Field fix harness, LT1 alternator, STILL having charging problems

[neat]

Maybe I am retarded, but I can't get the charging system to work properly on the 87 TR in my signature.

The factory alternator was bad, I purchased an LT1 impala alternator on the recommendation of turbobuicks.com.

I still had no charge, and I discovered that that the small wire that clips into the back of the alternator had no voltage. Again, on the advice of turbobuicks.com I bought a field fix harness from Caspers Electronics.

The car seemed to run OK now, but the battery would die in just a few hours if the car was left sitting. I discovered, again through turbobuicks.com, that the alternator was pulling 12V the entire time. Even with the car off. I took the LT1 alternator back to the store and had it replaced under warranty.

I installed the new alternator, and everything seemed fine. The new alternator did not pull any voltage with the car off. After 2 days, the battery was dead again. I jump started the car and checked for voltage at the alternator with the car running. The big post on the back of the alternator was dead. Zero volts. I removed the alternator and went to the local AutoZone where the alternator tested good, producing the required 14.4 volts or so. I came back to the car and reinstalled the alternator. I put a battery charger on the battery and started the car. Again, the big post on the back of the alternator was dead, no voltage. I pulled the field fix harness off the alternator and tested for Voltage at the 2 of the 4 sockets that contained pins. For simplicities sake we will number the sockets 1 threw 4. Socket number one was the largest of the sockets and was empty. Sockets 2 through 4 are the same size, and socket 2 and 3 contain pins. Socket 2 had 12V and socket 3 was dead.

Looking at the 4 sockets on the on stock connector, only socket 3 contains a pin, so the way I see it pin #3 has to be the pin that the alternator needs to see voltage at in order to charge. I called Casper's and John confirmed that the LT1 alternator did require a different plug. I again started the car and ran a 12V jumper wire to each of the pins in the back of the alternator and checked for voltage. On pin #3 the alternator finally produced the requisite 14V. The field fix harness was suppling power to the wrong pin in order for the alternator to charge. I took the alternator end of the field fix harness apart and swapped sockets 2 and 3. Now, the alternator would see power at pin #3 instead of pin #2. The car ran fine for 2 days.

This morning, the battery was dead again. I started the car with the battery charger again and started to check things. With the large cable not attached to the alternator, the alternator is only producing 11 volts.

The way I understand the system is that the field fix harness is supposed to mimic the voltage drop across the dash bulb, and feed the alternator with some voltage that is less than 12V. My field fix harness, which was wired wrong for my LT1 alternator application, is supplying what ever the battery voltage is to the alternator. If I understand things properly, that will destroy the voltage regulator inside the alternator. To me, that sounds like the problem I am having.

What voltage should the clip on connector provide to the LT1 alternator?

Why doesn't my field fix harness limit it to the proper voltage?

Why did everyone tell me to get the LT1 alternator yet no one mentioned the plug was different?

Can the factory alternator operate with the proper sub 12 Volts applied to pin 2 or 3? The way my field fix harness was assembled, it was supplying 12V to pin #2, where the stock connector was applying voltage to pin #3.

Thanks!

 

[neat]

No one?

 

[David65]

Well, here's some info on our alternators: http://www.alternatorparts.com/cs130_sbpage1.htm
The CS-130 is similar to our CS-144's. If you charged the battery and started the car, then didn't get ~12-13V at the stud on the back of the alternator, I would think there's an open in the charging lead somewhere. Or did I read this wrong? I would take an ohmmeter, set to the lowest resistance scale, and measure the resistance in the charging lead. Disconnect the wire from the stud at the rear of the alternator first. Other end of meter to battery positive terminal. Resistance should be very low. Maybe a few tenths of an ohm. Try wiggling the charge wire around near the battery terminal and see if resistance changes. Maybe acid has been sucked up into it, might cause problems. If you want to test the dash light, ground the brown wire in the "L" (lamp) cavity on the 4 pin plug with the ignition key on. (might want to unplug from alternator) Don't need to start the motor. Light comes on, circuit is ok.

Additionally, you don't want to put 12V directly to the brown wire in the 4 pin plug (L) terminal. That's the lamp lead. What that does is get pulled to ground to light the dash light if there's a fault in the unit. Other side of light goes to 12V through ignition switch. The dash lamp provides some resistance so the regulator won't get damaged. 12V directly to L terminal could damage regulator.
I'm thinking what that fix thing does is provide an alternate path for the regulators lamp circuit in case there's a problem with the dash light in the instrument cluster. Those seem to be notorious for problems. Do a couple of tests and report back.

David

edit: Thought of something else. What did you mean, "the alternator was pulling 12V the entire time"? There should be 12V at the stud all the time. Did you take the wire off the stud and test for current draw going into the stud or something?

 

[neat]

The CS-130 is similar to our CS-144's. If you charged the battery and started the car, then didn't get ~12-13V at the stud on the back of the alternator, I would think there's an open in the charging lead somewhere.

That is exactly what is happening. When you say, "an open in the charging lead somewhere" what circuit are you referring to? Do mean the large cable that goes from the post on the alternator to the battery, or the plug on connector that clips to the back of the alternator?

Or did I read this wrong? I would take an ohmmeter, set to the lowest resistance scale, and measure the resistance in the charging lead. Disconnect the wire from the stud at the rear of the alternator first. Other end of meter to battery positive terminal. Resistance should be very low. Maybe a few tenths of an ohm.

The big wire ohms out at close to zero ohms. Depending on how I hold the ohm meter, the wire has .01-.04 ohms of resistance.

Additionally, you don't want to put 12V directly to the brown wire in the 4 pin plug (L) terminal. That's the lamp lead. What that does is get pulled to ground to light the dash light if there's a fault in the unit. Other side of light goes to 12V through ignition switch. The dash lamp provides some resistance so the regulator won't get damaged. 12V directly to L terminal could damage regulator.

I think that's my problem. The field fix harness was supplying whatever the battery voltage was to the L terminal. Sometimes, that was as much as 14 volts. I though the field fix harness from Caspers was supposed to mimic the voltage drop accross the bulb, but I guess mine was defective or something. Either way, I have now taken an ignition switched 12 V source and wired it to the L pin of the alternator. I installed a 194 bulb in that wire, and the light operates as the battery light in the dash should. It light's with the key on, and goes out as soon as the car starts. Hopefully, this will solve my problem.

I'm thinking what that fix thing does is provide an alternate path for the regulators lamp circuit in case there's a problem with the dash light in the instrument cluster. Those seem to be notorious for problems. Do a couple of tests and report back.

The field fix harness gets power from the waste gate solenoid and supplies the L terminal with voltage. That way, if the bulb goes out, your charging system will still work. I know that the bulb in the dash is supposed to have a resistor attached to it so that the alternator will work if the bulb dies, but the contacts for the bulb are worn through on the soft circuit board on my regal. The harness I bought from caspers was supplying 12 V to the P terminal and nothing to the L terminal. I assume that if something were to go wrong, the harness would somehow supply the ground to the L terminal to light the idiot light.

edit: Thought of something else. What did you mean, "the alternator was pulling 12V the entire time"? There should be 12V at the stud all the time. Did you take the wire off the stud and test for current draw going into the stud or something?

I turned the car off, unhooked the large cable from the alternator, unhooked the positive cable from the battery, and connected the positive cable to the to the battery with my test light. The light was out, no draw. I attached the cable to the alternator and it lit the light brightly. The next alternator did not light the light, regardless of wiring configuration, until the key was in the 'run' position.

 

[SloGN]

first do you have a constant 12V going to the main lug on the back of the alt?


the way the factory idoit lite works is the switch applies 12v to one side of the 194 bulb in the dash. With the key on engine off on the other side of the 194 bulb the regulator is grounded and the bulb lites up. once the engine is running and the alt is charging it then applies 12-14V to the neg side of the bulb. 12V and 12V on the bulb it's not gonna lite up.


i'm not sure how the later model CS144 regulators work.

 

[neat]

first do you have a constant 12V going to the main lug on the back of the alt?

Yes. The large battery cable is attached there. What ever voltage the battery has in it, the alternator is seeing there.

the way the factory idoit lite works is the switch applies 12v to one side of the 194 bulb in the dash. With the key on engine off on the other side of the 194 bulb the regulator is grounded and the bulb lites up. once the engine is running and the alt is charging it then applies 12-14V to the neg side of the bulb. 12V and 12V on the bulb it's not gonna lite up.

That makes sense, but I thought the L terminal on the alternator had to see voltage in order for the alternator to charge? The system you described above would charge as long as the alternator was turning and connected to a battery. I can assure you that's not the case with the turbo buick, lol. If the L terminal does not see power the alternator will not charge. On the original TR alternator, 12 V to the F terminal will make the alternator charge as well. On the LT1 alternator that I have, the only terminal that will make the alternator charge is the L terminal. I have tried supplying 12V to all the terminals, and the only one that makes the alternator emit 14 Volts is the L terminal.

Thought's?

 

[neat]

The problem is solved. I wired a 194 bulb inline from a 12V source to the L terminal. Eventually I will test the resistance of the 194 bulb and replace it with the appropriate resistor. I was damaging the voltage regulator in the alternators with the harness from Casper's.

The Casper's harness is designed for an alternator that uses the L and I terminals. The 140 amp LT1 alternator uses L and F terminals.

The Buick alternator will charge when you apply the appropriate voltage to the L terminal, or 12V to the I terminal. The I terminal has an internal resistor to cut the voltage to the correct level to avoid damaging the regualtor. The L terminal gets that resistance from the bulb.

The LT1 alternator uses a terminal labeled as F in place of the Buicks I terminal. The F terminal is for diagnostic purposes and it will not energize the regulator. The harness from Casper's was supplying 12V to the F terminal because the haress was designed to be used on an alternator with the I terminal. When I switched the pins on the harness, that would of solved the problem, except the voltage was not regulated and I damaged the voltage regulator.

It sounds complicated, and was a nightmare to figure out, but in the end it was actually pretty simple.

Those diagrams really did the trick, thanks!

 

[ijames]

That's good info on the L, I, and F pins. I never knew you could put 12V on I instead of a bulb on L on our alternators. Thanks.

 

[neat]

That's good info on the L, I, and F pins. I never knew you could put 12V on I instead of a bulb on L on our alternators. Thanks.

That's how the field fix harness works. That's also exactly why the field fix harness will not work with the LT1 alternator.