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Discussion in 'Technical Q&A' started by zapper/dapper, Dec 3, 2019.
My 360 doesn't seem to hold a charge on a new batter due to some short.. Any ideas??
You need to figure out what circuit is drawing current. This is done with a DVM on current mode. Then you can figure out what is wrong.
I would probably start the search looking at any non-factory equipment that has been added to the car.
What was it like with the old battery?
The fact that you are asking this question makes me strongly suggest taking it to your mechanic. If he is not very strong in the electrical diagnosis area find a new guy.
What kind of "new" battery did you get? I followed a lot of bad advice and got a smaller battery, left it off charge for a week and came back to a battery reading <5VDC. Recently had an issue with my current battery where a door switch was causing my battery drain faster than normal. Apparently working the door locks every so often is a good thing. If you leave your car unlocked normally, try working your door locks and locking it for a couple days....or vice versa. If you have any stereo equipment, etc, disconnect it and try again.
Just as a reference, I have a 360 with a modern radio (Alpine). My battery is three years old. I've gone two weeks without driving the car and have never had a problem with the battery. I own a battery minder but haven't taken it out of the box yet. From my experience, I'd say the 360 is like any other car. You can let it sit and not drive it for a couple of weeks without the battery going dead.
From what I've read, the typical culprits for a dying battery are the immobilizer system, alarm system and factory radio. I suggest checking the current draw by circuit and find which one of these things is killing your battery and address that. It is not normal for the battery to go dead in a matter of days.
first you check the battery draw by putting DVOM in amps mode 10 amps to handle the initial draw. You put the amp meter in series with the battery. disconnect one battery cable and hook the amp meter between the cable and the battery have all doors closed and key out of ignition, you can open the passenger door to do this but latch the door latch so it thinks the door is closed. hook up the meter and give the car 10-15 minutes to go to sleep.
Max draw on any car is .035 amps or 35 milliamps. as a general rule. if it passes this test there is no draw if it fails then begin by disconnecting any aftermarket stuff the usual suspects.
I found a 360 had a draw caused by the lighting module located on left side panel under dash - don't know if this is common but unplugging that module and passing the test proves it.
Since you need to disconnect the battery to test it, why not just disconnect it and 3 days later reconnect is and see if it held the charge while disconnected? If it doesn't hold charge while disconnected it dead.
if you find the battery is still good 3 days later it doesn't tell you anything, a bad battery may be incredibly weak, it will hold a small charge for weeks but if you hook a small draw to it, it wont last. The way it is done in a shop that does things properly is first charge the battery because you need a battery charged to pass the tests you do on it, then test the battery, if the battery fails then you replace it but still is there an excessive draw on the battery that caused it to fail? You still should get a number on what exactly does the vehicle draw? 35 milliamps is acceptable but a stock Ferrari 360 should draw zero if it is working properly. It is a very simple test to show the state of the vehicles electrical system. it may have a draw of 50 milliamps which is excessive and indicates something is wrong which could become worse. that could draw a good battery down twice as fast as what is barely acceptable. Also there is a charge test to make sure it is charging and not overcharging which could destroy a battery. Also if you do find a draw you need to find it which requires disconnecting things (pulling fuses) until you see the draw go away and narrowing the problem down to a specific circuit and then a specific component you simply dont have 3 days for each fuse. This type of testing can take many hours by a person who has a lot of experience so how many hours do you want to pay the dealership or even a small shop for? Are they putting their best man on it? Some owners may want to do some initial testing themselves and perhaps save a lot of headache maybe they actually enjoy working on it and learning something in the process. There are more tests possible than I have mentioned but these are the basic things you do to inspect the health of a systems and begin tracing the problem.
Here is what usually happens, a car with a brand new battery comes into the shop but the battery is dead. They replace the battery (again) and this time check to see if it is charging and it is so they sell the guy a battery, the next morning the car gets towed in (again) and they find the battery is dead they check for charging (again) and it is still charging so now they begin to suspect a draw and they call me. Don't think this doesn't happen in a dealership , you'd be surprised.
Did I say, "if it hold's charge it was good"? No!
I said, "If it doesn't hold charge while disconnected it's dead."
Tremendous advice. I will follow much appreciated,
let me know if it gets deeper if you pull a fuse it wakes up the CAN bus so you need to let it go to sleep again, some fuses will cause the bus to stay awake so be mindful of what modules you are pulling power from if you go there. If it does have a draw and it is not an aftermarket device I would go straight to the lighting module first just because that was found before