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Old 04-23-2017, 09:28 AM   #1
Raf99
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Parasitic Draw on master lock fuse

Hi,

So I narrowed down a parasitic draw on the power lock fuse (#27). It was drawing 12v and when i unplug the power control lock module in the drivers side door all volts go to zero. Does anyone have any experience with this? Should I just replace the module or could the door lock motors be causing this? I tried following this but didn't get too far. Didn't see the point of testing the lock motors when i know they work fine. Been reading for a while on it and some say to just replace the unit.

- All doors lock and unlock just fine.
- Unplugging the switches has no affect
- I'm thinking the relays on the unit are draining the power, but wouldn't this imply that the door locks would not work or would want to stay locked all the time?

Any thoughts?

Last edited by Raf99; 04-23-2017 at 03:19 PM.
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Old 04-23-2017, 10:17 AM   #2
sonikaccord
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Fuse #27 is the Battery input to the door lock control unit.
The door lock switches control the power to the relays inside of the control unit, so you could potentially have a faulty switch, however, if that were the case then you would have a door lock that is not responsive.

When you unplug the lock module, you get 0 volts where? on the output side of the fuse? Does your meter have an ammeter function? That would be more accurate in determining an unwanted current draw.
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Old 04-23-2017, 02:15 PM   #3
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Quote:
Originally Posted by sonikaccord View Post
Fuse #27 is the Battery input to the door lock control unit.
The door lock switches control the power to the relays inside of the control unit, so you could potentially have a faulty switch, however, if that were the case then you would have a door lock that is not responsive.

When you unplug the lock module, you get 0 volts where? on the output side of the fuse? Does your meter have an ammeter function? That would be more accurate in determining an unwanted current draw.
I have the meter inline on the negative battery terminal. There is where I am reading 12V and when unplugged drops to 0V. Also I get 12V on the white wire for the plug to the control module on the door itself. Now i realize the wire should be live 12V to unlock doors with key out, but with the unit connected I shouldn't get 12V still at the battery (meter in line).

The module looks fine, and i re-soldered the relay joints for giggles. No change. Just not sure how to proceed. I could disconnect the lock motors or maybe test the relays by giving them power (although my locks work fine).

edit: yep, it was fuse 27, not 29.

Last edited by Raf99; 04-23-2017 at 03:19 PM.
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Old 04-24-2017, 08:21 PM   #4
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Inline on the negative battery terminal? Can you clarify that for me, I'm having a slow moment. Your black probe is on the negative terminal and your red probe is on the white wire?

The white wire should always have 12 volts as it is connected to the ignition switch.
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Old 04-24-2017, 08:39 PM   #5
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Quote:
Originally Posted by sonikaccord View Post
Inline on the negative battery terminal? Can you clarify that for me, I'm having a slow moment. Your black probe is on the negative terminal and your red probe is on the white wire?

The white wire should always have 12 volts as it is connected to the ignition switch.
Umm, Yep, this. Black on negative terminal and red on the connector for that terminal. Using DCV scale set to 20 will do. My condenser wire pulls 0.7, but that's another story plus I don't have AC. But this drivers power lock unit pulls 12V, like it's stuck on. Pretty annoying....
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Old 04-25-2017, 04:58 PM   #6
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Thinking I'm just going to order a new unit...
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Old 04-25-2017, 09:54 PM   #7
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Ok. Had a chance to see the video. A couple of discrepancies between Eric's method and your method.

You are using voltage to measure a "draw." This can be accurate in some cases, but not this one.

In order to see if the door lock module is drawing excessive current, you'd have to ground pin 4 of the lock module, put your black probe (or red probe, can't think of the right orientation...either way the only difference you'll see is a negative sign) on pin 12 of the harness and the other probe on pin 12 of the door lock module. Then you can read the current draw. It should be milliamps of current.
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Old 04-28-2017, 03:43 AM   #8
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Quote:
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Ok. Had a chance to see the video. A couple of discrepancies between Eric's method and your method.

You are using voltage to measure a "draw." This can be accurate in some cases, but not this one.

In order to see if the door lock module is drawing excessive current, you'd have to ground pin 4 of the lock module, put your black probe (or red probe, can't think of the right orientation...either way the only difference you'll see is a negative sign) on pin 12 of the harness and the other probe on pin 12 of the door lock module. Then you can read the current draw. It should be milliamps of current.
Hmmmm.
I don't think it's going to matter where i "tone" the draw, whether it's at the battery, the fuse, or at the wires itself (pins).
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Old 04-28-2017, 08:33 AM   #9
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Raf I think what Sonik is saying is that you need to measure the actual draw from that circuit. Yes it has 12v going to it. How do you expect your door locks to work without power? The thing is it might only be drawing the tiniest current while just sitting but at 12v. Your really looking for how much amperage is being drawn, like Sonik said it should only be in the milliamp range. This is one of the items that will slowly kill the battery over time, the same as the clock draws power all the time to keep the time correct.
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Old 04-28-2017, 09:04 AM   #10
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Raf I think what Sonik is saying is that you need to measure the actual draw from that circuit. Yes it has 12v going to it. How do you expect your door locks to work without power? The thing is it might only be drawing the tiniest current while just sitting but at 12v. Your really looking for how much amperage is being drawn, like Sonik said it should only be in the milliamp range. This is one of the items that will slowly kill the battery over time, the same as the clock draws power all the time to keep the time correct.
Ya, so this is why i started the thread. I understand what you are saying as I have my AC condenser fuse pulling 0.5 amps. I may be backwards on this but so far I don't think I am. If you put a multimeter in-line on your battery do you see 12V? I'm guessing no. Having 12V supplied to the control unit is expected but the draw should be 0V until the relay switches on for the door lock. Until then the draw should be 0V. Hence the relay is completing the circuit.
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Old 04-28-2017, 03:54 PM   #11
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If your multimeter has a ammeter, read that with the meter inserted between either terminal and its respective cable to read the actual current.
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Old 04-28-2017, 05:12 PM   #12
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The door lock module white wire has 12v at all times. The only way it could be 0v is if there is an open wire or your black probe is on a 12v line.

How are you measuring the condenser current? In the same way?
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Old 04-29-2017, 06:04 AM   #13
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well.......... i feel like an idiot.....

It was the meter setting I was using. You folks were right. 0.01amp draw now with everything plugged in. And open a door and get a 0.6amp draw from the door light.

Ug........
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Old 04-29-2017, 02:22 PM   #14
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No worries man. We all miss the simple stuff sometimes, even when it's staring us in the face.
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Old 04-29-2017, 04:47 PM   #15
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That's cool. I think we've all been in that situation.

10mA looks like a normal draw, nothing I would consider parasitic. The search continues?
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Old 04-29-2017, 07:46 PM   #16
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We are down to 0.04ma with everything plugged back in. So just me making mistakes the whole time. Thanks everyone for their help.
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