Help with Battery PLEASE!!

[JMallows]

Hi everyone, i have a problem with my battery, that i cant work out!

I had a new battery a month or so ago, and it has been fine everyday since. I was using the car all week, and with no problems at all. On Thursday, i went to use it and the battery was flat, not 10V or 9V, but 0.02V. I got a new battery, but before i put it in, i found the car was drawing 19A! My first thought was the HRW, as surely as bulb would drain it to like 9V then the bulb would stop working? Whereas the HRW would keep drawing to zero?

I then pulled out a fuse at a time, the HRW made no difference, so that left me back to the drawing board. When i pulled out the horn, the current dropped right down. Seemed to be the problem... So i put it back in, and the current didnt go back up! So i dont know if it is the horn, or something unrelated? I cant see why it would be the horn?! What else can i look at?

[Ben Lessani]

19A? You sure you hooked your multimeter up right > I don't know many non-industrial ones that even read above 10A.

Only real way to find a parasitic drain is to do as you've done, watch the MM as you pull wires/fuses. A bulb will continue to draw current until the batt is flat - but like you say, a relay will cut off flow around 9v.

[danny_p]

19A  is a lot of power you chould not fail to notice a drain of that size.     260 w  ish  onlt things that can plull that much on there own are the, radiator fan, rear heated screen and the headlights.  any other componets drawing that  would be getting hot and smelling.  inlet manifold pre heater on a carb engine chould do draing rather well.

also may find that 19A was peack load when you connected the multimeter when first connect battery to car there is surge of current for a few moments probaly want to check the multimeter as well now 19A will have poped it or if lucky just the replaceable fuse most of them as ben said they are only meant to read upto 10A normaly

190mA  would not be an unrealistic drain from the battery but that wouldnt cause a problem

bulbs are a resistive load they can happily flatten a battery to zero infact  the less voltage applyed to a bulb the cooler the filament so its resistance is actualy lower.  but the whole lighting up bit gives them away.

 

[JMallows]

I am fairly sure it was 19A, then it went down to about 14A. I cant understnad it myself, as the meter does have a 10A fuse...! When i pulled out the horn fuse it went to about 200mA, which i thought was fine, as my radio was on.

I also thought that a bulb was a 12V bulb, thus would need around 10V minimum to switch on, and if it fell below, it would switch off?! Also, if my horn was drawing a large current, surely i would hear it?!

I will check the inlet preheat as well, hadnt thought of that. Though, that is relay controlled isnt it? The other thing is, if theres 20A going through the horn system, surely it would fuse the 15A fuse?!

[danny_p]

bulbs are just a long length of thin tungsten wire coiled up in a vacume or inert gas.     current flows, resitance of the filament causes a voltage drop whitch means power is disapated int he form of heat and light,     a 12v bulb will quite happily draw current froma 6 volt source,  it just won't light up very well.

also fuses lie,   take a 10 amp fuse you can pass 10 amps though it all day long  as it's desinged to protect a circuit that normaly takes 10 amps.  at 15 amps the fuse link iself will just get warm but not actualy melt normaly take 2-3 times fuses rated current to make it blow.  by the sound of it you have a magor issue with something connected to the horn circuit 

[Agreeable Slick]

alternator regulator.

[Wayne]

^^As above Alternator, I had one fail once and it would drain the battery in a about 10mins.

[Ben Lessani]

... when the car is off

[Wayne]

... when the car is off

No mine was running but cannot think of anything else that would draw thet much current.

[Wayne]

Only other thing I can suggest is has your fuse box burnt out and you have a short.