Power draw?

08hybridok · Oct 17, 2016

So passing on the ranger to the youngest kid; it's had it's share of electrical issues; but lately seems pretty stable.

So this weekend we swapped out the radio for an upgrade; everything seems fine. Drive around the next day, still good, so he goes to school today, started fine this morning; but battery was dead after school, jump started just fine; then it was dead again after practice (4hrs later); again jump, drive home.

I go out to look it over, figure he left the headlights on or something stupid; nothing obvious, go to start it (5 min after driving) and it's dead, ~9.5V, battery is only like 3-4 months old

So I put the meter into Amps, and key out, doors closed, lights off I'm seeing a .33 - .5A draw (it switches back & forth but stays on .5 most of the time)
I assume the computers need some power, but that much? With the door open (dome light on) it draws ~2.5A

Disconnected the radio completely (well removed the cable harness from the back of the radio) and its still drawing .5A

Before just pulling random fuses, any suggestions where to start?

Running its reading 14.5V, so Alt should be good

RonD · Oct 18, 2016

Whats battery voltage with engine off?

12.3v to 12.8v is OK, under 12.2v is failing battery

When car batteries are run down they don't come back to 100%, no matter how new they are.
They are not designed for that, they have thin plates.
Deep Cycle batteries are made for that, they have thick plates.

Having many thin plates allows more AMPS to be delivered quickly than fewer thick plates, but also makes them short internally if run down too often.
So don't take battery off the table because it is newer.
And if still under full warranty I would exchange it just because it has been run down at least twice.

Unhook battery from vehicle and put a volt meter on it, if voltage is dropping while meter is attached then it has an internal short, for sure, exchange it

Your 1999 Ranger will have a Battery Saver Relay, it stays closed after key is off and doors are closed for 20-30 minutes, it will then open and cut power to most of the cab electrics, to "save the battery" if something was left on.

The GEM(generic electronic module) controls and has the timer that opens and closes the battery saver relay.

The battery saver relay circuit makes it hard to test amp draw because GEM will be on and drawing power until timer turns it off and battery saver relay opens.

Spec amp draw after battery saver relay opens is .03 to .07, .05 is average, so .5 is, of course, too high, but not unusual if battery saver relay is closed and GEM is still on.
The .05A is the KAM(keep alive memory) for computer, radio clock/presets and then the power for RAP module if you have keyless entry, that's all that's on after battery saver relay opens and cuts power

The GEM and battery saver relay are usually located behind the radio, so............

Maybe something got unplugged when installing the new radio

08hybridok · Oct 20, 2016

Thanks, Batt tested bad cell; got it replaced

Still pulling .4-.5A with original GEM; put a junkyard GEM in, drops to .2A and .01 after 30min

So either problem with the GEM; or something that the new GEM doesn't control, ie the new one I have no power windows; but as far I can tell everything else works. Haven't test driven yet to see how it shifts.

RonD · Oct 20, 2016

GEM doesn't control automatic trans, Computer(PCM) does that.
GEM does control 4WD shifting on some years.

So I assume GEM timer circuit quit working on the old one.
.01A is pretty low, I assume no keyless entry either?

Power draw?

08hybridok

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RonD

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08hybridok

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RonD

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