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T-Series cut off switch in MGB?


Jedi Warrior
HI, been on the spridget list for a few now, but just got a nice 1978 mgb. It was a daily driver for the guy and i put it in the garage over night and the battery died. Ugh!! Anyway, battery was so big i could barely get it out. It was a real trick to do! Anyway, I found this silver lever behind the passengers seat that I messed with and found out it is a cut off switch. It looks stock but is this typical in a 78 MGB? I wish i knew why the battery died. doors seemed closed. everything in the car works including the clock! and all of the lights and when i got out in the am, the little light that comes on under the radio was barely lit. I put it on a trickle charger and it is back to full charge. I am not sure how I am going to check to see what caused it to die. I took the $250.00 battery from my MGb and put it in there for now.thanks!


tony barnhill

Great Pumpkin - R.I.P
Not typical for an MGB - added by a previous owner.


Jedi Warrior
thank you


Jedi Trainee
Common causes are a bad alternator and bad trunk light switch. The trunk light shouldn't discharge the battery in one day. A bad diode pack in the alternator will.
With the car off and the battery connected, remove the fourth fuse, use a meter or a test light to see if there is a draw. If there is a power drain, try unplugging the alternator. If unplugging the alternator gets rid of the power drain, you have found your fault.
If the alternator is the problem, there are a couple of higher output alternators some have used as replacements.


The PO likely couldn't find what was flattening the battery overnight so he installed the cut off switch. Then "forgot" to tell you about. Work-a-rounds are fairly common among the great unwashed with LBC's instead of proper fixes. Find the draw, fix it and then use the cut off as a safety/theft prevention item.


Jedi Warrior
AS Shawn said, quick fixes far outnumber proper fixes, especially in "fun" cars. Once you've got the short or drain located, you'll be able to rest easy knowing you'll never have another electrical problem with the B. :crazyeyes:


Country flag
I have the cut off behind the passenger seat. A quick reach behind and all is dead. All electrical work in my car but this was a safety measure. If you ever had to cut all power in an instant, it's a great thing to have.
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