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post #1 of 8 (permalink) Old 03-21-2018, 04:27 PM Thread Starter
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Parasitic Current Draw Normal or ???

I have a 1997 4.6L Thunderbird. Iím measuring a parasitic current drain of 83ma as measured by a digital amp meter in series with the negative battery cable. When I pull fuse # 7 in the high current fuse panel (under the hood and adjacent to the battery) the parasitic current drops down to 8-13 ma. Everything is stock except the stereo electronics but that is on a different circuit and is only drawing about 3 ma. Fuse #7 which is responsible for the bulk of the parasitic current, controls these circuits: Main lights, Courtesy lamps, RKE Module, Integrated Control module (ICM), Power Mirror, Auto Lamp, Air Bag Diagnostic Monitor.

On plugging fuse #7 back in, the parasitic current goes back to 83ma as expected but 45 minutes after plugging fuse #7 back in, the parasitic current drops to 10-20ma range. I checked every 15 mins to find that current unchanged. However, at one point I checked to find that 300ma fuse in my DVM was blown indicating the current spiked above that point for at least an instant. I had to re-start the measurements using the 20 Amp scale on the DVM.
My guess is that there probably isnít anything wrong here. The ICM (same as PCM?) probably does a bunch of initializations and smog tests for I guess 45-mins before it goes into a lower power state drawing 10-20ma which is not bad. Not sure how to explain the apparent spike that blew the 300ma fuse except maybe the ICM woke up briefly to do who knows what causing a higher current draw.
I was motivated to run this test because after a day or three of sitting parked, my battery drops down to 12.3 to 12.5 volts which seems like its loosing some charge.
Can anyone respond to what Iím seeing to let me know if the parasitic current seems normal or not normal for this car??
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post #2 of 8 (permalink) Old 03-21-2018, 04:35 PM
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Those numbers seem reasonable.

The ICM is I believe the ICRM, which is integrated control relay module.

It runs a bunch of solenoids, and the fans, so it draws a shitload of power when running anything.

A relay contact that's going bad could make it draw more power when off, but it wouldn't be a few mA.

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post #3 of 8 (permalink) Old 03-21-2018, 04:55 PM
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I believe the specification for normal key-off drain is <50 mA. That 83 mA is somehwat concerning, but the way it drops back down suggests that it's probably not going to leave you with a dead battery anytime soon.

That's curious, though. I wonder if there's there any chance that the RKE module is picking up an errant signal and briefly sending lock or unlock voltage to the door lock motors. That could explain the spike.

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post #4 of 8 (permalink) Old 03-21-2018, 05:16 PM
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Quote:
Originally Posted by Grog6 View Post
Those numbers seem reasonable.

The ICM is I believe the ICRM, which is integrated control relay module.

It runs a bunch of solenoids, and the fans, so it draws a shitload of power when running anything.

A relay contact that's going bad could make it draw more power when off, but it wouldn't be a few mA.
The ICM is NOT the IRCM, the ICM is that little box attached to the primary junction block (the interior fuse box). It's what controls the interior lamps and also is the source of the *chime* you hear.


The RKE box has a battery saver feature that will automatically cut power to the ICM after a period of time - 45 minutes sounds about right - so if the door or glove box is accidentally left open, or a dome light is left on, they can't drain the battery overnight, and since it has a relay keeping this circuit closed for that period of time it will be drawing a bit of current until it opens.

Plus the clock, PCM and stereo will draw a small amount of current for memory as well.

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post #5 of 8 (permalink) Old 03-21-2018, 06:31 PM Thread Starter
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Thanks for all the help. Here is a link about ICM which sounds consistent with what XR7-4.6 describes:
https://www.justanswer.com/ford/0vv3...e-located.html
Itís for a 1995 but itís the same idea. One thing I noticed was after 45-mins when the current drops to 10-20 ma, neither the interior dome light or glove box light work which is also consistent XR7ís explanation. I didn't try anything else and I didn't open any door either. I suspect opening a door would wake up the ICM and energize these lights. The fact that the current drops down smartly at 45 mins repeatedly, suggests to me that it is by design and consistent with the purpose of the ICM to protect against interior lights left on as XR7 described. However, 10-20 ma over 3 days is ~0.5% of the battery capacity so I wouldn't expect much of a change from the 12.7 v full charge reading. Instead I often read in the range of 12.3 to 12.5 volts after its parked for that time. Maybe the battery is aging or maybe its normal when under an 83ma draw, just not sure. Iím also a little mystified about that apparent momentary current spike which I didnít get to see in real time, just the result. I donít think the RKE would respond to a wayward signal by activating the door lock as per post #3. It needs to see a unique and long digital code before activating the door lock. The RKE will hear other codes but take no action.
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post #6 of 8 (permalink) Old 03-21-2018, 07:30 PM
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Quote:
Originally Posted by XR7-4.6 View Post
The ICM is NOT the IRCM, the ICM is that little box attached to the primary junction block (the interior fuse box). It's what controls the interior lamps and also is the source of the *chime* you hear.


The RKE box has a battery saver feature that will automatically cut power to the ICM after a period of time - 45 minutes sounds about right - so if the door or glove box is accidentally left open, or a dome light is left on, they can't drain the battery overnight, and since it has a relay keeping this circuit closed for that period of time it will be drawing a bit of current until it opens.

Plus the clock, PCM and stereo will draw a small amount of current for memory as well.
That's a completely different box than I thought, sorry.

These numbers seem pretty good; our batteries are ~750 AH, so they really should run 1A for at least 200 hours, without any issues.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
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post #7 of 8 (permalink) Old 03-21-2018, 08:49 PM Thread Starter
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Quote:
Originally Posted by Grog6 View Post
...our batteries are ~750 AH, so they really should run 1A for at least 200 hours, without any issues.
I think you meant 750 CCA. Very different from AH. Mine is 850 CCA Interstate battery. I'm estimating ~100AH based on Peukert's Law and its specified Reserve Capacity (RC) of 150 (minutes). I think part or all of the reason the battery measures a little low after a few days of sitting is the moment I opened the door to get at the cigarette lighter to measure it, the parasitic current bumps up to 83ma thus making the voltage sink a little from a true open circuit reading. Its either that or my battery is on the way out. I think if I want to get a measurement I can hang my hat on, I need to disconnect the battery, charge it, and let it sit for awhile and then do a real open circuit voltage reading. Might be more trouble than its worth now that i know the car is not parasitically draining the battery!
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post #8 of 8 (permalink) Old 03-21-2018, 09:23 PM
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Have you checked the water level, or did an equalizing charge?

I'd start there.

EDIT: No, I meant AH, that's the measure of capacity.

After some checking, batteries really suck these days, mostly.

Only Interstate actually still quoted Ah, and that was on an older battery design.

You could be right, tho; I need to check the new battery that's in Lazarus; I tend to run a lot of things from batteries.

Reserve is not Ah; it's RC* .4167 of it, apparently.

The last battery I had in the Subaru barely fit; it was 1000Ah, and custom mounted. But it would run the Alpine just fine.
This was ~1090 or so, lol.

Batteries suck now, apparently.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, ďMost Outrageous DiversionĒ by MSNBC for this quote

Last edited by Grog6; 03-21-2018 at 09:44 PM.
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