Just replaced my 1994 300ZX Twin Turbo's battery and noticed that the headlights and taillights were on, and the turn signal indicators were both lit up. Checked that the light switches and emergency flasher were off, and then the horn suddenly sounded all on its own. Had to disconnect the battery to stop it.

Any ideas about what might be wrong?

Thanks,

Tosh

Wow, that would be a surprise for sure...and sounds like a hard ground somewhere to light up all of that stuff.
I am one of those guys who does not do well with electrical issues on my own so all I can do is say check all of your battery connections for correctness and that there has not been a short somehow, I hate to say it but check for the correct battery/connector orientation as we all have had a bad moment and made silly errors.
If no help I'd do any checks mentioned in the factory service manual ("Everything you meed...Z32" sticky at top of page) and failing that, talk to a electrical specialist for ideas.
Sorry I can't help more than this, hopefully someone else may have better ideas and areas to check.

Thanks for the input. The battery connections are correct. Most of what I've found online so far has to do only with a stuck horn. Then I ran across a thread on the Infiniti forum that ties in airbags and clocksprings and engine lights. Interesting, but it's this specific set of preconditions (headlights and taillights on and both turn indicators lit steady), in the Z32 300ZX that I'm wondering about, and whether there's a common component that could fail and cause this.

Here's an update on this strange problem. A Nissan automotive shop found a keyless entry module located underneath the battery that had failed. They report that the modules are no longer available, so they removed it. I've not yet picked up the car to know any more details, but I'll find out later today and update the thread as necessary.

TangoMike3 wrote: ↑

Tue Jan 08, 2019 8:26 am

Here's an update on this strange problem. A Nissan automotive shop found a keyless entry module located underneath the battery that had failed. They report that the modules are no longer available, so they removed it. I've not yet picked up the car to know any more details, but I'll find out later today and update the thread as necessary.

That sounds like a good answer to your problem, it covers the hard ground and also the act so many things were lit up on the dash.
Here's hoping that your problems are solved!

The mechanic who discovered the problem mentioned how he was able to get the horn to stop sanding, but that didn't eliminate the other symptoms. He finally traced the common point in multiple circuits to isolate the source. The offending part # is 28594-48P00. I can do without keyless entry, but I Googled it and found an ebay page titled "Other Computers, Chips & Cruise Control for 1994 Nissan 300ZX." Haven't yet scoured the source for that specific number, which might be necessary to ensure it will work in this car. Will update with any new info.

Haven't yet tried to find a replacement keyless entry module, but I just discovered today that the cruise control has failed, which may be another component rendered inoperative by removal of the module. I've found a possible replacement module with a part number of 28594-48P00. My mechanic is checking to find out if that part from a '96 Z32 will work in my '94. Crossing my fingers here, and will advise on results.