battery drain - need help

harrylime · August 5, 2019

I have a slight electrical issue, which in terms of fault finding, is my worst nightmare. I believe my Battery problems stem from a parasitic drain, which has been there since I bought the car six years ago. My Battery is usually flat within a week. I have a CX 5 charger but for various reasons, it is not always in place. I have trawled the forum and I'm clearly not the first to have this problem. Following guidance on the internet, I have tested for a current drain, while removing fuses one by one. The two fuses that seem to be the culprits are the 20a fuse- Radio 1, and the 10 amp fuse - MPX-B. I then realised that I have not "put the car to sleep" by bypassing the bonnet latch, which may explain the high reading. I am waiting half an hour or so, and will then check the current drain again.

If I am reading my tester correctly, the drain is in excess of 1 amp, which seems excessive

1. The bonnet latch thing, is it just a case of pushing the centre of the latch down and then inserting a small screwdriver into the hole that appears at the right hand side of the latch, to open the circuit? I'm assuming this deactivates the alarm?

2. If the car is functioning properly, how long does it take to reduce the drain on the Battery?

3. My rev counter does not seem to be working, any obvious/easy fixes for this?

I'm getting a bit frustrated with what is otherwise a very reliable and enjoyable car, so would appreciate an input.

plexus914 · August 6, 2019

I wrote an instruction some years ago. Good luck.

Before you measure any rest current your car has to get into "sleep mode". Keep in mind that in order for the car
to sleep at all it must be off and nothing can be "touched" (no opening of the trunk or doors, no pressing any buttons
on the key fob etc.) If something is touched the timer starts all over again. How long it takes for it "to go to sleep"
I am not quite sure, but 30 minutes should be enough and rest current should be under 0,05Amps (50mA). For comparison
my 1997 LS400 has a rest current of 24,8mA. Alarm went off at about 11,82Volts.
Battery should be charged when less than 12,4Volts (75%).

Procedure of how I did it and got a reading of 24,8mA:

- Turn ignition off and pull the key

- Open engine bonnet and close its lock with a screwdriver

- Close all doors

- leave the Battery connected and arm the anti theft deterrent system either by key or by key fob.....and check
security lamp if it works

- to be sure leave the car alone for about 30 - 60 minutes (I went back to the car after about one hour)

- go back to the car's Battery and measure rest current without interrupting the current.

Before disconnecting the Battery put the pair of test leads (black one/-)to the negative Battery terminal and
the other (red one/+/amps or mA) to the negative terminal clamp.......now disconnect carefully terminal and clamp.

PS: I put a Varta E23 (70ah 630a) in. That was 5 years ago and without any problems since.

Varta E23

(Weight:    17 kg
Length:    261 mm
Width:    175 mm
Height:    220 mm)