Car won't start, horn won't honk, headlights won't come on, what could cause this?

Question

Vehicle: 2005 Honda Accord LX 2.4L FI DOHC 4cyl

Symptoms

Car wouldn't start today. In the past had occasionally had it hiccup before starting but that was the only indicator of problems. No accidents or special maintenance done recently that seems to be linked to this issue. Did replace the starter twice (first one didn't last long), but that was about a year ago. Symptoms don't seem to be acting like it did with a bad starter.

No Key

• Interior lights come on.
• Hitting brakes: Brake lights come on and interior lights dim.
• Turning headlights on: headlight indicator on dashboard blinks and interior light dims and blinks in sequence, can hear a clicking/grinding in sequence with the blinking. Under the hood can hear clicking/grinding more clearly and seems to be coming from near fuse box area.
• Honking horn causes symptoms of dimming lights, horn doesn't honk and grinding noise can be heard instead.

Putting key in ignition

• Dashboard lights up like normal
• Previous symptoms plus dashboard blinks in sequence to headlight indicator and interior lights.

Turning key to I position

• Radio can turn on (acts normal)
• Turning headlight on causes previous symptoms and radio goes off
• Trying to lower power window did not lower window (caused a grinding noise). Also stopped radio for a bit and caused lights to dim. Subsequent attempts to lower window did not cause radio to go off, did not cause lights to dim, and no grinding noise).

Turning key to II position

• Lights dimmed, grinding noise (figured out this was the windshield wipers trying to move, as they moved slightly). Turning off windshield wipers removed grinding noise.
• Turning headlights on, windshield wipers on, or trying to use power windows caused lights to blink and interior lights as well as dashboard went dim. Radio turned off also. Gas gauge on dashboard jumped around and dropped to empty, other indicators on dashboard were blinking oddly and went dark after a few seconds.
• Was able to honk the horn a few times. After playing with the key a few other times (going back to off then position II again) wasn't able to get the horn to honk and instead got the grinding noise. When I was getting the grinding noise it cause the lights to dim, fuel gauge to go to empty, and radio to go off.

Turn key to III position

• Everything dims or goes off (which seems normal to me)
• Starter doesn't seem to try to spin, though listening with the door open I do hear a single click noise so it sounds like it is trying to engage.
• Dashboard goes dim, ABS and Brake indicators on dashboard are faintly seen, go dark after a few seconds.

Turn key back from III position to II position

• Fuel gauge jumps down, then jumps again to empty
• A bunch of the indicator lights on the dashboard turn on, the lights for the open doors blink rapidly 4 or 5 times and I hear a clicking noise for each of those blinks, then they all go dark.
• After a few seconds it returns to the state of "Turning key to II position" where the fuel gauge comes back up to current, radio comes back on, etc.

Troubleshooting

• Removed the battery, brought it to AutoZone, they reported it tested GOOD.
• Bought a new multimeter (my previous one was broken) and tested the battery myself, was getting a reading of 12.78 VDC.
• Looked up online how to test relays, pulled quite a few fuses and relays from the hood fusebox, everything seemed to be indicating it was working ok (as far as fuses and relays themselves).
• Only thing that stood out was when I tried checking the voltage going to the headlight fuses, I was getting 0 VDC. Was able to get 12.78 VDC to some other fuse terminals (including the horn, which hasn't been working most of the time).
• I'm new when it comes to testing this electrical stuff, may have made a mistake, but I did hear clicking for each of the relays as I hooked them up to battery power and checked the resulting resistance of the other terminals on the relay. Checked the fuses to make sure resistance was near 0 (thought for some relays it seemed to jump around a lot, but some others went to 0 or close to it quickly).
• I didn't check every single fuse or every terminal. Not sure if I'm doing this completely correct and I've been at this for a few hours (and it is time to go to bed), so wanted some feedback to see if I'm doing this right or should focus on anything specific.

Useful links

Honda fuse box diagram

What's next?

Any idea to the nature of this issue? It seems pretty obviously to be electrical, but are we talking bad relay (all seemed good under the hood), bad fuse (all seemed good that I tested), or bad wire (I didn't seem to get a voltage reading to the headlight fuses, not the high or low beam for either left or right side headlights). Is this maybe a short? Do I need to trace the wiring from X to Y and check for any fraying, lose connections, etc.?

Edit:

Turned the headlights on and put the multimeter on the battery terminals. Voltage was jumping all around as I heard the same clicking noise before. Voltage was in the 9.XX range to 10.XX range. A few times it managed to jump up to a low 11.XX range. So it does seem like a battery issue. Will be swapping it out later when I get the chance and will confirm that this fixes my issue.

Edit 2:

Was able to jump start the car with another good vehicle. Wish I had tried that yesterday instead of the hours and hours of testing electrical connections. Thought I had been doing well by having the battery tested FIRST. Even tried with a multimeter to confirm, but should have tested it under load (forgot about that detail). Could have saved me quite a few hours and having to go into work late. Now I'm off to go buy a good battery and swap it out for this dead one.

Thanks for the help everyone!

Answer 1

The symptoms all point to a faulty battery, and an incorrect test result for the Autozone battery test.

Starting with this: Hitting brakes: Brake lights come on and interior lights dim: a good battery should have no problem driving both the brake lights and interior lights without dimming. The same goes for many of the other tests you've done. If switching on a component that draws 10 A causes dimming, your battery is never going to be able to supply several hundred A to the starter motor.

Edit:

Try testing the battery voltage under load. Switch on the headlights and measure the voltage. If it's still 12.7V on the battery terminals, one of the battery leads may be broken or corroded. If there's a big voltage drop, the battery is faulty.

Answer 2

All symptoms point to a dead battery, but as you have already attempted to rule that out, the next thing I'd check would be bad connections or cables.

Turn on the headlights or something else that consumes a fair amount of power - this makes the results of these tests clearer. If the battery is fine, the voltage at battery terminals should stay close to 12 V.

Try to check the voltage between different points that should be at same voltage - e.g. voltage between positive battery terminal and positive battery connector at fuse box. If there is significant voltage difference (say, 1 V), a cable or a connection between the two measurement points is faulty. Check both the positive and the negative leads.

Similar test: try to check voltage between the positive and the negative terminal at different points along the path from battery to some device. If you find a spot where the voltage is significantly lower than at battery terminals, the faulty part is towards the battery from your test point (along either positive or negative lead).

Answer 3

As others have noted, corroded or broken battery terminals could be the cause if the battery voltage seems good. In that case you want one of these, available at any auto parts store:

Use it to clean both the terminals on the battery itself, and the inside of the clamps. Then apply conductive battery terminal grease, reattach, and tighten.