CS alternator question.

[BP68]

Should this be in the electrical section?

I have a 89 suburban motor in my truck and I am running the serpetine belt with accys on it. I used a EZ wire wire harness and got a new plug for my CS style alternator that was on the donor suburban.

From everything I found the way to wire my alternator (and the way a gm schematic shows to wire this aternator) is a key on hot wire running to a 194 bulb then to the L terminal at the alt plug. My battery wire runs from alt stud down to starter stud, where battery hot is connected.

When I turn key on, bulb lights, when eng starts light goes out. When checking voltage at alt stud with meter, I was showing 13.0 volts (which is too low) after a quick trip around the block, I was showing (12.5).

Unplug alt and voltage goes to about 11.99 (battery is weak and has not be charged up)

To me this sounds like a faulty regulator in the alt that is only partially charging. With alt plugged in and eng running I get around 12.5 volts at alt stud. With alt unplugged and eng running I get around 11.99.

Sound right to you guys? Any other advice?

Thanks

[gkesseru]

I had exactly these same problems with the same alternator. I replaced the battery with a good one and it all cleared up. take your battery down to AutoZone or Advance Auto and have it tested for free. They can also test the alternator. Also, make sure that the wire and connections going from Alternator to Starter are clean, well connected, and large enough. These connections should be soldered for best performance. Likewise check the negative connection path from the battery to the engine block. If you still have low voltage problems, you can run that alternator with a remote sense wire connected directly from the S terminal on the Alternator to the battery positive terminal. This will use the voltage directly at the battery to control the built in voltage regulator.

[BP68]

Originally Posted by gkesseru

I had exactly these same problems with the same alternator. I replaced the battery with a good one and it all cleared up. take your battery down to AutoZone or Advance Auto and have it tested for free. They can also test the alternator. Also, make sure that the wire and connections going from Alternator to Starter are clean, well connected, and large enough. These connections should be soldered for best performance. Likewise check the negative connection path from the battery to the engine block. If you still have low voltage problems, you can run that alternator with a remote sense wire connected directly from the S terminal on the Alternator to the battery positive terminal. This will use the voltage directly at the battery to control the built in voltage regulator.

Thanks for the info. The battery was new a few months back, but the truck has mainly been started and shut off. I just got back from paint, and have only driven out on the road a few times.

I have a buddy running a CS style alternator off a 90's Camaro and his uses the wire from the S terminal to the bat positive stud. I thought that alt and the truck one like I have had different regulators. But you say the S terminal can be used on a truck alt that originally had only the L terminal hooked up?

thanks

[Fitz]

I don't believe your problem is battery. I use the same alternator and the lamp should STAY on. This model requires continuous excitation to generate any output. Go to radio shack and buy two 1/4 watt 100 ohm resistors and solder them together in parallel to make the 50 ohm one shown in the diagram below. Wire the plug for the alternator connection as shown and try the alternator again. Before everyone points out that your alternator did not come as a part of GM's serpentine belt drive accessory package, the alternator in that package is the same CS alt you have!

[screamin_c10]

Keep in mind that there are a couple different style "CS" alternators... Here is a couple of diagrams I found helpful when doing the CS swap on the Chevelle.

I chose to use the "L" terminal method for simplicity and it charges fine...

[VetteVet]

Painless wiring recommends an 85 ohm 3 watt resistor in the L wire and most conversions say 10 ohms is not enough.
here is a conversion for those without the light.
http://temp.corvetteforum.net/c3/zma...ternator01.htm

[BP68]

Ok, just read the responses. I checked my truck more last night. I found that when boosted off and running the alt stud shows about 13.0 volts. The "l" terminal wire is show about 1.2 volts when connected with eng running and lamp out. If I uplug the connector with "l"terminal, meter shows 11.98 at alt stud.
I brought my battery to work today and put it on the fancy new GM battery tester/charger that just came out. I showed deeply discharged battery, after charging it only had 517cca out of the rated 710cca.

Another note. I did not do all the wiring and when I started checking I found the neg battery cable running down and bolted to the frame. The frame has a pretty thick coating on it and was not cleaned off to metal where cable bolted up. I have fixed that, but have not had time to recheck with a good battery. I know you need a good ground for things to function properly, could that cause my symptoms?

Next step is good battery, recheck body and eng grounds and go from there.

[BP68]

Success! Got a new battery and did some more checking. With new battery, alt was putting out 13.0 volts at idle running a electric fuel pump and two cooling fans.
I used a jumper cable to connect my alt case to a good ground and the frame, and volia, 14.4 volts!
Just a reminder that good grounds are very important. The engine to frame cable is not on a clean metal surface. I need to clean off some of the frame coating.

I will be getting out in the garge and checking/repairing all my ground connections very soon. I also went all out and got a red top Optima battery. Costco carries one with a decent price and 3 yr free replacement.
I have never had a Optima, but since my truck will sit more than my daily drivers, I figured I would give them a try.
A Buddy of mine has a 69 Camaro that sat all last winter, and he figured he may have to boost it the first time. The fans and fuel pump came right on (fuel injected 383) and she fired right up.
Anyway, hope this saves someone else a headache down the road.

And thanks again for the info/input/advice of all who took time to answer my post.