parasitic draw

2002 ford pickup Voltage drop test shows a draw Pulled every fuse and relay under dash and hood nothing stopped the draw measured draw at 5.8 amps for 5 second, then it dropped to 4.6 V. Repeated many times. always 5 seconds then the drop. any ideas?Oklahoma

Any thing else on the vehicle, after market; amps? inverter?

No extras, inverters or aftermarket anything. Battery top is clean and dry. I am trying to think of non fused possibilities, alternator diodes come to mind, and I will test this next, but I cannot see how this fits with the 5 second change in amp draw. If I remove alternator output wire and check the draw, would this eliminate diodes as the problem?Oklahoma

Yes, but you should disconnect the battery whilst removing and replacing it (+ve or -ve terminal but -ve is the norm). Else make sure the +ve alternator lead and spanner does NOT touch the engine or GND!

And when you say it dropped to 4.6V what & where - at the fuse, across a resistor, at the load? I'd reckon the only 5.8A draw could be a motor - maybe ensuring windows are up or some other "return to home" system (canopy; personalised seating; cycle electric water pump; vent the catalytic converter; EMS shutdown; etc.

Thank you all. I am new to forums and somehow one of my follow up posts did not appear. I removed battery + and then the alternator output connection. then I put an amp meter inline between the bat + and Battery + cable again. The draw has changed. The flow has dropped to 2.4 amps where it had been 5.8 before alt output was disconnected. The intriguing reading happened precisely 5 second later. Flow dropped from 2.4 to 1.2 amps. Every time I disconnected the meter lead from Battery+ and reconnected, it would read 2.4 amps for precisely 5 sec, then drop to the 1.2 amps and hold there. Recall before the alt output was disconnected we started with 5.8 amps that would drop to 4.6 after exactly 5 seconds. At this point I believe I can condemn alternator diodes and replace alternator and test again. I am still confused by the 5 second syndrome and cannot imagine how this relates to alt diodes. Such is my lot in life that I have made so many mechanics say the same thing. "never seen that before". I am an old school mechanic and value simplicity. Anyone have a theory to this puzzle? Might I be dealing with something besides Alt problem or 2 problems at the same time. Some days I just miss my "model A".Oklahoma

Capacitive effect????

What extras have been added - alarm, audio etc?

good question There are absolutely no added electronics, inverters or anything. everything is factory. This is a 2002, first year "King Ranch" f150, so it is loaded with options. Battery is fully charged. Nothing has ever triggered the check engine light.Oklahoma

I was just thinking - you "must" be able to determine it's fuse/cable source. If you pulled all fuses, it must be a direct connect - eg, stater heavy cable (or something running off that from the starter?), and the alternator on older vehicles (eg, especially if unfused). Ensure ALL fuses are pulled, then replace one at a time in case it's a thing that takes multiple feeds. I'd pull the master fuses (fuselinks) first if they exist. If one solves the problem, THEN drill into the individual fuses of its downstream fusebox (if any) or any direct feeds. Also do the alternator with all its wires disconnected - maybe its voltage sense circuit is playing up. If it's an older external regulator alternator, disconnect the regulator's connector (ditto - sense and charge light circuits are to/from the regulator).    Certainly IMO 1A and higher is not a "parasitic" load - that's a load! It's equivalent to a 10W bulb, & 5A is a headlight or equivalent (50-60W). Maybe even the heat from the problem can be felt or found if it's a point load - ie, not distributed along a cable. Interesting that alternator disconnection halved the current... (... temporarily? )