HiFlite999

iTrader: (2)

I can't remember seeing this particular problem in the forums before.

Sunday night, clear weather, 65 degrees, transitioning from one interstate to another, car fully warm ...

While accelerating up the ramp in a slight right-hand turn, going thru about 5k rpm, my car quit cold. No sputters, flickers, or gauge warnings. Engine, headlights, stereo, and nav died. All throttle input was ignored. I coasted off onto the shoulder and pushed the emergency flashers "on" - but the flashers didn't work.

Pretty quickly it became clear that the interior lights were the only lights still functional. There was no response at all from any attempted restart. I have the credit-card type key and the lock cylinder turned fully. There was also no response when using the physical key. I disconnected the negative battery ground to "reset" the system, without any effect afterward.

Without lights, and stuck in a pretty dangerous spot, I flatbedded it 39 miles to my local Mazda dealer and left my key in the dropbox.

I went out there this morning. When they attempted a start, the condition had not changed. They also noted that the horn didn't work. They pulled it in the bay and started diagnostics.

The battery was fine. Inside the front fusebox however, the tech noted that the row of fuses that included the ignition fuse was only getting 6 volts of power. He swapped the adjoining relays in this row (not recalling atm what they are labelled) and the power to the fuses went to 12.4 volts. He swapped the relays back into their original positions, and the voltage remained at 12.4 volts.

The car at this point became exactly normal.

Somewhere, somehow, something was causing the low current circuits not to get full voltage, low enough that the relays would not actuate.

Any ideas what might be causing this?

9krpmrx8

iTrader: (46)

Weird. I had crazy electrical issues when my alternators was overcharging but stuff was damaged it was not a quick fix like this.

RIWWP

iTrader: (2)

With a few exceptions, I had this problem on my first car. Driving along the highway and suddenly the car goes completely dead, all electrical and mechanical shut off, coasted to the shoulder. Tried firing it up, and not even a click. Popped the hood, looked around, was still a car idiot so I didn't see anything remotely interesting, closed the hood with a bang, got back in the car, noticed I had cluster lights, tried starting, it started up for half a second and everything died again. Popped the hood again, looked at the engine bay blankly, slammed it shut, got back in and found I had lights again. Fired it up, this time it stayed started and I drove home.

It ended up being my battery connections had corroded between the clamps and the posts, and the hood slamming or the engine shaking on start was enough to break or restore the connection.

You have some differences there, and your list of things done should have found that same problem...but maybe something that was removed and replaced broken then cleared corrosion enough to get a solid connection? Maybe not at the battery, but maybe a fuse or relay blade, or another grounding point, etc...

HiFlite999

iTrader: (2)

^ Anything's possible at this point, but I should have noted that my car is pristine. It's garaged, never driven winters and is in rain maybe 2x per year. I've yet to find any evidence of corrosion (not to say it couldn't happen.) It did sit in the rain the night before this happened, but not driven in the wet at all. Since, as is typical, the latch on the fuse box cover is broken off, I've even fashioned a substituted that pushes the cover down tightly.

Yet there's clearly some critical point in the electrical system. Poring over the electrical diagram is my evening's task.

RIWWP

iTrader: (2)

I probably don't need to give you a dissertation on what factors need to be present for corrosion All of them are there unless the humidity remains super low, even garaged, and it can happen between the two electrical surfaces out of sight.

HiFlite999

iTrader: (2)

Yeah.

It took me 3 glasses of wine to find the wiring diagram manual. Where do all those ziggy lines go?

RIWWP

iTrader: (2)

You are drinking wine in order to start solving an electrical gremlin. That is either a deliberate handicap or a stroke of genius

HiFlite999

iTrader: (2)

^ Mmmm well, opinions vary. The (warm) bottle was in the (hot) trunk when my car quit. The first half made waiting for the tow truck more pleasant. I was thinking the (now chilled) second half will be even better!

So far, so good.

One (1) path easily explains the symptoms: the most direct path from the (+) terminal goes straight (through (intact) fuses) to the horn and hazards. Unless both horn and hazard switches are defective, the only possible interruption of voltage has to come either from the wire or the connections on the battery or to the fuse box.

Simple!

More wine!