20 replies to this topic

[Michael Colangelo]

I recently replaced the battery in my SM with a new one from NAPA.  The old battery was dead and looked old so I figured replacing it would be a good idea.  The new battery was fully charged prior to installing in the car.

 

Over the past few weeks, with the car sitting in storage and the kill switch set to OFF (open), the new battery has twice been drained low enough that the starter won't engage and the lights are dim.  In both cases, I started with a fully charged battery.

 

I'm hoping to start trouble shooting this weekend (or later), but was wondering if this sounds familiar to you guys.  My plan is to check the wiring and grounds, kill switch, and alternator.  I'm assuming that the battery is good. 

 

Thanks in advance for any advice.

[Jim Boemler]

Check for current with a multimeter, at the positive battery terminal.  Any current found is a problem.  The battery should last months and still fire up the car reliably, even in the moderately cool weather we've had.

[DES4]

Yeah, you'll need to do a static (parasitic) draw test at the battery. Either terminal (+ or -) disconnected from the battery will work, as were measuring all current passing to or from the voltage/current source. Multimeter set on "amps/A" or "milliamps/mA (preferred)", meter needs to be hooked in series (inline) to do this correctly. Because the initial draw when reconnecting the battery can spike, you should use a shunt when first connecting the meter whenever a draw test is performed (replacement fuses for a Fluke, for example, are over $12).

 

Most modern cars have normal static draw of about 40 mA, but if your kill switch is wired correctly, it should be zero. Begin by looking for simple stuff (i.e.: Is my voltage meter reading battery voltage with the kill switch off?). Pull fuses one by one until the draw goes away to isolate the source. If you can disconnect the battery supply lead from your kill switch, and the draw does not go away, you'll need to at least correct that; your car is not compliant.

[DCP]

I have the same problem. I found that with my kill switch in the off position, 6 volts where still going through the switch.  I am replacing the switch.

[Bench Racer]

Michael and DCP, whose wiring diagram did you follow when installing you battery/switch system? There is one system out there that when you have the switch turned to off there is a voltage draw and the battery drains. Mind is one of them and drains when in the off position.

[Blake Thompson]

You can take the battery out completely, charge it, and see if it retains a charge.  There is always a chance it's defective.  Most batteries are rebuilt cores, it could have been a failure somewhere.

[DCP]

Michael and DCP, whose wiring diagram did you follow when installing you battery/switch system? There is one system out there that when you have the switch turned to off there is a voltage draw and the battery drains. Mind is one of them and drains when in the off position.

I did not install my switch and am a little lost on how it is  wired. It is the Pegasus 4430 switch with two big posts and four pins on the bottom. Whoever installed it fit the wires that go into the bottom pins into an connector that was too small. As a result, when I got the car the wires to the bottom pins were not connected at all.  With just the two big posts connected, I had the battery drain and measured the 6 volt throughput in the off position. I just assumed that had to mean the switch was bad

[mdavis]

I have the same problem. I found that with my kill switch in the off position, 6 volts where still going through the switch.  I am replacing the switch.

Dave may want to chime in on this one.  As Bench Racer said- it's likely not the switch.

[DES4]

I did not install my switch and am a little lost on how it is  wired. It is the Pegasus 4430 switch with two big posts and four pins on the bottom. Whoever installed it fit the wires that go into the bottom pins into an connector that was too small. As a result, when I got the car the wires to the bottom pins were not connected at all.  With just the two big posts connected, I had the battery drain and measured the 6 volt throughput in the off position. I just assumed that had to mean the switch was bad

 

Voltage is not a measure of current being used (which is how a battery is depleted), but a measure of "electromotive force"; which is to say, the potential behind the current. If you are reading 6V, you might be only reading the potential voltage (unloaded) between two planes, which could be as simple as a backfeed/static reading, signifying little. Current is what you need to focus on here.

 

Make it easy on yourself, do the draw test as described (fully charged battery) to first determine if a draw is your problem; it's easy to do. It is possible the battery is faulty, as Blake pointed out, and there are tools to measure battery health, which would be step #2 if the draw test is okay. 

[Bench Racer]

Dave had a hart issue several weeks ago and is in recovery so may not be posting.

[DCP]

Voltage is not a measure of current being used (which is how a battery is depleted), but a measure of "electromotive force"; which is to say, the potential behind the current. If you are reading 6V, you might be only reading the potential voltage (unloaded) between two planes, which could be as simple as a backfeed/static reading, signifying little. Current is what you need to focus on here.

 

Make it easy on yourself, do the draw test as described (fully charged battery) to first determine if a draw is your problem; it's easy to do. It is possible the battery is faulty, as Blake pointed out, and there are tools to measure battery health, which would be step #2 if the draw test is okay. 

Dave: Thank you for your help. Electricity has always been a bit of a mystery to me; I will try that test.

 

Michael: Sorry. I didn't mean to hijack your thread.

[fishguyaz]

I also would say never assume that anything is good(working correctly) just because it is purchased new or just came out of a box.

test the battery, if it is bad, you just saved yourself a lot of time.

[Michael Colangelo]

OK, it appears that the issue was my misunderstanding on how this particular kill switch worked.  I contacted the shop that maintained this car prior to my ownership and it was confirmed that this kill switch WILL drain the battery if left in the OFF position.  Chalk it up to operator (me) error.  

 

The car has a new battery (thanks NAPA!) and I'm ready to go!  

 

Thanks for the insight, guys.  It never occurred to me that some kill switches operate this way.  It's a bit counter-intuitive, especially as the kill switch on my previous car (an ITA CRX) didn't do this.

[DCP]

OK, it appears that the issue was my misunderstanding on how this particular kill switch worked.  I contacted the shop that maintained this car prior to my ownership and it was confirmed that this kill switch WILL drain the battery if left in the OFF position.  Chalk it up to operator (me) error.  

 

The car has a new battery (thanks NAPA!) and I'm ready to go!  

 

Thanks for the insight, guys.  It never occurred to me that some kill switches operate this way.  It's a bit counter-intuitive, especially as the kill switch on my previous car (an ITA CRX) didn't do this.

Michael:  Which switch do you have? Does this mean you need to disconnect the battery each time you put the car in storage?

[LarryKing]

So, leave the switch on?

[DCP]

So, leave the switch on?

I have to disconnect the battery cable or I end up with a dead battery regardless of what what position my kill switch is in.

[Jim Boemler]

That indicates that while the switch may kill the engine (did you test that?), it's not really doing the job of protection that's intended -- that is, there's still electrcity available to start fires.  And in addition, it's not providing the secondary benefit you're hoping for here.  Time to rewire it.

[Jeff Wasilko]

A friend with a Miata had a similar issue, and it turned out to be a problem with how the cutoff was wired. Current was leaking to the starter.

[DES4]

I'm with Jim on this. My take on the GCR is that if the cutoff switch does not kill ALL power (quiescent draws included), it is not wired correctly. My understanding is that all electrical consumers must receive their power through/after the cutoff. 

 

Please straighten me out if I'm wrong.

[Michael Colangelo]

<p>Yeah, I'll check it out this weekend. &nbsp;I haven't owned the car that long and I'm still learning its idiosyncrasies. &nbsp;</p>
<p>&nbsp;</p>
<p>I'm unsure of the brand but hopefully can figure that out, too.</p>