Electrical Problem
Thread Starter
Navigator
Joined: Feb 2006
Posts: 9
Likes: 0
From: Weatherford Oklahoma
Electrical Problem
This is my first post here, seeking help with an electrical short in a 1976 Vette. Battery goes completely dead within three days. When connecting a new battery, the a/c fan comes on even if the key is not in the ignition! The car starts and runs fine, all seems normal, but battery will be dead within three days again. Charging system checks out OK. A related? problem was that a month ago the backup lights were on with no key in the ignition, but this problem seems to have disappeared. A friend suggested replacing the starter solenoid? Could this be the cause of my problem? All suggestions appreciated!!!
Burning Brakes
Joined: Oct 2006
Posts: 1,089
Likes: 43
From: Native Californian CALIFORNIA
Army
Are you saying the fan runs all the time with the battery connected? If so there lies your problem.
To detect a drain on your battery with the ignition key off there are numerous threads posted. Search for "battery drain". With a DVM and pulling of fuses you will be able to isolate the problem.
To detect a drain on your battery with the ignition key off there are numerous threads posted. Search for "battery drain". With a DVM and pulling of fuses you will be able to isolate the problem.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,027
Okay, Here is the trick the old timers taught me, and it works well.
Disconnect the positive post of the battery, and place a 12 volt lamp in series between the battery cable and the battery. Use a long 10' wire, like a lamp cord is best.(You can carry it with you around the car).
If there is any drain, the lamp will light. Now, 1 at a time, pull out a fuse. When you find the circuit that is draining, the lamp will go out. Then, trace that circuit downstream untill you find the problem. J
Disconnect the positive post of the battery, and place a 12 volt lamp in series between the battery cable and the battery. Use a long 10' wire, like a lamp cord is best.(You can carry it with you around the car).
If there is any drain, the lamp will light. Now, 1 at a time, pull out a fuse. When you find the circuit that is draining, the lamp will go out. Then, trace that circuit downstream untill you find the problem. J
Burning Brakes
Joined: Jul 2006
Posts: 829
Likes: 4
From: Mexico NY
wow
Okay, Here is the trick the old timers taught me, and it works well.
Disconnect the positive post of the battery, and place a 12 volt lamp in series between the battery cable and the battery. Use a long 10' wire, like a lamp cord is best.(You can carry it with you around the car).
If there is any drain, the lamp will light. Now, 1 at a time, pull out a fuse. When you find the circuit that is draining, the lamp will go out. Then, trace that circuit downstream untill you find the problem. J
Disconnect the positive post of the battery, and place a 12 volt lamp in series between the battery cable and the battery. Use a long 10' wire, like a lamp cord is best.(You can carry it with you around the car).
If there is any drain, the lamp will light. Now, 1 at a time, pull out a fuse. When you find the circuit that is draining, the lamp will go out. Then, trace that circuit downstream untill you find the problem. J
what if the drain is a solenoid on a fuseable link>?
But man I must say that this method would have saved me alot of frustration in my life
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
OK, let me throw this in here. If you already KNOW the fan runs with the key off, fix that FIRST, then look for any further "Leaks". This should be done ueing an AMPMETER, not a light bulb. This alley oop technigue might work if you have a Large drain, but the spec is something under 200 Ma, thats .2 amps, out of spec and yet the bulb will not glow.
Get a decent multimeter and learn how to use it, it really is easy.
In the meantime, chase down the short causing the fan to run, then do the other stuff.
Get a decent multimeter and learn how to use it, it really is easy.
In the meantime, chase down the short causing the fan to run, then do the other stuff.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
LOL, not a "Published Spec" but thats about where I have found most cars are with nothing on. The keep alive circuits on ECMs, radios etc will usually pull something less than that. A healthy battery should be able to support that for weeks.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Computer cars are about 20 milliamps....not two HUNDRED.....which would be .2 amps..... .02 amps is 20 mills.....
most lights would be say at least an amp per bulb.....
computer cars MAY drain a fresh new battery in 6 months, but not much less.....these new chips don't draw jack for load....
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Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Computer cars are about 20 milliamps....not two HUNDRED.....which would be .2 amps..... .02 amps is 20 mills.....
most lights would be say at least an amp per bulb.....
computer cars MAY drain a fresh new battery in 6 months, but not much less.....these new chips don't draw jack for load....
most lights would be say at least an amp per bulb.....
computer cars MAY drain a fresh new battery in 6 months, but not much less.....these new chips don't draw jack for load....
Point is, these cars should be well under 200 Ma which is not enough for a light bulb for a test tool. If the fan is blowing then yes the bulb may light, bit you don't need a light to figure out the fan is on.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
OK I agree the fan has to be fixed first-probably a bad blower relay.Now moving on to this test light verses multi meter.I have questions here.I have always used the test light in series on 1 of the battery cables.If you use a meter do you use it in series like the test light?What do you set the meter on after setting it to 12 volts? If you have it in series and you say open a door(big draw)does it damage the meter?I have seen the 110,220 volt clamp on induction type meters-do they make these in 12 volts that will sense 200 Ma ? When it comes to digital multi meters I get confused-When working in ohms I have a board with 5 different "known"resistors mounted so I can get my meter set to the range I need.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Mornin Roger
For this test the meter goes in in series, just like the bulb woult. you set it up for AMPS and mine has a 10 amp setting so start there. First verification should be that the interior lights are not the problem, once that is verified, tape up the switch so you can open the door withut disturbing the setup. I have a couple clamp ons but I will need to check and see if it will read that low, good question.
This is one of the few places I use a meter on the car, most stuff I use a test light for checking anything that goes on and off. But for battery drain you need to read fairly small currents. Lights, blowers all pull a big load and are redily aparent, but light timers, relays, alarms, some stereo gear, that all are small loads that won't light a light, but it will show up on the meter.
For this test the meter goes in in series, just like the bulb woult. you set it up for AMPS and mine has a 10 amp setting so start there. First verification should be that the interior lights are not the problem, once that is verified, tape up the switch so you can open the door withut disturbing the setup. I have a couple clamp ons but I will need to check and see if it will read that low, good question.
This is one of the few places I use a meter on the car, most stuff I use a test light for checking anything that goes on and off. But for battery drain you need to read fairly small currents. Lights, blowers all pull a big load and are redily aparent, but light timers, relays, alarms, some stereo gear, that all are small loads that won't light a light, but it will show up on the meter.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
the clamp on induction meters will not sense dc current, only ac. be sure your amp meter has a large enough capacity, or you could melt it! putting a fuse the same capacity of the meter in series wouldn't be a bad idea just in case you accidently short something.