The field wire has three prongs and ain’t the cleanest connection but it’s mostly dried grease and worked fine with the bench test computer at the auto store
The connector is about 9-10 volts on the outside prongs and 0 in the middle when the ignition is in the ON position
Tried checking the ECM per the Chilton: didn’t get a reading between the prongs suggested but got 10v between the prong and body ground plus a closed circuit to the body ground. I’m not sure the Chilton diagnosis is right or I’m doing it exactly right… it seems though the power might not be going through the ECM per the diagram though…
Best option for repair, replace? There are several like models nearby that I can pull the part from. Does it need to be programmed to test a swap?
Downloaded the factory level manual and seems to point to ECU or bad wire. More likely just ECU or inconsistent power to the ECU.
Can I just swap like model ecus to test that theory? Like pull a same gen, same engine, same connectors ECU and swap it in. I think it’d only take a half day at most and there are several like models at the pull a part places near me…
I’ve seen more than one good/working alternator replaced over a blown fuse… just saying…
I have also seen a lot of alternators recommended over a battery with low voltage, sometimes they go in to a limp type mode to keep from burning themselves up…
I made the conclusion to proceed to the next test in the chain of diagnosis, not concluded the alternator is bad.
If the alternator does not get power from the field wire, the alternator will not produce voltage and current.
Yes, it does mean the alternator is not working. It is showing lower than battery voltage which means the car is pulling current from the battery, not the alternator. It does not determine WHY it is not working… bad alternator, or no field signal… but it clearly is not working.
This test showed the alternator to be good, eliminating “bad alternator.”
So the next step is:
Which the OP did, or is trying to do with a Chilton manual.
I downloaded the factory manual… Lots of wire tracing to possible happen in my future… I’m gonna study up… Won’t be able to work on the car for about two weeks… Field wire to ECM, EFI to ECM alternator field wire doesn’t explain the speedometer going out… Power to the ECM is in the check…
The ECM in the car has no wire at B+ (+) bottom right corner… I don’t understand how that could be the positive then… It actually looks a little burnt… The ECM has some light rust around the casing indicating possible moisture… I gotta probably first check the wires more closely and probably get a tester or two that poke in through the insulation to test the harnesses…
Relays tested good for what I can tell… Gonna study the wiring diagrams more…
Are you trying to repair the speedometer? You stated the engine stalled after two minutes and no output from the alternator.
What is the problem you are trying to diagnose? The alternator field circuit in inside the alternator, it has an internal voltage regulator. There needs to be an “on” signal to switch on the alternator when the engine is running, that comes from the ignition switch.
Continuity is measured in ohms, that test is to verify the ground. You must have misidentified the wire cavities. What lead you to testing these circuits? I thought you were working on the charging system.
On both of my vehicles I press at a point in the middle b/t two pulleys on the belt firmly w/my thumb, and belt deflects about 3/8 inch. Engine off of course.
I presume by “off” you mean the engine is off, not idling, key in the “off” position. This indicates the battery is is in discharged state. Fully charged, the battery voltage would be around 12.6 volt.
The battery voltage should be 13.5 to 15.5 volts when the engine is running. Something is definitely wrong.
I presume you mean 11.5 volts. That is not current unit.
Maybe. Alternators generally require three inputs: (1) a voltage input for the field coil, varies by the car circuitry’s current demand (2) a solid ground connection, and (3) a mechanical input; i.e. the inner part is spinning along w/the pulley. Suggest to verify the inputs before replacing the alternator.
I
Any time you are working on the electrical system safest (& less chance of damaging something expensive that isn’t currently broken) to disconnect the battery first.
The alternator wouldn’t bench test good if either was faulty.
You’d likely get better results by hiring a pro for the diagnosis, then you can replace/fix whatever the pro says needs replacing yourself if you like.
The ECU doesn’t seem to communicate with the alternator or the radio per the diagrams. The ignition switch has been sticking recently being hard to turn the key…
My friend complained of no speedometer, poor engine performance (sputtering), starting and then dying, radio going out, no start situation
I think I’ll try to test the ignition switch and probably replace it…
Ignition is connected to ECU, alternator, and radio.
A lot going on here, not all of it good, and after all of it I still don’t know if we are looking at a “no crank” or “crank, no start” situation. Also, since when does a “good” alternator not generate enough voltage to charge the battery? And why so much ink spent on fixing belt squeal when the engine doesn’t run reliably?
In a 20+ year old vehicle with the range of symptoms described I’d get my hands on a wiring diagram and look where power for all symptoms meet. The last thing written about the ignition switch sounds promising. If not the switch itself then wires to and from.
Borrowing from another poster, my advice to the OP is don’t assume, diagnose. Your approach so far seems a little scattered and some of your comments suggest you may be new to this.
The main problem here seems most likely an electrical intermittent, the hardest to find. Concentrate first on the start/run problem.
