Parasitic draw

[buddhabelly]

Learned a lot on this site and could use some help:
84 Scottsdale, swapped with a 1990 350, dual batteries. Power draw. Door light is clamped shut and hood light is removed, still getting 13v draw on battery. Went through all the fuses in the bussing under dash twice. What am I missing?

 

[JoeR Jr]

It's a common goofup to measure draw with voltage. It doesn't work though. It's kind of like saying that you're 6 gallons tall, or that you weight 50 inches. If you're using a DMM with really high impedance, they'll always read close to battery voltage if you put them in series with the battery cables.
If you don't already have one, get a meter that measures amperage. Take the reading in series of either the positive or negative battery cable. That'll give you a draw reading in amps.
There's a ton of good youtube vids on how to do it.
Joe

 

[fast 99]

Another way is hook a test light in series at the battery post. Preferably on the negative side. If it lights up there's a draw. A common non-fused draw is the alternator, disconnect it.

 

[buddhabelly]

The sad part is I’m a licensed electrician. DC is not my forté.

 

[buddhabelly]

Another way is hook a test light in series at the battery post. Preferably on the negative side. If it lights up there's a draw. A common non-fused draw is the alternator, disconnect it.

Can you explain that like I’m 5? I have a meter, and I also have a cheap 12v tester. Which lead goes where?

 

[buddhabelly]

Update: I tested my alternator at oreilly and it passed. I bought a starter and upon install when I turned the key it fired right up but the starter would not stop “starting” I panicked and disconnected the battery cables and have been sulking for hours since. Edit: my batteries are brand new and both have 13v

 

[fast 99]

Can you explain that like I’m 5? I have a meter, and I also have a cheap 12v tester. Which lead goes where?

Doesn't matter as long as it is inserted into the circuit.

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On the starter sticking, it is either a bad starter or electrical such as the ignition switch.

 

[squaredeal91]

Update: I tested my alternator at oreilly and it passed. I bought a starter and upon install when I turned the key it fired right up but the starter would not stop “starting” I panicked and disconnected the battery cables and have been sulking for hours since. Edit: my batteries are brand new and both have 13v

Hot wire on starter is touching solenoid post.

 

[fast 99]

As an electrician this might help. I use a shunt with Fluke on the millivolt scale for draws. It allows anything to be turned on or off except starter. Max draw is .05 millivolt across the shunt.

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[buddhabelly]

This forum is so dope I wish i joined a long time ago. Could’ve saved a lot of headaches

 

[YakkoWarner]

I like that shunt - where did you get it? I have used an antique DC ammeter to hunt down phantom draws in British cars (it is a relic from my grandfather which he used back when houses were fed with DC current - measures up to 300 amps) - that shunt and a modern digital meter would be a lot easier and safer....

 

[fast 99]

I like that shunt - where did you get it? I have used an antique DC ammeter to hunt down phantom draws in British cars (it is a relic from my grandfather which he used back when houses were fed with DC current - measures up to 300 amps) - that shunt and a modern digital meter would be a lot easier and safer....

Picture is from Amazon. But the one I use has only one bar, cheaper. Don't think that really matters. Made leads for the battery. Good idea to use the neg side, won't short to ground. Below is how it's used.

 

[Uberbeans]

Never used this before and I'm having the same problem. Where are you putting these clamps? Between suspected circuits that have a draw of on the battery leads? Sorry if this is a dumb question.

 

[Bextreme04]

Never used this before and I'm having the same problem. Where are you putting these clamps? Between suspected circuits that have a draw of on the battery leads? Sorry if this is a dumb question.

Disconnect negative battery cable. Set digital Mulitmeter to read "A". Connect one lead to the battery cable, connect other lead to the negative terminal on the battery. If you have a parasitic draw you should see something more than 0.5A on the meter with the key off. Start pulling fuses one by one and look at the multimeter after pulling each one. When the draw drops below 0.5A, you have found the circuit that has the draw in it.

 

[fast 99]

Disconnect negative battery cable. Set digital Mulitmeter to read "A". Connect one lead to the battery cable, connect other lead to the negative terminal on the battery. If you have a parasitic draw you should see something more than 0.5A on the meter with the key off. Start pulling fuses one by one and look at the multimeter after pulling each one. When the draw drops below 0.5A, you have found the circuit that has the draw in it.

Thats an option but have to be careful the load doesn't exceed the fast blow fuse. Last I knew they were about $10. After buying several I use the shunts.

Never used this before and I'm having the same problem. Where are you putting these clamps? Between suspected circuits that have a draw of on the battery leads? Sorry if this is a dumb question.

Remove negative cable, one clamp on the cable other on the battery. I say negative because no grounding issues. That is unless it is an older British car. In that case positive side.