i found out that the CPU under the driverside dash above the hood latch is causing my slow drain on my car. when the car is off why is the CPU drawing power??? the CPU shouldn't be drawing any power because the car is off right??? do i have a bad CPU??? i need someone who is a professional at wiring harnesses... please help me

 

It's possible. Anything that receives power full time has the possibility of failing and causing a drain. The CPU does have connections that receive power at all times from the battery. Normally, this shouldn't cause a drain, but could if the CPU is bad. Are you certain this is the cause? How did you trace it down?

If you are sure it is the problem, just replace it and you should be good.

Kent

 

Get a new battery....

A small drain won't hurt a battery if your not getting cranking amps it's something else. Like wires and alt if not the battery.

 

why Get a new Battery?..If the car is Draining the Battery then it is Not "right".The Source of the Battery Drain should be Found..If you can Get at the CPU.First measure the Battery Voltage..and also See if the there is Current Draw with the Car off.then ,Disconnect it,and Measure Current draw again..or Wait overnight and Test the Battery again..that will tell you IF Indeed that Particular Part is Drawing Current,and Draining your battery..One of the Ways to Test For Current Draw on the car is to Put an AMMETER in Series with one of the battery Cables(usually Positive)..and look at the Current "being Drawn'..then Start to Slowly Pull Fuses,in the car Until the Draw Stops..then you have a pretty good idea of which Area to look for problems..it could be anything from a Hood Light(if they have them) to a Door Switch...anyhow Good Luck.

 

Agree with MisterstyX69's advise to check those components.

I am not sure about older cars like ours, but when you have a drain that is killing your battery on a modern car one of the things to check for is the parasitic drain. On modern cars it is normal to have a parasitic drain for up to as long as 30 minutes after the key is taken out of the ignition. Usually you look for a amperage draw of over 50 milliamperes, if you have more than that you have a CPU that is on or some other module that is not turning off when it should be.

Like I said before, for our cars the ECU may not be advanced enough to have this type of problem... but it is worth a shot.

 

i aprreciate the quick responses guys... now heres the info:

i used a mulitimeter to find the slow drain (tired of charging the batt every 6 months). i have a red top optima, a new alternator, and i've figured out the the drain is on the LY circuit. this is located on the hazard fuse in the fuse box. now only when i have the CPU plugged in when the CAR IS OFF the LY circuit is still drawing power 10.5V. as soon as i disconnect the plug the drain is GONE. the only item that should be drawing power is the auto clock which i already disconnected. i've come to the conclusion its when the CPU is pugged in its drawing power to something.

is the CPU suppose to draw power at all times??? how do i eliminate all the possiblities from the CPU?? i dl the electrical diagrams but i just don't know where to go from the CPU to ????

 

Okay So without me pulling up a FSM, what is the LY circuit composed of? It sounds like there is something wrong with the circuit be it a ground or crossed wires or whatever.

As for your computer, as I said before, not even the computers on modern day cars (excluding things like clocks or alarm systems that are functioning properly) should be still drawing after 30 minutes, though some foreign cars may be up to an hour...

 

oh i see. so is it possible for the computer just to constantly draw power rather than shutting off within 30 min to an hour?? yeah as for the LY circuit, i've eliminated"

if i'm not mistaken this is what the LY circuit controls:

- lights off reminder buzzer (not really necessary)
- ignition key reminder buzzer (not really necessary)
- autoclock (i can rewire)
- luggage compartment light (not really necessary)
- door lock cylinder & ignition key cylinder lights (not really necessary)
- interior & spot lights (not really necessary, i'd rather have no lights than have slow drain on my battery)
- seat belt warning buzzer (not really necessary)

items i haven't eliminated:
- audio system
- power antenna
- turn & hazard lights
- meters & warning lights

as for the items i haven't checked, it can't be the audio system or power attenna because those items don't connect to the CPU (i'm assuming, not really sure). the only items thats hooked up to the CPU is the "turn and hazard lights, and meters and warning lights (i think). i'm not really sure. can anyone confirm this info???

 

if the cpu is drawing power, shouldnt it be outputting something too? powers gotta go somewhere

 

well isn't the clock on that circuit i noticed a drain on that circuit before check and make sure none of the buzzers are going off with the doors closed . also make sure there isn't any power to the interior lighting and stuff with the doors closed .
i had a similar problem due to my switch not fully closing . and a buzzer was constantly going off and every month or so i had to jump start the car .

 

Yeah, like heat. Was the CPU hot or warm?

 

from what i've been reading the clock is the only thing that should be drawing power. i already disconnected that item so it can't be that.

1gennutt: now as far as for the buzzer being disconnect, i have no clue. i don't know where the buzzer is located or what it looks like. my car's buzzer never worked but it is possible that the buzzer is still connected and could be drawing power, does anyone know how i can check whether its the buzzer??? what does it look like?? where is the location???

jeff20b: i'm not sure if the CPU was warm because i've been disconnecting the battery to prevent power loss in my battery. should i leave everything plugged in and test to see if the CPU is warm. what would the CPU being warm or cold mean?? that it's drawing power???

 

Any good battery can take a drain. I have more gear than Kitt in one of my other cars and I can let it sit draining for a week without starting it. There are RX7's that have sat for months with alarm on draining juice and will start right up. If your battery won't take a charge it won't hold up to a normal drain.

 

my car has other items that the battery can be drain from but i eliminated all of those items already.

-radio
- alarm
- autoclock
- luggage compartment light
- ignition key cylinder lights
- interior & spot lights


there's a drain and it is my mission to figure it out. i think it might be the buzzer. i need to find the location of this item and what it looks like. the manual also said its connected to a door lock cylinder???

 

replying to your question from jeff, The question was posed about the power has to be going somwhere. Power transfer such as heat in bad electrical devices is common. If your CPU is warm/hot after leaving it overnight you can be sure that is the problem.

 

I had to swap out a CPU when the blinker part stopped working. That's all I know about them. Yeah, feel around it for warmth on a cold morning.