6

I've been finding my 2007 Mazda6 battery low in the mornings. This morning, with moderate temperatures, I had to jump it to start the engine.

I put a clamp ammeter on the battery cable and pulled every fuse one by one. Only the 10A "HAZARD" ("Turn signal lights") was drawing measurable current, and the ammeter indicated it was about 200mA. Is this normal? Or do I have a problem in that circuit?

  • 200mA is far too high .You will be getting flat batteries if this goes on .Leave your meter in the circuit and hope that the current falls . – Autistic Nov 11 '16 at 21:56
  • 1
    were you pulling fuses with the door open? did you allow time for the body computers to shutdown? you need to close the latch or switch that tells the body control module the door was open. Wait an hour then retest for parasitic draw. the hazard fuse in your case is a power source for the body control module. – Ben Nov 11 '16 at 22:28
  • Door was open, but the first fuse I pulled (and left out for the test) was for dash and internal lights. Of course I didn't realize other circuits might still be active because of this. I'll close everything, let the car sit, and then check again! – feetwet Nov 11 '16 at 23:20
2

The whole vehicle as measured with an ammeter at the battery should be less than 50mA

  • Source? That sounds hugely subjective. I have had perfectly healthy vehicles that I know draw substantially more current than that when sitting. – justinm410 Nov 11 '16 at 23:24
  • 1
    @justinm410 We work on these cars daily and, routinely, check the amperage draw as part of testing for customer stated dead battery symptoms. They usually draw in the 30-40 mA range when normal. Indeed, others vehicles do draw more. Often there are no specifications for amperage draw in service info so we collect them on known good cars. We work on about 4000 cars per year so we have lots of known good specimens from which to collect data. – Fred Wilson Nov 12 '16 at 3:08
  • Alright you win. ;) – justinm410 Nov 12 '16 at 15:04
  • Any idea how many amps a 2011 Nissan quest draws while at rest? Our van seems to pull 126mA and the battery doesn't have enough cranking power to start things up after a couple of days of sitting. Advance auto tested the system and declared the battery, alternator and starter all good. Battery and starter were replaced a year ago anyway. – user23756 Nov 12 '16 at 18:40
  • @user23756 Assuming the 126mA load is constant. Calculating the amps used in 48 hours by that load yields about six amps. This means that the battery only had six amps available or the load is changing over time. The typical automotive battery stores about 30 amps hours of energy when new. This drops as it ages. – Fred Wilson Nov 13 '16 at 3:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.