Battery drain

David1965 · October 12, 2015

I recently bought a 2002 2.5 s type, i immediately bought a new battery as i was told the one fitted needed replacing as it wouldn't hold its charge.

The day after i got it home the new battery was dead. I got it started by an RAC man but the following day the same thing happened again. Only this time i had noticed something when coming home after a walk with the dog, i noticed the radio had turned itself on.

I done a bit of research on the internet and it pointed to the ignition switch being the cause,apparently a micro switch doesnt switch off and causes the radio to come back on.

I went out to the car and turned on the radio with the engine running then turned off the radio then took the key out of the ignition. After a few minutes the radio came back on. I removed the fuse to the radio for the time being to save my battery.

So i went and bought a replacement ignition from a breakers yard and found it wouldn't work without being programmed so i discounted this now due to cost.

My plan now is to fit an on off switch between the live on the radio. My problem is now i'm not sure which wire to break into as there is a constant live and another live described as a live for the radio accessories, can anyone advise me on this please.

Thanks in advance.

Raistlin · October 12, 2015

The permanent live is there to power the head unit memory, including the security code. If you put a switch in that wire, you'd have to re-enter the security code each time. There is also the possibility that the car's security system would interpret it as an attempt to steal the head unit.

It isn't definitive from your narrative but I'd suspect that the problem you have is probably due to the ignition switched supply.

What causes me more concern though is that ( I thought) that the audio power on - off switch, integral with the volume control, should completely disable the radio, regardless of whether the ignition is on or not, although I will admit to having minimal experience with the earlier audio head units.

David1965 · October 12, 2015

Thank you for your reply, that all makes sense. Do you mean by the ignition switched supply that it will be the other live feed i mentioned or could it be the radio unit itself, as you said if it is switched off then it should be disabled.

Raistlin · October 12, 2015

I've been out to the garage and checked. With my car, I can't turn the radio on without the ignition switch being set to acc, which is the first position, also, if the radio is switched off, it stays off when you cycle the ignition.

If you switch your radio off, then switch the ignition off for say, 30 seconds, then switch the ignition on again, does the radio remain switched off?

David1965 · October 13, 2015

Hi, I have tried your scenario and the radio stays switched off, it normally comes back on some time later of its own accord. I have checked it 30 minutes later and is still off, i will check again in an hour or so.

David1965 · October 14, 2015

Well the radio stayed off for a whole day but came back on this afternoon, it is definately something to do with the ignition switch.

I would like to put an on/off switch in between the supply from the ignition switch and radio and not the cjnstant live from the battery.

So can anyone advise me which wire it will be at the rear if the radio.

Raistlin · October 14, 2015

Looking at the 2002 MY electrical manual, it should be the yellow wire (FC949) at the main connector on the audio unit.

If you intend to insert a switch, I'd suggest breaking into the wire at the audio unit end, not the ignition switch as that provides ignition controlled services all over the car David.

David1965 · October 14, 2015

Much appreciated, I will let you know how i get on.

David1965 · October 15, 2015

I have got the radio out and there are 3 plain yellow wires on the top row of the plug, anyway of identifying the correct yellow wire.

David1965 · October 15, 2015

I have checked the scemayic for mine and it looks like the ignition supply to mine is FC94 2 which is showing WR (WHITE&RED) I think. I will post diagram below.

Any thoughts please before i cut any wires.

David1965 · October 15, 2015

Just to confuse things there are 2 red and white wires. One is thicker than the other so confused.

David1965 · October 15, 2015

Because i'm impatient I have cut both of the red and white wires and both are wrong.

My aircon doesn't work now so i'll have to rejoin these wires somehow.

I need more advice please.

David1965 · October 15, 2015

I have now cut the nearest yellow wire nearest to the red & white wire which appears to be fc949, but radio still on.

Raistlin · October 15, 2015

At this rate you'll have cut all the wires before I get home from work. Have you ever worked in bomb disposal David? That was very much tongue in cheek by the way... please don't be offended :)

I concur that the yellow wire(s) are not involved, being the SCP network bus. I was thinking about a different wiring concern... ooops.

I also agree that the correct wire according to the diagram is a white / red to FC942.

Using your photo for reference, it is the wire on the BOTTOM row, second position in from the RIGHT. That traces back to the ignition switch accessory function. If that is the wire you've cut then it should isolate the ignition controlled supply to the audio module. So I'm now at a loss as to why the radio still switches on.

I think at this stage, I'd test for B+ on FC942 with the ignition off, then accessories, then on, just to test the function of the ignition switch. I would then keep checking FC942 with ignition OFF over a period of time. It should not ever become live with the ignition off, even after the periods of time you've mentioned. If I'm right, that would, in turn, suggest an intermittent B+ within the audio module.

Further, if the ignition switch has produced B+ when switched off, all the other accessory circuits should be live as well. Have you checked that David? Figure 01.4 ( Ignition Switched Power Distribution: I (Accessory) ) will tell you what pother circuits are live on accessory.

BTW, soldering or barrel crimps for re-joining. These are power supply wires so you don't want to take any risks. PLEASE do not use Skotchloks.

David1965 · October 15, 2015

I think I won't be looking for employmemt with the EOD. I'm not familiar with electrics so i don't know what you mean by B+, i do not have any electric testing equipment either. What is the audio module.

Raistlin · October 15, 2015

Sorry David.

B+ is car electrics shorthand for Battery Positive voltage, ie 12 volts. If you do not have a Volt meter (DMM) then if you have a 12 volt Bulb, that will do. Anything which runs or lights up with 12 volts. Connect one side to earth and the other to FC942. Keep testing at intervals to see if B+ does suddenly appear. As I said, I'm of the opinion that it will not appear, as you haven't mentioned any of the other accessory controlled circuits live with ignition off.

If I can recommend, a small cheap DMM from fleabay is an ideal piece of kit to have around. They cost a few pounds and are invaluable. They do not need to be extremely accurate but are sufficient to give indications. The following link will take you to an ideal candidate.

http://www.ebay.co.uk/itm/LCD-Ammeter-AC-DC-Voltage-Checker-Tester-Digital-OHM-Multimeter-Voltmeter-/251800519897?hash=item3aa07b04d9

This is most certainly NOT state of the art diagnostic equipment but is ideal for most purposes in terms of car and household electrics. I have this very model on my workbench and another of the same in my car.

By audio module I mean the radio, where connector FC942 is. I tend to say audio module because there are several different ones depending on spec / year.

David1965 · October 15, 2015

Just to confuse things a bit more, prior to me cutting the wires I had removed fuse F18 (20amp) from the primary fuse box under the steering wheel and this did not seem to cause anything else not to work other than the radio.

Now looking at fig 01.3 this fuse has a brown & red wire coming from It then splitting into 2 brown and green wires. The diagram shows it going to 2 boxes numbered 82 & 83, i'm assuming here one is the radio.

I have just checked the plug that i removed from the back of the radio and there is a brown & green wire. I think maybe i should cut this one and see what happens, any thoughts.

David1965 · October 15, 2015

Ok I will order the multimeter it looks like it will come in handy.

I won't be able to do any more work on it now until tomorrow evening, i will keep this thread updated as I go along.

David1965 · October 22, 2015

I've reconnected the wires and fitted a switch which will be temporary until i get the replacement ignition switch fitted at some point.

I have had to connect to the battery side as i don't want to start cutting more wires, its the wrong thing to do really as I need to re enter the radio code when the switch is turned off but it will only be once a day.