I've owned my RX-8 (2004, 192, MT) for several years but have never bothered to sign up here, seeing as every question I've ever wanted to ask has been asked (and answered) by someone else. I've finally encountered a problem I can't find the answer to, so I signed up only to be told I can only post in the New Members forum for the first month...

After leaving the car for a few weeks, the battery went flat, so I recharged it and used a multimeter to work out where the power was going (the battery is about 2 years old, and seems fine otherwise).

Firstly, what sort of current should I be reading when everything is off? I'm getting about 0.1A.

When I disconnect the fuse labelled 'IG KEY 15A' (presumably the ignition switch) the current drops to 0.01A, so I'm guessing that's the culprit. Is it normal for that much current to be going to the ignition switch when the car's off? I assume it must be one of the few systems that needs power when everything else is off, but I'm guessing ~0.09A is not normal?

Does anyone else have experience of a similar problem? Any suggestions as to what is on the same circuit that could be causing a drain? Is a circuit diagram available anywhere?

 

Moved to Troubleshooting for you. Definitely not a normal new member question

I can't answer this question myself, but i'm guessing someone can.

 

Thanks

 

I will help you on this one....

First thing...you need to leave the whole system undisturbed for at least 30 min before you measure the current levels.....otherwise you will have high readings... ( 300Ma or more) That means everything..from turning on the key to opening the door etc

If you have an immobilizer the backup current draw is 45Ma when the light is on...and 25Ma when it is off....so averages out to around 30Ma on tester
If it is higher than that go looking for additional draws.

Do you have any aftermarket gauges or accessories installed? Alarm? Stereo?

Often they get wired into the ignition circuit to have a constant power supply...and some can have high draws

 

Yep, just like dannobre stated. I recently had to do the same steps to verify a battery with a dead cell.

 

Thanks for the help. As suggested, I left the car for over 30 minutes, and the current dropped. It seems to alternate between 10-20 mA, occasionally jumping up to 50-60mA. I guess this is normal?

I also checked the voltage, which after the car had run was 12.6V, however after leaving the car for about 2 days it dropped to 12.2V (and that was with the IG KEY fuse taken out).

Im beginning to suspect the problem may be with the battery after all, but I'm wary of spending money on a new battery only to find out the problem lies elsewhere...