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Old 10-30-2008, 05:28 PM   #1
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Default This parasitic power draw has me running in circles.

So 5 weeks ago my battery started draining while sitting, the Miata usually sits for two weeks without being driven. I thought someone left my key on the first time, so I jumped it and went to the track, but the next time I knew I had the key off and no one moved it.

Tested power draw, there is a 30mA draw with everything OFF. IIRC you want no more than 4mA, so that is obviously way high and the cause of my slow drain. I started pulling fuses and relays and found this:

Pull the BTN fuse, drops low enough for me to not care (maybe 1mA)
Pull the 10A meter (I think) fuse from the under dash fuse block, draw drops to around 1mA as well. This must just also be on the BTN circuit.

I found that something on my injector circuit is causing the 1mA power draw, thats another story but for now I am not concerned, that won't drain my battery. Just trying to figure out where the 29mA is coming from.

Anyways I got more into it and unplugged EVERY connector on the car that I could think of, and there is one connector under the steering column that that appears to have the culprit on its circuit. Unplugged it and draw dropped to 1mA, now I'm getting somewhere.

I attached a pic of the connector, does anyone know what is on this plug? I am at a dead end right now, I've seriously unplugged everything I could think of, I am beginning to think that it is a wiring problem.. I'll start looking through the wiring diagrams tonight.
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This parasitic power draw has me running in circles.-photo-6-.jpg   This parasitic power draw has me running in circles.-photo-7-.jpg   This parasitic power draw has me running in circles.-photo-8-.jpg  
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Old 10-31-2008, 02:23 AM   #2
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Found it.
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Old 10-31-2008, 02:27 AM   #3
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What was it?
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Old 10-31-2008, 03:06 AM   #4
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Yeah...talk about a cliffhanger.
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Old 10-31-2008, 03:17 AM   #5
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Found it.
Noooooooo, don't tell us! It's way more fun, if we search for ourselfs...

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Old 10-31-2008, 09:41 AM   #6
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I have that connector in my car too, figure out what thats for?

Also, what was causing the draw?
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Old 10-31-2008, 10:27 AM   #7
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Ha sorry guys, didn't mean to leave a cliff hanger, I was dead tired last night. It was something I did, well something I installed. My POS GlowShift (AKA ProSport) boost gauge was the culprit. Pulled it out and guess what, no more draw! Bench tested it and sure enough it was drawing 29mA. Thats what I get for going cheap.

That connector goes to the dash harness, I did figure that much out. I just happened to tap my power wire off the radio harness (Which is apparently on that harness as well) when I installed it a year ago, hence the drop when I unplugged the connector or the meter fuse. This is why you should run dedicated power and grounds!
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Old 10-31-2008, 11:37 AM   #8
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Interesting ... I've got a the same problem, and have the same gauges. Been fighting it with a 2A trickle charger. Guess I'll have to look into the gauge wiring. :(
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Old 10-31-2008, 12:10 PM   #9
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FYI, the connector in question is one of many "common connectors" which, on the factory diagrams, are the ones labeled with an X.

The car does not have one large harness. Instead, it consists of several sub-harnesses which join together at these points. Some of these harnesses are quite large- the "front" harness, the "rear" harness, the "engine" harness, and the "instrument" harness for instance, which others are quite simple, like the injection harness and the one for the speakers.

Here's an example from the '92 FSM of an interconnection between the Front and Rear harnesses:

I've highlighted where it says "X14", which is referring to the fact that this interconnection takes in place in Common Connector X14. In total, that connector has 9 wires on it, so it's passing more than just this circuit. You can see in parenthesis that the wires on the top say (F), indicating that they're part of the Front harness, and on the bottom (R) indicating that they're part of the rear harness.

Here's a pictoral diagram of the major harnesses in the '92, and where they are physically routed. As you can see, the so-called Engine harness goes all the way to the back, so names can be deceiving:


Also, note that the Common Connectors are specifically pointed out. My guess is that you were on X-17 (or whatever the '94 equivalent of it is) which as you can see is called out in both the Front and Instrument diagrams.
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Old 11-01-2008, 03:10 AM   #10
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Quote:
Originally Posted by jayc72 View Post
Interesting ... I've got a the same problem, and have the same gauges. Been fighting it with a 2A trickle charger. Guess I'll have to look into the gauge wiring. :(
Definately look into it. This is the wierd part, while I had ground and constant hooked up to the gauge, the ignition input wire was outputting .5v. Try testing for that, or simply disconnect your negative battery cable, run a DVOM in series with the negative terminal and negative cable on amps and see if your draw goes away when you disconnect the gauges.

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Originally Posted by Joe Perez View Post
FYI, the connector in question is one of many "common connectors" which, on the factory diagrams, are the ones labeled with an X.

Also, note that the Common Connectors are specifically pointed out. My guess is that you were on X-17 (or whatever the '94 equivalent of it is) which as you can see is called out in both the Front and Instrument diagrams.
For some odd reason, I didn't come across that when looking through the FSM. Thanks for the info!
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