Well,

Some of you may have seen my posts regarding my LT1 IROC frying countless alternators since its inception. The last straw was when I destroyed a $400 Powermaster. I talked to many of you on this board about the problem. Some suggested a resistor and others suggested using a different lead. Well, after talking to Dana at lt1350.com, he told me exactly what resistor to use. I wired a 33 ohm 5 watt resistor inline on the wire running into the L lead of the regulator plug. The car started up right away, with the voltmeter steady at 13. It has barely fluctuated from that position. I got to drive it all day yesterday, for the first time in 7 months! WOOHHOOOO.... Thanks DANA!

 

Why was it frying alternators? I am doing the swap w/ a LT1, and that seems as something I might want to do. I'm going to run the stock C-144 alt.

 

Well, the alternator was receiving a constant 12 volts, which was keeping the regulator on at all times, thus burning out the regulator prematurely. However, I'm no expert, but this is what I was told. So, to combat the problem, I had to reduce that voltage by adding a resistor inline.

 

Was it a 1 wire alt, or the stock 3 or 4 wire? I can't recall what the splicing thing was w/ the alt, but I'm pretty sure you just leave the stock connection off the LT1 harness, and splice just the regular stuff up as normal...ie, gauges, main/fused power, etc.

 

I remember something about a 480 Ohm, 1 Watt resistor inline w/ the red wire on the 4 pin connector

 

Well, you are partially right. When my LT1 was swapped in, we did just what you mentioned. We cut the bulkhead connector off of the TPI harness, and mated up the LT1 harness to the appropriate pins on the TPI bulkhead connector. The problem is that, all of the wiring in the engine bay is from one year car, but the wiring on the inside of the car is from another year. Differences in wire thickness, things inline such as gauges / lights, length of wire, etc all play into the final voltage when it comes into wiring (or so Im told). Take the wiring diagram for a 1995 Camaro, which is where my LT1 came from: http://shbox.com/1/starter_charging_95.jpg If you look on the right, in the dashed box entitled (Instrument Cluster), you see a 470 OHM resistor. From there, the circuit runs straight through the firewall into the `L` lead of the plug that goes into the alternator.

Since none of the wiring was touched on the inside of the car, the resistor was overlooked. So, on my quest to figure out how not to destroy any more alternators, I started doing my research. I found countless posts on thirdgen.org of people having the exact same problem as me. I talked to Howell, Painless, Powermaster, and LT1350, along with some of the members on this site, and 85% told me to run the resistor. Since there are so many factors that play into the final voltage, I didn't know if the 470 ohm resistor would work or not. Dana from LT1350 told me what resistor he uses on his harnesses, and that I should have no problems.

Now, I was also told that there is another way to get around the "run your own resistor" fix. Apparently, there is a `built-in` resistor in the alternator on the F lead. See, my plug was of the SFLP type, with only one red wire running into the L lead. So, I went and bought a new plug that had three wired leads (SFL). I was initially gonna run straight to the F lead, because I had talked to two different guys on thirdgen.org and the guys at powermaster, and they all said it would be okay. Although, the guy at powermaster did tell me to run an external resistor, even though the built-in one could work. That worried me a little, so I went with the other option. I'm still learning this stuff, so I have to rely on what I'm told. I tried to get several different opinions, so I'd at least make a somewhat informed decision. All I know is that it runs pretty well, so it must be working.

 

Did you try the 470 before you did the 33?

 

I did not, and the reason being is... Dana from lt1350.com said that slapping a 470 inline would not provide the right resistence for the final voltage. He explained that the final voltage has to be calculated pretty pricely in order to produce the correct results. Plus, I was in contact with another gentleman who tried the 470 ohm resistor, a charging bulb, etc, and nothing worked. 33 OHM 3 watt (although I used 5 watt cuz that's all I could find) will do the trick.

 

Gotcha! Good job! Something to definately look into once I get to that stage of the swap

 

Good job on finding a solution.

I never ran a resistor and my original '94 alternator is still going strong after about 5,200 miles.

 

Trans Am #5...Now that you said that, it's gonna blow up! lol

 

Yup... I had a '93 alternator on there, that lasted for about the same amount of time, then POOF If you start frying them, you know what to do.

 

The thing is, you shouldn't HAVE to fry 'em to know what's up. No downside in running the resistor. I'm just going to do it as like it has to been done. That way, shouldn't be an issue.

 

Well, you know what's weird is... The guy who did my engine transplanted a '93 Vette LT1 into his 88 GTA, and he never had to run the resistor. Literally, he had the stock '93 alternator on the car for 3 years, which during that time, he was making 11.2x passes in the quarter. Recently, he did another LT1 swap on a 1985 or 1986 TA (cant remember), which he didn't run the resistor, and that car has not shown any alternator issues. It remains at a constant 13 on the voltmeter. Maybe its a Camaro only issue.

 

That IS pretty weird. Well, like I said, I don't see any reason why running the resistor would be an issue anyway. I'll put it just as a fail safe

 

You're probably right

 

If it's an alternator with the 4 terminal connector all you had to do was run the F/I terminal to the run terminal on the ignition switch which is usually a brown wire. Resistor not needed. The L lead is for an idiot light. The S and P connector- one is used in cars where the computer turns the alternator on and off, the other is a remote sense used when the voltage has to be stable at a specific point in the wiring harness, I don't remember which is which. but wherever the remote sense terminal is connected, the voltage will be constant at that point, the regulator will increase or decrease the output of the alternator to make up for resistance and loads on the wiring harness to insure the voltage is stable wherever the remote sense lead is connected.