No electric power

[AR1995]

1995 NSX. I attempted to start the car and after I turned the ignition key, all electric power to the car went away. Starter cranked momentarily and then all electric power went dead. I thought I heard a brief click or pop sound just before electric power went dead. There are no power to interior lights, instrument cluster, etc. Turning the ignition key fully doesn't do anything. I believe the battery is charged (typically on a tender). I tried to jump start it by using the terminals in the engine compartment and the car doesn't receive any power. I tried removing and inserting the key into the ignition switch several times, and one time it was hard to turn the key. After a few minutes the interior lights were back on, but when I attempted to turn the ignition key, the power went out again.

Any ideas? Thanks.

 

[Superhatch]

My first thought would be main relay issues. It's a common problem as the car ages. Lots of info on that issue and resolutions already on the forum. Start searching those and see if it fits.

There is an electrical troubleshooting manual, but I don't think we have it available as a download, although we have the factory service manuals here: https://www.nsxprime.com/resources/factory-service-manuals.11/

 

[drew]

Clean both ends of the big wires that go to the battery. Sounds like some serious corrosion.

 

[AR1995]

Thanks for the ideas. Problem solved by getting a new battery. The existing battery (Optima yellow top) was 7 years old and I installed a new battery to see if it would solve the problem.

After I installed the new battery, there was power to the car - inside lights, instrument panel indicators came on, but turning the key to start resulted in immediately the electrical power being cut. I disconnected and reconnected the wires to the battery, ensuring both leads were securely connected to the terminal, and attempted to start the car again. This time turning the key to start the electrical power remained and the car started.

Given the age of the Optima battery, I suspect it was not working correctly or dead. I do not know if this caused issues with the electrical system or the alarm that resulted in the car from having no electrical power. Anyway, it seems to have been resolved.

 

[Superhatch]

Thanks for the ideas. Problem solved by getting a new battery. The existing battery (Optima yellow top) was 7 years old and I installed a new battery to see if it would solve the problem.

After I installed the new battery, there was power to the car - inside lights, instrument panel indicators came on, but turning the key to start resulted in immediately the electrical power being cut. I disconnected and reconnected the wires to the battery, ensuring both leads were securely connected to the terminal, and attempted to start the car again. This time turning the key to start the electrical power remained and the car started.

Given the age of the Optima battery, I suspect it was not working correctly or dead. I do not know if this caused issues with the electrical system or the alarm that resulted in the car from having no electrical power. Anyway, it seems to have been resolved.

That's much easier than a main relay!

Glad you got it running again with an easy fix. Main relays are such an issue that a lot of people have a spare in their glove box just in case, so if the batter is good, that's always another common problem.

 

[AR1995]

Thanks for the heads up on the main relay issue.

 

[Old Guy]

The Optima battery may be now be dead; but, that may not have been the root cause of the problem. Given the details in your post #4, I suspect that your battery post clamps were probably loose resulting in a high resistance connection which resulted in the battery getting a lower voltage and probably never achieving full charge which results in an early death. Check your battery post clamps for damage. The clamps have likely been stretched / damaged and may need to be replaced because they will never completely tighten.

That said, battery post clamp problems should not prevent the car from being started from the jump terminals in the engine compartment. Based upon what you described in your first post, I think you may have a problem with your ignition switch. On a 28 year old car it would not be unusual for the ignition switch to start failing. They typically start to operate intermittently before they fail completely. You can remove the switch and inspect and clean the internal contacts; however, they are not hugely expensive

More Information for WVE 1S6403

Because working under the dash is never fun, I would be inclined to order a new one and replace it while I was 'under there'. You can clean up the old one and keep it as a spare if you are so inclined.

For reference, the only thing a main EFI relay failure will do is prevent the engine from running. All the other electrical things in the car will work as normal (except the check engine light probably will not illuminate) and the starter motor will crank the engine as normal; but, the engine will not start. If your car is a 1995 and it still has the original main EFI relay; purchasing a new relay and installing it would be good preventative maintenance. The main EFI relay on my 2000 died stone cold in 2021 with no early signs of intermittent operation. Fortunately it did it on the street in front of my house and in one minute I knew what the problem was (no CEL self test at power up and no fuel pump prime cycle). A trip to my garage to get a screw driver, trim removal tool and some needle nose pliers plus the new in a package relay in the trunk and I was back in operation after about 30 minutes of fiddling. It would have been a lot more expensive and time consuming if it had failed some place far away.

Aside form RockAuto, Amayama.com has good prices and you can probably ship both a new ignition switch and the main EFI relay for the same cost. You might want to include some of the little plastic clips that hold the rear interior trim pieces in place with the order because they will probably ship for free. When you remove the interior trim to access the main relay the 28 year old clips don't like being moved and usually break. You will find that some of those clips are NSX only parts and will not be in stock at your Dealership. The dealer told me Acura Canada did not have them in stock so it was going to be a 3 month wait for delivery since they were not critical back order items.