Rover 400 - regular flat battery

It would help if you could establish the size of the power 'drain'. Disconnect a battery lead and insert an ammeter between it and the battery. See what current is flowing even when everything is 'off'. If it's more than about 40 milliamps then try disconnecting various bits of equipment until the drain stops.

Are you sure the battery is OK? I mean, will it hold its charge overnight even if not connected to anything?

Rob Graham

The battery is 3 weeks old..!

Going off to buy a multimeter right now..! Can I remove either battery terminal to do the check??

All the Best, John

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the reading was 90 - 95 milliamps..! removing the fuse for the tail lights and horn bought it down to 41 milliamps

not sure where i should check for faults/shorts on these circuits.

All the Best, John

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90-95 mA is high but it'll still take over a week to discharge a fully charged battery, is the charging circuit working properly?

The only check I've done is put the meter across the battery terminals with engine running, headlights on, rear screen heater on.... result was 13.6V

All the Best, John

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If it raises to 13.8 when you run the engine at ~3000rpm then that's fine, if not then either the regulators a tad low or the multimeters not accurate.

Well, it appears that the tail lights and horn are drawing about 50 milliamps even when off. They shouldn't draw anything. Are you sure there's nothing else on the same fuse circuit? If there isn't then there must be something amiss with this circuit. It's unlikely to be a short though because that would blow the fuse or melt a wire.

Rob

I suspect that's where the alarm is fed from. And thus is revealed a weak spot on many vehicle alarm systems...

Mike

According to the handbook...it's just stop lights and horn...the alarm still arms without this fuse in.

All the Best, John

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still arms without this fuse in.

It's difficult to know, then. Try taking the stop light bulbs out or disconnecting the horn and seeing if that changes the current draw. It's really a case of disconnecting bits of the circuit and tracing the fault in that way.

Rob

Unplug the alternator lead after you've stopped the engine and see if the battery still discharges overnight. Don't forget to reconnect it before starting the engine!

Darren