My truck has a 4.2 amp parasitic drain. I pulled the negative cable and put my multimeter in line. Pulled every fuse (actually everything that would plug into a fuse box) under the hood and inside in the passenger footwell and never saw a change (disappointing). I went back under the hood and started to pull the wires on the positive post of the truck to see what would happen. I do not have a wiring diagram so I am not sure where all the main wires go but #1 goes to the fuse box under the hood atop the radiator. If you remove wires 1, 3, 4 the draw is gone. If you connect any one, or combination of 1, 3, 4 you will find the load again.
I have an OBD reader but it shows no fault codes.
Now this thing does some other weird stuff. On occasion when driving down the road the speedometer will go to Zero mph while you are running at highway speed. When that happens things like the cruise control will quit. Sometimes when this happens you will also get a large orange wrench graphic on the dashboard where the fuel economy would normally be.
Do your same test... With a multimeter in line... But pull fuses one at a time to see which one changes the draw... That will help you isolate what is doing it. If you pull a fuse and nothing changes, put it back in and move on to the next one.
Hi Les, That is how I did my test. I pulled then replaced each fuse to see if there was a change and then went to the next one and did the same. No fuse caused a change in the reading. The only thing that changed a reading as removing wires 1, 3, 4.
Alternators can produce current with a diode that is on its way out. They’re like a one way switch but also convert AC current to DC current. In certain circumstances a leaking diode will result in an alternator being warm when the vehicle is sitting. Many shops and parts stores have equipment that will easily detect a bad diode.
Here’s a description I pulled from another site:
Usually, a bad alternator diode will cause your headlights or instrument panel lights to flicker or dim and, sometimes, drain battery power overnight, or in minutes.
To check for a possible bad alternator diode, switch your voltmeter to a low setting on the AC (alternating current) voltage scale.
With the engine running, touch the meter probes to the battery terminals.
Your voltmeter should read 0 AC volts.
Any amount of AC voltage would indicate a bad diode, so you'll need to replace the alternator.
Alternators can produce current with a diode that is on its way out. They’re like a one way switch but also convert AC current to DC current. In certain circumstances a leaking diode will result in an alternator being warm when the vehicle is sitting. Many shops and parts stores have equipment that will easily detect a bad diode.
Here’s a description I pulled from another site:
Usually, a bad alternator diode will cause your headlights or instrument panel lights to flicker or dim and, sometimes, drain battery power overnight, or in minutes.
To check for a possible bad alternator diode, switch your voltmeter to a low setting on the AC (alternating current) voltage scale.
With the engine running, touch the meter probes to the battery terminals.
Your voltmeter should read 0 AC volts.
Any amount of AC voltage would indicate a bad diode, so you'll need to replace the alternator.
Do your same test... With a multimeter in line... But pull fuses one at a time to see which one changes the draw... That will help you isolate what is doing it. If you pull a fuse and nothing changes, put it back in and move on to the next one.
Yessir. If it plugged in I pulled it one at a time. I actually did this twice, once solo, and once with my trusty dad who is pretty sharp mechanically too. Both times no changes to amp draw pulling every fuse one at a time.
I believe there are only two, One underhood mounted near the radiator, and the other in the front passenger footwell. If I missed one please let me know.
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