Ignition Off Current Draw

[Jetaway]

Hi, all.

Maybe a silly question. I've been meaning to have the battery checked on my 1972 240Z for a month now, kept forgetting, and yesterday morning it wouldn't turn over. Not as dead as a doornail, the headlights came on dimly, and the voltage-driven LED domelight shone brightly. I hooked up a multitester this morning and measured a current of .05 amps with the ignition off. That's about 6/10 ths of a watt, not much in other words, and presumably accounted for by the radio head units memory.

However ... about a month ago (see where I'm going here?) I made some upgrades to my sound system. While I don't think the only new electronic piece (an equalizer) is the problem, I'm wondering if I either screwed up on the wiring of the trigger and power supplies or if I have created a partial short (like a strand of wire resting against metal).

The system is wired as follows:

Previously:

The head unit trigger is sent to a power amp under the driver's seat. The power amp has a direct (fused), huge (could be 10 gauge, maybe even 8 gauge) and more than adequate line to the battery. The power and the trigger for the antenna are taken off the amps connections. The power amp does not have a power indicator, but the antenna served as an indicator. No problems in 18 months with this setup.

A month ago I added:

Four more drivers (no effect possible) and an equalizer. The equalizer trigger and power are taken off a splice in the run from the amp to the antenna. The equalizer does have lights and works as expected, i.e., lights off when head unit is off, lights on when head unit on.

I'm going to pull the battery and have it tested, though I'm pretty resigned to replacing it. The battery came with the car, which I bought a little over 2 and 1/2 years ago and looked fine, which doesn't tell you much about a battery other than it not having been horribly physically abused. My concern is killing the new battery with a slow current drain. I haven't tested any other part of the charging system, nor other than replacing the belt about 8 weeks ago, made any changes to it.

So, am I right to be unconcerned about the .05 amp "off" draw? Or, just thought of this, could this small current draw be artificially and misleadingly low due to the weakened condition of the battery? If so, what sort of ignition off current draw should be expected with a low-middle line, nothing fancy audio head unit? What size draw should compel me to pull out the driver's seat and investigate further?

Chris

[Mikes Z car]

The clock on my 70 240Z car was causing a current drain and didn't work so the PO unplugged it. It was mechanically stuck on trying to rewind the clock so the current kept flowing through the coil. Bad alternator diodes can cause a current drain I believe, could try briefly unplugging the alternator and recheck the drain or unplug fuses one at a time until the drain goes away to get an idea of what circuit the drain is on though the ignition from another thread doesn't go through the fuse box.

[FastWoman]

Well, I can suggest the obvious:

(1) Start the car, and measure the voltage across the battery. It should be in the neighborhood of 13.5 - 14.5 V. If it's not, then your alternator and/or voltage regulator is bad, and you're not properly charging your battery.

(2) With the ignition off, measure your current draw while pulling fuses one by one. At least identify where the current draw is coming from.

A 50 mA draw isn't going to deplete a healthy and charged battery overnight. Maybe you have an intermittent short somewhere that crops up when you slam the door. You can test that with your multimeter, of course, while doing a bit of door slamming.

[Jetaway]

Thanks for the replies, I'll do the battery voltage check this afternoon.

This is what transpired.

Took the battery into an auto parts store. To my surprise, tested out good, quite good as a matter of fact. Brought it home, and though the terminals didn't look dirty, took sandpaper to both of them. Connected the battery up, turned the key and fired right up. Leaving it on fast idle, I tracked the ammeter while programming in my two essential radio stations. The ammeter went up to 2, maybe almost 3 needle widths at first, then fell to its customary position of almost, but not quite a needle width to the positive. Normal, in other words. Turned the car off, waited 5, 10 seconds, flipped on the lights. Nothing. Lights off, turn key. Nothing. Turn key off, wait a few seconds, turn on lights. After a short delay, a second or so, lights came on. Lights off, turn key, fires right up. Puzzling to say the least.

I had an appointment that I had to leave for in 20 minutes so I stopped futzing, got ready to leave and made the decision of death or glory. Turned the Z's key, started right up. No presets on the radio, however, so I wasn't imagining that the headlights hadn't turned on and it wouldn't turn over. Drove the 15 miles to the meeting, lasted about an hour, turn the key on the Z, fires right up. Drive home. Before I even got the garage door closed, a buddy stopped by to BS a bit. Maybe 10 minutes in, I said, heh, check out my new LED dome light. Whoa, he said, put blue and red plastic over that and people will think you are a cop. Not a minute later, he says Hey, look at the antenna. It was 1/3rd of the way up. "It wasn't like that before," he said. I wasn't sure, I would think I would have noticed if it were 1/3rd up, but it sure wouldn't have registered if it were fully retracted, so I'm not 100% positive that it wasn't partly up. I strongly suspect that he was right as in the 2 and 1/2 years that I've had the Z, the antenna has never failed to be either fully up or fully retracted.

After he left I pulled the cables off the battery and sandpapered the clamps. It's worked for 3 or 4 starts and a half dozen light checks since then, but given the weird intermintent failures, I'm not declaring problem solved quite yet. Later this afternoon I'll pull the body and engine side connections, give them a cleaning, and then do the voltage check.

Thanks again for the suggestions.

Chris

[FastWoman]

Solved??? Hmmmm.... I'm skeptical. Don't count on it just yet.

It sounds very much like it could be a corroded wire somewhere. The most likely culprits would be a fusible link wire or a battery cable, and the most likely and most sneaky location for the corrosion would be underneath the insulation, near the connector. Look for a tell-tale bulge in the wire/cable.

[Unkle]

Shot in the dark here, but how about replacing the ignition electrical switch ?

This is the round plastic electrical switch located at the back end of your ignition assembly on the column. It's driven by the key turning at the other end, and may now be loose / worn enough inside to make partial contact .

Just a shot......

P.S. Your antenna is also powered through this switch as well ? Will it go up when you turn the radio on with or without the ignition in the ''accessory'' or ''on'' position ?

Edited October 17, 2010 by Unkle

[ktm]

The head lights do not go through the ignition switch and as he stated they would not turn on at times.

By the description, the point of commonality is the battery feed wire to the fuse box and ignition switch. You may have an issue with one of the factory spliced connections.

Measure the voltage at the head light fuse and also measure the voltage on the white/red wire at the ignition switch plug.

[Jetaway]

Solved??? Hmmmm.... I'm skeptical. Don't count on it just yet.

It sounds very much like it could be a corroded wire somewhere. The most likely culprits would be a fusible link wire or a battery cable, and the most likely and most sneaky location for the corrosion would be underneath the insulation, near the connector. Look for a tell-tale bulge in the wire/cable.

As the title said: Solved -- Hopefully.

That's the thing with electrical issues. Assuming things don't get out of hand, a little smoke is often preferable to determining if you have solved an intermintent problem by tracking down every possible loose or corroded power or ground connection.

I'll take a closer look at the wires and some of the other suggestions next weekend -- or sooner if it won't start.

Following up: I cleaned up the engine / body side runs from the battery and checked the voltage across the battery. 13.0 volts. And everything still works!

To answer another posters question:

The head unit is ran through an ignition-keyed circuit in the fuse box. The amp, equalizer, and antenna are powered off a completely separate power circuit, namely a very large wire with an in-line fuse connected directly to the battery. When the head unit is turned on, either because it left on when I last turned the car off or turned on with the car running, it sends a triggering signal to the amp, equalizer, and antenna telling them to amplify, modify, or stand up proudly.

Of possible use for future reference: The amp and it's power wire are 20 years old (and yes, the amp, a 14 watt Harmon-Kardon kicks today's 50 watters as easily as it kicked more expensive 50 watters two decades ago). They were unused for close to 10 years before I brought them back a year and a half ago. When I fired up the modified system (added drivers and the equalizer) the in-line fuse blew (with the volume control all the way down). I replaced the fuse with one of the same specifications and it didn't blow, and hasn't despite high-volume stress testing. This has happened to me several times in the past -- an "old" fuse blows when a change is made in its circuit, but its identically spec'ed replacement doesn't. I admit that I have no rational explanation for this and that as a young whippersnapper, I'd thought the old man crazy in the head for suggesting such a thing could occur. Well, i may well be crazy, but the "old" fuse observation isn't evidence of it.

Chris

[Jetaway]

A follow-up:

No problems for 2 weeks after my last post. Then it began to take a long time to start, particularly in the morning. 20, 30 seconds of turning over before firing up. Ran fine, though, and the ammeter, while spiking, understandably, early, descended to normal levels within a minute or so whatever the problem was wasn't putting a huge strain on the battery. A couple of days after the slow start problem showed up and after a long day at work (15 hours) I jumped in the Z, turned the key and "click." Click, click, click. Now we're getting somewhere (figuratively, not literally) as before nothing would happen when turning the key to start. Lights came on strong, barely dimmed when turning to start. Got out of the car to look for a couple of students to give me a push start, didn't see any, got back in and tried again. Kkkggh -uhh- rrrRRRR Uuummpph burble, burble, burble. I recognized that sound!

Drove home, shut down, restarted no problem. Next morning: Click, click, then a clattering sound accompanied by an unusual vibration. Stopped, tried again and Kkkggh -uhh- rrrRRRR Uuummpph burble, burble, burble.

I had Friday off so I pulled the starter, and having nothing better to do, took it to a chain auto store to have it tested. First time, tested fine, to the kid's credit, he went, hmmm, hold on, I saw something there. Retest, nothing, as in nothing, the solenoid didn't engage. He looks up a new starter, quotes me $30 bucks, and could have it by Tuesday. He then says, somewhat puzzled or amazed, "$30 bucks? That's the cheapest part I've seen this week." I said to, him, "Tuesday? Hmmm, let me take a look around town, don't really want to leave it jacked up all weekend." This gave me a graceful excuse to go to the local independent parts store where I was told: "30 bucks, get it here by Tuesday. ... Let me check this other place. ... I can get you a higher output Bosch starter at 3:00 this afternoon. $70.00 though." I thought it over for about two seconds and said: "Do it." Not only do I prefer throwing my money at the locals, but I really didn't want to leave the Z hanging all weekend.

Picked it up that afternoon, a handsome looking starter, as starters go, installed it, reconnected the battery, jumped in, turned the key and: WWWWHHHHRRRR bmp bmp. I almost s(*$% my pants, sounded like it turned the engine over at 5000 rpm. Two year replacement _and_ a two year roadside towing package in case of failure included in the price.

So, I think this little adventure had two causes: First, while no individual connection was particularly bad, a little crusty here, a little corrosion there, combined with a failing solenoid worked together to cause the mysterious nothing on start syndrome. Once that was cleaned up, the solenoid sped along its way to its death, finally exhibiting the behavior and sound that I've associated with a dying starter. Second: The frog in the pan effect. The long time to start problem that started a couple of days before the starter died was caused simply by the motor not being turned over quickly enough by the starter to fire. Maybe if I had a couple of Z's I would have noticed that one was turning over slower than the other a few months ago, but with nothing to compare it to, the slow loss of cranking speed went unnoticed.

Chris

[EScanlon]

You cleaned off the BATTERY connections, but until you replaced the starter you hadn't finished cleaning the supply circuit to the car.

Aside from the starter being new and helping start the car better, I suspect that R&R on the connections to the starter (including the main and only fusible link) may have been a bigger correction than anything else.

FWIW

E