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Finding a draw in the electrical system Q's

tRustyK5

tRustyK5

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On my 90 K5 there is some sort of electrical draw draining the battery. I thought the batt it came with was just not able to hold a charge at first, so I bought a brandy new red top Optima for it. That was three weeks ago and yesterday the Optima was pretty much dead. :doah:

I have the optima charging now, but I want to find where this draw is coming from. There are no aftermarket electrical goodies anywhere, stock am/fm radio, no hack electrical that I've seen.

I have a multi meter, but am no electrical genius. Is there a way to measure draw from the battery with a multi meter? If so I was hoping someone would explain how to me, then I could hook that up and pull fuses one by one until the draw goes away.

Thanks in advance if you can help.

rene
 
I had to do this a couple years ago. IF I remember correctly, you disco the NEG side of the battery, you essentially put the Multi Meter between the batt term and the batt cable, think of the MM as the link connecting them. You put the MM on Amps I believe.

On my K5 I was drawing .75 a normal vehicle will sit with a draw of zero to .15 sometimes up to .25 if you have alarms, clocks, etc.

I then just pulled fuses til it went down to nothing. It ended up being my Tach was wired hot. Even though the truck wasnt running, the tach was drawing power just sitting there. So I moved the tach hot lead to a KEYED switch and havent had any issues.
 
On most multi-meters you have to physically switch one of the leads to the amp plug. It's usually a 10amp max too. Keep that in mind.

I have a Fluke 179, so I attached a picture of the page in the manual that shows how to measure current. I don't know what meter you have, but that should give you an idea.

fluke179_current_check.JPG
 
Thanks, i did find that and switched to the 10 amp spot. Steady draw of 0.01 amps. that doesn't seem like a lot. I don't see anything patched into the fuse box either...this is very weird.

The first fuse I pulled I left the door open, so when i touched the second lead to the neg on the batt I got a 2.28 reading (interior lights) I pulled every fuse one by one and with the door closed I had the same 0.01 every time.

Is 0.01 enough to discharge a batt in 3 weeks? Possible the batt wasn't very charged when I bought it? When I installed it the int lights were very bright.

Rene
 
Yes, it's near new. When running the volt guage reads 14.5 V. The prob is that it's sitting here while I'm working on it, so not running every day to say the least.

When I was driving it every day I had no trouble at all with battery discharge.

Rene
 
The altenator can sap the battery if a diode lets current reach ground,and since GM altenators have three diodes in a trio,if one fails that way,it will still charge OK but not 100%,and allow a drain when the engine is off..you'll have to take off the thick red wire on the back of the altenator to see if that stops the draw..

My '74 GMC always had a draw at the HEI power wire,just enough to make a test lamp glow like it was getting 2V..never did figure that one out,the battery in the truck never went dead so long as I drove it at least weekly!..

A factory clock is always "on" too,and can drai a bettery flat in a matter of days..underhood lamps with mercury switches sometimes fail and stay on too..
I think computers and some other electronics draw a slight current constantly too,to retain the memory,and if the vehicle is left sitting too long it'll eventually drain the battery..
 
I'll try the alt wire.

Clock is in the radio (digital) which isn't displayng anything with the key off. Factory radio...

I still had the same draw with the ECM fuse pulled. Truck doesn't have an underhood lamp that I've been able to find.

Thanks Bob.

Rene
 
The test you did and the results you got are good and that isn't going to drain a battery. Like was said if one or more of the diodes in the alternator trio are bad that WILL drain a battery. The other thing is that optima batteries have become **** over the last 5 years or so. I would NEVER trust an optima battery EVER. I am a die hard Interstate battery fan myself and with the results i've had over the last 25 years I will never run anything other than an Interstate.
 
.01 amps is 10ma and thats nothing.It should be able to sit for mounths and be good.After you charge the bat let it sit overnight unhooked and check the voltage.should be 2.5-12.75 min after being fully charged.
 
4X4HIGH said:
The test you did and the results you got are good and that isn't going to drain a battery. Like was said if one or more of the diodes in the alternator trio are bad that WILL drain a battery. The other thing is that optima batteries have become **** over the last 5 years or so. I would NEVER trust an optima battery EVER. I am a die hard Interstate battery fan myself and with the results i've had over the last 25 years I will never run anything other than an Interstate.
Click to expand...


Love interstate batteries! And everyone has hit the nail on the head, most likely a bad diode in the alternator.
 
Well, when i bought this battery I never put the test meter to it, never tried to start the truck and for all I know it was not fully charged when I got it. I had it on the 6A charger for about 9 hours total, and when I got up to go to work at 2 am the charger indicated a full charge.

I just checked with my meter and it says 12.67V.

I'll reconnect it and see what happens in the next couple of days. I'm kinda thinking with only .01 amps of draw the alt diode is fine.

i'll post up if it happens again.

Rene
 
I agree that you do not have a shorted diode. It would show up as a pretty heavy drain. But, you might have a blown one. If so, the alternator would not be putting out full power.
If the truck has a radio, crank up the truck, turn the volume all the way down and listen close to the speakers.
If you hear a high pitched whine, the alt is probably ok, If it sounds like a quiet buzzsaw, you have a blown diode.

If you don't hear anything, you probably have the radio hooked straight to the battery, or it has some filters in the power input section.
 
10 milliamps is pretty low for a draw. Keep in mind most newer vehicles with all the control modules have an amp draw spec of 25-30 milliamps. Possible the battery was not fully charged or you have an intermittent problem that may not be showing right now.
Keep in mind that all of the interior courtesy lights are ground triggered so if there is a shorted wire or partial contact on the ground side of that circuit it could cause a draw with only dim lights on.
The newer Optima batteries are definitely not what they used to be, they actually used to manufacture them here where I live in CO.....now they say "Hecho en Mexico" :(

We used Dynacell batteries at the dealership and they were great & come with a full 72 month FREE replacement. No prorate at all and they're manufactured by Deka, one of the leading battery companies out there.
 
I know I've said this before by Optima battery's are junk! I always go to a industrial battery place here that all the oil rigs use and get myself there big 1000CCA dual post battery and they guarantee it for 5 years! On my second one now
 
George_Pimpdaddy said:
I know I've said this before by Optima battery's are junk! I always go to a industrial battery place here that all the oil rigs use and get myself there big 1000CCA dual post battery and they guarantee it for 5 years! On my second one now
Click to expand...

I wouldn't be bragging about 2 batteries in 5 years. :dunno:

My Interstate batteries (I have an auxillary battery) have been in my rig for 9 years now without any issues.
 
We'll see how this red top does. I was pretty happy with the blue top in my old boat. It had two batteries, one regular lead acid battery, and the blue top I bought for it. Both batteries were fully charged when it was laid up for winter. In late spring when it came out of mothballs the optima was still 100% charged, the other battery was in pretty sad shape and need a pretty good charge. Both were left unhooked.

At any rate, I'm not about to bring the damn thing back at this point.

Rene
 
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