Parasitic draw

[GTbird]

How y'all doin'? GTbird's battery voltage goes down over a few days and my voltmeter has no amp settings. There are k-ohms of resistance from battery positive to negative cable, so it's a slow leak. Is there a common issue with draws that anyone has found? I'll get a better meter tomorrow, so just checking in here in the meantime. Any insight greatly appreciated!

 

[theterminator93]

Most of the time it's an aftermarket stereo that causes it.

 

[KevinVarnes]

Aftermarket radios and alarms are always popular. Other than that, nothing I am aware of that is a common contributor. Just have to start pulling fuses until the current draw drops down.

 

[Generalee0527]

If you have a laser temperature gun you could check fuses and relays in the distribution box. If you have access to a flir camera it will show warmth compared to others. Has there been any work done recently like cooling fan, coolant leak or headlights? A/C?

 

[GTbird]

Seller said the heater core was replaced recently. What would that do?

Aftermarket radios and alarms are always popular. Other than that, nothing I am aware of that is a common contributor. Just have to start pulling fuses until the current draw drops down.

What about the original radio? Probably has an internal battery that can go bad, no?

Most of the time it's an aftermarket stereo that causes it.

Still stock, but this car has been a hotrod for years, so who knows what's been done to the wiring.

 

[KevinVarnes]

To replace the heater core requires pulling the entire dash out (at least the way I do it). All kinds of wiring and connections back there. No point in guessing though. All we are doing is spitting into the wind until you have some test data to share.

 

[GTbird]

The ignition is getting funky, that's for sure.

What's everyone's favorite multi-meter with amp setting?

 

[Generalee0527]

Power probe is what I have. I also recently bought a $90 centec clamp meter at harbor freight that does DC current where multi-meters typically only do AC. It worked on wife's car that had a bad alternator which can drain if the diode inside craps.

 

[KevinVarnes]

I just have an old Craftsman multimeter. I think it is only fused for 20A current draw, but it is good enough for current draw testing. You don't necessarily need anything real fancy. Amp setting will depend on the draw you have, but if it takes a few days to draw it down I'm guessing you should be below 1A.

 

[Grog6]

Just about any cheap multimeter from amazon, ompja.com is a surplus site I like, will work for this.
Disconnect the + batt terminal, put the meter on the highest current setting, ind clip the meter in line with the + battery terminal, and then see what is being drawnoff the batt. adjust the meter scale more sensitive if you can.
Start pulling fuses, keeping track of what goes where. I'd put each one back as you go, recording which fuses affect the reading. If you have the evtm, there are some hints that might help. otherwise post up what you find.
Last dvm I bought was $10 from mpja.

 

[theterminator93]

My cheap Home Depot DMM (like $20 back in 2007 or so) can measure a current up to 200 mA. Not good for much.

 

[Grog6]

Most have a 10 a scale, but 2a will work with a key and lights off situation. Buy a box of fuses before you start, a head,tail,or brakelight will blow a 2a fuse.

Digital Multimeter, DMM UNI-T UT33B

Light weight 6 function, Backlit, 3-1/2 digit hand held meter with 1/2 LCD display. Includes 9V battery, test leads, instructions & Protective Boot. Fuse Overload protection. CE listed; IEC 1010 CatII-600V Compliant SPECIFICATIONS DC VOLTS & CURRENT Volts: .2,2,20,200,500V Current...

www.mpja.com

This one is what I'm using currently. 10A scale,10 bux. I don't remember if it comes with alligator clips, but they help.