Parasitic draw -old 1970's car

[HealeyV8]

Using a multimeter I've tested this and come up with a 10.5ma draw. Should I be concerned, as in title car is old so no computer and no radio.
The only things that should be live when ignition off is the cigarette lighter and I fitted a dedicated USB port.

[richhead]

HealeyV8 said:

Using a multimeter I've tested this and come up with a 10.5ma draw. Should I be concerned, as in title car is old so no computer and no radio.
The only things that should be live when ignition off is the cigarette lighter and I fitted a dedicated USB port.

Its not that high, but if your worried, pull fuses one by one with the meter connected, should show the culprit, does it have a clock?
That would probably use that much.
10ma isnt going to flatten a battery for a long time tho.
In the 90's about 30-50ma was about normal

[E-bmw]

richhead said:

Its not that high, but if your worried, pull fuses one by one with the meter connected, should show the culprit, does it have a clock?
That would probably use that much.
10ma isnt going to flatten a battery for a long time tho.
In the 90's about 30-50ma was about normal

^^^ Wot 'e said, that isn't a lot at all, certainly not enough to worry about 10 thousandths of an amp.

[droopsnoot]

Wouldn't the lighter socket be on the "accessory" position on the key, so not powered when the keys are out? They are on my seventies cars, I replaced the lighter sockets with USB sockets, but left them so they're not live all the time as I'd just be worrying about the battery draining otherwise. I only have four fuses so pulling them one at a time doesn't narrow stuff down much, but if it's something relatively simple it should be possible to disconnect each item individually to find the culprit.

[E-bmw]

droopsnoot said:

Wouldn't the lighter socket be on the "accessory" position on the key, so not powered when the keys are out? They are on my seventies cars, I replaced the lighter sockets with USB sockets, but left them so they're not live all the time as I'd just be worrying about the battery draining otherwise. I only have four fuses so pulling them one at a time doesn't narrow stuff down much, but if it's something relatively simple it should be possible to disconnect each item individually to find the culprit.

Whether it is or not is not really relevant as, without it being pushed in it won't be drawing current anyway, however many were.

[droopsnoot]

E-bmw said:

Whether it is or not is not really relevant as, without it being pushed in it won't be drawing current anyway, however many were.

I wrote that wrongly, I was thinking about the USB socket mainly, if that's wired in place of the lighter socket, and only because mine has LED illumination around it. I'm sure the OP would have spotted that, if that's the cause of their drain.

[illmonkey]

droopsnoot said:

E-bmw said:

Whether it is or not is not really relevant as, without it being pushed in it won't be drawing current anyway, however many were.

I wrote that wrongly, I was thinking about the USB socket mainly, if that's wired in place of the lighter socket, and only because mine has LED illumination around it. I'm sure the OP would have spotted that, if that's the cause of their drain.

To add, I fitted one and it has a button to activate. It's wired to switch +, but still off until I press the on button. If you didn't know they existed...

Seems like a very small draw, but also would be easy enough to narrow down, got to be worth an hour to try and find.

[HealeyV8]

I wired the cigarette lighter and USB into permanent live under dash. As to whether something is live or not if it breaks down it can cause a drain even if working correctly. I did have a proper drain on this car once and it was the relay fitted for the electric fan, the thermo switch for the fan was wired through ignition only but the main feed was off the back of the alternator. The fan operated OK coming on when required so I had no idea the relay was faulty. When the ignition was turned off the fan would stop even if running.
Car only has three old fashioned glass fuses so pulling one only identifys about a third of all systems.
I'll have another contortionist under the dash fiddle with the wiring I added for lighter and USB.

[droopsnoot]

HealeyV8 said:

I wired the cigarette lighter and USB into permanent live under dash. As to whether something is live or not if it breaks down it can cause a drain even if working correctly. I did have a proper drain on this car once and it was the relay fitted for the electric fan, the thermo switch for the fan was wired through ignition only but the main feed was off the back of the alternator. The fan operated OK coming on when required so I had no idea the relay was faulty. When the ignition was turned off the fan would stop even if running.
Car only has three old fashioned glass fuses so pulling one only identifys about a third of all systems.
I'll have another contortionist under the dash fiddle with the wiring I added for lighter and USB.

I have read that these USB circuits can draw power even when there's nothing plugged into them, because the components that drop from 12v to 5v take a small amount. The context I read it in was discussing those mains sockets with USB charging sockets built in, and the point they were making is that because the circuit is running all the time, the lifespan is not as great as it would have been had it been on a switch. In a mains socket it doesn't matter that it'd run all the time from the point of view of power drain, but from a battery maybe it would. If you can get access to the wiring it's fairly simple of course to stick your ammeter in line with the USB socket and see if that's the drain.

[richhead]

droopsnoot said:

HealeyV8 said:

I wired the cigarette lighter and USB into permanent live under dash. As to whether something is live or not if it breaks down it can cause a drain even if working correctly. I did have a proper drain on this car once and it was the relay fitted for the electric fan, the thermo switch for the fan was wired through ignition only but the main feed was off the back of the alternator. The fan operated OK coming on when required so I had no idea the relay was faulty. When the ignition was turned off the fan would stop even if running.
Car only has three old fashioned glass fuses so pulling one only identifys about a third of all systems.
I'll have another contortionist under the dash fiddle with the wiring I added for lighter and USB.

I have read that these USB circuits can draw power even when there's nothing plugged into them, because the components that drop from 12v to 5v take a small amount. The context I read it in was discussing those mains sockets with USB charging sockets built in, and the point they were making is that because the circuit is running all the time, the lifespan is not as great as it would have been had it been on a switch. In a mains socket it doesn't matter that it'd run all the time from the point of view of power drain, but from a battery maybe it would. If you can get access to the wiring it's fairly simple of course to stick your ammeter in line with the USB socket and see if that's the drain.

This might be the case, i had a plug socket in my kitchen with added usb points, and you could hear it hum faintly even when nothing was plugged in to it, no idea about the 12v ones.

[HealeyV8]

Weird the alternator packed up so I've just fitted a new one. After checking everything was working correctly with new one I did the draw test as I was there and now it starts at 9.6ma when the prongs are connected and then drops to zero.

[Dogwatch]

droopsnoot said:

I have read that these USB circuits can draw power even when there's nothing plugged into them, because the components that drop from 12v to 5v take a small amount. The context I read it in was discussing those mains sockets with USB charging sockets built in, and the point they were making is that because the circuit is running all the time, the lifespan is not as great as it would have been had it been on a switch. In a mains socket it doesn't matter that it'd run all the time from the point of view of power drain, but from a battery maybe it would. If you can get access to the wiring it's fairly simple of course to stick your ammeter in line with the USB socket and see if that's the drain.

My thought too.