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Discussion Starter · #1 ·
I drove home from the SoCal meet-n-greet on the 15th (a nice long drive), parked my car, and headed off to Hawaii for two weeks. The C was locked and no lights were on. When I returned, the car would not start or turn over. The windows and whatnot worked, so I suspected the starter or some relay, but for the heck of it I put it on a charger. The charger showed full charging (i.e. dead battery) so I waited a few hours and the car started up just fine. One has to wonder what the heck can flatten the battery in only two weeks. That little clock on the dash can't be the culprit. I know the computer is always drawing power, but I don't want to think that this car can't sit for more than a week without killing the battery.
 

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If you have a multimeter that can do amp/milliamp measurements, you can disconnect one of the battery terminals and hook your meter inline in the circuit. You can then measure how many amps/milliamps are being drawn by the car. Chrysler suggests that the car pull less than 50 mA when the car is off.

If you do this procedure, note two things: (1) upon reconnection of the multimeter, the cars draw will quickly spike to possibly a couple of amps as all components "wake up" on the network. Once the car realizes it is not on and all doors are closed, no key in ignition, etc. it will go back to sleep mode. This could be up to 60 seconds or more. At this point, it should be less than 50 mA. (2) DO NOT TRY STARTING YOUR CAR OR TURN YOUR IGNITION ON DURING THIS TEST unless you have a capable multimeter that can handle the amperage. If you are doing this with the trunk open, remove the light bulb in there so it does not affect your readings.
 

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deegee said:
I drove home from the SoCal meet-n-greet on the 15th (a nice long drive), parked my car, and headed off to Hawaii for two weeks. The C was locked and no lights were on. When I returned, the car would not start or turn over. The windows and whatnot worked, so I suspected the starter or some relay, but for the heck of it I put it on a charger. The charger showed full charging (i.e. dead battery) so I waited a few hours and the car started up just fine. One has to wonder what the heck can flatten the battery in only two weeks. That little clock on the dash can't be the culprit. I know the computer is always drawing power, but I don't want to think that this car can't sit for more than a week without killing the battery.
I just found the section in my owner's manual about vehicle storage; it says

"if you are leaving your vehicle dormant for more that 21 days you may want to take steps to protect your battery.
You may:

  • Disconnect the negative cable from your battery
  • Anytime you store your vehicle or keep it out of service for two weeks or more run the air cond. system at idle for about 5 mins in fresh air high blower setting to ensure adequate system lubrication"


Your battery was not fully discharged or it would not operate the "windows and whatnot"

- I bet your service advisor loves decoding your terminology :33: :biggrin:

Anyway be advised that's what you have to do before a future trip


Zilla
 

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JonW said:
If you have a multimeter that can do amp/milliamp measurements, you can disconnect one of the battery terminals and hook your meter inline in the circuit. You can then measure how many amps/milliamps are being drawn by the car. Chrysler suggests that the car pull less than 50 mA when the car is off.

If you do this procedure, note two things: (1) upon reconnection of the multimeter, the cars draw will quickly spike to possibly a couple of amps as all components "wake up" on the network. Once the car realizes it is not on and all doors are closed, no key in ignition, etc. it will go back to sleep mode. This could be up to 60 seconds or more. At this point, it should be less than 50 mA. (2) DO NOT TRY STARTING YOUR CAR OR TURN YOUR IGNITION ON DURING THIS TEST unless you have a capable multimeter that can handle the amperage. If you are doing this with the trunk open, remove the light bulb in there so it does not affect your readings.
Harbor freight has a great little Float charger on sale for $7.49

It trickle charges at about 600-800ma's and will taper down so not to overcharge the battery even if left on for a year. I use them on my quads, motorcycles, motorhome. golf carts.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42292
 

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Discussion Starter · #5 ·
Disconnecting the battery is something you might typically do before parking the car for the winter. I drove it over 150 miles on the 15th, parked it, and it would not start on the 24th. There's no way I could consider that acceptable. I've never known anyone to disconnect a battery for a short trip like that.

goddardzilla said:
I just found the section in my owner's manual about vehicle storage; it says

"if you are leaving your vehicle dormant for more that 21 days you may want to take steps to protect your battery.
You may:

  • Disconnect the negative cable from your battery
  • Anytime you store your vehicle or keep it out of service for two weeks or more run the air cond. system at idle for about 5 mins in fresh air high blower setting to ensure adequate system lubrication"


Your battery was not fully discharged or it would not operate the "windows and whatnot"

- I bet your service advisor loves decoding your terminology :33: :biggrin:

Anyway be advised that's what you have to do before a future trip


Zilla
 

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Do you have any stereo or lighting mods which may have not been wired properly?
 

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deegee said:
I drove home from the SoCal meet-n-greet on the 15th (a nice long drive), parked my car, and headed off to Hawaii for two weeks. The C was locked and no lights were on. When I returned, the car would not start or turn over. The windows and whatnot worked, so I suspected the starter or some relay, but for the heck of it I put it on a charger. The charger showed full charging (i.e. dead battery) so I waited a few hours and the car started up just fine. One has to wonder what the heck can flatten the battery in only two weeks. That little clock on the dash can't be the culprit. I know the computer is always drawing power, but I don't want to think that this car can't sit for more than a week without killing the battery.

My 2005 "C" does not have the "whatnot". Was this an option or is yours a 2006? :wave:

Sorry.... but seriously though it could be as simple as a week battery, especially if your car was on the lot for a while before you bought it. That would be pretty rare for a 300C given how fast they are selling, but my sister bought a new Crossfire last year and it had been on the lot for 6 months; It had to have a new battery installed before she even took it home. Even though there's no way a "C" sat on the lot that long, as simple load test on the battery might reveal your problem.
 

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Dead Battery

Okay, here's my make on the problem: your trunk light is on and you don't know it.
I did a little testing tonight.
First, I determined that the light is switched by the mechanism in the latch in the trunk lid. With the lid up and the light on, I carefully pushed the lever in the latch with my key, and the light went off before the latch snapped shut (which I did not allow it to actually do).
Second, I left the trunk lid up for 40 minutes to see if the car was smart enough to turn it off. It's not that smart. The light stayed on.
You've got a bad trunk light switch OR the trunk lid was never fully closed!
Did you do the trunk pull strap mod, or are you still pushing the lid shut?
Check it out and see if I nailed it.
If not, you still have a problem.
 

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Discussion Starter · #9 ·
kevenj said:
My 2005 "C" does not have the "whatnot". Was this an option or is yours a 2006? :wave:

Sorry.... but seriously though it could be as simple as a week battery, especially if your car was on the lot for a while before you bought it. That would be pretty rare for a 300C given how fast they are selling, but my sister bought a new Crossfire last year and it had been on the lot for 6 months; It had to have a new battery installed before she even took it home. Even though there's no way a "C" sat on the lot that long, as simple load test on the battery might reveal your problem.
You didn't get a whatnot? Well, I got all the options except for the engine block heater, and it included a wonderful heavy duty whatnot and a triple-plated thingamajig.

Seriously, no electrical mods yet. I bought my C last October in Michigan and the build date was (IIRC) in September. I'll have to look into the light switches and the non-operating load question when I get a chance.
 

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deegee said:
You didn't get a whatnot? Well, I got all the options except for the engine block heater, and it included a wonderful heavy duty whatnot and a triple-plated thingamajig.

Seriously, no electrical mods yet. I bought my C last October in Michigan and the build date was (IIRC) in September. I'll have to look into the light switches and the non-operating load question when I get a chance.

So, you've had a couple of weeks to seek a solution to your battery problem. What, if anything, did you find?
 

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I have the same problem, I had some warranty work done to my C - replacing the seat control switches. I parked the car in the garage that Tuesday and this morning (Monday) the car wouldn't start but all the interior accessories work fine.

I was guessing that the dealer techs left a door open or something when they installed the new seat switches, to drain the battery. But that might not be the case. I was looking at the TSB's, and there is this one:

08/09/05 … 2006 … RR-05020 … FLASH - Wireless Control Module Ignition Off Draw … (3MR)

Anyone know what this TSB is about and would it help?
 

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Discussion Starter · #13 ·
Hi, Desiree. I spent those weeks on vacation. Yes, a second one. Two weeks in HAwaii, two weeks back at work, and another two week vacation. I had to use some time up. I drove the C up the coast, stopping whenever we felt like it. That meant several days in Cambria, visiting wineries, a few days in Carmel/Monterey, Santa Cruz, San Francisco, and back to Cambria again. Lots of fun, no problems with the car, and I still have no idea of the cause of the dead battery.

Now that I'm back I have to hunt down a shop to install the sway bars and springs and the Gibson headers. And the dealer needs to fix that darn rear window that won't work.


DESIREE said:
So, you've had a couple of weeks to seek a solution to your battery problem. What, if anything, did you find?
 

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Bubab said:
I have the same problem, I had some warranty work done to my C - replacing the seat control switches. I parked the car in the garage that Tuesday and this morning (Monday) the car wouldn't start but all the interior accessories work fine.

I was guessing that the dealer techs left a door open or something when they installed the new seat switches, to drain the battery. But that might not be the case. I was looking at the TSB's, and there is this one:

08/09/05 … 2006 … RR-05020 … FLASH - Wireless Control Module Ignition Off Draw … (3MR)

Anyone know what this TSB is about and would it help?
That looks like a TSB for the Grand Cherokee

http://www.wkjeeps.com/rapid_response/wk_rr_0520.htm
 

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deegee said:
Hi, Desiree. I spent those weeks on vacation. Yes, a second one. Two weeks in HAwaii, two weeks back at work, and another two week vacation. I had to use some time up. I drove the C up the coast, stopping whenever we felt like it. That meant several days in Cambria, visiting wineries, a few days in Carmel/Monterey, Santa Cruz, San Francisco, and back to Cambria again. Lots of fun, no problems with the car, and I still have no idea of the cause of the dead battery.

Now that I'm back I have to hunt down a shop to install the sway bars and springs and the Gibson headers. And the dealer needs to fix that darn rear window that won't work.
So the C didn't sit unused for any extended time during which another flat battery might have evolved.

Oh well, until the next such event!
 

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joey said:
That looks like a TSB for the Grand Cherokee

http://www.wkjeeps.com/rapid_response/wk_rr_0520.htm
Interesting, as the subject is "SUNROOF WILL NOT CLOSE", whatever that has to do with a dead battery except that the communication bus continues to draw battery power. And, that after I invented my automatic sunroof closure modification, I had some sunroof not closing issues that I could not resolve. My car has never sat long enough (as described by others) to kill the battery, and (because my car is not garaged) I kept at it and was always able to eventually manually manipulate the sunroof open/close buttons to get the dumb thing to close, thus perhaps circumventing the communications bus problem.
Thing is, I don't recall any WCM (Wireless Control Module) mentioned in my excursions through the service manual. Looks like I may have some homework to do.
Out o' here!
 

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Here's my take on the dead battery problem... this is based on my own observations while developing my iPod interfaces.

Any CAN based vehicle module that fails to put itself into powersave mode when the vehicle powers down may cause the car to drain the battery. The power used by any single module is not overly significant by itself, but if a module does not stop transmitting on the CAN bus when it is supposed to, it will actually keep all other modules alive as well - thus no module goes into sleep mode.

All modules "wake up" when a command is transmitted on the CAN bus. So if one module fails to respond to the vehicle off command, it will keep transmitting on the bus and all the other modules will immediately wake back up after they had already went to sleep. This is not visible to you as you think the car is off and everything has powered down. The only way to see it is to actually have something connected to the CAN bus and see that there is still active traffic when there should not be.

This is also probably difficult for the tech's to diagnose as they would see that the bus is still active, but they will have to hunt down which module didn't go to sleep. I'm guessing they would probably have to do module by module testing with a StarScan to see who wasn't behaving.
 
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