Parasitic Drain
 

Hello folks, thanks for letting me in. I'm working on an '02 blazer, which is sucking the battery dead in a couple of days. I have tested the drains at the fuse box and there are several, I'll go through them one at a time so I can remain focused. The RAP circuit is one of them and I'll start with it. When I turn the key off the radio shuts off with the key and does not continue running until I open the doors. It also never stops causing the drain. Should it drop to zero after a short while or should it continue to use some amps?

Thanks for any help with this,
Mark

See especially post #2 and #7 here for links to additional info and the factory parasitic draw tests.

https://blazerforum.com/forum/lighti...e-19-a-101585/

Thanks, looked through there but wasn't able to cipher anything out that helps me. I'm good with logic and mechanics but when it comes to electrical schematics I'm like my wife looking at a road map. Is there anything that tells what's normal draw for different things? I did find that the driver's seat has some issues as there is a yuuuge reduction in draw with it disconnected. The seat heater got left on and cooked the seat. Seat heater is another line that has some draw to it but I'm not on that one yet.

Thanks!

OK, I'm making good progress here. The driver's seat has some sort of a short in it and the courtesy lights do as well. If I could get ma draw readings for the ABS and seat heaters with the key off, engine off that would be great.

Thanks,
Mark

It sounds like you may have a bad door switch. If the truck "thinks" the door is open, the RAP circuit will not stay energized, but the courtesy light circuit will.

OK, I'll check them next, thanks!

Well...Driver's door checks out OK, passenger's door has no wires connected to it and I'm having trouble finding them. Still looking for what the ABS, seat heaters and horn draw when the vehicle is sitting with the key off.

Had to use a battery cutoff switch, only room enough for the kind you open the hood up and use. I do that when it will sit more than a few hours. Garage said no need to, looks like I killed off the second battery in a month.

Check for parasitic battery drain. I've had to use a battery disconnect switch if it's sitting more than a few hours. Like Charley Brown says, ARRRRGGH! That's ARRRRGGH!

Nothing here proves the battery is good!

According to Yuasa engineering, ONE discharge below 10.6 volts will permanently damage one of their lead acid automotive- type batteries. (GC-6)

One time!

Its possible a deep discharge has damaged the battery maybe from the heated seat, and now the drain is near normal and the battery is damaged.

Guessing wont work. Need a DC ammeter in line with the battery.

The max discharge current is easy to calculate. Amp hour rating of the battery (not cold crank rating) divided by hours.

Auto lead acid batteries are designed for high cranking currents not overall amp hours. The AH rating might be something like 45 for a CCA rating of 300.

Guessing by disconnecting things isnt much help without current measurements.

Be absolutely sure the alternator is 14.5 ish volts, the battery is not damaged, not being fast charged ( fast charging only puts a surface charge on the battery plates it doesn't charge the whole plate).
Must charge completely, 24 hours or so slow charge. No fast chargers. They sulphate the battery.

If you have a 12 volt power supply try using it instead of the battery. It wont discharge.