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'00 DeVille battery drain

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1.6K views 10 replies 6 participants last post by  dogbiscuit  
#1 ·
Ok another battery drain issue



so I changed the alternator, no fix

my moms car drains the brand new battery in one day

yes I checked no lights are remaining on even trunk.
i hook my meter in series to negative battery lead negative on battery positive on battery cable.
with doors closed waiting 10 min about a 2.7 or 2.8 draw. Goes a little above 3 if doors are open (it’s Texas summer too hot to keep everything closed or I will pass out)
FYI in my testing the battery drain is with the car sitting, key is NOT in ignition, stagnant as if it is sitting there parked.
here is where is gets wierd. If I disconnect red lead to fuse box under rear driver side seat then drain goes away. One by one I pull every fuse and relay. But the drain remains the same. I have looked at the wiring diagrams which was no help. There has to be something getting its power from that fuse box that is shorting out but I am not sure what other than the stuff that has a fuse or relay gets its power from that fuse box.
Already spent thousands with the mechanic fixing this car for my mom (freeze plugs, head gasket, window motors and regulators, computer box that controls trunk and fuel door release, power steering line, etc etc lol)
Other than replacing the radio which doesn’t work although I have replaced half the speakers and have the rest I am just gonna let the shop that puts in a new head unit put the rest in, this is this is the last thing to fix on this car.
Car runs good and smooth all day but next day battery is dead. It’s not a small drain so it should be jumping out at me but it’s been about 3 months now and I am pulling my hair out at this point.
any help or suggestions?
 
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#3 ·
Probably not the battery.

Did you remove the relays in the rear fuse box, too? Some have had problems with a hung IGN or FUEL relay.

A 2 or 3 Amp vs 25 mA drain will kill a battery in less than 10 hours.

Your (?aftermarket?) sound system - if the amp does not auto-disconnect it WILL drain the battery quickly.
 
#4 · (Edited by Moderator)
It's the battery, trust me! I just went through the same issue. These vehicles are very demanding on batteries.
On second brand new battery

Probably not the battery.

Did you remove the relays in the rear fus box, too? Some have had problems with a hung IGN or FUEL relay.

A 2 or 3 Amp vs 25 mA drain will kill a battery in less than 10 hours.

Your (?aftermarket?) sound system - if the amp does not auto-disconnect it WILL drain the battery quickly.
Yes I have pulled every relay and fuse and the draw remains but if you disconnect the whole fuse box it goes away. This leads me to believe something is getting power from this fuse box (but not from a fuse or relay) so it seems something is in series does the front fuse box get its power from this fuse box?
 
#7 · (Edited)
You have a fuse and relay box under the back seat pad, opposite side from the battery.

Rogueknight which "Deville"? base, DHS or DTS - it makes BIG differences in some parts and repair advice offered.

Some Devilles and later "DTS" models have had a rear battery box problem with a part of the under-seat bracing squashing the fuse box and shorting one or more relays.
 
#9 ·
Is something plugged in to a power port ?? (even a dime or penny)

The 12 Volt power ports (cigarette lighters) are normally controlled by RAP (Retained Accessory Power) and should turn off 10 minutes after you remove the ignition key. Some models use 2-way fuse receptacles for the power ports - one side of the receptacle is RAP controlled, the other side is always hot 24/7.

Example from my 2002 STS underhood fuse box -

Image
 
#11 ·
Hope you have a pile of $100 bills if you go to the dealer, you will be MUCH better off finding a local independant garage that is willing to work on it. Stay away from the chain stores, their techs are mostly young ppl without a lot of experience with older vehicles. Ask your friends and neighbors for recommendations. For now I would remove the relay that's heating up. My 04 has a power port under the front passenger seat but I don't remember there being 1 on the 01