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Cannot Find a High Parasitic Power Draw

 
  #1  
Old 05-19-2019, 01:02 PM
dlconley
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Cannot Find a High Parasitic Power Draw

I have a 2001 extended cab RWD, 4.2L F150 XLT with 110K miles. I am the original owner and have never installed any aftermarket electronic parts. It has a high parasitic power draw of around 4.7amps.I cannot figure out where it is coming from, or how to solve it.I have read more forum threads and watched more YouTube videos than I wanted to.From those, I have done the following:

1) Replaced the battery.Unplugged the under hood bulb.Closed all doors. And turned off all cabin lights before testing.

2) Looked for the parasitic draw by hooking my volt meter in series, between the negative battery post and its negative lead.I then opened up the fuse boxes under the hood, and under the driver side dashboard and pulled every fuse and relay, one by one looking for an amp drop.I didn’t see a drop on any of the circuits.I did it again, just in case.I got the same results.The parasitic draw is not connected to one of the main fuse boxes.

3) For full disclosure, I think I have an unrelated ABS issue.I isolated it from the parasitic draw by pulling the fuse 102 (50A) and pulling both ABS module connectors.The truck still has the 4.7A draw. (The issue with the ABS is a continuously running ABS pump, had a service replace the MOSFET chip, but ABS pump is still running.I am getting ready to open it and check the circuit board’s solder joints myself).

4) Finally, I pulled all three connectors from the alternator to isolate it from the battery.The battery still has the 4.7A draw.With the three connectors off, I did a quick checked of the diode from the post of the heavy lead to the frame of the alternator, and it had 870(?) ohms one way and OL the other way.

5) For the heck of it, I unhooked both battery terminals checked the ohms across the leads with the multimeter with the leads one way and then reversed them.The ohms in both cases were in the range of Mega-ohms when I first unhooked the battery. As the capacitors drained, the ohms between the leads also dropped in the truck.With a residual voltage of 0.08VDC, the ohms dropped to 630K ohms.So, it is looks like a circuit short and not a simple short to the frame.

Any suggestions of what to look at next? Or, should I take it to my local Ford dealer?

Thanks in advance,
David
 

Last edited by dlconley; 05-19-2019 at 01:04 PM. Reason: include misc info
  #2  
Old 05-19-2019, 02:20 PM
Bluegrass 7
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Pull the heavy lead off the Alternator, then recheck.
If the drain goes down, the Alternator either has shorted Diodes or the Regulator has the field winding turned on.
Good luck.
 
  #3  
Old 05-19-2019, 03:36 PM
projectSHO89
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Originally Posted by Bluegrass 7 View Post
Pull the heavy lead off the Alternator, then recheck.
If the drain goes down, the Alternator either has shorted Diodes or the Regulator has the field winding turned on.
Good luck.
See item #4 in the above list.
Any suggestions of what to look at next?
Hmmm.. Need to get a handle on which sub-circuit is at issue. Most expedient way I can think of is to pull the wires off the starter relay on the firewall and see which one of them "sparks" when you make/break the connection. Also, note that there are two ALWAYS HOT connections to the starter- one directly from the battery positive terminal, the other is on the starter relay post.

Miscellaneous note: Fuse F103 (50 A), in the underhood fuse box provides al power to the interior fusebox. Pulling it will make everything in interior box dead so that can split the circuit in half.

Your test #5 has significant possibility of either damaging your meter or causing results that are confusing. If you decide you want to repeat that test, disconnect the battery cables from the battery, then short the two (disconnected) cable ends together to discharge and capacitors that may be retaining a charge before making your resistance check.
 
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Old 05-19-2019, 05:08 PM
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I missed item 4.
Small print I guess.
Thanks.
 
  #5  
Old 05-19-2019, 08:07 PM
dlconley
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I was getting a P1000 code before and was told that that happens when you clear the trouble codes, and that I need to drive the truck for 15 miles.

After recharging the battery (I accidently left the battery connected), I took the truck out for a 20 mile trip. Everything ran, and worked great. However, I am still getting the P1000 code and still have the 4.7A drawn on the battery.

Good to know about the 103 fuse. I rechecked it again, but it didn't change in the draw.

I will check the starter relay tomorrow after work.
 
  #6  
Old 05-19-2019, 08:18 PM
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The P1000 will be the result every time you disconnect battery power. Ignore it while you are pursuing the parasitic draw.
 
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Old 05-20-2019, 04:47 PM
dlconley
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I took the leads off of the starter relay and isolated a red wire that has the 4.7A draw on it. It is the large, single red lead on the right side of the starter relay that goes up towards the top of the firewall. If it is connected to the red lead from the battery, I could measure the 4.7A draw. If It was disconnected, I dropped down to 0.26A draw. I am also assuming that the 0.26 draw will drop down to 0.05A, once the computers go to sleep.

Just to confirm, I hooked everything back up, except I left the large red wire out of the system and tried to crank the truck. Nothing happen. No dashboard lights, no starter relay clicking, and no starter motor.

I am assuming that the large, single red lead on the right side powers the starter motor and both fuse boxes (interior box via fuse 103).

Could the windings or something else in the starter motor be going bad, and causing the short?
 
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Old 05-20-2019, 07:28 PM
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I am assuming that the large, single red lead on the right side powers the starter motor and both fuse boxes (interior box via fuse 103).
No. That single wire would what feeds the underhood fusebox (which then sub-feeds the interior fusebox via F103) based on your reported results.

Pull F103 to disconnect the interior fusebox and test again. If the draw is still there, remove the fuses one at a time again (take a photo first!). I know you said you did this already, but the data suggests that something has been missed so it's a good idea to re-do the test.
 
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Old 05-20-2019, 09:12 PM
dlconley
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Got it. I will re-check the fuses tomorrow. Thanks again!!!
 
  #10  
Old 05-21-2019, 01:51 PM
paker
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I am puzzled. 4.7 A x 12.6 V = 60W. I cannot see this not causing a fire or a damage if shorted to ground. So some device or devices are using up the current as designed.
 
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Old 05-21-2019, 02:08 PM
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Originally Posted by paker View Post
I am puzzled. 4.7 A x 12.6 V = 60W. I cannot see this not causing a fire or a damage if shorted to ground. So some device or devices are using up the current as designed.
With everything turned off, the draw should be less then 50 mA after everything goes to sleep.

A 4.7A continuous draw will run the battery down in short order.
 
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Old 05-21-2019, 05:11 PM
dlconley
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I re- pulled all of the fuses and relays in the fuse box under the hood and still did not find the draw.

I suspected the large, single red lead on the right side of the starter relay to the fuse box as the culprit. I unhooked the large red lead from both ends and replaced it with a jumper between the two point to see if the draw goes away. It didn't go away. So, the large, single red lead is not the problem.

And, I still have the 4.7A draw thur the meter at the battery.

I also tried to look for a heat signature with a non-contact temperature gun. I didn't see anything. Any thoughts on where to aim it?
 
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Old 05-21-2019, 07:37 PM
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Well, disconnect the cables from the starter and see what happens. Be sure to disconnect battery first.

BTW, have you verified performance of your meter?
 
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Old 05-21-2019, 08:42 PM
dlconley
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Project,

First, I really appreciate your help!!!

When I was checking the Starter Relay, I isolated the draw to the large, red lead going to the fuse box. Am I looking for some power that runs through the fuse box and then to the starter motor? Or, just a bad starter?

Instead of checking each fuse, one at a time, I thought about pulling all fuses and relay out of the box at the same time and then looking for the draw. (I took a good picture of the fuses and the fuse box tonight.)

I have been using a Fluke 75 that I got back around 1988. I will test it against another meter. But, I think it is reliable.

Finally, I am very cautious around large batteries and large power tools. I must have hooked and unhooked the battery about 10 times tonight.

Thanks,
David
 
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Old 05-21-2019, 09:42 PM
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If you're absolutely positive that the red cable with the draw is the one to the fuse box and not the one to the starter, then skip the bit about disconnecting the cables at the starter. There are two red wires and I wanted to be sure that you haven't identified them backwards.There's not supposed to be any circuit path from the fuse box back to the starter motor. Can you easily isolate the power feed coming into the box and disconnect it? That would be a definite check of whether or not you're on the right cable.

I made the suggestion regarding the meter just to eliminate the possibility that you're chasing a false ghost due to a faulty meter. Don't ask my why or how I learned to do that...
 

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