Finding a Short

rjv125 · #1 (**permalink**) 01-18-2008, 03:51 PM

What is the best way to find a short? Or a drain on the battery? I have a Milano that if not driven within 2 days, the battery is dead. If I Drive it everyday, the battery usually has enough power to start the car, but lately in the cold weather, it has been dead after 1 day. Any ideas on where to start? How do I go about finding this drain?
The battery is brand new and the alternator is working.

**Gubi** · #2 (**permalink**) 01-18-2008, 04:23 PM

With the car off, start by pulling the negative battery cable and putting an ammeter in between the cable and the battery post. Should be <30 mA or so with everything off. If it's not, try pulling fuses one at a time until you find the drain.

If you have *any* aftermarket stuff (like an alarm) start by focusing on that.

rjv125 · #3 (**permalink**) 01-18-2008, 05:29 PM

Sounds easy enough, will definitely try that first thing in the morning. Thanks for the suggestion.

rjv125 · #4 (**permalink**) 01-19-2008, 01:31 PM

As it turns out, I don't have an amp meter, but I have two wires connected to a light bulb. I disconnected the negative terminal and connected the wires to the negative battery cable and negative battery tereminal. I tried pulling all the fuses but the light remained lit. When I pulled one of the relay's on the passenger side, the light went out. I know one of those relays is for the fan, but what is the other relay for?

**Gubi** · #5 (**permalink**) 01-19-2008, 03:52 PM

The one with the 30A fuse is the fan and the one with the 10A fuse is the AC compressor clutch.

I'd take the opportunity to buy a decent digital volt/amp meter. If you own a Milano I guarantee you're going to need it in the future.

Hit an Apex · #6 (**permalink**) 01-20-2008, 11:23 AM

RJV125 - Craftsman has some sweet little volt/amp meters for about $50. Or call your friendly neighborhood Alfa electrician!

Rookie ROX · #7 (**permalink**) 01-20-2008, 04:03 PM

$50!

Heck you can pick up a reasonable multimeter that will last for years and be suitable for anything general for $15AUD down here! $50AUD gets you an automotive multimeter that will do duty cycle, dwell, RPM etc

ROCK ON
R~R

**Gubi** · #8 (**permalink**) 01-20-2008, 05:04 PM

$15 AUD is like $1250.75 US last time I checked. Damn exchange rate.

rjv125 · #9 (**permalink**) 01-20-2008, 09:17 PM

Ok, so I got the right relays in with the right fuses. I will leave the car overnight with a fully charged battery and we will see if it starts. I have a question about relays. Can generic relays without fuses from any automotive store be put in place of the stock ones with fuses? I think they are black. Just in case they fail and I need to replace them.

rjv125 · #10 (**permalink**) 01-22-2008, 08:24 PM

Thanks everyone for all of your help. Left the car for 2 days and it started right up. The culprit was a bad AC compressor relay. Tossed it and put back an original with a 10amp fuse. Thanks again.

romroc · #11 (**permalink**) 02-14-2008, 02:49 PM

Using a multimeter I'm getting a current draw of 11 ma. Is that enough to drain the battery? An online source states that draw from accessories when ignition is off should be no more than 2 ma. I think a diode or two are bad on the alternator. The terminals accidently touched.

**Gubi** · #12 (**permalink**) 02-14-2008, 03:17 PM

11 mA is pretty tiny. I think on my '91 Spider the manual spec is < 30 mA or something like that.

romroc · #13 (**permalink**) 02-14-2008, 09:00 PM

I'll check it out inthe morning.