I'm stupid but please bear with me -battery testing again

[nik]

Guys,

Purchased a multimeter very similar to the one shown in the link by toolpants.

The problem I have is that I disconnect the earth lead from the battery with the key in the ignition so the alarm doesn't go off, however if I take the key out of the ignition the alarm will sound, having the key in the ignition plainly draws current as using the same 10a scale as toolpants I was getting readings of 2.74.

I did manage to take the key out of the ignition to give me enough time to take a reading and the reading came down to 0.54 still very high I think that is 540 miliamps, but then stupid alarm went off.

So my question is what is the exact step by step process to give me a benchmark reading that I can work from.

I know I'm rubbish at electrics but I really do value and thank you all for your advise, I've just been made redundant so don't really want to take the car to my local OPC.

Thanks again guys, I look forward to hearing your comments.

Nik

[nik]

guys just a quick thought that may or may not work, forgive me if i'm being stupid again.

1. Could I keep everything connected and just remove fuses and touch the 2 contacts on each fuse holder to get a reading , that way the ignition key would be out, the alarm wouldn't go off because it has power ( but shouldn't draw power because it isn't set) all I would have to do is close the drivers door latch so the courtesy lights don't work, I could evn shut the door and crawl iinto the space and work with everything as normal.

2. Is this possible or would I have to ground the negative lead , I could use the door hinge potentially

As usual all suggestions are welcome, and apologies if I'm thinking illogically.

Nik

[nik]

Whilst waiting for a reply I thought I'd try the fuse approach, so I left everything connected and touched the multimeter prongs on the fuses, to test I switched on my sidelights and the meter gave a reading of 78 miliamps, I then went through each fuse and the only one drawing a current was the radio at 40 miliamps.

Don't know whether this is the right way to test but if it is it would seem that all is well with the circuits that are fused, any other ideas, Battery, relays etc, if so how do i test them.

Whilst at the car I checked the battery volatge at rest and it was 12.3 volts and 14.2 when charging.

All the above could be of no use whatsoever of course.

Regards

nik

[wvicary]

Nik- I've never tested for a draw through the fuse block like you describe so don't know if it's a valid procedure or not. With the Neg. cable dissconnected, do the signal lamps flash or just the siren? Could it be possible that the alarm has it's own power supply? I'll do some more reading to see if I can dig anything up. Sorry I can't be of more help right now.

540ma is an excessive draw but it could be the way you tested for it. By the way... are you in the UK and if so what part?

[nik]

Nik- I've never tested for a draw through the fuse block like you describe so don't know if it's a valid procedure or not. With the Neg. cable dissconnected, do the signal lamps flash or just the siren? Could it be possible that the alarm has it's own power supply? I'll do some more reading to see if I can dig anything up. Sorry I can't be of more help right now.

540ma is an excessive draw but it could be the way you tested for it. By the way... are you in the UK and if so what part?

Yep

Im in the UK in Leicestershire, I'm not brilliant at electrics so it might be that I'm doing it wrong, with regard to the alarm I'm pretty sure it has its own battery back up but again Im no expert so I dont know for certain. thanks for offering to do some research ill keep an eye out fopr your posting.

[Tool Pants]

I did not realize until now that you had a UK car with the alarm siren. We do not have this in the US. The siren has a rechargeable battery that is separate from the main battery that you replaced. As you have found out, if you disconnect the main battery and the ignition key is not in then that siren goes off. I have heard the siren is very loud....

[nik]

I did not realize until now that you had a UK car with the alarm siren. We do not have this in the US. The siren has a rechargeable battery that is separate from the main battery that you replaced. As you have found out, if you disconnect the main battery and the ignition key is not in then that siren goes off. I have heard the siren is very loud....

toolpants,

It's very very very loud, upset all the neighbours, but hey who cares they all drive euroboxes. Although they do find it extremely amusing that my so called epitomy of engineering excellence is giving me continuing problems.

[Rodger]

I don't think testing curent flow at the fuses is effective, as all of the current won't be flowing through the meter. Some will still go through the negative battery cable to ground, leaving your fuse measurements inaccurate.

First thing I'd try to do is disconnect the alarm siren power supply so you can work without it going off or drawing chage current. Taking the current measurement at the battery's negative terminal is paramount.

[pjslowik]

2. Is this possible or would I have to ground the negative lead , I could use the door hinge potentially

As usual all suggestions are welcome, and apologies if I'm thinking illogically.

WARNING - if you at any time connect the meter leads between +12v and ground, while in amps setting, you will cause a dead short. For checking current measurements, only connect between two hot or ground leads.