40amp fuse

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40amp fuse

Postby Mamore » Mon Jun 06, 2016 10:29 am

Hi
The fuse box under the bonnet of a Mk1 has a 40amp fuse marked BTN can anyone tell what components this fuse protects ?
Cheers Pete.
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Re: 40amp fuse

Postby WSBen » Mon Jun 06, 2016 11:25 am

There seems to be a lot of questions and answers to that question on the web: One guy on a Mazda forum says it is the 'Back to Normal' reset for the ECU..as in: Quote:

"The BTN fuse is the "Back to Normal" fuse. What this fuse does is resets the ECU (electronic control unit)... when you put the fuse in the BTN slot, it completes the circuit to reset the ECU.. when you remove it.. it's reset. This is not a fuse that should be left in.. only use it to reset your ECU if you're having problems. Hope this helps!"

Someone else says it is the same, as in: If you look under the hood there is a fuse box that will have a large fuse that is labeled btn. what you need to do is pull this fuse and then hold the brake pedal for about a minute. we call this fuse the back to normal fuse because when you do this it will clear every thing in the memory and put it back to normal operating specs
Last edited by WSBen on Mon Jun 06, 2016 11:38 am, edited 1 time in total.
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Re: 40amp fuse

Postby OldSpice » Mon Jun 06, 2016 11:26 am

Think you'll find it's the "slow-blow" for the ECU.
There is always an imbecile you never bargained for. Usually in a Tescon carpark with a dented Zafira minus hubcaps
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Re: 40amp fuse

Postby WSBen » Mon Jun 06, 2016 11:41 am

Hi Robin, this may also be a reason for my car not starting even with the new fully charged battery in it. I will carry out a reset of everything.
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Re: 40amp fuse

Postby OldSpice » Mon Jun 06, 2016 11:51 am

Now there's an idea! Let us know.
There is always an imbecile you never bargained for. Usually in a Tescon carpark with a dented Zafira minus hubcaps
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Re: 40amp fuse

Postby WSBen » Mon Jun 06, 2016 2:04 pm

Well, it seems the MK3, 3.5 have a well documented issue with 'dark current' drain and there is a well documented thread on the main MX5 Owner Club web site: http://www.mx5oc.co.uk/forum/yaf_postst ... -fuse.aspx

It makes a good read and worth checking. :wink:
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