04 4R electrical problems - very weird

[buckeyefb]

My 2004 4 runner will not start and the issues seem very weird. Here's the background info. Any help is appreciated.

Last week this same thing occurred. Tried jumping the battery, no luck. All power was gone (no interior lights, no keyless entry, nothing). We messed around with the fuses, didn't find any that were blown, but pulled them and looked and put them back and suddenly it started up on another try. I figured one must have come loose somehow and I just pushed it back in.

So for about a week it's started fine, BUT in the past day when I've pushed on my brakes sometimes the power to the radio will go out for a second or two and them come back. That seemed very odd to me. That's been the only issue, until I pulled in my garage tonight and saw the reflection of my headlights flicker (dim and then brighten again). I parked the 4 runner, turned it off, and now it won't start again. No power at all.

This seems very weird to me. Any thoughts?

I looked through the fuses and haven't found anything, but frankly I don't know how to check the Type B and Type C fuses.

 

[loner]

Just a wild guess:

Poor connection at the battery, due to corrosion on terminals?

Easy thing to rule out by cleaning the terminals....

Doesn't sound like a fuse issue to me.

Any aftermarket electrical accessories, alarms, etc?

When you say pressing on the brakes caused the radio to cut out, do you mean just when braking (slowing down), or did it also do it when the vehicle was not in motion? If only when moving, that would suggest that braking caused something (a wire perhaps) to shift and cause a short or lose connection.

 

[buckeyefb]

The connection at the battery seems good and there's really no corrosion.

Yes, I mean when braking or slowing down, not when stationary. Good clarification.

 

[Even Steven]

Sounds like it may possibly be a bad ground. I would start at the battery cables and go from there. Make sure the negative battery cable is grounded properly (the other end, not the battery terminal end) and go from there.

You might also want to check the battery cables themselves.

If everything checks out okay, the next step is to get your hands on some schematics and see if the brake lights and radio share a common ground point. It sounds like they might if you step on your brakes and the radio goes dead. If the ground connection isn't solid, it might not be good enough to always let the radio play and allow the brake lights to illuminate. In other words, the ground connection is good enough to support either the radio or the brake lights, but not both at the same time.

Anyway, it's a start... give us some more symptoms if you can't figure it out and I'm sure we can get you on the right track.

 

[jharris2]

+1 on the battery connections. Every time I've had a vehicle with sporadic electrical problems, it turned out to be the battery connections -- hidden corrosion in one case.