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Discussion Starter #1
I have a 2007 300C HE. While the car is off and all doors closed with the keys out of the ignition, every minute or so I'll hear a clunk in the rear end, followed by dash lights blinking once, followed by the gauges pulling down below zero, then returning to zero. This is draining my battery overnight. New alternator, new battery. Confirmed charging system. I've searched these forums for 1.5 weeks, and can't find anyone with issue.
 

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If you have an advanced code reader, use it to scan for DTCs. If you don't, pick up a cheap ELM327-compatible Bluetooth OBD adapter, and use that with a free version of either AlfaOBD or Torque to look for codes.

Something's not quite right there, and that's the first place I'd look.
 

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Discussion Starter #3
Agreed. I'm trying to get access to one, and the stealership wants huge money to scan it. In the meantime, if anyone's had this issue, feel free to speak up!
 

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The only effective way to approach this is to do like CtCarl said. Otherwise you'll just be chasing your tail and playing guessing games.
 

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Discussion Starter #5
Aren't DTC's available through the dash? If so, the only codes I have are for incorrect oil type, and bank 2 o2 sensor low voltage. I'm thinking my issue is more of a CAN bus/module fault thing, but I appreciate the help. Also: Will those little Bluetooth adapters read and interpret CAN bus data, or am I looking at trying to find someone who has a StarScan?
 

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Aren't DTC's available through the dash? If so, the only codes I have are for incorrect oil type, and bank 2 o2 sensor low voltage. I'm thinking my issue is more of a CAN bus/module fault thing, but I appreciate the help. Also: Will those little Bluetooth adapters read and interpret CAN bus data, or am I looking at trying to find someone who has a StarScan?
They key dance will not give you hidden codes, you need either an advanced handheld scanner or an ELM327-compatible Bluetooth adapter and diagnostic software for that. I don't know exactly what canbus data you're looking for, but if you're looking for a tool that will run an automated diagnostic on the canbus and come back with some kind of report, that's not something I can help you with.
 

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Discussion Starter #7
I ran diagnostics on it this evening using an adapter, and the torque link app. No crazy codes, pending or otherwise. Not sure what to think. Something is waking up my dash and resetting my gauges while the car is off, and I can't figure out what it is. Seeing that there's no communication errors or U codes, I have to assume that a component in the car is continuously resetting the dash. Even with the door ajar (and showing on the cluster that it is), it will still reset over, and over. I've pulled fuses 14 and 16 with no effect. Does anyone know the specific module and the related input devices (including fuses) that are responsible for powering and operating the gauge cluster? Thanks for all the responses thus far.
 

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You know what you might try, grab the free version of AlfaOBD. It'll allow you to test quite a few individual modules, that might tell you something.
 

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I have a 2007 300C HE. While the car is off and all doors closed with the keys out of the ignition, every minute or so I'll hear a clunk in the rear end, followed by dash lights blinking once, followed by the gauges pulling down below zero, then returning to zero. This is draining my battery overnight. New alternator, new battery. Confirmed charging system. I've searched these forums for 1.5 weeks, and can't find anyone with issue.
Hey

I had a similar issue with my 2012 /2013 300c and couldn’t identify for ages.

it ended up being the alarm siren - which had to be replaced.

try looking at that - took the dealership a long time and multiple visits to find it out - my battery would drain over a week or so.

hope this helps
 

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The "clunk" from the rear might be a clue. Could this be a door or trunk lock operating?
You need a decent code reader, such as diagFCA, which will diagnose door modules.
I think the instrument panel issues may just be a symptom of falling battery volts.
 

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Discussion Starter #12
I wish that were the case. This issue will drain a fully charged battery overnight. The issue only appears once the car is off, and it's definitely the dash initializing repeatedly. No switches or doors/trunk are actuating. I'm thinking the thud might be a relay that I haven't discovered.
 

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That is a huge power drain and unlikely to be caused by the instrument panel - rear screen heater maybe? As for the "thud", relays tend to be fairly quiet in operation. Have you fitted any aftermarket electronics which may not be turning off? As others have suggested, you should start by doing a scan with decent diagnostic software. Failing that, you could disconnect the battery and insert an ammeter in line. Then start pulling fuses until you detect a significant drop in current.
 

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Discussion Starter #14
No aftermarket electronics are installed. I ran AlfaOBD last night on my car, and nothing unusual came up. We tore into the lower dash and steering column and checked harnesses and grounds, and everything looks fine. After a few hours with a multimeter, my mechanic is stumped and believes it could still be the battery, even though it's newer and has passed 4 of those witch doctor handheld battery tests from different places. We're gonna put a virgin battery on the car while I'm at work today, and see what it does. Will update you guys this evening. Thanks for all the help, again.
 

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Discussion Starter #17
Thanks for that. The alternator was just changed because of a bad diode, which I thought was the problem. It's charging fine, and it's confirmed that there's no draw from the alternator while the car is off.
 

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No aftermarket electronics are installed. I ran AlfaOBD last night on my car, and nothing unusual came up. We tore into the lower dash and steering column and checked harnesses and grounds, and everything looks fine. After a few hours with a multimeter, my mechanic is stumped and believes it could still be the battery, even though it's newer and has passed 4 of those witch doctor handheld battery tests from different places. We're gonna put a virgin battery on the car while I'm at work today, and see what it does. Will update you guys this evening. Thanks for all the help, again.
AlfaOBD gives you the option to test modules individually. I would just run through and test every single one to see if you can reproduce the behavior manually. Once you find it, that's where I'd concentrate my efforts.
 

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Have you done a parasitic draw test?
YouTube has some good videos explaining the process.

Sent from my SM-N960U using Tapatalk
 
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