my escos has 13.8v on idle if i switch everything on and mean everything rad fans as well, both headed screens...etc... the voltage drops to 11.8 does this mean my alternators hadit underload??

cheers

 

you need to test at around 2000rpm, not idle

you need to be seeing around 14v + ideally

 

you want over 12v really at idle,disconnect your battery and see what the battery is on its own without the alternator or running that wants to be a tad over 12v alone.

 

it should never go under 12v even at idle
check the fan belt is right tight
if it is then looks like alt has seen better days

 

sos forgot to mention i did try it at 3000rpm, the belt has its own spring loaded tentioner so it cant be lose... where a cheap place to get a replacement? Camberly Autos?

 

thats what i get for for not reading it correctly, just realised you said escos so belt is self tensioning( for me)

dont know who's best for yo local mate i'm in glasgow
just shop around, wont be that dear they're very simple alternators

 

Does the situation ever occur where you have everything on at idle ?
I suspect the answer is NO, there is nothing wrong with this alternator, they cannot do mega loads at idle speed, simple as that, doesn't cause a problem as they don't do it in use anyway.
Do the test at 2000rpm, with a FULLY charged battery and so long as over around 12.2/12.4 stop worrying, is the alternator singing, as they willoften do this when overloaded.
The 90 amp(or whatever) is a peak reading, realistically the peak is a normal continuous max output.
tabetha