Earth/Current Leak on 940.

Hi, Having been playing around with injectors and recently had a new battery fitted I was surprised to find a flat-as-a-pancake battery in my 940 when trying more on the injector side... So, I have a leak somewhere, which may explain the need for the new battery in the first place.. I have checked through the fuses to find which circuits should have current and have found a couple with a 0.01 draw on them.. If there a detailed sheet with fuse number and current draw available or handy somewhere.. Thanks for pointers. :) Des. . . ;)

Des, I wouldn't have thought that a 0.01 amp draw would be enough to flatten your battery in short order? Have you tried disconnecting the battery completely, then seeing what, if any, current draw is being taken via the main +ve or earth connection. I'm wondering if it could be something like a rectifier diode breaking down, and allowing back feed, or tracking across the starter contacts, something that would not show up through the fuses? Shoot me down in flames if I;m talking rubbish, 'twas just a thought.

Checking for leakage across the starter contacts, I'd use a megger tester, but you'd need to make sure that everything else was disconnected first so you didn't fry any electronic components. If I megger mains voltage plant, anything less then 4megohm is regarded as reportable.. keep an eye on it. Under 1 megohm is indicative of an earth leak somewhere. For a 12v system, not sure what I'd regard as an earth leak, but under 0.5 meg would be enough to look further. If you haven't got a megger, then an ordinary multimeter should show a resistance reading of infinity really. This is across the starter contacts, not the windings. You can't really meg the motor itself with a chassis earth return, half the circuit system like in a car, but you'd not be worrying about that, you're looking for something leaking across the contacts when it shouldn't, not bad windings

Hi, Ohh look.. Something flew straight over my head.. :) Auto electrician it is then.. :) Des. . . ;)

Could it be that there is not something draining the battery, but the battery not being charged properly? A megger is a make of insulation resistance meter - basically an ohmmeter, but testing with 500v. Check the battery state with the engine running.... you know the drill! What is the overall current drain from the battery with ignition off and alarm active (armed, but with bonnet open)?

Hi, Checked the voltage across the battery posts with the new alternator and was getting about 13.7v But the car has not been on a run for a while... Des. . . ;)