"Phantom" Parasitic Draw.

[88lowrider]

Not sure if anyone is going to jump in on this or not as, I have been here before with this issue.

Mine is a 1988 GMC 1500 SLE Sierra that I made the low rider out of.
Electric windows, door locks.
350 V8 EFI, automatic trans.
Air, Power brakes, steering etc.

This is not a New problem. Been fighting this now since maybe the year 2000.
Park the truck on a Friday night after work, go to start it Monday Morning, Rrrr Rrrr, click click click, but Not Dead dead. Between 9 to 10 volts.

I let it set a Week, same thing, 9 to 10 volts but Never dead dead. Something is smart enough to shut down once it sees the battery is down to the 9 to 10 volts.

So, within 72 hrs (?) it will draw down the battery. Jump it, its fine driving and parking just over night.

I had put on a boat battery switch to the negative post to the battery and just kept turning it off if I had to let it set for more than a couple of days. (at that point, I was living Off the Grid, but now living On the Grid, I put on a small 1.2amp float charger now)

Over the years, since this problem started, no change in phantom draw:
Replaced starter.
Replaced Alt (2)
Replaced Battery (every two to three years)
Replaced brake light switch.
Replaced Computer.
Replaced heater control and door motor.
I know I am forgetting things too.
Checked grounds, checked wiring plugs and the list goes on.

Now new. The float charger has been holding it as I only drive the truck maybe once or twice a week. This time the truck sat for at least a week, maybe 20 days, down to 8 volts, 1.2 float charger was not able to hold it.

Charged the battery, checked the draw (stereo has been changed out too) and there she is reading .002 amps.....

I even read one time someone found it in the Instrument Cluster. Found some fellow in the mid west that rebuilds them and tests them for $150 bucks. Used on Ebay, they want around $120 to $150 used.. I might give that a try but just can't see were that could pull enough amps :-/

OH, and a Fellow gave me a Circuit design (that I can't find on line or I had printed it out) that I was able to put it on the battery or between the battery that would trigger a small relay that I could run it though a drop cord into the house and next to my bed as to Hear when the draw went above a Amp. I never got that built but my thinking now, I need to have it Drawing the amps and Then get out and start jerking fuses out until the alarm goes out.

Anyone know of a device or have a diagram on how to build something like that?

Something will come on and draw enough amps to pull the battery down.
Anyone want to take a stab at this, please ?

[speedygonzales]

Have you checked the draw on the battery with everything connected electrically like normal?

Have you then tried removing one fuse a time until the unusually high draw is gone?

Other than putting an ammeter in series with the battery that's all you have to do to find the circuit that's the issue.

The assumption is you have a good battery since a bad battery can exhibit the same problem.

[88lowrider]

Originally Posted by speedygonzales

Have you checked the draw on the battery with everything connected electrically like normal?

Have you then tried removing one fuse a time until the unusually high draw is gone?

Other than putting an ammeter in series with the battery that's all you have to do to find the circuit that's the issue.

The assumption is you have a good battery since a bad battery can exhibit the same problem.

Yes I did, 2 milliamp draw is all, just parked.

Yes, did remove all of the fuses in the Inside of the cab after mapping it to know know to get them back in the right spot. After 72 hours, something still took the battery down to 8 to 10 volts.

Yes, I did put a Amp meter in line between were the main power feeds the truck and battery. I scan see a charge and discharge, when looking at it.

Yes, in the post, I replaced the battery and do so every two to three years and this has been going on for about 18 years. I just choose not to give up.

My thinking is, if I can some how come up with some form of tattle tail circuit so when it draws 25 milliamps, it warns me, I can go to it and Then start pulling fuses and disconnecting major plug ins.

[ratrod67]

probably not your issue but I had an 85 Chevy SWB that would go dead after a few days. after going through the truck numerous times trying to find out why I found out the brake pedal stop light switch was constantly engaged just enough for current draw but not light up the brake lights. adjusted it out some and the battery drain went away.

[88lowrider]

Originally Posted by ratrod67

probably not your issue but I had an 85 Chevy SWB that would go dead after a few days. after going through the truck numerous times trying to find out why I found out the brake pedal stop light switch was constantly engaged just enough for current draw but not light up the brake lights. adjusted it out some and the battery drain went away.

One time I was walking away from my lowrider and happened to look over my shoulder and seen the brake lights on...I thought, Ah Hah, Gotcha. I adjusted the brake switch to give it some play but then also replaced it. I checked it for Any kind of draw and nodda. Good one though..
I even went as far as checking glove box lights, ash tray light, pulling bulbs and made up a small blade type tool that I was able to put my test leads on and can push it into the bulbs place to check for current. All showed good.

I thought, Computer maybe as no matter what, it will Never or has Never pulled the battery Dead dead, Always down to 9 to 10 volts and then whatever it is, it let go or shut itself off as not to kill the battery totally..
Check door switches but whatever it is, I can't seem to find it when its shorting or coming on. I keep thinking, some day it will just Stay on and I will find it.....So far, not so good. A true Phantom.

[speedygonzales]

It is now clearer that you don't see the draw when you look for it. Because obviously a 2 milliamp draw is not near enough to do what you are experiencing. In fact I'll bet the 2 mill is from the radio, which again is normal.

You reiterated that you been replacing batteries every 2-3 years in response I assume to saying "the assumption is you have a good battery". Don't assume ANYTHING, particularly when it comes to replacement parts. Last fall I had a terrible missfire. I bought a Delco cap and rotor. The problem was the same. I had my neighbors shop look at it and it was the old AND the new cap were both bad. He got another cap and it was fixed. So don't assume anything about parts these days. Although you would assume at least one of the last 6 batteries you bought were ok. Anyway back to your problem.

My sister had a Suburban that would kill the battery in less than 2 days. When I put the ammeter in line to the battery the current would go high for about 2 minutes then would drop down from the highest point to a point that was still too high.

I knew from experience to start with audio equipment first and I pulled the radio fuse. When I reconnected the ammeter, the current again went way high for about 2 minutes and then dropped to an acceptable level. All was then good with the radio out of the circuit. My point here is something took 2 minutes to settle down. I assumed it was the PCM

Over the years I've been bitten when helping others because I assume certain things had already been checked. So I'm going to ask you:

What is the voltage across the battery when the engine is idling?

While you're there getting a reading, take a second reading from the ground lug of the battery to the output post of the alternator. If those 2 readings differ, take a 3rd reading from the outside case of the alternator to the output post of the alternator.

One other question I thought of: Does the problem get better when the battery is new and get worse as the battery ages?

[68C15]

It's possible the ignition switch is causing a draw after a while being unused. I have trouble explaining it but I can see it in my mind.

Put ammeter between cable and battery then check it every couple hours. If/when you see it above 20mA wiggle key to exercise the sliding contact in switch and see if draw goes away.

I check parasitic draw by using a digital meter and check voltage drop at fuses. I have a chart at work showing acceptable readings for each fuse rating.

[88lowrider]

Originally Posted by 68C15

It's possible the ignition switch is causing a draw after a while being unused. I have trouble explaining it but I can see it in my mind.

Put ammeter between cable and battery then check it every couple hours. If/when you see it above 20mA wiggle key to exercise the sliding contact in switch and see if draw goes away.

I check parasitic draw by using a digital meter and check voltage drop at fuses. I have a chart at work showing acceptable readings for each fuse rating.

Thanks for jumping in here :-)
I had replaced the ignition switch and thought I had found my issue in it as it would not work in accessory mode. I ended up having replace the key switching part as well..
In doing that, I noticed that I had been leaving the Cruise control on too. I thought maybe the switch was leaking some how across and firing up the cruise control so like you said, replaced everything plus always rock and wiggle things testing with amps. My DMM does do 20 amps too.

Never considered voltage drop at different fuses. Most of what I am looking for is the amp draw that sucks the voltage down. Not sure in my mind how that might tie into this. But interested in hearing more.

I know I have forgotten a Lot of things I have tried and replaced over the years. Most of the time, I tend to test everything before it gets installed and then of course, looking for Any changes in what is going on.

[speedygonzales]

Did you not catch the part about using the DVM min/max setting?

Apparently not......

You connect your DVM like normal for current and set it for Min/max then leave it over night. Next day see what the min and max was.

Now you get it?

[88lowrider]

Originally Posted by speedygonzales

Did you not catch the part about using the DVM min/max setting?

Apparently not......

You connect your DVM like normal for current and set it for Min/max then leave it over night. Next day see what the min and max was.

Now you get it?

You are right, I missed that. Mine goes up to 20 amps and does do the Min Max so good idea, I can find out at least what it is drawing. Going to set that up tonight too

[speedygonzales]

Alright we're here waiting patiently if you're right or I'm right. Not like it's a competition though.