Bobac455

I have a 70 Cutlass with a new single wire alternator and a new battery. The alternator is a 100 amp chrome PowerMaster unit from Summit. It does use the "exciter"wires (2). I've traced the battery drain to the wire that goes from the ingition switch to the volt meter mounted to the bottom of the dash. The gauge is well grounded. With the volt metr wire connected to the fuse box, I get a readinig between the negative battery post and the terminal cable. When the negative cable is hooked up, I can see a spark on the positive terminal by lightly touching the cable from the starter to the positive battery post. If I leave everything hooked up, it can drain the battery in 24 hours. I've tried to isolate it by removing one "appliance" at a time to see if the drain goes away. (electric radiator fan, alternator [main 10 gauge wire only], power top motor, etc.) Finally when I removed the little orange wire from the volt meter to the fuse box, the drain went away. My problem is I don't know where to look for the short. The alternator is also well grounded. I filed off the Chrome where it mounts to the bracked and block to make sure it is grounded. The volt meter reads correctly when the car is running. Where is that whole circuit would the short be? Am I supposed to have a resister somewhere in this circuit? Would that be part of the problem? Thanks

jaunty75

Couple of quick, possibly dumb questions. Exactly where on the fuse box do you have the voltmeter connected? The voltmeter should NOT be connected to a constant 12V source like, for example, the cigarette lighter. It should be connected only to a source that is on when the ignition is on. I don't know for sure that keeping the voltmeter connected 100% of the time would drain the battery, but I'm guessing it would because you are providing, however small it is, a pathway for current to run from the battery to ground.

When I put an aftermarket voltmeter in my car, I connected the positive terminal to the same lead that powers the radio. Works great.

joe_padavano

It will. As noted, use a switched power feed on the voltmeter, not a constant source.

Bobac455

Thank you for the quick response. I am not at the house right now so I can't check the connection. That could very well be the case. I'll check it an let you know. That simple a solution would be a real kick in the butt. I've spent 6 or so hours tracing wires and testing to find the source. I hope the fix is that easy.

Bobac455

You know I just remembered the volt meter was connected through switched power because it only worked when the car was being started or was running. As soon as I turned off the key, it went dead. Any other thoughts?

jaunty75

No, but then I've been confused all along by several statements in your original post:


Why is there a wire going from the voltmeter to the ignition switch? There should be only two wires to the voltmeter. One to a good ground, and the other to a 12 volt source controlled by the ignition switch.


I'm also confused by this:

Again, what voltmeter wire connects to the fuse box? Above you said it's connected to the ignition switch. And where on the ignition switch? Aren't there several terminals on it? I wouldn't connect the voltmeter to anything on the ignition switch. It's too hard to get at and too easy to perhaps connect the wire to the wrong thing. Find something easier to get to, like the wire that powers the radio. On my '67 Delta, that wire was very easy to reach behind the dash and splice into.

There should be only one wire besides the ground wire coming from the voltmeter, unless it's the wire that powers the lamp that illuminates the gauge if the gauge came with that.

And what do you mean you get a reading between the negative battery post and the terminal cable? Reading from what? The negative battery post should be connected to ground, so connecting a wire to the negative battery post is no different than just attaching that wire to any good ground on the car. And what do you mean by "terminal cable?"

Bobac455

I apologize for all the confusion. By terminal cable I mean the battery cables. Also, I am hooking the correct terminal on the back of the volt meter to a switched fuse on the fuse block. I shouldn't have used the word Ignition switch but a fuse controlled by the ignition switch. There are 3 wires on the back of the volt meter. One goes to ground, one goes to the switched fuse and one is for the lamp. Now then, if the wire from the volt meter to the fuse block is hooked up, I get a reading of around 12volts by measuring between the negative battery post and a disconnected black ground battery cable. If I hook up the negative battery cable and disconnect the 10 gauge red wire that carries power to the fuse box from the positive battery terminal while leaving the red battery cable from the starter to the battery hooked up, I get the same reading on a multi meter by measuring between the 10 gauge wire and the positive battery post. If I disconnect the wire from the volt meter to the fuse block, then the drain goes away and I get no reading on a multi meter from either of the two tests mentioned above. It appears something in the volt meter circuit is causing a drain. As I mentioned earlier, the volt meter seems to work well. I don't know if it makes a difference but the prior owner had a complete after market alarm system installed with auto solonoid door locks, ignition disabling and everything. I have taken the entire system out of the car and reconnectred all the wires that had been cut or spliced. I did this without a wiring diagram and just used the color of the wires to match them up. Actually only one wire was severed and it is a heavy gauge light purple wire which goes up the steering column to the ignition switch. The others were merely spliced into. Before doing that, I had a severe drain on the battery but the removal of the alarm system cured the severe part but left me with this nominal drain that I am currently seeking your help with.

jaunty75

OK, let's go through this step by step.

First question. Why are you measuring this this way? What is the reading on the voltmeter when the battery negative terminal is connected to ground as it normally would be? It should show nothing with the ignition off and 12V or thereabouts with the ignition on. If it does this, you're fine. The project is complete.

Whether not your aftermarket voltmeter is hooked up, you should ALWAYS get 12 volts if the battery positive cable is properly hooked up, the battery negative post is not connected to anything, and you put a voltmeter between the battery negative post and ground. But my REAL question, is why would you ever do this? All it shows is that the battery has 12 volts. You can measure that by just putting a voltmeter across the battery terminals. I don't know what it would tell you about the circuitry for your aftermarket voltmeter.



To me, this suggests that the 10 gauge wire is grounded, which doesn't sound right. This 10 gauge wire is just coming from the battery and is not connected to anything once you disconnect it from the fuse box. A voltage reading between this wire and the positive battery post should show zero volts as it would be no different from touching both leads from a voltmeter to the positive battery terminal. Maybe THIS is the source of your battery drain?


So now it does sound like something is grounding through the voltmeter that shouldn't be. Time to get another aftermarket voltmeter and try it. It could be that the one you have is defective.

It might work, but it might still have a partial ground problem.

OK, this is weird. I don't believe in coincidences. A properly installed aftermarket alarm system, just like an aftermarket remote starter or anything else, should not be a drain on the battery. If yours was, then it was not installed properly, and removing it might or might not have cured your problem. You might have left behind some jury-rigged wiring that you are unaware of. You say you didn't have a wiring diagram. You should get a chassis service manual for your car. It will have a diagram with all of the wires identified by color, and you can figure out what should be where. Without this, your problem-solving approach will just be hit-and-miss.

It may turn out that your voltmeter has nothing to do with the battery drain problem.

Bobac455

Thank you for all your input. I really appreciate your trying to help. Electrical problems are the worst kind of problem to find and fix.
Jaunty75 - I tried to be as clear as possible and sometimes I am too wordy. The only fact I didn't mention is that the key has always be out of the ignition switch entirely. I am testing that way because I should not be getting any reading between the negative battery post and a disconnected negative battery cable. Nor should I get any reading when disconnecting the heavy gauge red wire and testing between it and the positive battery terminal. I believe I stated it correctly. With both battery cables attached to their respective battery posts, I get a slight spark by touching the heavy guage red wire (coming from the fuse box) to the positive battery terminal. This should never happen especially since the car doesn't even have a radio installed with a memory wire. I do have a 70 Cutlass manual from "The Parts Place" and it is awful in terms of the copy quality. The wiring diagram is almost impossible to make out. I paid $29 over the web for a colored wiriing diagram which is nicely sandwiched in clear plastic. The problem with it is that it tries to cover every conceivable option that was available. It shows two engines (6 and 8 cylinder), two alternators (one for the 442 with an internal regulator and one for the Cutlass using an external regulator, etc. and wires for all these things.) It is very confusing. Someone ought to make an electronic editable version in Visio or SmartDraw (free) so people can erase the wires they don't have. It would make it much easier to read. At the very least, it would be nice to be able to order a diagram specific to my car which has a V8 and internal regulator, no power seats or windows, etc. At least I have it narrowed to the volt meter circuit.

Bobac455

By the way, I just read an article in one of my magazines on "Finding a short" and it specifically singled out "after market" alarm systems as the most responsible for drains on batteries because they have to be active whenever the car is not being driven and require so much more power than factory installed.