Hot Rod Forum banner

battery keeps going dead, i need some f#*%&!g help

3K views 21 replies 8 participants last post by  406 ss monte 
#1 ·
i'm having trouble keeping my battery from going dead in my 85 ss monte carlo. i can put a new battery on it, & 3 weeks later it will be dead if i leave the battery cable hooked up. it's done this ever since i've owned the car. i've had the alternator checked several times & it checks out good. i've checked to see if the battery was being drained by with a test light. when i touch the test light to the battery post & the other end to the unhooked cable it will light for just a second & then go out. i figure that is the radio memory. i just have no idea where to start looking. i'm tired of it looking like a piece of ***** when ever i kill it & then pop the hood & unhook the battery.

i'm having no luck finding the problem. please help, i'm not good with electrical problems at all
 
#2 ·
hey buddy

sorry to hear the news

first of all there is another forum for "electrical" issues in this Hotrodders Forum. Try your post there. there are a few guys who always monitor that forum and really enjoy helping people with electrical problems.

is your car factory wired or was the wiring and charging system changed by you or someone else?

do you have a voltmeter? you will need one. when the car is running you should have approximately 14 volts at the battery terminals. check the voltage with the car off - typically about 12 volts. When the car is running, if the alternator is charging the battery and the wiring is good you will have about 14 volts at the battery posts - a noticeable rise in voltage. If you don't the alternator, voltage regulator, or wiring is faulty. I suspect there is no change in voltage when the car is running, meaning your charging system is not working and everything is being run off your battery.

also you kind of had the right idea about the test light, but not exactly. if you have a "multi-meter" that can check amps (current flow) you can check for current flow when the car is off. there should be none, maybe a tiny trickle like milliamps, but not AMPS. with the car off, remove the positive battery cable. attach one lead from the multimeter (set to amps) to the positive post of the battery. attach the other lead to the disconnected positive battery cable. Look at the meter. what does it show? make sure the meter scale is set correctly. try different ranges if you don't have the autorange feature. if you are showing more than an amp or two current flow when the car is off something is draining the battery slowly when the car is not in use. I believe you should show almost no current flow whatsoever when the car is off.

make those checks then post your response.
 
#3 ·
If you had it checked at one of the chain places (Autozone) they may have only checked to see if its charging. The problem you have can be caused by a shorted diode, and sometimes the alternator will still charge normally.

Disconnect the battery cable and use a VOM to measure the amperage draw between the battery terminal and the disconnected wire. It should be much less than an amp, and should not even move the needle.

When I had a bad diode I got reading of about five amps load, and it would kill my battery overnight.

Bruce
 
#5 ·
Doc here, :pimp:

Overnight draws usually are caused by a forward Biased Diode in the regulator diode pack..(leaking power backward.)

Get your DVOM out , Configure it for AMPS, set it to the highest scale, (usually 10 amps) , and place it in-between the cable and the battery post. Now reduce your amp scale back down to it's lowest scale Without pegging out the readout..This will be your true draw..

If you have a CD/Radio with active presets, A Vehicle computer, Clock, or Alarm system, Normal draw on a modern vehicle traditionally is about 0.3 to 0.8 amps (less than an amp..) Higher than that you have a problem.

Go for the lighting round..Pull all the wires off the alternator first, and then re~measure, If it drops back to spec, or zero..you need to replace the alternator, or you could get a simple rebuild kit for about $16.00..with a regulator diode pack included.

If it does not drop back, the problem is elsewhere..

IF your fuse buss is well marked..pull all the fuses and relays out..retake your reading..It should read zero..If so replace the fuses and relays one at a time until the draw shoots up..That branch circuit is the offender..troubleshoot that circuit and repair / disable as required..

Doc :pimp:
 
#6 ·
re: battery keeps going dead

these are good test but make sure while you are testing there are no lights activated examples: hood light, doom light, glove box light, trunk light. they won't be lit up with the cable unhooked, but they could be causing a draw. after you fix the problem ck it agian w/ every thing put back together just to make sure it won't go dead agian. good luck :thumbup:
 
#7 ·
well i'm more screwed up now than i was. i did the test to see how much draw the battery had & it was only .003 amps. shouldn't be draining from that. i reattached the hot wire & it read 12.36 across the battery terminals with the car off. i started it & it read 14.40. i did notice the longer i let the car run the lower the numbers got. the last i seen was 13.96 before i shut the car off. i'm thinking the alternator might be bad, but at this point i have no idea.

i'm including pictures just to show the settings on the meter. i had the hot wire disconnected with the red meter wire clamped to it, & the black meter wire clamped to the hot post on the battery.
 

Attachments

#8 ·
406 ss monte said:
well i'm more screwed up now than i was. i did the test to see how much draw the battery had & it was only .003 amps. shouldn't be draining from that. i reattached the hot wire & it read 12.36 across the battery terminals with the car off. i started it & it read 14.40. i did notice the longer i let the car run the lower the numbers got. the last i seen was 13.96 before i shut the car off. i'm thinking the alternator might be bad, but at this point i have no idea.

i'm including pictures just to show the settings on the meter. i had the hot wire disconnected with the red meter wire clamped to it, & the black meter wire clamped to the hot post on the battery.
dude:

great job. at least you're learning a lot right?

anyway. take a look at the first picture. the multi-meter leads (red and black) are plugged into the middle and bottom right ports on the meter. that's ok if you are measuring volts and ohms. But.... If you are measuring amps, one of the leads needs to be pulled out and plugged into the other port on the bottom left of the meter. It should say "amps" or something indicating amps next to it. That .003 reading you got was really a bogus reading because the meter was set to amps, but the leads were connected incorrectly.

try it again and let me know.

also that volt reading that was dropping.... how long did it take before it dropped to 13.96? was it 2 minutes, 20 minutes?

did you ever replace the alternator? you said it was tested ok, but was it ever replaced?
 
#9 ·
Doc here, :pimp:

Leejoy is quite correct in his assessment of the configuration of your DVOM..

Voltage Readings= Parallel (Across power and ground)

AMPS readings = Series (In line with the load [vehicle electrical system] and the source current [battery].

docvette said:
Get your DVOM out , **--->Configure it for AMPS,<---** set it to the highest scale, (usually 10 amps) , and place it in-between the cable and the battery post. Now reduce your amp scale back down to it's lowest scale Without pegging out the readout..This will be your true draw..
Configure it means: place the probe in the AMP test lead plug..set the scale for AMPS, and the highest Current setting the meter has (usually 10..) then reduce it to almost max readout that is the correct scale, correct reading...may be Ma ..may Be 1 amp depends on the scale..

What you have done, is an example I use all the time to prove a "Loaded ground" ..pull a lamp from ground, set your VOLT meter between it and ground..it will read 12 volts but the lamp is not lit..WTH?? right? The voltmeter only See's the filament as a wire to the battery, and shows 12 volts..EVEN though..It is DRAWING NO CURRENT (lamp out in the presents of power).. simply because the circuit is NOT doing any useful work...has no resistance (the filament ) To ground..Ground that wire, your meter goes to zero..and the lamp lights.

Doc :pimp:
 
#10 ·
well i check it again today like you said with the red wire in the other lead. it tested out at .15. i pulled all my fuses & it was still .07. i pulled the wire from the alternator & it went to zero. i put all the fuses back in & it went back to .15. i pulled the voltage regulator plug out & it went back to .07. i suspect it's the alternator, but would this be in the voltage regulator, diode, or something else?

sorry it took so long to reply, it's been raining here & i have no garage.
 
#12 ·
Doc here, :pimp:

The .07 is high...but acceptable..The .15 is not...the range is 0.3 to .08..

The Regulator Diode pack inside the alternator is Shot and reverse biasing (leaking backward just sitting) Imposing a load on the battery.

You Can replace the alternator, Or get a rebuild kit for it..(about $15 , and you will have a better alternator than you can buy off the shelf today..) And simple enough to rebuild if you do it right..





If you decide to go that route..post back and let us know, I can advise you so you get a first rate rebuild..

Doc :pimp:
 
#14 ·
Bryan59EC said:
And keep in mind--that these sometimes will check okay at AutoZone.

Bryan
Doc here, :pimp:

Not to mention SOME of the guy's at Auto Zombie are not the sharpest crayons in the box...

Need to know what year the fragrance trees fit, and Super-size those trees for ya??.....

Uhhh...Alternator...That's like a starter ... Right? ...

Humm...Voltage Regulator??...OK...How many PSI??...

Be sure you get a guy that at least LOOKS like he knows a spark plug from a trailer lamp plug..

Doc :pimp:
 
#15 · (Edited)
docvette said:
Doc here, :pimp:

Not to mention SOME of the guy's at Auto Zombie are not the sharpest crayons in the box...

Need to know what year the fragrance trees fit, and Super-size those trees for ya??.....

Uhhh...Alternator...That's like a starter ... Right? ...

Humm...Voltage Regulator??...OK...How many PSI??...

Be sure you get a guy that at least LOOKS like he knows a spark plug from a trailer lamp plug..

Doc :pimp:

doc, you are so very right. why do they need to know if my car has a/c to tell me which u-joint it takes? cross referencing is a thing of the past.

i'm going to rebuild the alternator. where should i get the rebuild kit? i have rebuilt this alternator before, but the only thing i didn't put in new was a rectifier. it's a 78 amp alternator, but if i can get it to put out more than that, that would be alright too. :thumbup: thanks for all everybody's help, i couldn't have done it without it.

by the way, whats the differance between a 10 si, 12 si, & 15 si alternator's?
 
#16 ·
406 ss monte said:
doc, you are so very right. why do they need to know if my car has a/c to tell me which u-joint it takes? cross referencing is a thing of the past.

i'm going to rebuild the alternator. where should i get the rebuild kit? i have rebuilt this alternator before, but the only thing i didn't put in new was a rectifier. it's a 78 amp alternator, but if i can get it to put out more than that, that would be alright too. :thumbup: thanks for all everybody's help, i couldn't have done it without it.

by the way, whats the differance between a 10 si, 12 si, & 15 si alternator's?
I usually get my stuff at the local NAPA.. ASE certified parts guys know their stuff I tell ya! :thumbup: The prices aren't bad, the parts are pretty goodm and at least at the one near my house the service is awesome.
 
#17 ·
Doc here, :pimp:

The kit can be had an any good reputable auto parts house like napa or others..Hell, Auto Zombie carries them too..Last one I bought was about $15 , but given the price of everything else may have gone up..

If you feel the need to upgrade..I suggest the CS 140 Alternator..IF your running extreme loads..Couple of hundred bucks..basically simple to wire..and into the 21 St century..

If you plan to rebuild the alternator...
  • Remove it from the car
  • Get about 2 or 3 cans of gunk, go to the coin wash, spray it with the gunk..let it soak 5 minutes..THEN set the wash to degrease, spray that for 5 minutes..Then rinse for 5 to 10 minutes..Allow dry time OR better yet air blow dry..

  • Halve the cases
  • Remove the brushes, brush holder/followers (depending on kit)
  • Remove the Bearing
  • Remove the bush (depending on kit)
  • Remove the regulator and install the new one.
  • Remove the rectifier Diodes and install the new ones.
  • With a fine Emory or Croakas Cloth, Burnish the brush pickups or (Slip rings) on the rotor assembly until smooth and shiny.

  • Install your new bearing, but before you do..get a SMALL sharp punch, carefully put a dimple in the race each 1/3 rd the way around. This will prevent the Bearing from EVER spinning in the race..is a tiny bit harder to put the cases back together, you have to tap the halves with a rubber mallet.

  • Install the bushing. (depends on kit)

  • Where the brushes are at the rear end bell, there should be a small hole that goes through to the brushes..insert a #40 drill bit or paper clip with the brushes fully compressed up..this will hold them off the slip rings while you insert the end bell.

  • Before reassembling the end bells to the body, inspect the windings..you are looking for no warn insulating paint, or glypt, and where the windings terminate, no melted or splattered solder or cracked joints If needed, Ohm the windings out..but these usually last forever..and if they failed before..you'd know it..

  • Install the end bells to the body and properly "Clock it for your application, be sure the end bells are straight..and (if needed) tap the bearing half end-bell with a mallet..and secure with the bolts..

  • Lastly spin it up by hand and insure it spins free and quiet..Inspect the front fan blade, and reinstall on the car..




If you notice the brackets or hardware is power white, remove them and media or water blast them , you have electrolysis going on there (mounts are aluminum and hardware/engine is steel..What were they thinking??)

Get some electrical bonding paste for aluminum wire..and coat the bolts, and mounts anywhere they touch steel..



That should give you a much better unit than you can buy over the counter..that will probably out live the car..

Doc :pimp:
 
#19 ·
docvette said:
Doc here, :pimp:

Not to mention SOME of the guy's at Auto Zombie are not the sharpest crayons in the box...

Need to know what year the fragrance trees fit, and Super-size those trees for ya??.....

Uhhh...Alternator...That's like a starter ... Right? ...

Humm...Voltage Regulator??...OK...How many PSI??...

Be sure you get a guy that at least LOOKS like he knows a spark plug from a trailer lamp plug..

Doc :pimp:
I always assume the guys at auto parts stores are "dummies" before I even get there. that way if they turn out to be helpful I am unexpectedly pleased and satisfied. If they are total "dummies" I do not get upset or aggravated because that is what I expected anyway. Same with fast food. I expect it to be lousy or just ok. If it's better than that, well then good for me.....

One time I went to one of those national chain auto parts stores (expecting a dummy to be helping me) and there was this "genius" dude that offered to help me. He had like an IQ of like 10,000 and was a graduate of some specialized exotic auto service school. I always wondered why he was working there when he could have probably been a lead engineer at some automobile manufacturer.....

ok - enough of my ramblings for now. I'll shutup and go away.
 
#20 ·
406 ss monte said:
what does the rectifier do? doesn't it conver a/c to d/c current? what do the diodes do?
SIMPLE QUESTION WITH AN INVOLVED ANSWER:
Long read...

Doc here, :pimp:

A rectifier does exactly that...Rectifies AC to DC voltage..and depending on how configured, is how well it does just that..1/4 wave, 1/2 wave, Full wave..usually From one to four diodes..(Battery charger to Filtered DC bench supply)

Diodes are usually semiconductor devices...(unless you are an old radio tech...then they are Passive devices) Or as fondly remembered ..TUBES..


A Diode, within reason (and tolerance) will conduct in ONE DIRECTION only..(OR Forward bias..) Think of it as a Check Valve for electrons..one way flows smooth, the other hits a brick wall..(again , within tolerance) To follow the flow..just follow the printing on the diode or schematic..



The direction of flow here will be from anode to cathode..

If you put a lamp on the cathode side to ground and 12 volts on the Anode side the lamp will light..reverse the wires on the diode..The Lamp will NOT light..in Fact, put the ground on the Anode side and power to the Cathode side...you have effective isolation..NOTHING happens..reverse it and the diode goes up in smoke.

When selecting a Diode..your concerns are Max Current..say, 1 amp...and PIV or peak inverse voltage..Say, 50..that voltage which WILL travel back through the diode and crowbar it shut..(making it just a Bidirectional wire..)

There or several other types of Diodes also, that can pick up Transmitted signal,(signal, switching, gunplexer) Reverse polarity protect a device (Zenier) Rectifier (single to Bridge types)

A Zenier is a voltage sensitive diode that auto~reverse biases when a specified voltage is seen between its conductors and purposely causes the diode to fail closed to prevent damage to a digital device that has seen a reverse polarity..(Faster than a speeding Fuse..More effective than a hamhanded Tech..) basically it senses a reverse voltage and crowbars shut across the power and ground of the device..no matter how many fuses you put in there they will just blow out UNTIL you repair / Replace the zenier..so you can't damage the unit EVEN if you correct the polarity issue..

A signal or switching diode does just that..detects signals in the air, in the circuit or however you configure it..Remember the "Cats Whisker " radio you made in school?? that was a diode..

A Gunplexer is a Diode array, that is configured as an antenna..used in devices from everything to PD Radar Guns..To Television Satellite antennas..to wave guides for your home dish antenna..

Switching diodes configured in the right manner will give you a transistor...and more than that on a chip..an Integrated circuit..to millions of them, a Microprocessor..you can follow the evolution from TUBE to Dime size Chip..

A Bridge rectifier, is commonly used in Well filtered, Regulated power supplies (bench supplies) as well as Power supplies for Radio and television , computers (with a slight twist..) to Car Alternators..and consists of 4 diodes placed in a "Bridge" configuration..


Full wave Bridge rectifier (Bad Dwg..Ignore AC~+ /- ...does not exsist in AC..sorry..)

If you note, the AC enters the bridge in Half wave stages..Then look forward of that..you'll see the the DC voltage WITH + and - polarity..

Were this a bench supply, the stage before it, would be a transformer that plugs into the wall..110 VAC, and drops it To 12 VAC..(for example)

The stage after it would be Capacitive filtering done with Electrolytic Caps and Mica bypass caps..

The stage after that would be a bleed off resistor..then on to a Regulator Chip..

From there out to a a Current meter , and Voltage meter as well as a fuse protection device ON BOTH the DC output side and The 110 Volt Transformer side..

Sounds pretty complex? Nope bare bones stuff..lower scale supply I wouldn't use for Digital powering..but good for a Novice to test a harness in the car..The current is dependent on the value of the transformer amperage , the Current handling of the Bridge, the WVDC (working Voltage DC ) of the caps..Depending on how Configured..from 1 MA to 10000 Amps..(slight exaggeration..)

NOW, yall wonder WHY I get up on my soapbox when I read it's OK ..I can use a battery charger for a testing supply...Without the fuses..without the current meter..this is a diagram of a Basic $29.95 charger...



On the top drawing , almost all 60 cycles of the AC are filtered out in each cycle..The Caps, the Regulator..help shape and buffer anything else..

On the lower diagram you'd be lucky to see 1/4 of a wave filtered at all leaving 3/4 of each cycle to AC..Don't know about you..Which would you rather have powering your $4000 Stereo..or your $800 performance ignition..or your $400 Dollar Computer..and it's sensors??

Try it yourself with a trash radio..put it straight to a charger and turn it on..I betting you won't hear a thing except a Very loud hum..I'm going with a top line bench supply!

An Alternator works the same way as the Bridge above..and more (usually 6 diodes) to rectify Raw AC generated within..The more diodes that fail or break down the LESS useable output it has...Same applies to the regulator EXCEPT it can slightly bias backward and impose a load on the battery just sitting...(Morning Sickness..) Overnight Dead battery's will start showing up..

OK , off the soap box... There is everything you DIDN'T want to know about diodes..Oh , this is just a breif overview..for more get a basic Electronics book..and do your own research...

NOTE: No Text was harmed in the creation of this post.. :drunk: :sweat: :nono:

Doc :pimp:
 
#22 ·
well i put a new alternator on it & it seems to be doing better. i tested it again like before & it read .08 amps. any thing under .8 amps are fine right? if it is .08 amps should be great then. i'm leaving the battery connected & we'll see if it's any better in a couple weeks. i believe it's fixed but i don't want to jinx myself.

with any luck this bad boy is fixed, now i just need to fix the rear caliper that popped on me today. never had this happen before, i nailed the throttle, hit 2nd gear, then hit the brakes & they worked for a second then went to the floor. i looked & there was brake fluid running out of the back right drum. it has brand new wheel cylinders on both side & one popped. wonder why?

thanks for everybody's help. i've learned a little something & that why we're all here right?.. i couldn't have done it without you guys helping me. thanks a bunch. :thumbup:
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top