Batteries Going Flat.

[Raul]

Hey,

posted here about a week ago about my alarm playing up. Turned out it was a dead battery, so i then got a new battery and has been all good until now (a week later). This has lead me to suspect that something is running my batery flat! couldit be that the workshop that installed my alarm installed it wrong and may that be the cause of my batteries being sucked dry? Before the alarm was installed it was fine.

Also it has been suggested that the alternator may be the problem, however wouldnt their be a dash light going off if this was the case?

Cheers

[wilch]

No dash light for the alternator.

To test if the alternator is stuffed:

- Grab a multimeter. Put it across the positive and negative terminals on your battery with the car off. Make sure it reads about 12v.

- Turn the engine on. Do the same thing. Put the multimeter across the positive and negative terminals on your battery. It should now read about 14v give or take a 0.5v or so.

- If it still reads the same as when the engine was off then your alternator is dead.

The other thing that could be wrong is that your battery is on it's last legs. How old is it?

If it's not the alternator or the battery then it has to be the alarm install. In which case you should take it back and get them to check what they've done. It could be something as simple as an incorrect ground.

I had an internal piezo screamer installed in my car that I had to remove due to it constantly draining my battery. It was a case of the alarm sending a ground signal instead of sending 12v to set the siren off. With the piezo screamer not being grounded properly and being connected to 12v, this meant that the battery was being drained constantly.

[mad082]

there is always the chance that the new battery had been sitting on the shelf for a while and was half dead.

also check that the boot light isn't staying on or something like that. (don't hop in, just push the button).

[SilverECR33]

Wat wilch said, do that first, then obviously you will find out if its that, or battery.

[blind_elk]

- Turn the engine on. Do the same thing. Put the multimeter across the positive and negative terminals on your battery. It should now read about 14v give or take a 0.5v or so.

Rev the engine to around 2k. If the volts increase with revs, the regulator is cooked, and will result in your battery being overcharged. Overcharging will kill it.

[Raul]

Jsut got my hands onm a multimeter, and the battery was reading 6 so i jump started it and it read up to 14v constant. Even when reving the engine it was constantly on 14v.

So can i assume that my alarm that was installed at one of SA's reputable wokshops has been installed incorrectly? If so i wont be happy as i have had so many headaches with this alarm its not funny.

Cheers for the replies guys

[Bl4cK32]

14v for a running motor is fine. It will go down to around 12v though after a short time when running.

Check the alternator output as wilch and blind elk said. It shouldnt cost too much to have it rebuilt, or just buy a new one.

[blind_elk]

14v for a running motor is fine. It will go down to around 12v though after a short time when running.

Check the alternator output as wilch and blind elk said. It shouldnt cost too much to have it rebuilt, or just buy a new one.

Switch everything off. Switch the multimeter to amps, remove the +ve cable, and measure the amps between +ve battery terminal and the +ve cable. Reconnect battery. Then remove each fuse in turn, and measure if any amps across each fuse slot - that will tell you which circuit is drawing the current that is killing the battery.

[Raul]

Hey,

Just to clarify ont he multimeter where should i be leaving teh knob to test the fuses?

Well i had the knob turned on the icon with an arrow and a '+' sign nextg to it and it gave me a reading of around 5-6v between the batterys positive terminal and positive cable. Then in the fuse panel under the drivers side dash, the fuses under ign had a reading of around 4-5v.

Any suggestions? Basically i want to pinpoint where the power is getting sucked as i want to know whether or not it was the alarms installation fault or not.

Cheers

Edited December 28, 2006 by Raul

[blind_elk]

You are measuring VOLTS, you need to measure AMPS (ie current). Volts are measured in parallel with the device you are testing, amps are measure in series.

It will probably vary with the design of the multimeter you have - mine has A (makes sense) near the various scale settings.

And you only need to check the fuses if you find a significant current flowing from the battery.

[mad082]

it may have dcv and dca on the multimeter. that means direct current volts and amps. it may also have aca (alternating current amps).