So this morning I went over to my friend's house who is a mechanic to see about getting my AC recharged. It didn't really need any, so we left it and I drove home. As soon as I pulled out of his driveway, the voltmeter pegged at 18 and the charge/brake light came on. Then the AC turned off. I turned it back on a few times, but now it doesn't come on at all. The voltmeter still reads 18 as soon as you rev it anywhere above 2000 rpm. Needless to say I have no clue what's going on. We didn't do anything other than hook the gauges up to the compressor. That's all we touched.

Any help would be appreciated!

 

BTW this is an 87 4Runner 22RE

 

Double BTW the voltage regulator is integrated into the alternator. Tried banging on the alt. a bit but to no avail.

 

1) check the voltage with a meter at the alternator terminal and the battery, to verify the gauge reading
2) don't operate it with the voltage that high any more than necessary- the battery will act as a sink to absorb and filter some of that extra juice, but it will burn off the electrolyte and when it does, the rest of the system will fry
3) check the battery for proper electrolye levels- not just that the cells are full, but get a hydrometer and check the specific gravity of the cells
4) check for loose of missing grounds from the engine to the chassis and from the battery to the frame
5) check the wiring around the AC compressor to make sure that something isn't touching ground, other than the compressor clutch ground lead.

 

Thanks for the input. Its an Optima battery. The grounds were the first thing we checked. Also we tried to disconnect the alternator and just run off the battery going home, and the socket came in contact with an exhaust stud and sparked. Is that terminal supposed to be hot with the engine off?

 

that alternator wire is in direct contact with the positive terminal of the battery- that's how the alternator output gets to the battery... so yes, it's supposed to be hot
and since you can't check the electrolyte in an optima battery, skip that step.

 

check the maxi-fuses in the fuse box behind the battery too.

 

ok thanks. well our best bet is that the alternator went bad at that exact moment. i'm gonna take it off and have it tested, then have to deal with finding what it screwed up on the A/C. checked all fuses and everything is ok. Anyone know where the fuse/fusible link to the compressor is?

 

bttt. i know someone here knows which fuse is the one for the compressor. my runner doesn't have the fancy little diagram on the fusebox anymore...

 

There is a third fuse box in the dash behind the glovebox. It has a black plastic cover. It contains two fuses, the top one is the A/C fuse and should be a 10 amp.

 

i found it. sure enough the 10amp was blown. apparently the alternator went out at THE VERY INSTANT we were screwing with the AC, and also decided to blow the AC fuse, thereby making it seem like we screwed with something.

new alternator, new fuse, and about an hour of cussing toyota's placement of the lower radiator hose and everything is back in order! thanks guys!