IOD Fuse Causing Huge Battery Drain

Hey guys. So the battery in my friend'a 2003 Dodge Grand Caravan is getting drained when the car is off for any more than an hour.

I've checked the drain on the battery and it is around 100-140 mAmps.

I've followed the service manual guide and pulled fuses to find the culprit and it is the IOD fuse. No other fuse causes a drop in amperage.

So I know what the IOD fuse does and I know most of the items that run through it (radio, done light, key fob, etc).

What I can't figure out is what on this list is causing the battery drain. I was hoping somebody had access to a wiring diagram or maybe had some additional insight into what could be causing this problem.

The current workaround is to either pull the fuse indefinitely or remove the negative wire from the battery when the car is off. This is obviously not ideal.


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just a thought, but the cargo area light is not permanently on is it?

Also not quite sure what you mean by "getting drained when the car is off for any more than an hour". Do you mean that the battery goes flat?

A good car battery should be able to cope with a discharge current of 140mA for a lot longer than 1 hour. I suggest that you check the battery S.G. (specific gravity) using a hydrometer. Each cell in a fully charged battery should read around 1.255-1.270, a half charged battery will read 1.180 -1.200 and a flat battery will read 1.100-1.130. Be safety aware when you do this, it is acid that you are dealing with..

Use a Voltmeter to check that the alternator is charging the battery properly. With the engine running there should be approx. 13.8-14.2 VDC across the battery terminals. Be safety aware when you do this, the motor will be running.

How old is the battery?



The battery loses enough power to not start the car. I didn't have my multimeter on me at the time to see exactly what the voltage of the battery was after an hour with the car being off.

I believe this is a brand new battery, but I'll suggest he get it tested anyways.

The alternator is charging the battery. I've tested it as you suggested.



I only suggested the battery may be faulty or not being charged properly because most batteries are around the 45AH+ mark. That means that they can supply either 45A for 1 hour or 1A for 45 hours and obviously a lot more when starting the car for the 5-10 seconds it takes to start.

Therefore a 140mA load should take between 1-2 weeks to flatten the battery, if the car was not started and nothing else was done to the battery, like prolonged attempted starting etc. and incorrect charging.

Out of interest did you check the cargo area light?


Yes, all the lights in the car have been checked and none remain on.



You might find that 140mA is the normal discharge from the battery, if you take into account, maintaining radio settings, any security alarm circuitry remote key control circuits etc. It is not really that much of a current flow when put in context of flattening a battery in a short time i.e. 0.14A from a 45A battery or if you prefer 140mA from 45000mA

Either get the battery S.G. checked to know the state of charge of the battery or fully charge the battery using a battery charger and then see if it reacts the same way i.e. discharges in just over an hour or so

Does the car only do a lot of short trips? If so it may be that the battery is gradually being discharged each time as the short trip duration does not allow enough time for it to be recharged properly. It will replace some of the discharged power but maybe not as much as has been discharged if you get what I'm saying.


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