Battery Voltage Loss

[AHall]

I have a problem starting my car. I have replaced the starter I have even purchased a new battery and the car will still not start. I have tested the voltage at the starter and it is the same as that at the battery. When I try to start the car it is as if there is not adequate voltage or amperage to make the starter work. I can jump start the car just fine. Also after I attempt to start the car the battery power drops way down to a level where there is not enough power for the automatic seat belts to work.

[AHall]

By the way, I have a 1992 Nissan 240sx with no mods.

[droll]

Did you check all the cables from the battery to the starter to make sure there weren't any bad connections, currosion, shorts? Also check the ground cable from the battery to the engine block.

You can check the voltage of the battery when off, then check the voltage while it is cranking to give you an indication of how much power is being sucked up. You'll see how far the voltage drops down. (what you really need is a clamping ammeter) Also, once the car is running, check the battery voltage again. I should be higher then when off, around 14V. This will tell you if the alternater is working. The part about the seatbelts not working shouldn't happen of the alternator is working right. Try reving the engine.

[AHall]

I believe there is only one cable from the battery to the altenator. I checked the voltage at the terminal and it is always the same as it is at the battery. 12.96 volts when the engine is not running and 14 volts when the engine is running. I checked the battery when it was trying to crank off a single battery and the voltage droped down to around 5 volts. It would then go back up to 10 and then 12 several minutes later. I do not know what the cranking amps are. That would be helpful info, but I can just take the battery and have it tested. Shouldn't this test accurately reveal the cranking amps without me having to purchase an additional meter?

All electric devices, seatbelts, lights, etc., work fine after the car is jump started. The problem occurrs after I try to start the vehicle without a jump. Then the car does not start and everything kind of goes dead. I can hear the relay click but that is it, nit enough juice to turn the starter.

[droll]

Dropping to 5 volts when cranking is not good. It shouldn't drop below 10ish volts. That would indicate a bad battery, but isn't this battery new?

[NISTECH]

your losing a connection at one of the 4 ends of the battery cables. when your doing this battery test while cranking and the voltage drops down are your tester leads on the battery posts or the cables?? that test can only accuratly be done with the test leads on the battery posts directly.

[AHall]

NISTECH & Droll,

Is it possible that the interlock relay could be the problem? What exactly does that relay do anyways.

I have tightened down the ends of the baterry cables where they attach to the engine, the starter, the battery tray and the battery terminals.

Thanks for the help

[vancouverbc]

are your battery cables tight on terminals? look for rotten wire in start circuit.

isn't a relay either on or off? i guess you could jump the relays and switches.

[AHall]

I have the bolts on the connectors as tight as I can get them, but there is still a small amount of looseness.

What do you mean by rotten wire in the start circuit?

Also how do i jump the relay and switches?

[AHall]

Found the problem. Turned out to be a defect in my battery. The thing that threw me is that had the same symptoms that I had about 5 months ago, and I tested my battery at that time by switching the my battery with the battery in my wifes prelude as well as buying a new battery. When I did this i still had the same problem. Luckily I was able to return the battery I purchased. Anyway, this time around I took the battery had it tested. It failed I replaced it and all is well.

Thanks to everyone for your suggestions.