How to diagnose an electrical fault??
Discussion
The Cerbera has suffered from the battery going flat over a long w/e. I think something is drawing current from the battery but I'm not 100% sure how I go about finding the fault.
I think I disconnect the +ve terminal on the batterly, shove a multimeter set to AMPs between the +ve post of the battery and the +ve cable, see what is being drawn. Then I go round to the rfuse box, pull fuses out until the current draw drops off.
does that sound right?
Anything common to draw current on early cerbs?
TIA
D.
I think I disconnect the +ve terminal on the batterly, shove a multimeter set to AMPs between the +ve post of the battery and the +ve cable, see what is being drawn. Then I go round to the rfuse box, pull fuses out until the current draw drops off.
does that sound right?
Anything common to draw current on early cerbs?
TIA
D.
My experience of trying this (admittedly on a Cosworth, not a TVR) was that the pull-in current from all the relays that were active, even when the ignition is off, plus the inrush current to the EMU (which is powered up all the time) blew the 2A fuse in the meter.
I thought about juggling bits of wire to connect & then insert the meter, but couldn't find the round Tuit.
I thought about juggling bits of wire to connect & then insert the meter, but couldn't find the round Tuit.
How old is your battery. It's getting colder in the mornings and this usually causes a spate of flat batteries at this time of year.
If you connect a meter in series with the battery you'll probably end up poping the fuse in the meter. Better to measure the volts at the battery terminals.
Recharge the battery, leave for 24 hours or so and measure the voltage across terminals, should be 12V. Less than this would point to a dud battery.
If you connect a meter in series with the battery you'll probably end up poping the fuse in the meter. Better to measure the volts at the battery terminals.
Recharge the battery, leave for 24 hours or so and measure the voltage across terminals, should be 12V. Less than this would point to a dud battery.
Your technique sounds fine assuming your multimeter can measure reasonably large DC currents. I don't know what capacity your battery is, but being a bit pessimistic it might be a 100Ah battery going flat in 50 hours ... i.e discharging at about 2 amps. So if your meter has a 0-10A DC current range, you should be fine.
Would another way be to haul fuses in turn and put the ammeter across the fuse terminals, until you find one with significant drain?
I'm assuming that the current draw on any one of these shouldn't be too high, and that replacing a low rated fuse, briefly, with a potentially higher rated ammeter shouldn't be a big risk?
Just thinking out loud, and running the risk of the old ASSuME problem.
I'm assuming that the current draw on any one of these shouldn't be too high, and that replacing a low rated fuse, briefly, with a potentially higher rated ammeter shouldn't be a big risk?
Just thinking out loud, and running the risk of the old ASSuME problem.
Marshy said:
Would another way be to haul fuses in turn and put the ammeter across the fuse terminals, until you find one with significant drain?
I'm assuming that the current draw on any one of these shouldn't be too high, and that replacing a low rated fuse, briefly, with a potentially higher rated ammeter shouldn't be a big risk?
Just thinking out loud, and running the risk of the old ASSuME problem.
oh yes good point...
D.
Marshy said:
oh yes good point...
'course, you'll be upside down in the footwell with your legs out of the window, but don't let that stop you...
Or standing up by the boot (Cerberas are far more civilised you know). In fact I could probably use the inside of the boot lip as a handy tray for a G&T whilst I complete the aforementioned task.
Chin, chin.
D.
kojak69 said:
As the battery is a barsteward to get out to recharge.., if you recharge in the car, make sure the charger is not more than 7 amp, as apparently it can damage electriacl items in the car. Better still, buy a trickle charger from Leven-£45.
I have a decent charger, I charge with the battery in the car, max of 4 amps.
The problem is that the car is on the street so running cables is a bit of an arse.
D.
D.
I think you can get an adapter from Leven which goes into your cigar lighter, if you are parked on the road and dont want wires all over. Theres also one which Maplins sell, which i think is solar powered, that also plugs into your cigar lighter.
As for the original problem, i dont know, but at least it should keep you 'topped' up.
Are you sure the battery is the correct one, and that the previous owner put the correct one in? Just a thought.
As for the original problem, i dont know, but at least it should keep you 'topped' up.
Are you sure the battery is the correct one, and that the previous owner put the correct one in? Just a thought.
davidd said:
Just buy a new battery?
I don't think there is much wrong with the battery, as it was new last summer and this problem has been happening since christmas (and I know the last owner suffered as well).
D.
Car batteries *really* don't like being discharged completely. Before I got a trickle charger, I was getting about 8 months life out of the battery on my Cossie - it only needed running flat once or twice and it wouldn't hold charge any more. So, get a trickle charger and religiously plug it in.
kojak69 said:
I think you can get an adapter from Leven which goes into your cigar lighter, if you are parked on the road and dont want wires all over. Theres also one which Maplins sell, which i think is solar powered, that also plugs into your cigar lighter.
As for the original problem, i dont know, but at least it should keep you 'topped' up.
Are you sure the battery is the correct one, and that the previous owner put the correct one in? Just a thought.
I have a maplins solar one which is outputting some power, however the battery went flat in spite of that. Fine this morning though.
I have a feeling there is an intermittant fault in the electrics somewhere. I suspect the alarm/door sensors but not sure. Anyway someone has lent me a decent multimeter so I'll have a fiddle over the next few days.
D.
Right, tested at each fuse with the car locked.
Only the radio and the alarm are taking anything (the radio .1 and the alarm about .2 of an amp).
Nothing else seems to be drawing power, and the car has been fine for a couple of days. I'm therefore wondering if I have an intermittent fault with the door sensors or the alarm.
Is there anything which takes power from the battery which is not connected via the fusebox? Which fuse does the fag lighter take its power from? As the book has no mention of it (early Cerbera 4.2)
TIA
D.
Only the radio and the alarm are taking anything (the radio .1 and the alarm about .2 of an amp).
Nothing else seems to be drawing power, and the car has been fine for a couple of days. I'm therefore wondering if I have an intermittent fault with the door sensors or the alarm.
Is there anything which takes power from the battery which is not connected via the fusebox? Which fuse does the fag lighter take its power from? As the book has no mention of it (early Cerbera 4.2)
TIA
D.
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