Massive Electrical Failure

Hi Everyone, newbie here from North Idaho. Have a 2004 4runner V8 as my daily driver and it had a major electrical problem last week. Been searching the internet and talking to local mechanics and can't find where to even start so hoping someone has some advice?

The symptoms: was backing up a horse trailer with AC on high and all of a sudden the entire AC/Heater display shut off and the fan stopped working. I lost turn signals, but still have hazards, lost rear defog, and the battery won't charge. The horse trailer lights and turn signals were working prior to the failure.

What I've tried and still hasn't solved the problem: new battery, checked fuses, checked relay's (to the best of my ability), took alternator out and it checked out good (that was 5 hours of anger), saw a post there might be relay's near the glove box so completely disassembled passenger dash and didn't find any relay's. Tested for parasitic drain and surprisingly showed no drain, put my volt meter into the fuse and relay positions and found the charging relay, towing relay and ac relay had no power. Tested the fog lamp relay position and it showed it had power. Fog lights work so I put that relay into the AC spot, but didn't help.

That's where I'm at, and my thought is perhaps there is a common wire those major draws might go into? I wonder if the trailer lights have an inline relay? I suspect a ground issue, but since lots of other things work, radio, clock, lights, dome light, dingers, horn, fuel pump etc I'm confused if a bad ground would allow some to work and others not?

I apologize for the detailed information, but I've read a lot of the threads on here and a lot of reference to not having enough information so thought I'd let you know what I know. Any insight would be greatly appreciated as the best advice I've heard so far is from my son who said let's part it out.

 

is there a fuse block under the hood too?

 

Hi Jester, yes that's where most of the fuses and relays are. I've looked at all of them and watched a youtube video on how to test relay's which all of the suspect relays tested fine. I'm not sure if my testing methods were good, but the relay acted like the youtube video and I substituted the working fog lamp relay for the AC relay and it didn't help.

 

I found a couple of threads on another site that might be the same issue you're having, one guy said to check:

here's the links: not sure if it's exactly what you're up against

 

Thanks Jester, I'm going out to check now.

 

Unbelievable. The IG1 15A fuse was blown just as Jester had found. Put a new one in and the battery is dead. Charging right now. Concerned a little as I charged the battery yesterday while dealing with the alternator, but thinking perhaps a bad battery cable might be the underlying cause. The problem is I can't even see the starter so guessing changing the cables might be worse than getting to the alternator.

Who came up with these emoticons? I want to watch them vs deal with the problem.

 

Jester you got it. The AC and turn works. I wonder how that's interrelated? Not sure if the alternator is charging as VSC lights are on which seemed to come on when the battery was weak. I'll put the fresh battery on it tomorrow. Thanks a million.

 

Good luck man, there is a definite problem with that system looking through some other sites, hopefully a fuse is all you will have to deal with, let us know.

 

Thank you for this life saving thread. I tapped into my reverse light wire to install rear camera and lost my turn signals, ac, reverse lights and alternator wasn't charging. It was all just that dang fuse.
One fuse to rule them all!!