to replace fuses not nowing exactly all the amps for all the fuses so maybey if i have a low amp fuse i could be loosing charging power?

 

i forgot one fact that may or may not help you guys with diagnosing my proble.... when my batt is drained and i hook up the jumper cables to a friends VW, i can then start the car (duh) but heres the thing, usually after a jump( on a good working car), the car will continue to run even after you disconnect the jumpers, but in my case if i disconnect the jumpers, whatever i have gained in charge from the VW will be drained but while i am connected my car batt guage reads just under 13 volts and it will stay running as long as it is connected.

just a little fact ive left out if it helps in any way?

 

get that voltage checked, i'm telling you its a bad connection or a blown alternator.

 

ok so i checked the alt doing as you said and i was reading right around 12 volts. i am also reading the same when i check the batt (red lead on pos, black on neg). so you say if its not 14 volts from alt then its bad? why would the places that have tested it say it works fine, i saw the voltage it was putting out when they tested and it was 14?

 

i was thinking...is this possible: if i have some kind of problem with my batt, then would it "eat" the 2 volts that i am missing when the car is on? like said before, the cars off and the charged batt will read 12+volts and will hold that charge, but when i turn it on it stays at that 12 volts and sometimes even drobs to 10 volts. could this all just be my batt?

 

ok so i decided to go off and get a new cheapo batt at wally world and i hooked it up....no change, the voltage is still at 12 when car is off and when running wtf? my batt cables dont look corroded or in bad shape. what the hell could be draining 2 volts from my car when its on? considering gettin a new 140 amp alt but i don not want to spend big bucks if theres no need for it. someone please help!