disconnect the radio earth from the battery, and stick it on the non-battery side of the isolator switch.

although you are using an isolator switch, which effectively disconnects the battery cable (depending on which side it is placed i.e +ve or -ve), you are still creating a circuit through the radio -ve wire which will still allow the unit to work because you are not disconnecting the feed side, just the earth side AFTER radio connection (if that makes sense?)

*edit*

Before you connect the earth to the isolator switch, leave the isolator switched on and disconnect the radio earth from the battery to see if the unit still works. May have another earth from amp/aeriel/speakers mountings.....

Ok my thoughts is your chasing an earth. Something in your car is trying to draw a currant when you isolate the battery. Do you have an immobiliser or alarm. Whatever it is will most likely be on the same circuit you connected the red wire from you radio to as the radio turns on.. Its not the radio as it still has its earth when you isolate the battery.
Hope this helps.

Rodney

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

Like he said....

some other component in the car is using power and is getting around the isolator by making a circuit to earth through the radio.

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..

Thanks for all the help guys
as said it is a earth leakage type problem
and guess what ?
I found IT
It is the interior light door switches !
Ignition off, isolator switch off [no power flow through switch ]
open door radio comes on , push door button in radio goes off ,
remove light globe from interior light radio goes off .
with the isolator switched on [power flow ] everythhing is as should be
I can turn the radio off on the front of the unit itself , but once the doors are shut it turns it self off , so now I know it is not going to be going non stop and flatten the battery ,

MARK

Well done...

_________________
The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

That is so random...

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I call the little ba$t*rd "PC " [ problem child ]
one of a kind my little PC

OPTIONS would you like curtesy light
or curtesy radio ?

Mark

nice find weird but nice find

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I have an Addiction just not the time.......
1966 Morris Mini Deluxe http://www.ausmini.com/forums/viewtopic.php?t=80459
1968 Morris 1100 viewtopic.php?f=3&t=101555

Who'da thought eh , that would of tested your patience eh , .

OK all sorted now
I rerun the earth wire to the body of the car , didn't really want to do this because it by passes the isolator , I have a fuse in this line , from this body earth to the radio harness earth ,to the body of the radio itself and to the aerial earth
every thing is as it should be with the radio now , the interior light works with the isolator isolated ,
it is drawing earth through the body earth .
I will replace the fuse with a reset circuit breaker when I get it

Installed an electric brake light switch today as the hydraulic one has failed , AGAIN

Mark

Yeah most of the hydraulic switches are rubbish now. The old original Lockheed ones lasted for a zillion years.
"it doesn't matter how cheap it is if it doesn't work"..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.