CS130, 100 AMP, 3 wire alternator...

I put a rebuilt alternator in last week, charged fine, go out this morning and its not charging, so i get a warantee alternator from the rebuilder and in the mean time charge and load test the battery, all is good.

So i put the new alternator in and it charges fine, drive it from the parking lot into the garage, shut it off, put new connectors on the wiring for the field and such, start it up and its charging at 16.8 volts, so i shut it off, start it again and its not charging again.

It seems like the regulators are blowing, i think it went to full field then overheated itself and now won't charge.

The other thing is that the alternator "field" wire has no resistance in it, I've been told to wire it with some resistance, either a bulb or resistor, when i run a resistor in line it fried the resistor...but i ran the original gm alternator for 2 years with no issues. It is run straight to a switched 12v source...

The other other thing is i tore the rubber boot that goes on the backside of alternator over the battery post, and the post is about 3/8" from my valve cover, so could i have arcing across that gap ?? Would that fry the regulator, We had it running for 2-3 mins and checking the charge when it was near 17 volts and there was no snapping that would have signified arcing.

I'm going to get one more tomorrow, throw a new insulator boot on and see what happens, we have a parts guy that used to work for the parts store that i got the rebuilt from and he said he's had problems with them.

Any ideas??

Here's a good site for info.
http://www.chevelles.com/techref/ftecref14.html

The CS plug should show 4 wires, postion 1 - 4 are as follows. S wire, F wire, L wire and P wire. S is larger than the others and is on the end of the connector that is also larger.

The wiring you will use is the L wire and the S wire. The S wire is the voltage sensing wire. Ignore the F & P wires and tape them off unless your truck specificaly uses them. The L wire is the lamp wire. The resistor goes in the "L" wire.

You cannot connect 12v directly to the L wire or it will kill the regulator instantly. It sounds like this is what happened or mabye you used a diode instead of a resistor. Do not connect a Volt gage to the L wire. If you use a lamp instead of a resistor it must be a miniature buld not an LED type light.The bulb should be no larger than a #194, #57, or #1895. Its either a resistor OR a bulb. So if you have an idiot light on your dash you don't use a resistor.

The L wire is from switched ON/OFF power to the resistor then to the L terminal on the ALT. The resistance needs to be a minimum of 35 ohms. Get a 3 watt 75 ohm metal oxide resistor for this wire.

If you are also using an MSD 6AL ignition box you will need a Diode as well installed with the stripe toward the ALT. if have a MSD 6AL and you don't use the diode it will feed the ignintion when you shut off the key and the engine will run for the alt feed. this is only if you use an MSD 6AL.

If you are converting from an SI type alt to a CS you can get a converter that has the proper wiring and ressitor in it already. just plug it up and your done. below are to converters one for an idiot light and one without light.

Delco P/N 8077 you must have an Idiot light this P/N does NOT include a resistor

Delco P/N 8078 General Motors P/N 12102921 this one has the resistor so it's NOT to be used with a idiot light.

I don't think the boot is causing a problem but by all means get a new one. The voltage you should read at the back of the alt and at the sensing wire junction is 14 - 14.5 volts. 16 -17 is far to high and indicates the regulator is either bad or going bad or miss wired.

You can also use the above converter on a CS to CS by clipping off the SI connector and wiring in the CS end.

Hope this all made sense.

Yep it all made sense, and thanks for laying it out...i do know resistor codes and i ran a 75 ohm resistor during my last attempt so that i could try to keep it from overheating, but it got hot enough to melt the solder, so i ditched it. Maybe there was enough resistance in the old 1964 wire that was previously exciting the field, like i said, it ran for 2 years straight to 12 v. I will pick up the harness, if gm has it, and go back for one more alternator. Once i have that harness the wiring is perfect, brand new wire and connectors throughout the charging circuit. Then it can be blamed on a faulty alternator everytime.

I got my resistors from a local radio shack type place...i'll have to go to a proper electronics supplier to get a resistor that will handle the power i guess.

Thanks again.

Jason

I got my resistors from a local radio shack type place...i'll have to go to a proper electronics supplier to get a resistor that will handle the power i guess.

Thanks again.

Jason

if you get the harness with the resistor in it you won't need one from radio shack or some other supplier.

The harness is available through a Delco dealer only, and its $30 bucks,and can't be had until Wednesday... I found a few small indicator lights i had laying around, and just wired them in series with my exciter wire, got 36.5 ohms resistance, it will work but when i go to pick up my 3rd alternator i'll grab a larger bulb with wiring, it's just easier this way, run the bulb, even though i have a voltmeter so the bulb won't serve as an indicator.

The only problem with that idea is that if you blow one of those bulbs then you won't have sensing voltage to the alt and it won't charge.

Its only a temporary fix, it has worked for the last 3 days, gonna pikc up the resistor harness tomorrow and wire it in, i agree the bubls were kinda hacked, and i coudln't find a bulb/socket combo at the parts store that would give me more than 10 ohms resistance...so i would've had to step down a wire size, which is not optimal...Napa can get Delco parts so i saved 10 bucks on the harness vs a Delco dealer cause i get a discount thru work at Napa...now to figger out the 02 reading lean...