Mechanics

I CANT

2001 Jeep Grand Cherokee • 100 miles

After doing a draw on the battery drain, I removed the jb 50 amp fuse in the junction box under the hood, then I later found out that its the power source, so its like taking the battery off, I then decided to pull out fuses from the fuseblock under the dash, and found a.23 ampere draw. I jammed the door latch so the truck thinks its closed an hr before I started.I have two fuses that pull power. When I pulled fuse #8 the draw dropped to.17 when I pulled fuse #7 it dropped further down to 0.02. The weird thing to me is when I insert #8 back in the draw stays normal, but as soon as I insert #7 it goes back up and I have to remove both fuses to bring the draw back down.I then checked and found out its the interior light fuse (#7) and the other (8) was to power locks or something of that matter.I was wondering if you could steer me in the right direction. The car was under fl hot sun for two years without a hood. Any help would be greatly appreciated.
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Velcro6996
January 2, 2012.



I don't understand. By.23 ampere, do you mean less than a quarter of an amp? With a parasitic draw like this, I'm guessing you either have the stereo disconnected or have no stereo? And have no alarm system? And have disconnected the computer?

The 3 systems above will generate at a minimum almost 1 Amp of parasitic draw.
If your battery is dying, I suggest replacing it.

Rivermikerat
Jan 2, 2012.
I did replace the battery, the meter reads 230 milliamps with the car in sleep mode, isnt this a parastic draw from the systems inline with those specific fuses?

Tiny
Velcro6996
Jan 2, 2012.
According to my reference, fuse #8 is the power door locks and keyless entry system, which requires a memory function and transceiver power.
Fuse #7 powers the daytime running lamp module, the headlight switch, and the headlight delay timer. Again, constant power.

I misspoke. Parasitic draw is a current draw that isn't normal. All of the current draw I've mentioned is normal. You should be able to allow less than a quarter of an amp worth of draw for well over a week without experiencing any loss of starting ability from your battery. If you are, the battery is defective or the wrong battery for the vehicle.

Rivermikerat
Jan 2, 2012.
I got the battery from autozone and got it tested and it was fine, and is the right battery for the jeep. From what ive heard 30 to 50 milliamps is ok but not 230.I dont know what else to do. The truck drains overnight.

Tiny
Velcro6996
Jan 2, 2012.
The stereo in my Escort draws almost half an amp. Full time. My alarm draws about a quarter of an amp, full time. I've gone 3-5 days without starting the car and had no problems.

Have you had a starter draw test performed? If so, what was the starter drawing? How many Cold Cranking Amps is the battery capable of supplying? Battery reserve capacity?

Rivermikerat
Jan 2, 2012.
Hi guys. I've been following this to learn the fix. Velcro6996 is correct about the limit for a draw. Once the computers go to sleep mode, which can take up to 20 minutes, unless the manufacturer states differently, 35 milliamps, (.035 amps) is the industry-accepted maximum allowable drain. At that rate, Chrysler guarantees the engine will start after sitting for three weeks.

A three quarter amp draw will kill most batteries overnight. No radio memory circuit will draw more than a few milliamps unless it is purposely wired to keep it on all the time. There's no reason to do that.

Velcro6996, how are you doing the draw test? I see you're familiar with the need to go to sleep mode, but many people don't realize doing anything to momentarily break the circuit wakes the computers up, so you have to wait another 20 minutes. Switching the range on a digital meter in series with a battery cable breaks the circuit for an instant. That's enough to cause a problem. What you need to do is bypass the meter leads with a jumper wire anytime you want to switch ranges, then you can remove the jumper and read the meter. If you don't use a jumper wire when switching to a lower scale, the meter will read over-range until the computers go to sleep mode. The meter does not have to remain turned on. Turning it off doesn't break the circuit.

You must use the jumper wire too on meters that use a separate jack for the 10 amp scale. Some meters use an internal 2 amp fuse for the lower scales. Starting out on that scale can blow that fuse from the normal current flow before it goes to sleep mode. Many people use the 10 amp scale at first to prevent the 2 amp fuse from blowing, then it does just that when they move the meter lead to the other jack. That won't happen when you use the jumper wire.

Caradiodoc
Jan 3, 2012.
Cardiodoc, I've never had a battery drain overnight with more than 3/4 of an amp draw. Besides, velcro6996 says his draw is only 1/4 of an amp, not 3/4 of an amp.
A stereo memory can draw as much as a quarter amp by itself. That doesn't count an alarm. And if that alarm has a mass differential sensor (internal radar) or a motion detector, or a glass breakage detector, you're looking at over a total of half an amp of draw.

Rivermikerat
Jan 3, 2012.
Rivermike, I disagree because the standard for any given car, will be as follows, 20 max for old cars, 50 to 300 milliamps for newer models, factory. Now being I have all stock standard, if ur car is pulling a 1/2 an amp, your car wont last two days, unless balanced by a performance battery which doesnt correspond in this matter, we r talkin about a draw which is parasitic, draining overnight. Well I will continue looking for a solution wishing I could find a cure for my ailing jeep

Tiny
Velcro6996
Jan 3, 2012.
Velcro69996, old cars had analog stereos, with no draw. No power locks. No power windows. No power seats. No rear window defogger, etc.
The car is an Escort. Standard replacement battery. The only thing "performance" about it is that it's made by Interstate and not a run of the mill company.

I guess I'm special, because my battery lasts longer than just overnight.

Rivermikerat
Jan 3, 2012.
I don't know anything about non-factory alarm systems, but I've repaired over 2000 factory radios since the early '90s. There is absolutely no way any of them would draw a quarter amp for just the memory circuit. Many older GM radios draw over three amps when they hit a loud bass note. My power supply had a two-amp over-current cutout that regularly tripped so I had to upgrade to a better one years ago. Chrysler radios produce the same sound while barely drawing an amp. The needle on the ammeter doesn't even move when only the memory circuit is turned on for either of those radios or for Ford radios.

Also, I sell and repair radios at the nation's second largest old car show swap meet at Iola, WI. Twelve radios are powered up on display and run off solar panels and batteries. With one of the batteries later found to be defective, one radio turned on killed the battery each night about three hours after the sun went down. Later, those same batteries kept all 12 memories alive for two weeks when I forgot to turn the switch off. That shows how little current memory circuits draw.

Many memory circuits have a large surge current when the radio is first plugged in or the battery cables are reconnected. All microprocessor circuits including those in radios have a "reset" circuit that turns the thousands of transistors in integrated circuits on or off to their initialized starting points. Those reset transistors have to pass up to an amp during that surge but they are only rated at about 50 milliamps. I know this because there was a common problem with one model that developed bad solder connections. That one amp current surge didn't last anywhere near long enough to overheat the transistor, but road vibration and bad solder connections caused that circuit to turn on and off repeatedly until finally the reset transistor exploded. I spent a lot of time figuring out how that circuit worked and why it was failing, and in the end, testing showed those radios drew less than 5 milliamps for the memory. Once a capacitor charged up, (in a tiny fraction of a second), the circuit couldn't possibly draw higher current. There was nowhere for it to go.

Given that cars today need Body Computers, Transmission Computers, Remote Keyless Entry Computers, Memory seat modules, auto-load leveling computers, Air Bag Computers, and Anti-Lock Brake Computers to do things computers were never needed for before, (and they all have memory circuits that constantly draw current), Chrysler STILL lists 35 milliamps as the maximum allowable battery drain. You can even add a GPS radio to the list. If "ignition-off draw" is found to be over.035 amps, you have a legitimate warranty claim.

A 159 "peanut" bulb left on in a glove box draws half an amp, and that will kill a battery overnight. Too many maps and other papers stuffed in the glove box of a Dynasty caused the light switch mounting tab to bend so the light never turned off. That became a common problem but the first one took a little detective work. The drain was just under half an amp. I was involved with dozens of those. The complaint was always the same. "Car ran fine last night; battery was low this morning". The repair was always the same. Take 10 seconds to bend the tab straight and another minute to explain to the owner how to prevent it from happening again.

Rivermikerat, if your radio is wired to remain powered up all the time, it could easily draw the half amp you listed, but the memory circuit alone absolutely, positively will not draw anywhere near that much by itself. Simple math will prove that. There are too many large-value resistors in that circuit that limit current flow to a very low value. You can't get much water through a garden hose when you're standing on it, and you can't have much current flow when it's restricted with resistors. The only exception would be if the diode between the switched and memory 12 volt lines is shorted but that's very rare. The symptom would be the radio can be turned on any time, even with the ignition switch off, and with the radio wired properly.

Is it possible your aftermarket alarm is wired into the radio's memory circuit and you're reading the current drawn by both items? And why would you put an alarm in an Escort? That makes as much sense as putting one in my '88 Grand Caravan. I love and trust my van immensely, but I'd also love to have someone steel it so I could head south and find a nice rust-free one just like it. : )

Caradiodoc
Jan 3, 2012.
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