94 sunbird will not start

get a better battery with better cold cranking amps

Where both rebuilt alternators any good
& retested at store?

Your explaining a constant voltage drop,
once the battery is hooked up.

How about the ignition switch?
Does that have anything to do with
the regulator control in alternator?

You haven't said you have 14 plus volts
with motor running,so basically you don't
have an alternator charging your new battery
& the ignition currant, even without the lights on,
is running down the battery

All I said is what you already know

I'm is missing something?

Don't unhook any battery cables with
the motor running,were not living in the 1960's

Those type tests will ruin many things on newer
vehicles, than yours,loose that practice & also avoid
jump starting any vehicle from 1996 on

the voltage from the big red wire is battery power
the smaller wire will not have voltage until the alternator is running
one wire goes to the charge light to the voltage regulator
check that the voltage regulator is operational
better still get an accredited auto electrician to check the charge circuit , voltage regulator and alternator for operation

My wife and I have owned three 1994 Sentra cars. One of them went through batteries and alternators like crazy. Last time the 1-year old battery died, I replaced it and went straight to an auto electric shop. The technician found the alternator was putting out about 77 amps the entire time the engine was running (factory alternators are rated for 80 amps, but only when charging nearly-dead batteries). He also found that the harness running to the alternator was hot enough to scald you if you touched it. Miraculously, I found a factory NOS harness on eBay and bought it. Easy to put in, and the car went from a maximum charging voltage of about 13.1 volts, to a MCV of up to 14.1! Haven't replaced a battery or alternator on it since. Hope this helps someone...

Options are a couple things like faulty ignition switch... or neutral safety switch either out of alignment or going bad... what does the car do when you try to start it... because it could also be the charging system ... such as the battery not having enough voltage to start or a bad alternator not charging the battery. You need to ***** the situation and check everything step by step. starting with the battery. if you have a voltmeter, you can set to DC and put POS to + and NEG to - and if it reads 12.5V with the motor off then the battery is charged a dead battery will read 11.8V. Start the car and place the POS lead of the voltmeter to the POS terminal on the alternator (the big red cover) and ground the NEG lead and you should get a similar reading steadily... It should not drop ... if you get a low reading then the alternator is going bad and cannot charge the battery. Next check your starter underneath the car and put the POS to the big terminal going to the battery, It should read a similar voltage. To check that the starter solenoid has enough power you can run a wire with a switch direct from solenoid to switch to battery and try or you can put the POS to the spade connector end and the NEG to ground and have a helper turn the key to start to check for voltage (12V) if not then it suspect a faulty ignition switch... If when you try to start after ensuring a good charge and get a cluck noise with no start or start sometimes then your starter may be bad... If you get nothing at all and your lights and accesories work with 'bright' lights then your starter solenoid may be bad... If nothing happens and the lights dim then the ignition switch may be bad ... If you're not much of a DIYer you can take the car to your local autozone or advanced auto and they do a free alternator and battery check...If they are good then you can remove the starter and have them perform a bench test. Hope this helps... Good Luck.

HAVE BATTERY RECHARGED OR VECHICLE JUMP START.WITH VECHICLE RUNNING MAKE SURE ALTERNATOR IS CHARGING THE BATTERY.ALTERNATOR OUT PUT AT BATTERY SHOULD BE 13.5 - 14.5 VOLTS.IF NOT CHECK ALTERNATOR FUSE.CHECK ALTERNATOR + BATTERY FEED WIRE AND VOLTAGE REGULATOR WIRES MAKE SURE NONE OF WIRES LOOSE BROKEN OR DISCONNECTED.IF ALL IS GOOD AND ALTERNATOR OUT PUT LOW ALTERNATOR FAULTY.IF ALTERNATOR VOLTAGE OUT PUT OKAY. YOUR BATTERY DRAIN PROBLEM COULD BE FAULTY AC HEATER BLOWER MOTOR RELAY.CHECK INSIDE CAR WITH THE IGNITION SWITCH OFF.MAKE SURE RADIO TURN OFF.INTERIOR LIGHTS TURN OFF.HEAD LIGHTS TURN OFF.LISTEN FOR ANY NOISES LIKE BLOWER MOTOR RUNNING, OR FAULTY DOOR LOCK SOLENOID CLICKING NOISE.IF EVERY THING SO FAR OKAY.OTHER POSSIBLE CAUSES BATTERY DRAINING COULD BE FAULTY ALTERNATOR,FAULTY STARTER SOLENOID CONTACTS SHORTING OUT.THE PCM COULD DRAIN BATTERY IF FAULTY.THE NEW BATTERY COULD BE DEFECTIVE.

Tell us more details.
For example, how do you know the alternator really is good?
You say new "ignition", but that could be the ignition switch, plug wires, distributor, etc.
Regardless if the battery was new, you can easily drain the battery in less then 20 minutes, so we need to know if the battery still has a charge or not. Put a test light or volt meter across it.
We also need to know if it does nothing, not even drain the lights, or if it clicks at the solenoid?
The best would be if you put a voltmeter across the battery.
If the ignition switch is bad, then nothing at all with happen.
If the battery is bad, it will start around 12 volts, but drop down below 9 and not come back up when you stop trying.
It is drops but comes back up, it is probably the starter.
But you could try turning the engine over by hand on the alternator nut, because it could be seizing up from a bad bearing.
Try jump starting it also.
If that helps, then check the voltage when reved up.
It if does not reach over 13.5 volts, the alternator is not working.

How much amperage is the alternator putting out? To check this, put a volt meter across the battery terminals. Boost car & let run. Remove booster cables & read the meter. It should read over 13.2 & if battery is weak or uncharged it should be as high as 14.5. You could have part of your diode trio burnt causing the alternator to only charge when reving high & current in low demand i.e. when lights radio, & other electrical equipment off. I think this is the problem. Good luck! Also you may have the trunk mercury switch malfunctioning & leaving the light on in the trunk thus draining the battery. Temporarily remove bulb & see if problem persists.

the wire that tells it to excite is the battery wire to the alternator through the light bulb
not charging is a problem voltage regulator
while the alternator may be new if it requires an external regulator or internal regular is a problem

here ya go check for power to the alternator good luck ............ justuscc Charging & Starting System Wiring Circuit - VIN K