1991 NSX JDM Not starting/ No lights

[idk706]

Hello all again. In need of soms assistance. 1991 JDM AT here and After a good few hours of driving in the day, I go start up the car at 5am. It's cold and a little damp. I turn the key lights turn on I hear one click and everything goes dead. No other noise nothing. Try to turn key again just to be sure still nothing. I use my meter and battery seems fine and jump terminals in engine bay still getting good voltage. I still have not changed my main relay yet so not sure if that's the issue or something else.
Can't move the seats now and nothing else turns on. Any ideas? Thank you

 

[idk706]

Well this is embarrassing but I just jiggled the negative connection on the battery and the lights came on. It doesn't even feel loose. Still unsure why that happened

 

[stevecct]

check the big relay which behind the seat, next to ecu that one

 

[Old Guy]

Its not the main EFI relay.

The 'tell' is the power seats which are on un switched power. With a high resistance electrical connection it is pretty common that you would measure good voltage until you switch on something that draws a lot of current at which point the voltage crashes to zero on the load side of the bad connection.

If you could jiggle the battery post clamp it clearly was not really tight or it had significant corrosion. I suspect that your battery post clamps are probably toast as a result of years of being over tightened. This is well traveled territory that new owners always seem to need to discover. Battery post shims can tighten up the clamps. The fact that they even make shims indicates that this is not an uncommon problem for lots of cars.

General PDP Template

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However, the better solution is to re terminate the cables that connect to the battery with new, more robust clamps. There are a number of threads on Prime discussing re termination options. I re terminated mine and posted back in about 2012; but, the more recent posts are definitely more elegant in appearance than my original post.

 

[idk706]

Its not the main EFI relay.

The 'tell' is the power seats which are on un switched power. With a high resistance electrical connection it is pretty common that you would measure good voltage until you switch on something that draws a lot of current at which point the voltage crashes to zero on the load side of the bad connection.

If you could jiggle the battery post clamp it clearly was not really tight or it had significant corrosion. I suspect that your battery post clamps are probably toast as a result of years of being over tightened. This is well traveled territory that new owners always seem to need to discover. Battery post shims can tighten up the clamps. The fact that they even make shims indicates that this is not an uncommon problem for lots of cars.

General PDP Template

www.canadiantire.ca

However, the better solution is to re terminate the cables that connect to the battery with new, more robust clamps. There are a number of threads on Prime discussing re termination options. I re terminated mine and posted back in about 2012; but, the more recent posts are definitely more elegant in appearance than my original post.

Thanks Old guy, as always you're awesome.
I was looking at my clamps and they honestly look like crap so I'll replace them. Will look at the other threads on that.
I just thought it was interesting that when I turned the key to the on position the dash lights came on fine then turned it to turn over and one click then dead. I wonder if how cold and damp it was this morning had anything else to do with that.
Been driving today and it's been starting up fine.
Anyways, the car needs more work. Will update. Thanks again

 

[Old Guy]

Thanks Old guy, as always you're awesome.
I was looking at my clamps and they honestly look like crap so I'll replace them. Will look at the other threads on that.
I just thought it was interesting that when I turned the key to the on position the dash lights came on fine then turned it to turn over and one click then dead. I wonder if how cold and damp it was this morning had anything else to do with that.
Been driving today and it's been starting up fine.
Anyways, the car needs more work. Will update. Thanks again

Electricity - invisible and mysterious.

The dash lights don't draw much current so there was probably enough voltage for them to illuminate. Once you try and power up something that uses a lot of current like the starter motor the V=IR law causes a huge voltage drop right at the battery post leaving nothing for everything else.

I discovered my battery post problem when I was taking my car out of winter storage the year after I bought it. I reconnected the negative battery terminal and got nada. Grabbed a voltmeter to check the battery and it was not obviously dead. I did the same thing as you, wiggling the clamp and miracle of miracle - life. That is when I discovered that even though the clamp bolt was tight I could pull the clamp right off the post sans effort. I borrowed a small finishing nail from my friend and jammed it between the post and the clamp. Just enough to keep the clamp tight so that it did not fall off the post while I was driving from the storage compound to my home where I could do a more permanent fix. Been there, done that, got the tee shirt!