Car shorts on startup?

[electronicsunlmted]

Hey folks,

I'm new to the board as this is my wife's car but I'm hoping you can help. My wife's battery had discharged several times before I replaced it and then as I was driving down the road with her a month back I found her lights would dim and sometimes the car itself seemed to "reset" at stops or when current draw increased(high beams, heat blower on, etc..) so I tested the alternator and it turned out to be bad so I replaced it two weeks back.

After replacing we ran into a situation where when she stuck the key in the car would chime, when we turned to "Acc" everything would power on, "On" would light the dash up and "Ign" would kill everything. I believe this is the pattern although it may also happen when turned to "On" as well. I thought it was the ignition switch so I tested the switch when it was functional and it test good. I disconnected the ignition harness and jumped the car from the harness and it worked the first time. The second time it did the same thing upon connecting 12v to the ignition. Right after I did this I decided to start test voltage on the harness. Now the harness was showing 2 to 3 volts instead of 12.7.

I jumped under the hood and test the battery, 12.7 volts. I test the terminals beyond the battery 12.7 volts and then I test the fuses at the main housing and they all test 2-3volts. What's odd is if you wait a few minutes all this resets back to 12 volts and sometimes it starts right up and sometimes it starts the cycle again. Also I disconnected what I believe is the main connection into the fuse box, when connected it was measuring 3 volts, when I disconnected it the cable from the fuse box it measured 12.7 volts. I am thinking starter or starter solenoid but honestly I don't know enough to test those or even know where they are on her car. I replaced the alternator in the dark and I guess I could do a starter but I don't want to throw more money into that until I figure it out.

[MasterTecInSTL]

Have you tried removing the battery terminals and cleaning them and reinstalling them, making sure they are tight?

It could also be a defective battery I've seen some with a bad connection inside the battery itself.

Repeat the voltage test at the battery terminals. I know it shows 12.7 volts now but leave the voltmeter hooked up while you try to start the car (to make it "short out"). If it drops to nothing then the problem is at (or inside) the battery. If it continues to show 12.7 volts even though you lost all power then the problem is a connection issue - possibly in the fuse box or wiring.

[electronicsunlmted]

Ok more on this it's intermittent but I've isolated it's not the battery. When the car, dash, ignition and all show 1.6-1.8 volts the battery at the post shows 12.5-12.8. However, there are three wired plugs in the fuse box. One for the alternator, green and black. One small eight pin I believe with a small red and black wire with 12 volt constant and a third 10 AWG. Only the last shows 12 volts disconnected from the fuse box so I'm assuming this brings power to the fuse box. When the car won't start this wire shows 12v disconnected from the fuse box and as soon as I reconnected the wire the voltage drops to 1.6 to 2 at the plug. I then took out every fuse and it still shows the low voltage so I started to the relays and when I got to the headlamp relay it seemed to reset back to 12.5 volt once I removed it but not immediately I don't believe(it was dark and cold). Could a bad headlamp relay cause this voltage drop? Is this not fused? Thoughts anyone?

[invader]

What year is your Corolla, and is it an automatic?

How are your ground connections from battery to chassis and engine to chassis, etc?

[electronicsunlmted]

Originally Posted by invader

What year is your Corolla, and is it an automatic?

How are your ground connections from battery to chassis and engine to chassis, etc?

2005 automatic. I'll double check them. I tried to measure resistance across ground points and I don't see anything that stands out but I don't know all the points.

[hardtopte72]

There are several under the batter on the transmission. IF the battery was leaking electrolyte it is possible it leaked an corroded these ground points.

Most of this sounds like a bad ground.