Battery drain where to start?

Post by **matthew1** » 30 May 2004, 09:17

Battery died. Just bought a new battery, drove the car once, when I went to drive it again the car/battery was dead again.

Where and how should I start searching for the battery drain?
What type of eletrical meter I should buy?
What should I test first?

Thanks

Tsquared · Post by **Tsquared** » 30 May 2004, 11:56

matthew1 wrote:Battery died. Just bought a new battery, drove the car once, when I went to drive it again the car/battery was dead again.

Where and how should I start searching for the battery drain?
What type of eletrical meter I should buy?
What should I test first?

Electrical problems are always frustrating. You need to first determine the electrical draw that you are experiancing. You need to get an Ammeter that is fairly sensitive (radio shack) and hook up in series with you battery - neg side will probably be easier because ther are fewer wires.

With the car off see how many amps you are drawing. Pull the fuse for the clock and see how much the amperage drops. Provided the problem is not in the clock circuit you can use the process of elimination by pulling a fuse one at the time to see where the draw is. Keep in mind there are multiple circuits that have power when the car is off.

Once you have determined the circuit you will need to trace the ckt to find the problem - usually a break in a wire rubbing against metal or failed component.

For tracing the ckt use the rule of halfs. Go half way through the ckt and determine if the problem is before the half way point or after it. This will reduce the number of components you need to check. If there are a lot of items still on the ckt go half way down again and check it out...

Get very familure with the wiring diagrams in your Haynes maunal - use multi-color highlighters to trace the different ckts.

Good luck

T

patmcclellan · Post by **patmcclellan** » 30 May 2004, 18:12

I've had the same problem for a while and 2 mechanics have failed to find the problem. I've replaced the battery with a heavy duty one, but if I go a week without driving it, dead.

I installed a little charger on the side of the battery, and I plug it in whenever it's convenient, so that usually keeps me out of trouble. However, a friend just gave me a solar charger from her VW that plugs into the cigarette lighter. That would be great, except that the Volvo cigarette lighter only works when the ignition is on.

So, my question is... is it possible/practical to re-wire the cigarette lighter so that it bypasses the ignition?

Tsquared · Post by **Tsquared** » 30 May 2004, 19:36

Yes it is possible to by-pass the switched cig lighter. An easier route may be to add another port directly wired (with fuse) to the battery. You could mount the solar panel in the rear window, running the harness down through to the floorboard, through the floorboard and along the bottom of the body to the engine compartment.

I also have a floating ground on my 89 Porsche 944. I have been tracing wiring for two years. Thought I found it in the AC harness this past February. I replaced the entire AC wiring harness, right through to the switches on the dash. The draw is no longer in the AC ckt but I still have an intermittant draw. I jumped into it last week after letting it set for 3 weeks and it was dead again. I have a 2-amp trickle charger for my motercycle that I have used to keep the battery charged. I swap it off between the Sportster and the 944 to keep both batteries they way they should be.

I would recomend a trickle charger before re-wiring for a solar charger. It will be easier and less of a hassle while you begin the tedious process of locating the problem.

Good Luck,

T

Post by **matthew1** » 31 May 2004, 10:23

The auto parts store is recharging the new battery now.

The guy wanted my to buy a tester light that glows brighter to indicate the current electrical draw. That didn't seem like a good purchase -- I already know that something with big draw is on when the car is off.

To find the problem fuse/circuit, he said to keep the tester light attached, and one by one pull the fuses till it goes off.

Alternately, like Tsquared said, pull each fuse and test its leads with a voltmeter, one by one, till I find the fuse/circuit with the big draw, right?

Question: can I buy a multipurpose voltmeter that will be suited for this, plus be suited to testing 110 volt appliances in my home?

Post by **matthew1** » 31 May 2004, 15:12

Just got battery back from the store, and on the way home it struck me that it could be the trunk light. You see, my trunk light swtich has never functioned correctly. It is either always on or always off, depending on the manual switch next to the light.

Sure enough, when I got back and put the battery in, the light was on. [bangs head against wall]. I'm doubly embarassed because this had happened once before, about 3 years ago.

Thanks to you both who responded. I'm just counting my lucky stars it was this and not an unknown ground somewhere.