Battery Drain issue

[HeadnSouth]

2003 GMC Sierra I recently replaced my blower motor resistor and HVAC control module. I don't drive it much except for towing. Towing season is over and the truck will just sit. It doesn't more than a couple of days and the battery will dead. Battery is new, alternator charges fine.

A buddy suggested removing the NEG terminal and attach a test light to the battery post. The test light is lit so I started pulling fuses and relays but the test light stays on. On top of that I have no climate control whatsoever. Everything else is stock besides some LED lights that are switched independently.

Any suggestions on what else to look for?

Edited December 28, 2021 by HeadnSouth

[Supreme Pizza]

1 hour ago, HeadnSouth said:

2003 GMC Sierra I recently replaced my blower motor resistor and HVAC control module. I don't drive it much except for towing. Towing season is over and the truck will just sit. It doesn't more than a couple of days and the battery will dead. Battery is new, alternator charges fine.

A buddy suggested removing the NEG terminal and attach a test light to the battery post. The test light is lit so I started pulling fuses and relays but the test light stays on. On top of that I have no climate control whatsoever. Everything else is stock besides some LED lights that are switched independently.

Any suggestions on what else to look for?

 

 

If the truck is not used much, I would just remove the negative battery post when its not in use.

 

 

 

[HeadnSouth]

 Disconnecting the battery doesn't solve the issue. Besides I like to have a ready to go backup vehicle just in case one of my others decides to crap the bed.

[Supreme Pizza]

Well, diagnosing a parasitic draw can be really hard or really easy - just depends on what the problem is.

 

First off, start with a measurement of the milliamps.

 

Some draw is normal, like from the computer or the clock. Some rigs are 20, some 50, some 85.

 

Also, make sure that your hood light is not throwing off your readings.

 

You can start pulling fuses and relays.

 

You can disconnect the starter, and the alternator.

 

You can disconnect the computer or body control module.

 

You just start pulling all the electrical connections until you see a drop in milliamps.

Edited December 28, 2021 by Supreme Pizza

[HeadnSouth]

Thanks, I'll dig into it. I'm hoping it'll be easy.

[Sharpz]

you could have a skinned wire that is grounding out somewhere.  The test light from the negative battery will stay lit as long as your security works, clock memory, bcm memory etc.  They rely on your battery to keep them on, but shouldnt pull much to actually drain the battery in only a few days time.  Faulty cluster panels can be a cause of this. To test that remove the cluster and let your truck sit for the time it normally takes to drain, if it starts, there is a good chance your problem is here.  After market radios are another big fault problem if not done properly.   I see you say everything is stock except the added LED lights though, so that shouldnt be an issue.

Edited December 29, 2021 by Sharpz

[HeadnSouth]

6 hours ago, Sharpz said:

you could have a skinned wire that is grounding out somewhere.  The test light from the negative battery will stay lit as long as your security works, clock memory, bcm memory etc.  They rely on your battery to keep them on, but shouldnt pull much to actually drain the battery in only a few days time.  Faulty cluster panels can be a cause of this. To test that remove the cluster and let your truck sit for the time it normally takes to drain, if it starts, there is a good chance your problem is here.  After market radios are another big fault problem if not done properly.   I see you say everything is stock except the added LED lights though, so that shouldnt be an issue.

Thanks for your reply. I'll look at what you mentioned and come to think of it. It does have an after market radio and I did install a tailgate lock. The TL being the newest addition. I'll start there.

[swathdiver]

On 12/28/2021 at 4:43 PM, HeadnSouth said:

2003 GMC Sierra I recently replaced my blower motor resistor and HVAC control module. I don't drive it much except for towing. Towing season is over and the truck will just sit. It doesn't more than a couple of days and the battery will dead. Battery is new, alternator charges fine.

A buddy suggested removing the NEG terminal and attach a test light to the battery post. The test light is lit so I started pulling fuses and relays but the test light stays on. On top of that I have no climate control whatsoever. Everything else is stock besides some LED lights that are switched independently.

Any suggestions on what else to look for?

 

Put a Battery Tender on it.  A Tech-2 can run a parasitic draw test on most models.