I can't be sure but I think a friend of mine reversed the polarity when jumping my 98 4runner. Blew the alternator fuse which I have replaced, but now my stereo, electric door locks, electric windows and dome light don't work. I've replace fuses but when i put one in for these - it blows right away. Tried disconnecting all systems to reconnect one at a time, but the fuse still blows with everything disconnected. Can still drive car with no other problems. What to trouble shoot next? Any ideas are welcome.

 

Just a guess have you checked any of the relays??

It is possible one of them is shorted so every time you install a fuse it opens.

Just what fuse or fuses keep failing??

 

I wonder if these have fusible links? Reversing the polarity can do all kinds of bad things. My brother in law's 86 MR2 hasn't been right in 10 years since he hooked up cables backwards. Now it's completely dead electrically and he's bugging me to get to it sometime. Your best bet is to get your hands on a good wiring diagram for the truck. Chances are all of these things are connected through a ground or a power source somewhere. Could have cooked something at one of the splice connectors. A relay would be a nice easy fix if you could determine which one it is. You'll need a good wiring diagram and be able to read it to figure that out.

 

Try pulling the PWR relay. I think you can swap it with some of the others if the fuse does not blow when it's removed.

 

I've seen CB radios that were shorted out due to reverse polarity and I bet your stereo is the culprit. There is probably a protection diode internally that sacrificed itself. The stereo is ok itself but the diode is shorted. If you can clip the shorted diode out of the circuit then all will work. I re-read your post....verify that the stereo is really not the issue by pulling it's power plug off.
There is likely some reverse spike diodes on the relay coils....so check your coil resistances with an ohm meter. The coils normally have about 100 ohms resistance....if you see only 2 or 3 ohms then you found it.

 

Finally getting back to this issue. Fuse is 15 amp that goes to stereo, dome light, power door locks and power door window. Disconnected all of these and fuse still blows. Took out control unit and fuse still blows.

 

Did you try this?

 

Not sure what you are referring to as the power relay. I removed the integration relay box (yellow box) and fuse still blew. Is the power relay something else?

 

PWR relay is on back side of interior fuse panel. Small relay in top right corner. As I read the circuit diagram, if that puppy shorted it could cause your symptoms. It is a likely place for a quench diode. See bottom half of first page of this:

http://tacoma.site40.net/4Runner_96-...c/relayloc.pdf

Here is diagram I was looking at:

http://tacoma.site40.net/4Runner_96-...emci/031pw.pdf

EXACTLY which fuse are you blowing? I hate guessing.

 

The fuse I keep blowing is the 15A dome fuse.

 

That's what I figured. Thanks. Full list of stuff DOME fuse goes to if you don't have it:

Auto Antenna
Cigarette Lighter and Clock
Combination Meter
Garage Door Opener
Headlight (w/ Daytime Running Light)
Interior Light
Radio and Player

Something is crossed--windows (except rear) are a key on circuit and should not link to DOME. Could be Body ECU is shorted as both DOME and windows go through there.