I've had a batt drain in my 90 for a while now and just been unhookin the batt at night but it's getting beyond annoying so I recently got out the multi and tested the draw at the negative terminal with my own wire rig and a 1 ohm resistor. I first got a .50 Volt reading (500 mV) and the sparks were flyin the minute I touched the negative terminal to the post. Enough to drain the batt over night if left hooked up essentially. So with the rig out and connected, I start pulling the fuses one by one. Pulled all of them that I'm aware of and watched the multi for changes(both on the side instrument fuse panel and the 4 under the passenger side). I found only a slight drop from the radio fuse and a couple others that are normal, but none making that dramatic of a drain. Until of course I pulled the fuse plug from the alternator, I noticed the drain immediately drop to .16 Volts (160 mV) which is still a big drain but not nearly as big obviously. The norm that should be allowed from what I understand is 35 mV which is .035 Volts when the car is off for the radio/stereo clock settings etc. Anyhow, I stupidly figured it was a bad diode thinking it was the alternator that was causing a continuous draw when the car was off so I replaced the alternator(one that's been in there for almost ten years). So now I had a new ac delco alternator in there. It ran great and runs great so it seems. Immediately after I put it in though, we tested it on the multi and we got the exact same readings of draw in total .50 V(500 mV). SO now I thought wasn't the alternator afterall and was something with the wiring. Next thing I did was bring it to a reputable electric shop here in town earlier today and have them do a diagnostic for the wiring and see where the draw's coming from. So they look it over after I leave it there all day and finally call me up and say I have multiple draws and one of them is a bad alternator. They tell me the draw's 500 mV total and the alternator is the problem that's drawing most of it with 160 mV owed to something else. Obviously the same numbers I got with the multi, old news. I told them its highly unlikely that its the alternator since it's pullin the same exact readings of draw as I had gotten with the first one which I tested and replaced myself. For a 10 year old alternator to pull the EXACT SAME energy draw as a brand new AC Delco unit even if the new unit was malfunctioning would seem extremely unlikely I would think. I asked them if they were sure its the alternator 3 times and they said yes, which I now know to be bu11sh1t. What I did tonight is took the old alternator I myself took out the first time when I tested it in the car down to an auto zone to have them do a multi layer diode test. That old one passed every test thus showing that there couldnt be a jacked diode nor a continuous two way current draw when the car's off from the alternator. This logic also shows that the new one I put in that they just tested can't possibly be bad all the same because if it was bad then the draw would be 1 Volt (1000 mV) instead of .50 V which was the reading they got and the reading I got for both alternators when I tested them in the car. Where the remaining .16 V (160 mV) draw is coming from remains the mystery that apparently they needed to keep my car overnight for them to diagnose. So I know the alternator most likely isn't bad at all, but a question I have is about the fuse plug that goes into the alternator. Is it possible that the plug is bad and some switch in it is stuck thereby causing the continuous current draw we see when the car's off? Also what else do you think I should look for? I noticed that when I reconnect or disconnect the negative batt terminal, there are two sounds; one that makes a brief kick sounds like its coming from the dual fan area(fans work and this alone does not turn them on just makes a kick sound when I connect the terminal), and the other of course is a low pitch whine type sound from the alternator when the fuse plug is connected(even though we just determined that it would be next to impossible to be the alternator itself). Also just fyi, I have a modded "auto fan" switch rigged that I keep the switch in the on position so the fans kick on at first turn of the key before the engine's on which I was thinking could possibly be some of the draw that I haven't diagnosed yet(they have my car tonight at the shop as I mentioned), but I wouldn't think it would be draining much. Any other ideas or suggestions?

 

When did this problem start? Was it sometime around when you installed your "auto fan" switch? From your description, you seem confused about the electrical workings of an auto. Testing for current draw involves placing an ampmeter in SERIES with the battery cable. You are testing for amperes or milliamperes, not volts or milivolts. I am not sure what you are doing with your wire rig with the 1 ohm resistor. Throw it in the garbage. Then, redo all the tests, pulling 1 fuse at a time.

 

"Current" was just a figure of speech. I was only measuring volts not amps. The 1 Ohm resistor is placed between two ends of wire and each of those ends are connected to clamps. One goes to the negative terminal and one goes to the negative area on the battery. Connected to the bare wire area just left and right of the Ohm the two clamps of the multimeter are connected. There's a vid on youtube explaining it. This is how I was monitoring the drain and I pulled the fuses one by one. The mechanic and the electrician both measured independently and got the same numbers. Why are you measuring amps?

The problem of drain's been goin on for quite a while because I noticed a slight zap when reconnecting the neg terminal to the batt, but it never drained completely overnight until about a few weeks ago. I've had the auto fan switch in there for years.

 

Are you serious? I am measuring amps because amperage flow is what drains a battery. That is your problem, is it not? With your gizmo, you are measuring voltage drop ACROSS your resistor with varying current draws. I guess it would give some obscure indication, but the proper way to determine accurate current draw is as I explained in my first post.

 

A mechanic explains it here with my method. http://www.youtube.com/watch?v=B__DqK90IIc Is it possible the draw is coming from the fuse plug connector connecting to the alternator?

 

Is it possible the fuse plug connector connecting to the alternator itself is the culprit? This plug's probably as old as the car. The guy in the parts dept didn't know if it was a fuseable link but by reason of deduction it seems this is one of the only remaining culprits since a wire itself couldn't draw power and the power draw is definitely lowered when that fuse plug is removed from the alternator. When I had issues with the fan relays burning out, no one ever suggested the connector plug to the relays should be changed. I changed it and havent had problems since.

 

If the power drain goes away when you disconnect the alternator, rational thinking would tell you that there is something wrong with the alternator. If there is no power drain with it disconnected, how can it be the plug. I watched the video link. I think this guy just makes videos to hear himself talk. If you look at the other videos on this Youtube page, there are several others showing the proper way of testing.(for the third time, connect your meter in series with the battery.) I see you are cross posting on general also. JFB is also asking you why you are not testing for current. He is an electrical engineer and I have been a master electrician for 30 years. If you are looking for accurate tests, why would you want to bring in unneeded variables like this guy's makeshift resistor?

 

With your test equipment hooked up, unhook the ignition switch from the system. If you have a faulty switch, it could be passing power, even if the key is in the off position.

 

However there's a problem with that "rational" thinking when you read what I just explained on my original post that I had tested both drains with BOTH alternators, the new one and the old one in the car to give me the exact same readout of .50 V drain. I also stated that I took the old alternator which I removed from the car, and tested it on a diode test at an autozone that it passed with flying colors on the machine. If two alternators are fvcked up, Question 1: Why would they both be giving the EXACT SAME energy drain readout on a multimeter despite whether I measured it in Volt or Amps? Question 2: Why would anything be wrong with the alternator if it passes a diode test? Isn't a jacked diode causing the power to be drained in the other direction the only way the alternator can be drawing power? And Question 3: Even if something was wrong with the NEW alternator, since I tested that in the car for the same .50 V readout, if it WAS drawing power, it would have to be higher than the .50 readout, since that was the readout I was getting when the old amp was in there(which later passed the diode test of course and I was told was fine).
And I always post on both tech and non for questions like this because of the 95 percent that views and the 5 percent that actually posts. I wasn't testing for current because no video I saw ever showed me how as they were always testing for volts. I also brought it down to an electrician because I'm in no way one as I explained, nor do I have any electrical expertise. To your question "If there is no power drain with it disconnected, how can it be the plug?", what I'm asking is if it's possible that the plug WHEN CONNECTED to the alternator is causing some kind of continuous drain without anything being wrong with the alternator.....say a wire that stays connected somehow internally in the plug to the wiring inside the alternator and completing a connection for draw while the engine's off?

 

Where is this? I'm not familiar with the location or how to unhook it from the system.

 

Under the dash, on the steering column. Has a steel actuator rod running up to the column lock mechanism.

 

Is the switch easy to get at just going under the dash or am I going to have to remove the wheel to get at it?

 

Haven't been there in awhile, but wheel does not have to come off. Switch is lower, close to the diagnostic link.

 

You both are basically right and have valid statements. I looked at the video and he should have converted the volts to amps using ohms law so as not to confuse people that current draw is not a voltage measurement. It was tailored to the real basic person maybe without real technical experience. It is a course way of getting basic information

In military electronics and automatic test equipment current measurements are made using voltage drops across resistors and doing the calculation for current also. However we use precision resistors and highly accurate voltage measurement devices to get the currents.

The one ohm resistor he uses could be a 10% tolerance resistor and for what he is doing he get close enough for a basic reading and simple procedure.

As it is an undisputed fact, a ammeter should be inserted in series to get the true reading. He might have thought it was too complex for his audience.

And just a interesting word about ammeters. It really measures amps using a calibrated shunt (or resistor) and measuring the voltage across it and converting it directly to a current reading visible to the user on the amps (current) scale on the meter face.

 

This is interesting because my vats system did indeed fail and the drain of batteries one after another seemed to have come right after this period. I put a VATS bypass switch in the car after I was told I had ignition issues when the car wouldn't start about a year or two ago, turned out it was the starter enable relay that was fried also which allowed the car to start, but I'm reading elsewhere that the ignition switch failing is a common cause for battery drain. And an ignition switch prob seems to be associated with the VATS which I've been now bypassing with the switch. It also might explain why there are multiple drains. jfb suggested from what I understood, that the fuse cable harness that connects into the alternator is wired to multiple areas and that this could be drawing power from another source instead of the alternator necessarily being faulty or having any bad diodes, IE, one of those wires in that harness possibly from the ignition switch? Is this possible? I also mentioned that there's a brief "kick on" kind of boot tapping sound in the fan or headlight area for a second as I reconnect the negative batt terminal and I get a spark along with a low pitch "on" sound of the alternator. Is it possible this bad ignition switch is essentially trying to "ready" the fans or headlight and/or alternator for powerup because its still passing power when the car's off? I do have the always on fan switch connection as I mentioned btw.

 

My 94 makes some clicks and sounds also when I connect my battery, I consider it to be normal. Some electronics are just finding their relaxed initial power on state. After it settels down (5 seconds) the battery current draw is 30 ma.

 

I agree with what you are saying, but the only reason this number is the same(volts vs. amps) is because he was using a 1 ohm resistor. According to ohm's law, if he changed this value to say, a two ohm resistor, all similarities end and this form of measuring current draw is out the window.

 

To pcolt94, it's actually easier using amp reading with the multi connecting them in series than it is with the one ohm resistor because you wouldn't need the resistor. Even though we were both right, I see now the idiot on the youtube vid could have just told us to hook the meter up for amps in series. Not only would it be technically closer to accuracy since current's measured in amps, but I'd assume easier for the real basic person as you put it. He makes it in due process only more complex. The only reason I could logically think he used the resistor method and thus with volts is because the direct amp reading with the multi has the potential to blow out the meter if you're measuring too many amps or amps for too long. Maybe he just thought extra low of the "real basic person" and would be equivalently astonished if most of them could even open the hood. That would be exceptionally ironic considering how goofy his *** looks and seems in the vid.