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Voltage draw help

454Sub

454Sub

5/8 ton status
Joined
Apr 11, 2012
Posts
3,222
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Location
Southern Illinois
Alright, I went out to start the Sub as its sitting in the middle of the driveway, and dead battery. :rolleyes:. Its never done this before, so I did a draw test with the test light and lo and behold, it has a draw. So I undid all my headlight/windstar fan relays, figuring since they are hooked up to the battery direct, and its the last elec work I have done, it would be the prob. No dice, still a draw. So now I have since removed EVERY single fuse, plug in, anything that looked suspicious, and it still has a draw. Now the confusing part. I have relocated my battery to behind the rear seat. Along with another separate amp only battery that I did the same test on and it was all good. So my primary battery has 3 wires leaving it not counting ground. One goes straight to the starter, one goes to the ALT, and one powers/charges the second battery. I hooked the test light up to the ALT wire, and it barely glows now, but hooked to the starter wire, it lights up the whole cab. I am suspicious of the starter, as it has acted funny since it sat for a 6 weeks submerged in a pond after we could not extract the Sub for awhile. (Whole nother horror story). I tested the alt and its pooping out 14vts at the charging lug, and the battery is receiving the full 14 at the other end of the ALT cable. Im assuming its possible that the starter can short out internally and cause a draw, any ideas? Im not a fan of just throwing money at it, and these starters aint cheap anymore as its a gear reduction small little guy that GM used on the newer 454s and 496s.
 
Are you still powering the truck fuse panel off the starter "lug" like factory? Sounds to me like you must, since you only have three wires off the battery and you don't mention powering the fuse panel.

If you do, then you'd have to disconnect those wires as well to make sure the draw wasn't the rest of the electrical system.

You aren't testing the system with the door open and dome light on are you? BTDT lol.
 
Haha, I did that with the domelight about 3 fuses and then smacked myself in the head. :haha:

And Im heading back out there now, going to unhook the starter itself, and unhook the entire ALT and see what happens. Only reason Im really leaning on the starter is A, I have a warranty, and B its just been making ate up noises and been acting weird even with a fully charged battery.
 
Ok, the starter is not causing the draw. I have unhooked all relays, pulled every single fuse that exists on this thing, unhooked every axillary wire that plugs into the fuse box for any ignition actuated item. Unhooked the alternator power lug of everything, unplugged it as well. Now, when I hook up the fusebox power wire to the starter, it shows a draw..... What would cause that after everything and I mean everything is unhooked. What still uses power that is direct feed?
 
I don't know about direct feed, but headlights, horn, dome lights, brake lights are all I can think of that work with the key out.

Headlights are a direct feed, as the switch has an internal circuit breaker. Not sure what would happen if the dome light fuse was removed but the dimmer of the headlight switch was turned to activate them....

Did you pull the 30A circuit breakers that I assume are also on your fuse panel? I don't believe anything is powered directly off of them, but doesn't hurt to check.
 
I pulled everything, even the breakers. unhooked the starter and just wired the big positive to the fusebox wire to remove the starter from the circuit. Still shows a draw. And it shows it on both the big positive wire to the starter, and the charging wire to the alternator. Im losing patience with this thing. I cant find any lights on, no melted or direct shorted wires that I can see. But it does seem to get worse with any light fuses. As in headlights, brake lights, dome lights, ect. Maybe the headlight switch?
 
Something else, I do realize that these systems should have a draw of some sort. For the relays, ecm, blah blah blah. So it does light the test light, but its barely lit. Now once I hit any light fuse, it lights up the cabin with the test light. I have no way of telling what amps or ohms, as I accidentally blew the fuse in my meter, and they dont sell these little things anywhere convenient, so for tonight the test light is my only option.
 
A bad diode in the alternator can cause a draw, so can the seat belt buzzer circuit (had an old boss that couldn't figure out where his draw was coming from and it turned out to be seat belt buzzer even though the buzzer wasn't sounding).

The best method for checking for a draw is to remove the positive battery cable and then hook a DVOM meter between the battery positive post and the battery cable with the meter set to AMP and then start pulling fuses until the draw disappears then look at EVERYTHING that is on that fused circuit.
 
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You can pull the plug off the headlight switch. That still doesn't mean the switch is the problem, but if the draw goes away, you are on the right track.
 
The best method for checking for a draw is to remove the positive battery cable and then hook a DVOM meter between the battery positive post and the battery cable with the meter set to Ohms
Click to expand...


NO NO NO!!!!

NOT OHMS!!!

Scott misstyped.

Use AMPS, not OHMS.

Ohms will blow the meter.
 
I've helped a friend chase down a short on a truck,similar to the symptoms described here--we un-hooked every part we could think of,pulled every fuse out,took the altenator cables off,etc,and the drain was still there...it wasn't a big amperage draw,just a few amps,but enough to kill the battery after a day or two of sitting...after "giving up",we told the owner we couldn't figure it out--didn't charge him much because we failed to find a cause.................................................................................................................................................................................................................a few days later he returned,complaining he failed an inspection test because his tail lights were not working...we replaced a bulb on one side that had one of the double filaments fail,and it leaned over and touched the other filament...shortly after we put the new bulb in,I heard a spark jump when I put the bulb in-(tic)-and smelled insulation roasting somewhere under the rear of the truck not long afterwards!.....................................................................--I put my hands along a trailer wiring harness someone spliced into the original wires,where the odor was strongst......where a lump of elctrical tape was wound around a 4 pronged plug,was HOT to the touch,and the rubber plug was all gooey,after we chopped that plug out and spliced in a new one,the tail lamps worked OK again,and his battery never went dead overnight any more...why the "draw" didn't go away when we yanked the tail lamp fuse out,I have no clue,but somehow I guess at least one tail lamp wire,the brake lights most likely,is "hot" al the time,no matter if the fuse is blown or not??....and it was shorted to ground somehow thru the bulb maybe...??...anyway,the battery stayed up after we fixed the trailer wiring...
 
Another thing I forget to add was on another car with a battery drain problem,it took us a long time to discover the fuse box was getting FULL of water from a windsheild leak,we found by accident when we went to remove the fuse box to better inspect the wires on the back side where they entered the fuse box for corrosion,etc,that a cup full of water was sitting inside the fuse box,it spilled on me as I flipped it upside down...I had heard a slight sizzle type noise coming from the fuse box and one of the many relays in it,which led me to remove it...the relays were all full of water too,one was completely rusted inside...after the water was drained and we blew everything dry with the air hose and replaced the corroded relay,the problem vanished......................................................................................................................................................................................................Water in electrical things is a common dilema on many vehicles...a few weeks ago my friend put a used automatic tranny in an Audi Quattro--by FAR the worst vehicle he said he ever laid a wrench on in his lifetime to work on!...anyway,the owner had a hard time finding a used tranny,finally a salvage yard a few towns away said "we HAVE one,but its been sitting outside under a peice of plywood,and the torque converter is missing--if you want it you can HAVE it free!..."..so he got it--my friend was reluctant to install it,as it was a real mother-blanker to get the old one OUT,and he wanted no part of doing it again should it turn out to be junk like his original tranny was..the thing was bigger than a TH400,and was stuffed into the car with zero clearance to get at the bolts,etc....Anyway,after battling 2 days on the lift to get the tranny installed with the old torque converter,we got the car going....it did propel the vehicle ,but it was very sluggish as far as shifting,and seemed to be slipping in the highest gear..the owner bought the car cheap at auction with a "bad tranny",so he was happy he could at least drive it again...we changed the fluid and filter and it was no different...told him "good luck" and off he went...my friend told him "If it needs to be done again,I'll have to charge you again,just so you know".................................................................................................The owner drove it for about a week--one day he pulls into the shop,and my friends stomach growled when he saw him coming.."OH NO,not THAT POS again!"...:eek:...but the owner was grinning from ear to ear...he'd taken it to some Audi "specialist" who had a scanner that could diagnose the tranny,and he said it was in "limp mode",so it most likely needed a computer for the tranny,which is located under the passenger side seat............he unbolted the seat,to discover the computer was bolted to the floor,sitting in a puddle about 2" deep,and it looked like it spent a few years on the bottom of the atlantic ocean!....he found a used computer at a nearby salvage yard from an identical car and he bought it for 35 bucks and plugged it in...it now drives and shifts perfectly,like a brand new car!...I bet the "old" tranny wasn't "BAD" at all!!...
 
Well, my plan to start early failed with the introduction to alcohol. Anyways, what is the normal draw on these things? And its not the radio or anything, checked them all.
 
How much is it drawing? I usually consider anything over 2 tenths of an amp enough to cause trouble.
 
Well, I burned up the meter, but it draws enough to kill the battery in 3 days. I have it narrowed down to the lights. On the ALT, there is a 14 gauge wire that is hooked up to the charging lug. It powers all the lights, wipers and memory circuit on the radio. Well its not the wipers, or the radio as I have pulled them fuses and no change. So Im goin back out and checking the back side of the fuse box for a problem, and narrowing it down. Its not the ALT itself either, just had it tested, tests perfect.
 
How do you test current draw with a test light? It's a small bulb you put in series with the battery? This doesn't sound like something with much dynamic range. How did you blow up the meter? Usually there is a fuse (or 2) for the Amps range(s) and you just replace it. If you have the meter set to Ohms, then you test without the battery, just measuring from the main battery terminal to ground. If you have the meter set to amps, you disconnect the battery and connect through the meter.

If you had a relay always on (i.e. reversed relay logic) then you would hear it click whenever you connected the battery. The draw of a relay and anything powered through that relay should be dead 0 when the vehicle is off.
 
electrical help

ok after reading this i can tell you guys know what your talking about. now i just bought a 84 k5 and after the first alt went out on me and a battery i have found out that my alt wont turn on to charge my bat im not real good with wiring but the ground is good and so is my alt so please help me out. :confused:
 
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