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Discussion Starter · #1 · (Edited)
So recently I was going to drive the MK4 to work and had a dead battery. 10v showing. Charged the car overnight and drove it later that week, no problems. I was out of town for a week and tried to start the car again but this time the battery was completely dead. Just took battery to battery store and it seems to be testing just fine, which suggests there's a parasitic draw somewhere.

This is a new issue in the past 18 mo. Coincidentally, I did replace the fuse for my seat warmers just prior to this issue occurring. I have the heaters wired up to my radio wire in the RF harness. They are the cobra heat heaters and each have an individual switch that lights up when on. This parasitic draw is occurring with key off, heaters off. Any ideas? My clock and FiTech ECU are the only 2 things I can think of that are always on, but haven't experienced this issue until recently. Would a bad ignition switch cause this issue? But still, the seat heater switches are off. Should I try removing the radio fuse and see if this solves things? The radio has an always on draw for radio memory, but again wasn't an issue until I replaced the blown fuse. Any other ideas?

A bit more info, my seat heater grounds are attached to a kill switch that I also have my fuel pump relay ground connected to. The seat heaters and fuel pump are both disabled if this switch is turned off, which is often the case when the car is parked and turned off.

Last question...Is there an easier way to get the hold-down for the Breeze front battery box on by yourself? I have feeling that I'll need to get the car up on jacks and have a friend hold one end while we tighten the other.
 

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I assume when you see the Fitech is always on you mean it is direct wired to the battery but the small gauge trigger wire that actually powers it up is key switched, yes?
 

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Discussion Starter · #3 ·
I assume when you see the Fitech is always on you mean it is direct wired to the battery but the small gauge trigger wire that actually powers it up is key switched, yes?
yes, but I've also read that if the handheld is plugged in, it can be a source of parasitic draw. My handheld is not plugged in fyi.
 

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I’m not sure on the Ron Francis harness as I didn’t use one but what do you mean by the seat heaters being tied in to the radio wire? If I had to guess a wire used to supply power to a radio would be too thin to adequately power a pair of seat heaters. Regardless, I’d pull the fuse for the seat heaters anyway and see if you still have the parasitic draw
 

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Without seeing the wiring in front of me, here’s my theory:
If you have a fuse in line between the radio power feed coming out of the harness and before the heaters (meaning a fuse specifically for the heaters added in, not the fuse for the radio that is in the block as the harness came stock) I’d be curious what the amp rating is on the added fuse, the fuse rating in the block, and the gauge wire that is for the radio. I could see, depending on the gauge wire, the wire overheating and melting causing a short and battery drain. Depending on the amp rating of the fuse that could happen without blowing the fuse, so the protection isn’t there
 

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Discussion Starter · #6 ·
RF dash harness has power sources that not everyone will use (radio, heater, wipers, etc).
I have my seat heaters wired to the radio power source and my USB chargers to the wiper wire.
Both are connected to 10A fuses at the fuse box.
The cobra heat seat heaters require a 10A circuit and have a 10A fuse that I did not wire into the power wire for the seats (I figured the fuse at the panel would be easier to access than the fuse for the seat power as the wiring is inside the transmission tunnel.
I'm guessing the gauge of the RF wire is adequate for 10A as that is the stock configuration. The wires for the seats should also be sufficient for 10A as that's the stock inline fuse.
Additionally, the seat heaters resistance is approx 4ohms, and in the high setting, the voltage should be approx 13.5 v and half that in the low setting. I hope this additional info helps.
I can always remove my tunnel top and check out all the wires to make sure nothing melted and is grounding out.
 

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But you also have an actual radio too, yes? Is that wired on the same circuit or did you connect to another circuit in the RF harness?
 

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Discussion Starter · #8 ·
But you also have an actual radio too, yes? Is that wired on the same circuit or did you connect to another circuit in the RF harness?
no radio. just using the radio power wire for my heaters.
 

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I looked at the RF diagram. So your seats are wired directly into the radio power fuse, not the radio memory fuse? And either way the seat heaters are the only thing wired to that particular circuit correct? Are the seat heaters intended to be run on separate circuits or just one? (When you say heaters I’m thinking you mean for both the driver and passenger seat) if the spec on them is 4 ohm and checks out that way they should pull 3 maybe 3.5amps each.

your earlier thought to pull the radio fuse is where I’d start because it’s the simplest thing to do to narrow it down. Only drawback is it takes a long time to test it as in waiting to see if your battery dies. If the fuse pulled on the radio does fix it, I’d then inspect that wire from the fuse block right out to the heaters to look for melting/chaffing.
 

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Discussion Starter · #10 ·
I looked at the RF diagram. So your seats are wired directly into the radio power fuse, not the radio memory fuse? And either way the seat heaters are the only thing wired to that particular circuit correct? Are the seat heaters intended to be run on separate circuits or just one? (When you say heaters I’m thinking you mean for both the driver and passenger seat) if the spec on them is 4 ohm and checks out that way they should pull 3 maybe 3.5amps each.

your earlier thought to pull the radio fuse is where I’d start because it’s the simplest thing to do to narrow it down. Only drawback is it takes a long time to test it as in waiting to see if your battery dies. If the fuse pulled on the radio does fix it, I’d then inspect that wire from the fuse block right out to the heaters to look for melting/chaffing.
Sorry. Double checked and it's the wiper wire. Still a 10a power. Will plan on pulling fuse and see if this fixes the issue. If so, will investigate the wire more closely
 

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To help expedite things you should be testing your current draw using a meter in conjunction with removing fuses. You will see immediately if your current drops after removing a fuse. Seeing 40-50 mA with the key off is normal with a ecm and or radio installed. Anything above that could be you issue and I always recommend testing on the ground side of things. Hope this helps
 

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Discussion Starter · #13 ·
I know, right? Just seems coincidental that the issue started after I replaced a blown fuse for my seat warmers.
 

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As Chris mentioned 40-50mA is a normal acceptable drain. The only way to actually measure this is w/ an amp meter put in line w/ the battery +cable. Disconnect cable from battery and clamp one amp meter lead to the battery post and the other lead to the end of the cable. The downside is that usually you need a fairly expensive meter to measure this low current flow. W/ the meter in position you should see a drain of maybe a couple of amps. Start pulling fuses one at a time to see which fuse drops the drain to that 40-50mA. If no fuse does that, start disconnecting parts. I'd start w/ the alternator.
 

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Discussion Starter · #15 ·
thanks CraigS. could you point me in the right direction for a "good" multimeter? there are so many options. I'm not sure what to look for.
 

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My theory was based on it’s a heck of a coincidence that it started happening after blowing and then replacing a fuse. While the circuit is only potentially hot when keyed on, if it had over heated and caused melting or chaffing at some point (resulting in the blown fuse) then it could be causing a short or drain from a neighboring circuit where the wires melted together etc.
it could also be completely unrelated to the blown fuse, just again, heck of a coincidence
 

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How about a inline battery kill switch.Cuts power to Everything.And probably why my last (Cheap Battery) lasted 11 years in the Cobra:).
Automotive design Vehicle Speedometer Gauge Tachometer
 

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Discussion Starter · #19 ·
How about a inline battery kill switch.Cuts power to Everything.And probably why my last (Cheap Battery) lasted 11 years in the Cobra:). View attachment 365348
I do have a kill switch, but it does have a low amperage self resetting fuse bypass. This allows the clock and ECU to get constant power if key is removed, but will blow if someone tries to start the car leading to a surge in amperage.
 
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I know, right? Just seems coincidental that the issue started after I replaced a blown fuse for my seat warmers.
The big question is, why did that happen? The fuse blew for a reason. You shouldn't just replace the fuse and move on.
 
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