Something is draining my battery on my 95 disco. At first I just figured it needed a new battery so I replaced it with a new one, but I am still having the same problem. If I let it sit for more than a day or two the battery will be dead. Any ideas on what I should check, or how to test what is draining battery? Thanks
Draining Battery, need help
- Thread starter pdxdisco
- Start date
Well, this prompted me to go get the Fluke from the Rig.
The first place I would start is to remove the negative lead (assuming you don't need a radio code or something), and take an Ohm meter and check the resistance....with that said, you already know you have a leak so the resisitance will probably close to 0. Then with the battery disconnected, remove fuses to the lights first, then the accessories, then any other added mods. If the resistance changes or goes to 0 after each fuse removal, then you know which system the leak is in. Put the fuses back after you test the system and go on to the next system. There are normal slow drains like the clock, but a fast drain is not a good thing. If you have a battery tester, now would also be the time to check whether the new battery is holding the charge. It is possible to get a new bad one. You may want to shoot to Autozone and have them check it in case. If thats fine...then proceed above.
Good luck
Ed
The first place I would start is to remove the negative lead (assuming you don't need a radio code or something), and take an Ohm meter and check the resistance....with that said, you already know you have a leak so the resisitance will probably close to 0. Then with the battery disconnected, remove fuses to the lights first, then the accessories, then any other added mods. If the resistance changes or goes to 0 after each fuse removal, then you know which system the leak is in. Put the fuses back after you test the system and go on to the next system. There are normal slow drains like the clock, but a fast drain is not a good thing. If you have a battery tester, now would also be the time to check whether the new battery is holding the charge. It is possible to get a new bad one. You may want to shoot to Autozone and have them check it in case. If thats fine...then proceed above.
Good luck
Ed
BTW, you are checking the resistance from the negative lead to the negative terminal....you can also check voltage at the same time and that may help pinpoint, as it will tell you whether its a high voltage drain or a lower voltage drain....clues you in... Not overly familiar with the Disco wiring yet, but I intend to be.
Another thought... Do you still have the factory alternator in the truck? If so, a bad diode in the alternator could be causing the drain. At about 115,000 miles our 95 had a 4 amp drain through the alternator with the engine off - would drain the battery dead in a day. Try disconnecting the main alternator lead when the truck is parked for a day, and see if the battery stays good. If it does, take off the alternator and have it tested. Good luck.
John
John
It is the stock alternator as far as I know. If it is it has 130K miles on it. The Disco is completely stock other than an aftermarket radio that has been in it for years. It sounds like I need to go get an Ohm meter. Thanks everybody for you help.jec said:
If your alternator is truly that old, then it is a very likely culprit. If you can go without driving it for a day, you can forgo buying the ohmmeter and just disconnect the alternator for a day and see if that cures the problem; if not then buy a meter. Or, an option I would prefer to measuring resistance with the ohmmeter (I seem to recall that hooking a sensitive ohmmeter in series with a live circuit has a good chance of frying the meter) would be to get a multimeter with a 10-amp current-measuring range on it (I'm using an old analog meter from Radio Shack), and measure the actual current flowing in each circuit that you test with the truck shut off. I'm betting real hard on your alternator being the problem.
John
John
Is the alternator supposed to make a high pitched whine when the car is off LOL. I opened the hood today when I got home and I could hear the alternator making a noise with the engine off. Anybody know where to get a cheap replacement? please don't say go to the stealer.
OK...here's the easiest, most visible way to track down an electrical 'leak'. Make up a low-wattage test lamp from bits at RatShack. Disconnect the battery ground and connect the test lamp between the battery terminal and the ground strap. The brighter the light the bigger the drain.
Now start disconnecting components, like unplug the alternator, as a bad diode or diode pack could be the source. If thre light goes out, you've found it. Mind you, there will always be some current drain, from things like the clock, but the draw is so small, the bulb will barely glow. This technique is low-tech, quick, and easily visible as you pull fuses or wahtnot.
Cheers
Now start disconnecting components, like unplug the alternator, as a bad diode or diode pack could be the source. If thre light goes out, you've found it. Mind you, there will always be some current drain, from things like the clock, but the draw is so small, the bulb will barely glow. This technique is low-tech, quick, and easily visible as you pull fuses or wahtnot.
Cheers
ptschram
Well-known member
I'll be in PDX next Wednesday through the following Tuesday working on a '93 LWB. If you'd like, I can throw my FLuke in the bag of tools/parts I'm bringing with me.
The problem with reading amps is most people don't have an amp reader...
Even my $400 fluke only goes to 10A. It will read miliamps...but if something is a dead short or a light to ground on a 20A circuit...you may fry your ammeter - thats how I said "bye bye" to my old and trusty radio shed cheapo meter.
I like the light Idea...you could probably splice into any 12V lamp, or even a spare dashboard light in a holder or a marker bulb in a holder. However I have found reading resistance, and voltage difference usually targets me on the culprit - if you have a meter. Amps would be nice and easy, as it pinpoints the type of circuit/drain/component.
No...the alternator should not be making a noise. Thats considered bad. Try disconnecting it. Replacements and alternates were discussed on a thread recently....can't recall, but a search might find it. (alternate alternators - haha)
Ed
Even my $400 fluke only goes to 10A. It will read miliamps...but if something is a dead short or a light to ground on a 20A circuit...you may fry your ammeter - thats how I said "bye bye" to my old and trusty radio shed cheapo meter.
I like the light Idea...you could probably splice into any 12V lamp, or even a spare dashboard light in a holder or a marker bulb in a holder. However I have found reading resistance, and voltage difference usually targets me on the culprit - if you have a meter. Amps would be nice and easy, as it pinpoints the type of circuit/drain/component.
No...the alternator should not be making a noise. Thats considered bad. Try disconnecting it. Replacements and alternates were discussed on a thread recently....can't recall, but a search might find it. (alternate alternators - haha)
Ed
ptschram
Well-known member
edthediscoman said:
Your Fluke has a fuse for just this very reason, as does my trusty old Simpson 250...
$400 Fluke? OMG, I paid $20 for mine in the parking lot of the local electronics surplus shop-no, it wasn't hot! For $400, one could get a working scopemeter, or for $1400, a used Snap-On Vantage with warranty.
Yup I too have a Fluke 87 and PT is right about the fuses. Mine were blown, cost me about $15 to replace.
10A is fine for measuring parasitic drain. If your truck is draining more than 10 amps then there is something terribly wrong. Measuring drain via amps is the most accurate way to measure it.
10A is fine for measuring parasitic drain. If your truck is draining more than 10 amps then there is something terribly wrong. Measuring drain via amps is the most accurate way to measure it.
I did the test light from the -terminal to the -cable thing and pulled all the fuses but it always stayed lit. I put the -cable back on the -terminal to test the alt. and that is when I heard it making noise. I don't think 130K is to bad for a stock alt.
Nope, Although my acura had 205K and still going strong, but I bet it needs a new one now.
Some of these guys should have a good place to get an alt. The PO of mine put one on right before I bought it.
Wait...was the light still lit with the alternator disconnected?
If it was then there is another drain.
I agree on the fused bit, but its a PITA when it blows mid diagnosis, so I stay away from that. Otherwise its another excuse to hit the parts store, and that ALWAYS gets expensive...cause you can't just buy a fuse...there are always soo many other gotta have's.
Some of these guys should have a good place to get an alt. The PO of mine put one on right before I bought it.
Wait...was the light still lit with the alternator disconnected?
If it was then there is another drain.
I agree on the fused bit, but its a PITA when it blows mid diagnosis, so I stay away from that. Otherwise its another excuse to hit the parts store, and that ALWAYS gets expensive...cause you can't just buy a fuse...there are always soo many other gotta have's.
mmmm...ok, have to check the diagram here.
I assume all power runs through the alt anyway...so light would be off with alt disconn.
duh...
again slurpees are affecting my brain.
I assume all power runs through the alt anyway...so light would be off with alt disconn.
duh...
again slurpees are affecting my brain.
ptschram
Well-known member
OK, let's discuss this circuit...
The fuse for the alternator is in the underbonnet fuse block... REmove that one and see if the drain goes away.
The fuse for the alternator is in the underbonnet fuse block... REmove that one and see if the drain goes away.
ptschram
Well-known member
pdxdisco said:
LOL! Now you're ready to start throwing parts at it to solve the problem?
I was serious, I'll be in Portland Tuesday if you want some help.
IF you've confirmed that the alternator is the problem, do a search here and read the various opinions on alternator replacement. The two primary schools of thought seem to be that if you buy a generic rebuilt, make sure it has a lifetime warranty so you can get a free one every time it goes bad, potentially shortly after you bought it. The other school of thought is take yours to a reputable local rebuilder and have them rebuild it. I did the latter, and it cost $209, and has been running fine.
John
John