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Discussion Starter · #1 ·
Hello,

I have a 1994 ford mustang gt, and it has a parasitic power draw of .075 amps. I am not an expert mechanic, so please understand why what I have done so far could be ridiculous.

I traced the power draw to fuse #8 under the I/P panel using a voltmeter. Next, I began unplugging all items powered by this fuse that I could easily access with the voltmeter attached in series, looking for a drop. I disconnected the instrument cluster, the clock, the trunk light, the radio, and finally, the keyless entry module in the truck. With the keyless entry module unplugged, the power draw dropped to .01 amp. There are three plugs to the module; I only needed to unplug C402 (Black) which should have six wires. It had seven wires. I could not identify the 7th wire (it was connected on pin 8 or 7), but the other 6 I was able to identify. Last, I began back probing the wires. I found a .01 amp going through wire 296 (W/P) Ignition switch input. Nothing on the rest. I then cut the wires one by one. After cutting wire 397 (BK/W) Signal ground, the voltage dropped from .075 amp to .01 amp. I lost the operation of the items powered by this keyless entry module as well. It seems like I could of just unplugged this connector and avoided this cutting mess, but I was getting a little desperate. I will fix those wires.

Now I am stuck, not sure how to further track this issue down. I assume I need to start going through all the wiring and items that lost power when I disconnect the keyless entry module.

Any advice or help would be greatly appreciated. Let me know, please. Thanks.

-Jeff

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Hello,

I have a 1994 ford mustang gt, and it has a parasitic power draw of .075 amps. I am not an expert mechanic, so please understand why what I have done so far could be ridiculous.

I traced the power draw to fuse #8 under the I/P panel using a voltmeter. Next, I began unplugging all items powered by this fuse that I could easily access with the voltmeter attached in series, looking for a drop. I disconnected the instrument cluster, the clock, the trunk light, the radio, and finally, the keyless entry module in the truck. With the keyless entry module unplugged, the power draw dropped to .01 amp. There are three plugs to the module; I only needed to unplug C402 (Black) which should have six wires. It had seven wires. I could not identify the 7th wire (it was connected on pin 8 or 7), but the other 6 I was able to identify. Last, I began back probing the wires. I found a .01 amp going through wire 296 (W/P) Ignition switch input. Nothing on the rest. I then cut the wires one by one. After cutting wire 397 (BK/W) Signal ground, the voltage dropped from .075 amp to .01 amp. I lost the operation of the items powered by this keyless entry module as well. It seems like I could of just unplugged this connector and avoided this cutting mess, but I was getting a little desperate. I will fix those wires.

Now I am stuck, not sure how to further track this issue down. I assume I need to start going through all the wiring and items that lost power when I disconnect the keyless entry module.

Any advice or help would be greatly appreciated. Let me know, please. Thanks.

-Jeff

View attachment 782319 View attachment 782320 View attachment 782321
I also have a '94 GT, but fortunately it has no keyless entry. But my story kinda parallels yours, parasitic current which drained battery in about a week, amount of current flow I forget now. I failed to be able to trace the drain to it's source, but decided it had to be some item powered when key is OFF, IOW hot at all times. The car had a complex entertainment system installed when I got it, in addition to the factory Mach 460 thing. A big fuse had been added to a heavy cable running into the trunk area. As I am partially disabled, unable to squirm around in tight places anymore, I disconnected what I could, but still had a 0.100 amp drain, presumably a lamp somewhere (like glove box not shutting off) but I couldn't find it. So, I pulled an old 12V relay off my junk pile and wired it to feed the fuse carrying the parasitic drain, which also fed a bunch of other stuff, such that KEY ON energized the relay, and thus that fuse. No more battery drain.

Your keyless entry I know nothing about, except that I imagine it being only capable of unlocking the vehicle. If it feeds power in addition to that, to who knows what, I imagine I would try to get rid of it altogether. Just my thinkin'.
 

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Discussion Starter · #4 ·
I also have a '94 GT, but fortunately it has no keyless entry. But my story kinda parallels yours, parasitic current which drained battery in about a week, amount of current flow I forget now. I failed to be able to trace the drain to it's source, but decided it had to be some item powered when key is OFF, IOW hot at all times. The car had a complex entertainment system installed when I got it, in addition to the factory Mach 460 thing. A big fuse had been added to a heavy cable running into the trunk area. As I am partially disabled, unable to squirm around in tight places anymore, I disconnected what I could, but still had a 0.100 amp drain, presumably a lamp somewhere (like glove box not shutting off) but I couldn't find it. So, I pulled an old 12V relay off my junk pile and wired it to feed the fuse carrying the parasitic drain, which also fed a bunch of other stuff, such that KEY ON energized the relay, and thus that fuse. No more battery drain.

Your keyless entry I know nothing about, except that I imagine it being only capable of unlocking the vehicle. If it feeds power in addition to that, to who knows what, I imagine I would try to get rid of it altogether. Just my thinkin'.
I have considered removing the keyless since I don't really need it but if I can fix it that would be ideal.
 

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The module itself may be shorting out and causing the drain. In the diagrams I see outputs to various items so it could also be coming from one of those.
 

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Seems to me you did a good job isolating the issue. So swap out the module.

Did you mean to type "voltage" instead of "amps"?
 

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Discussion Starter · #7 ·
Seems to me you did a good job isolating the issue. So swap out the module.

Did you mean to type "voltage" instead of "amps"?
I swapped the module to another one, nothing changed. Luckily the person I bought the different module from let me return it. I used a multimeter on the 10a setting, not sure if I should be calling my reading of .07 amps voltage or not. Again I am not an expert by any means.
 

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I swapped the module to another one, nothing changed. Luckily the person I bought the different module from let me return it. I used a multimeter on the 10a setting, not sure if I should be calling my reading of .07 amps voltage or not. Again I am not an expert by any means.
Voltage is pressure, amperage is flow rate.

Normally what I do is measure the voltage across the pins in a fuse (voltage drop). Since the fuse is a restriction in the circuit, a drop in pressure (voltage) indicates flow in the circuit. The greater the flow and the smaller the fuse, the higher the pressure drop.

Since you know that the module is good, then the issue is likely in one of the seven wires that feed it. The ground wire may or may not be it. A ground merely completes the circuit to the other six that apply voltage to that module. To rule out the ground wire, use a test wire to connect it to a good known ground then recheck the voltage drop at the fuse.

Physically trace the wires from the module back to the source and look for broken insulation, swollen insulation or grey deposits that indicate arcing. Chances are this is where a loom passes through an opening, or at an active bending area, like at a door hinge.
 

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I swapped the module to another one, nothing changed. Luckily the person I bought the different module from let me return it. I used a multimeter on the 10a setting, not sure if I should be calling my reading of .07 amps voltage or not. Again I am not an expert by any means.
Since you changed the module out and voided that as a possibility did you check any of the other wire routings that go in/out to that module for a short? You should look for any exposed wire insulation hitting metal or another wire connection or at the end points like a bad lock switch, lock actuator, or bulb socket connection.
Also, I assume you repaired your cut wiring mistake and just left it unplugged?
 

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I am new member and by using search function came across this thread, I have exact same issue with my 27K Cobra and done the same , purchased replacement keyless entry module and still have draw only when plug C402 plugged to module, even when I have small black C401 & small gray C400 plug unhooked from module still has draw, any ideas on what to check next ? I removed Ford installed piggy back alarm system on acct they are know to kill battery members thoughts on next step ? Any help appreciated !
 

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In the above supplied diagrams C402 has the Power(hot at all times) feed to the remote keyless entry module. This is supplying power to whatever the short/power draw is.
It also has the output to Anti Theft module and whatever Program B is as well. I would bet that wherever it is the short has to do with one of those two leads.
 

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Youll have to isolate the harness wires you wanna check from power/ground to do the following test,but it will tell you whether the wires themselves are shorted between each other or not.Once you disconnect the harness/wires at both ends of the circuit,set a multimeter to read ohms,touch the red multimeter lead to the power wire and the black lead to every other wire thats part of that harness.Each two wire test should show 10k ohms or higher.If the power wire & an adjacent wire read lower,that usually indicates the short is present between the two wires being tested,i.e.- likely from worn through insulation on both.
 

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When you were doing your draw test did you latch any open doors so the switches to the entry module would be triggered to sleep mode? The 402 connector in my 1994 wiring diagram shows a 7th wire 465 WHT/LT BLU on pin # 10 for Door Handle IN. Does your 402 connector wire colors match the pin out in your diagram shown, as my wiring diagram for that connector matches a 1995 Mustang. That 465 wire would go to pin #7 in my 1995 diagram. Maybe you have a late build 1994 or my wiring diagram is off. :unsure:
 
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