i have a 1986 3 door. i don't know if i have a 70 or 90 amp alternator. how do i tell the difference between the two?

 

You should have 70amp

 

there should be a sticker on it, otherwise they are virtually the same physically to look at

there was also a 55 amp fitted to some sierra's, as late as 90 spec cars, but these are physically much smaller

as said, you "should" have the 70 amp version, but the 90 amp one will fit if that's all you can get hold of

 

The defintive way of telling is the width of the stator gap, between the two halves, but it will be a 70 most likely, but as said fitment same as 90 as well.
tabetha

 

i couldn't find the sticker saying what model it was. but we have discovered that i have been using a 70 amp regulator in my merkur with a 90 amp alternator for about 10 years now with no ill effects. so i am thinking that the alternator in the cossie is still the original that came with it so should be a 70. and if it is a 90 then the 70 regulator should still work anyway.

thanks for the info.

 

Depending on make it will be the same reg/rec unit most likely.
tabetha