HELP! No alternator output. Searched, tested, checked, scratched my head.

[qat727]

Ok. Some of you may remember when I first started posting questions about my 240SX, trying to get the engine built and put back together. Long story short, I did, and I got it running. The biggest problem I've had is that it won't charge the battery. (For reference, we are speaking about a 1992 240SX fastback with a KA24DE with a factory 5 speed.)

Symptom: Brand new battery was completely drained after driving car during engine break-in period. Battery continued to die and require recharging on a regular basis. Battery light in cluster did not come on with ignition or at all.

Hypothesis: Dead alternator.

Testing:

Round 1) Car will not start, battery drained. Took battery to Advance Auto for testing. Found bad battery (just purchased two weeks previous). Replaced battery. Battery died again. Took battery to Advance Auto for testing. Battery found drained and was recharged. Replaced battery and car started and ran.

Round 2) Disconnected battery while vehicle was running. Car died completely. Removed alternator and took to Advance Auto for testing along with 2 spare alternators. All three alternators checked out as completely operational and fine. Reinstalled old alternator and disconnected battery with vehicle running. Vehicle dies.

Round 3) I dig into the wiring and find several miles of aftermarket wiring. There is an aftermarket cruise control apparatus, an Autometer electronic Oil Pressure gauge, separate wiring for at least two amplifiers and stereos, and a battery relocation to hatch area.

Round 4) I had previously relocated the battery back where it belongs under the hood due to an exceedingly poor install of the battery relocation parts. I verified that all under hood battery wiring was correct. I removed all cruise control wiring, disconnected all spliced stereo wiring, and rewired the oil pressure sending unit. I verified all necessary fuses were in place. Bulb for battery light in cluster is good.

Round 5) I obtained a copy of the charging system wiring diagram from the Factory Service Manual. Pictured below is the drawing I worked from.

I ran continuity checks as follows: Alternator is properly grounded and connected to the battery. White wire at 2 wire plug on alternator is connected to battery positive along with white wire connected separately to alternator. White/Red (W/R) good from alternator to SMJ inside vehicle. Brown wire good from under hood fuse to SMJ. Checked W/R from SMJ to gauge cluster and found it was good. Checked green wire from cluster to inside fuse box and found good.

I was unable to locate the Bulb Check Relay. According to the component location section of the FSM, it should be a blue relay below a brown relay beside the SMJ. I found a blue connection under a brown connection, but they were not relays. I was in the process of removing the SMJ to look behind it when it began to rain on me. The only reservation I have about the blue connection is that one wire going to it is white/blue and the other is white. According to the wiring diagram, it should be W/R and brown. I could find no such wires connected to any relay. After the W/R and brown wires leave the SMJ, they join the main harness and I have been unable to trace them.

If anyone has any suggestions of possible problems to look for, I would greatly appreciate it. I spent many hours today with a multimeter checking the wires, and the only wires I could not account for are those pertaining to the Bulb check relay which I could not locate. I am almost at my wit's end with this issue, so if anyone could give me some suggestions, it would be wonderful.

Cliffs notes: my alternator isn't working, but it tests out as fine, so does my battery, and most of my wiring, except a bulb check relay which I can't find. Help me find the bulb check relay or the reason my alternator has no output, please.

[yokota180sx]

obviously its your alternator

do some simple checks before you get too into it

Test your alternator to see if it works to begin with by removing one of the battery terminals while the car is runing

second, is your Main fuse blownthe 75 amp one in teh engine bayif it is, its a 98% chance your alternator is grounding out internally

to check that put the positive on the terminal, and negative on the casing,if you have continuity its bad.

[qat727]

obviously its your alternator

Well, I guess I can pull it out and have it checked a second time.

do some simple checks before you get too into it

Test your alternator to see if it works to begin with by removing one of the battery terminals while the car is runing

Round 2) Disconnected battery while vehicle was running. Car died completely. Removed alternator and took to Advance Auto for testing along with 2 spare alternators. All three alternators checked out as completely operational and fine. Reinstalled old alternator and disconnected battery with vehicle running. Vehicle dies.

second, is your Main fuse blownthe 75 amp one in teh engine bayif it is, its a 98% chance your alternator is grounding out internally

to check that put the positive on the terminal, and negative on the casing,if you have continuity its bad.

Main fuse is intact, and I have continuity from the alternator ground to the body ground, and I have continuity from the white + alternator wire to the battery +, as well as continuity between the white wire in the two wire plug for the alternator and the battery +.

Thanks for the reply, though.

[qat727]

bump it up

[yokota180sx]

dude your missing what im saying

Put hte red lead on teh POsitive post, that runs to hte battery, and the black to the case of the alternator

[qat727]

dude your missing what im saying

Put hte red lead on teh POsitive post, that runs to hte battery, and the black to the case of the alternator

Ok... Red test lead to positive battery cable and black test lead to alternator case gave me some resistance. Black test lead to alternator case and red test lead to positive battery cable got almost no continuity.

I tried the same tests on my two spare alternators and on a known good Honda alternator, all with the same result. So based on that, I don't think the alternator is shorted out.

[yokota180sx]

it is a troubleshooting test in the Nisan FSMif there is ANY continuity between the two, replace alternator.ther emight not be alot now, but over time it iwll increase continuity and blow that main fuse.

replace your alternator.

Ok... Red test lead to positive battery cable and black test lead to alternator case gave me some resistance. Black test lead to alternator case and red test lead to positive battery cable got almost no continuity.

I tried the same tests on my two spare alternators and on a known good Honda alternator, all with the same result. So based on that, I don't think the alternator is shorted out.

[qat727]

Ok... I got the alternator out today and had it checked at Advance Auto and AutoZone. Both showed the alternator to be good. I didn't get a chance to install one of the two I've got that tested good. I don't have the ~$140 it's going to cost to buy a reman alternator to install and hope it fixes it.

I got to studying the wiring diagram some more. Perhaps someone can lend some insight for me. It's my understanding that the battery light comes on when the ignition is in the on position without the engine running, and it turns off when the engine starts and the alternator starts working. If this is the proper operation, then the light should remain on if no charge is present. Is this proper operation?

My light does not come on at all and the alternator does not charge either. I found the bulb check relay behind the SMJ and checked it. All the wiring going to it is fine as is the relay.

There is only one wire I can not find. It is the wire going from the interior fuse box to the ignition switch. It's green up to the fuse box, but after that, I can't find it. Does anyone know which one this wire is?

Based on further review of the diagram, I believe there have to be two faults in the system. The alternator should charge regardless of whether or not the bulb is working, and the bulb should turn on if the ignition gets turned on and the alternator is not working. Since I've checked all the wiring in the bulb circuit except the wire between the fuse and the ignition switch, I'm thinking that one might be the problem. As for what's causing the alternator to not charge, I'm still at a loss. I've checked every piece of wire in that circuit now, and it all comes out as fine.

For some reason, the engine won't start now, either. I think it's probably related to some of the wiring I have taken apart. Once I get it started again, I think that if I jumper between the white wire and the white/red wire in the plug on the alternator, to the contacts in the alternator, it should bypass the whole bulb circuit and let it charge, so I can check the alternator's operation. Any clue if this would work?

If anyone else is out there that can give me some answers, I'd appreciate it. I really want this car done in time to take it to the Nashville NICO meet. If I can't get it running, I'll have to take my Civic

[qat727]

Bump it up... Come on, someone here has to know something. I'd hate to have to drive my Honda to the meet. It looks like crap.

[qat727]

Today I put all the wiring back together under the dash and installed the other alternator I had that tested good, just for kicks and giggles. The car started, and continued to run after I disconnected the battery. However, now the car continually tries to die, and the battery light still does not work at all. I'll be checking the alternator to verify that it has proper output, but does anyone know why the battery light doesn't work?

[krimsonviper]

i feel bad for ya, so im going to bump it...and why not splice that one green wire and try to get it to where it needs to go? remember if you splice it leave from excess so you can reconnect it later if it isnt the cure

[qat727]

Thanks for the bump. As for the green wire thing, I'm not sure where to splice it to. Based on the wiring diagram, I've been able to verify that everything in the bulb circuit is good except the wire from the fuse box to the ignition. There are multiple wires on the ignition, and I can't seem to find a note in the service manual as to which wire is which on the ignition, so I haven't been able to figure out where the wire is supposed to go, even to just jumper/splice it.

You know, that is a thought, though. I could just run an extra contact from that fuse through the front of the fuse box, and just start checking which contacts on the ignition would make it light up. I don't think that will necessarily give me the correct wire, but it might let me get it working.

Also, has anyone wired up an Autometer Phantom oil pressure gauge? This is the one with the electric sender unit. I'm having a few issues getting this one working, since the wiring sucks and wasn't right when I got the car. There are 3 contacts, and a little diagram has S, Grd, and I in order of which post is which. There is also a bulb with a black and white lead. Now the only manual I could find on the Autometer website shows the black lead going to ground, and the white going to an illumination source. I'm guessing that the Grd terminal is for a chassis ground lead, and the S terminal is for the sender. I figured the black lead could go to the Grd terminal. I'm just trying to figure out if the I terminal needs to go to a 12V+ source switched with the ignition, or if it should go to a 12V+ illumination souce. Is this the proper way to wire the gauge?

[krimsonviper]

you can also see if the previous owner used some sort of kit for moving the battery to the back of the car, if thats the case, see if you can get the wiring diagram to see what he/she messed with.

as for the gauge you can probably use the illumination wire for the stereo unit or the acc wire i dont know really never tried gauges and im just guessing

*edit*just a question but are you sure all the wires are connected after you rebuilt the engine?

[qat727]

It's kind of messed up with the previous owner situation. I got it from a former friend that I no longer see or speak to, who bought the car mostly as-is and blew it up in 3 months time. He never would tell me who he got it from, so there is just a whole lot that I don't know about the car.

Someone did run a battery relocation "kit" to put the battery in the back. By "kit" I mean a completely ghetto rigged piece of crap that was incredibly unsafe. They beat a hole in the bottom of the spare tire hole with a screwdriver, did not install a grommet, ran a length of battery cable through the hole to the engine compartment and zip tied the cable to the frame rail so that it was hanging down in places. The fuse box they had installed on the battery cable was just an amplifier fuse block that had bolts installed instead of fuses, and it had been glued down with liquid nails to the old battery tray. In order to run the kit, the only thing they cut were the 3 leads that attach to the + battery terminal, which I happened to have an extra set of. So, I reinstalled the + terminal leads, and everything checked out on the battery circuit.

I'm not sure if you caught what I posted last night, but when I replaced the alternator, it now runs without the battery, so I'm getting at least some alternator output, likely full, but that will be checked ASAP. The current problem relating to the alternator is the battery light. I've checked all the wiring for it, except the lead from the inside fuse panel to the ignition switch, which I can not find.

If I just use the illumination wire, then the gauge would only be getting 12V+ when the lights were on, correct? Does the gauge need a constant 12V+ supply when the ignition is on?

Regarding all wires being connected, yes and no. I am sure all the wires are NOT connected. There has been an emissions delete performed on this car, so some of the wiring relating to said emissions equipment is left hanging. All other wires are properly installed, with the exception of an unknown set of wires going to the transmission that were cut and I have not found where they belong. I have driven the car up to highway speed, and I encountered no trouble with the speedometer or anything else to indicate something major on the transmission was disconnected, so I didn't bother with it.