(xpost from http://www.mr2.com/forums/threads/97231-Supercharger-light-stays-on-misc-elec-issues?p=1011303#post1011303)
Hey all, had some issues crop up in my mr2 which I'm tearing my hair out over.
Backstory is that my water pump was making some horrendous noises so I replaced it (what an awful job).
Anyway we also rebuilt the front brakes and flushed the brake fluid. I took it for a test drive, noted a slipping belt and chucked some soapy water in to try and clean them off (I figured some coolant or oil got in the pulleys). I was taking it for a test drive to make sure it was all functional (the supercharger belt was still slipping) but as I was driving it back home, I turned left around a corner and my headlights dimmed and the warning light for the alternator kicked in, as well at the cat light and the S/C LED stayed lit.
Anyway, the lights are as follows (including the S/C light staying on):
https://fbcdn-sphotos-f-a...26966_1500170272_n.jpg
The cat one is... odd.
The battery definitely isn't being charged, and the engine fan light based off my googling is symptomatic of an alternator/voltage regulator issue, is there anything i can check at home or is it time to take it to an auto electrician? Or at least confirm the issue?
Thanks!

This is a dead giveaway.  Yes, you've got a charging issue.  First port of call - is the belt still there?  (Seriously, they have been known to jump ship.)
 
Do you have a multimeter?  If so, a quick voltage check across the battery terminals will seal the deal and confirm the alternators demise.  After that it just depends how handy you are.  Removing the alternator is relatively easy - certainly a piece of cake compared to the effort needed with an SW!

I just encountered this the other week. Exact same symptoms, was indeed the alternator.

Definitely have the belt, I had installed a new one right before the issue!
 
Probably should have mentioned that it was the supercharged version so not so easy to remove :( . Is there a way to isolate if it's a alternator or a voltage regulator issue?

Yes, there is a procedure for checking.  You need to have easy access to the terminals at the back of the alternator - yep, the ones effectively shrouded by the exhaust on an SC.  The regulator is internal, so it is easier to remove the alternator and bench test it.
 
Removal becomes easier with practice . . .

Just as a follow up my alternator had pretty much grenaded itself due to a slow oil leak I hadn't noticed on the engine. It's pretty much a bin job according to the guy I had looking at it, so I'm hopfully grabbing a replacement today :)

Would that be the distributor o-ring leak?  That's a standard factory feature on the 4AGE motors . . .