Does the Alt that comes on my these cars (Vin E) have an internal or external voltage regulator. I was curious. Is there a possibility that I fried my ECM, and this is causing my chargin problem?

 

No one has the answer to this?

 

The voltage regulator is internal to the generator or alt. When you plug in the plug to the gen you are actuallly plugging in to the regulator hybrid IC. The ECM has an internal MOV, or metal oxide varistor to protect against voltages over 17 volts DC. If you suspect that you can open the ECM and visually inspect it. The MOV is a round component and usually it is burnt and will smell if it was subjected to overvoltage. It's rare for the gen to get too high to cook the ECM, usually the battery will help keep the voltage low enough to prevent this. More info helps on posts like this.

 

ok, here is the story. I installed a Auto Meter tach with shift light. I went per the instructions that came with it. After installing it, I started the car to test it, and saw that I was on reading 12.5v. I had the batt and the alt tested, both were bac, so I replaced them. Still, I only had 12.5v (verified with DMM). It would hold a charge, but at the amount stated. After about 100 miles or so, the volts began to drop. Soon, it wouldnt hold a charge at all, would just start draining immidiatly. Checked the resistances in the wires to and from the alt and battery, including the ones going to the starter. I checked the voltage at all the spots, including the starter. Had no drop, still 12.5. Traced the brown wire from the plug on the alt to a relay in the firewall, and into the fuse box. Swapped relays around, still 12.5v. I am stumped and this is the only thing that I can think of left, the ECM.

Oh yeah, all the grounds seem to be ok.

 

The ECM has nothing to do with charging. Check this, remove the plug at the gen with the key off. Measure the red wire(the heavier guage one), it should read 12 volts with the key off. Measure the tan/brn wire, it should read zero with the key off and a little less than the red with the key on. There is a 10 amp fuse in the fuse panel labeled "chg/fan" or something close. Check it. Did the problem start immediately after you added the new tach? The red wire from the rear of the gen goes thru a fuse link to the battery. You can disconnect the battery and measure it to the positive terminal of the batt. It should read less than an ohm. Charging voltage at the battery with the vehicle running should be 13.5-14.9 volts.

 

did all that, still no avail.

And yes, the prob started IMMIDIATLLY after hooking up the tach to the ingnition source in the fuse box.

 

I rebuild gens in my spare time and have done all the different delco units. If you have those 3 voltages and the fuse link between the gen and the battery is OK the gen is bad, new or not. Hopefully you have disconnected what you did before troubleshooting. One thing to keep in mind, some of the rebuilt gens are using FET type components instead of the bi-polar type devices inside the reg IC. They can be damaged by a condition callled false-biasing. This occurs when the gen is installed with the battery connected and the rear lug is hooked up before the plug is put in. If you are sure all 3 voltages are there i would take the gen off and have it tested. All of the charging components are internal to the gen. LOL

 

i have a similar question. 88 350

I about 30 miles from my house and the battery starting dieing and i found that the alt. wasnt charging. The problem was the connector on top not making good contact with the terminals on the alt. The wire actually fell out of the plastic connecter and shorted out on some ground near by. ever since then those 3 wires dont have any power going to them. So temperaly I made a direct jumper wire to go stright from the pos on the battery to the middle terminal on the alt.( the only one where i noticed it charging). will leaving the jumper wire on there do anything bad, and how would i figure out how to fix the orginal wires to the alt?

thanks

 

What would it mean if I didnt have any power to the black wire in the plug with the key on?

Also, could it be one of the fusible links in the ignition, not neccesaryily on the charging system?

 

Thats the "sense" or gen turn on wire. Without that wire connected the gen will not charge. It is usually a resistance wire that ties back to that fuse I mentioned in the fuse panel. Follow what you did, perhaps you inadvertently damaged it when working on it. Sounds like you are close. Not familiar with 92 RS model, does it have a guage or a bulb light? If it is an idiot light does it come on when you turn on the key? My diagram shows the line going to a 20 fuse in the panel upper right top row labeled "fan", double check it.

 

mine has the gauge. We check the fuse. I took the fuse out, and put in the power wire for my manual switch for the fans there right before I hooked the tach up.

I put the fuse back in and still had the same problem.

 

Make sure you have voltage at that point(the fuse) with the key on. For a test you can take a 33 ohm 5 watt resistor and jump it to the black wire on the alt to the rear lug, the alt if it is OK should start to charge. Then you will have to find out why there is no 12 volts on that wire.

 

ok, lets say using the resistor it starts to charge. Can I run it like that until I figure out the problem, or is that a bad idea?

Also, I should check both sides of the fuse, correct. The reason I am asking is because when I plugged my fan switch into that fuse area, it worked, which means it got power, but I olny plugged it into one side.

 

No, it's only for test unless you hook it up to a key controlled 12 volt source. If you leave it that way with the engine stopped the alt will buzz and the reg IC will fail. I am confused, did you remove the fuse and plug into one side of the open circuit? That way, with the fuse out you will only get power from one side. If you left the fuse out thats your problem. Fuses are basically jumpers that are designed to melt when current goes past a certain point. When you remove a fuse one side of the open cavity contact will have power, the other side will be dead. Insert the fuse and both sides will have power. That fan fuse supplies power to the alt turn on or "sense" line.

 

We did put the fuse back in, after you told me about it. That didnt work, it still didnt turn on.

 

I cant seem to find a 33 Ohm 5 watt resistor anywhere. Radio shack carried a 47 ohm, 5 watt, but that was the closest.

 

Thats fine, actually anywhere from 25-50 ohms is OK. The higher the value of the resistor the harder it will charge. Just check the charging voltage when you perform the test, if goes over 15 volts for an extended period of time lower the value.

 

so, basicly what i am doing, is adding resistance to the curcuit to lower the current, in turn causing the alt to up the voltage to get the required current.

 

Yup, the aly has a resistance in that wire that feeds the sense wire. They do that to keep the alt a little higher than the batt to charge it and account for voltage drop in the wiring.

 

sorry to chime in here-- but I am converting a serpentine setup to use on an older small block in my Jeep. From looking at the alternator terminals, the "S" from SF LP joins the batt + lug to regulate voltage, and the "F" is the sensing wire?

When I hook up the "F" to my keyed 12v ignition on source, do I need to pay attention to the resistance of the sensing circuit for proper operation, or will the voltage regulator take care of that?

also, I take it the "L" is for the charge light, and "P" is not used.?

 

go to www.alternatorparts.com and look up the online manual. They give the different diagrams.