Utter lack of power.

[RocketOgre]

So, went to go start the car today and had absolutely no power at all. No dome light, 4-way flashers, nothing at all. After playing around with a few things and checking all battery/alternator connections I had power for just a second(gauges lit up and stereo turned on) but then it went away and now I get nothing. No audible clicks or anything unusual when the lights went out, just suddenly off.

Events leading up to this:
-Last week while driving on the freeway car stuttered a bit and my radio shut off then powered back on, in retrospect I'm fairly certain I lost all power for a split second.

- Couple days ago on a short trip the headlights were dimming/lighting up with the revs of the motor. Headlights went out completely after the revs dropped a touch below idle but came back on and car stayed on when I released the clutch to get the revs back up(I was in motion).

- Today went into Costco and came out to radio acting like the battery had been unplugged, no presets and asking me to run setup. I think this adds to my complete loss of power theory whatever is going wrong is preventing ACC power from getting to the radio.

Car:
1989 240sx SE
SR20DET swap
Electronically very stock, Harness rebuilt about 6 months by Doug at UP Garage.

She's been running fine for a long time leading up to this other than a little gremlin with the wipers coming on and off I haven't had electrical issues in years(swap is 10 years old). I'm thinking fuse or relay. I'll be picking up my DMM soon as I can but the car is currently at my apartment complex and my garage is in the next town over. Got a busy few days ahead of me too. Anyone have any suggestions of fuses/relays to check? Or anything else that may cause a total power loss when the battery terminals are fine, grounds are all still good, etc.?

[M374llic4]

Sounds like either one of the terminals on the battery are bad/loose/corroded or bad grounds somewhere. If it were the battery itself or the alternator, generally it would be all or nothing, not some times. Loose thing / corroded terminals can occasionally work.

I would check both positive and negative terminals on your battery and make sure they are not only snug an clean on hte part that attaches to the posts, but where the wires connect to the actual terminals.

[Chaluska]

....I would check both positive and negative terminals on your battery and make sure they are not only snug an clean on hte part that attaches to the posts, but where the wires connect to the actual terminals.

I once had a loose ground due to a bad connector, and it caused my car to completely go dead.

[Drifters]

My alternator went out last week and it didn't go out all or nothing, first my automatic seatbelts didn't work (s13) then my cluster and radio then the car wouldn't start, it could very well be your alternator, and KA24DE alternators do fit, I know because I did this last week good luck!

[jqn]

I would say it's your alternator too. I had the exact same thing happen to me last year.. my radio would suddenly shut off and turn back on when my car was at idle, my headlights were very dim, etc. I replaced my alternator and it fixed all those problems.

[The Saint]

The alternator has a set of brushes in it that are spring loaded to maintain contact. As the contact "commutator" finally wears out, the connection is finally lost and a spark has to jump across the gap. the higher the engine is revved, the stronger the spark. This arking further damages the commutation and "click" the alternator is now broken. So now where does your engine get the spark? You guessed it, battery. So your ECU starts shutting off nonessential systems, radio, wipers, lights, and finally engine.

[RocketOgre]

12volts across the battery and 14.4 from the alternator at 1k rpms moments before I shut it off for the last time. Alternator wouldn't explain the full power/not power thing the last time I tried to start it. I am finally back from work so tomorrow I'll get the DMM out and start checking things.

[turbos14]

Not relay or fuse. Terminals being loose would no ground alternator can't charge system. The battery terminals some times wear and get smaller due to corrosion. Check that then do a volt drop test for the power and ground wire to see if you are losing voltage to the cables.

Sent from my SGH-I747 using Tapatalk

[RocketOgre]

EGI relay. Wiggled it and it worked for a while, put in a new one and it works better than before. Next time I'll start at the battery and work my way in instead of starting at the perfectly functional ignition and working my way out.