New battery goes dead in two weeks.Test light shows a drain ,and I hear a relay open and close when the battery is disconnected .Any ideas?

 

I'm betting that if you can track down which relay is being energized, that will give you a good clue as to which components are suspect for the battery drain. After you get close to the source of the relay sound by ear, you may need to feel suspect relays for vibration with your finger while a helper connects the battery. That should allow you to zero in on the offending relay when mounted close to other relays. If that fails, unplug suspected relays one at a time to see if the sound is eliminated when the battery connection is made. Good luck.

 

It's normal to hear the relay when you disconnect or connect the battery.

Best way to tell if you parasitic current draw is normal is to measure it ... 20 mA is normal. Make sure you check it about 15 min after closing all the doors and make sure the hood light is off. The computers will not "time out" until about 15 min after the doors are closed.

 

Exactly right. The BCM goes into "sleep mode" after 15-20 minutes, you can hear a relay click when this occurs.

 

You CAN NOT test battery drain issues with a test light. PERIOD! Any car with a PCM and or BCM type of computer will ALWAYS draw some battery current. Our C5's draw approx 20 milliamperes once that BCM goes into the programed sleep mode just like Quicksilver Vert 01 and ZeeOSix stated. Your light is ALWAYS going to be on even if your current draw it text book perfect.

Use a DC amp meter capable of reading at least 10 amps and disconnect the NEGATIVE Battery cable. Install the amp meter between the battery cable and the battery terminal. When you first make the connection, you will hear relays click and the headlight motors will sometime operate for a very short period of time. Thats very normal. You may see as high as 8 amps when you first connect it. Then it will systematically drop off to 2 amps, then .5 amps. Once the BCM times out, that will be your finial current draw reading. Usually 10-15 min. If you disconnect the BCM or battery for any reason, or open a door or cause the BCM to come out of sleep mode, this process starts all over again.

Some of the most common things that can cause excessive current draw are:

- Drivers or power passengers seat multifunction switch fails to return to the neutral position and the seat trys to drive into the stops. usually in the rearward position. The air bolster in the seat back can also stay on (if you have that option)

- Drivers seat position feed back pots fail and the MEMORY seat continues to drive to the fully retracted fully lowered position. The seat motors are protected by a thermal fuse and they will trip and reset until the battery dies!! You can UN-PLUG the drivers seat to see if that solves the issue. Just makes sure it's in the correct position for you to drive it.

- The BOSE amp in the drivers side foot well (above the accelerator peddle switch) remains ON due to a bad Bose relay.

- You have an interior light or some interior dash lighting that is staying on. Check your car in the DARK. See if there are any dash of interior lights that stay on. Don't forget about the trunk lights and hood lights. Ive seen bad BCMs due to corrosion on the back of the circuit board cause this issue.

- Alternator diodes can be bad. Ive see an alternator draw 5 amps just sitting due to bad diodes. Once you determine your current draw, reconnect the battery and disconnect the large red wire on the BACK of the alternator and insert the amp meter between the red wire and the terminal on the alternator. You should see zero current draw. (engine not running key OFF)

- Sun visor lighted mirrors stay on.

- I have seen ignition switches go bad and cause normally OFF circuits to remain ON. The contacts arc together and the circuits do not turn off. I have an ignition switch repair thread that explains in detail how to repair and rebuild that switch.



-Thats all that I can think of off the top of my head.

I have also seen this problem be intermittent and when you do your current draw checks, everything will be NORMAL!

If you have any questions on what your seeing, let me know.

Bill Curlee,,,,In sunny Guam

 

There you go, Ol'Wrench.

From the BEST of this Forum, and from halfway 'round the world as well!

 

Here is how I set up my car to conduct the current draw test. I just used some green 18 ga stranded wire to connect the meter to the circuit. The meter is reading 0. 02 amps or 20 milliamps.







BC