Alternator light doesn't work need some help

[1993MTXSHO]

Heres the story, I have a 94 mtx and I put an 89-93 alternator in it. The alternator was charging for 250 miles just fine, but now it seems it died, but did not throw a light when it did. The bulb does not light up when I turn the key on, but I pulled the bulb out of the cluster and it works fine.

When I first did the swap I forgot to hook up the stator (???) wire I think, it's the main wire that hooks onto the stud coming out of the alternator. When I did this and started the car it threw the light as one would think it should. I just did this again and now the light doesn't work. I am at a loss, the only thing I can think of it maybe my cluster circuit board is screwed up, or that little 3rd wire on my starter is not making good contact. I am not sure if that has anything to do with this, just a guess since mine is kinda ratty looking. Anyone have any idea what this can be? It's starting to get on my nerves.

 

[hawkeye18]

One of the wires on the plug-in connector goes directly to the positive post on the battery through that light; if the wire is broken anywhere (say, at the plug), or the wire isn't in the correct slot in the plug, the light will not work.

It's a competing ground - as long as the voltage at the alternator equals the voltage at the battery, the voltage will fight from both sides, resulting in a tie, and the light won't turn on, but if the voltage becomes unequal on either side, the light should light up... but if there's a dead open on one side, then nothing happens.

 

[1993MTXSHO]

One of the wires on the plug-in connector goes directly to the positive post on the battery through that light; if the wire is broken anywhere (say, at the plug), or the wire isn't in the correct slot in the plug, the light will not work.

It's a competing ground - as long as the voltage at the alternator equals the voltage at the battery, the voltage will fight from both sides, resulting in a tie, and the light won't turn on, but if the voltage becomes unequal on either side, the light should light up... but if there's a dead open on one side, then nothing happens.

I had a feeling, and I did check my connections and they seem fine. Any ideas as to where a break might have happened (read: more likely area for it to happen) or am I going to have to do this the old fashioned way and just follow the entire wire?

 

[1993MTXSHO]

Ok I just did as much as I can and I am really at a loss here. I have battery voltage at the "I" connector in the alternator plug and all my fuses on the underhood box and my dash box are good. I don't know what else to really do here so any help is greatly appreciated I need this to work by Tuesday if at all possible.

I have been using the Ford service manual but can only find any real diagnosis stuff for the 94, not for a gen 1 alternator.

EDIT: Does anyone know exactly where the fuseable links are in the wiring, I don't want to rip my entire harness apart to find these things, I have a feeling that may be my problem.

 

[1993MTXSHO]

Bump? Anyone? I really need some help here, no one ever had fusable links blow out on them and had to find them?

 

[SHOZ123]

The fuseable links should be on the wires leading to the engine compartment fuse box from the starter IIRC. So if you have 12V there then they are good. Look at Cell 012 in the Ford manual.

There is a resistor in the alternator light circuit on the cluster. This may be open.

 

[1993MTXSHO]

The fuseable links should be on the wires leading to the engine compartment fuse box from the starter IIRC. So if you have 12V there then they are good. Look at Cell 012 in the Ford manual.

There is a resistor in the alternator light circuit on the cluster. This may be open.

I have 12 volts at the fusebox so I guess they're good then. I am going to try to check the cluster tomorrow.

 

[the4biddendonut]

Here's the diagram for the 94 MTX, in case it helps.

 

[1993MTXSHO]

Well I checked the load side of fuse 15 to ground and I got continuity, which tells me I probably have a short somewhere. But on the fusebox, the little number 15 that points to the red 10 amp fuse, that is the "load side" of fuse 15 correct? I pulled that out and tested from that prong to ground and it connects with the battery cable disconnected.

I also tried testing the ohm readings of pin 10 12 and then 10 again in the J1 and J2 connectors behind the cluster respectively. If I am reading it correct all of them are under 1 ohm meaning my cluster circuit board is bad. Also I tested the 510 ohm resistor on the back of the board and it read 4.5 ohms. All I did was put the probes on either side and test the cluster out of the car, would this mean my cluster is done? I hate electrical problems, especially when its 93 degrees outside and humid.

Anyway if someone can confirm that I tested this correctly and that I do in fact have a short or a toasted cluster that would be great. But could I have both problems? A short in the system that in turn destroyed my cluster?

EDIT: oh and one more thing, if it's shorted, why would my fuse not be blown?

 

[1993MTXSHO]

I just backprobed both of the upper alternator wires and both are reading 13.9 or so. Can anybody make any sense out of this because I am dying here without a car. I am worried to drive it because I am afraid of burning up another alternator or killing another battery.

 

[the4biddendonut]

I don't really understand much about the circuits you're testing. But just because you have continuity in the circuit doesn't mean you have a short.

If you were to test the continuity across a bulb, you would have continuity (unless the bulb was burned out). The continuity goes across the load, that is why you might be getting continuity in the circuit.

I don't know if the circuit you're working on should have continuity or not.

 

[1993MTXSHO]

I don't really understand much about the circuits you're testing. But just because you have continuity in the circuit doesn't mean you have a short.

If you were to test the continuity across a bulb, you would have continuity (unless the bulb was burned out). The continuity goes across the load, that is why you might be getting continuity in the circuit.

I don't know if the circuit you're working on should have continuity or not.

I tested it based on what the ford service manual said to do. It said i should not have it. But I want to make sure I Am testing the right spot on fuse 15.

I tested on the circuit with the red 10 amp fuse next to the little number 15 on the dash fusebox (After I pulled the fuse), I assume that is the hot side of 15. Can anyone confirm that?

 

[1993MTXSHO]

I just checked the current draw from the negative wire, and the negitive battery post and it showed zero draw so I don't think I have a short anywhere. What can this be I really need some help guys I am so lost and need this car to work.