SI to CS Conversion

[19brownie92]

Long time lurker first time poster.
I have spent days looking and reading posts here and other places on alternator conversions. Here is the short version. I need help.
1972 c-10 350 sb.
A couple of years ago I did the conversion to an 85 or so amp SI alternator.
I used a commercially available "kit" basically a jumper for the old voltage regulator and a new alt. plug. everything has been fine since then. I have since done an engine upgrade and added a EFI and dual electric fans. The current Alt. could not keep up. I got a CS144 250 amp Alt. to replace it. It is only putting out 13 volts. I was thinking it should be around 14.2ish
I have run all new 6ga wire directly to the batt. and have a direct ground to the case.
I have used the diagrams that I have found on the forums to make sure the wiring is correct, but something still seems amiss.


I have placed the jumpers on the old regulator plug
BlK to WHT
Red to Blue


The Blue wire then connects to the L terminal on the alt via the resistor
The White wire connects to the S terminal on the alt.


Im sure Im missing something simple. My truck does not have an"indicator lamp" it have a voltage gauge. So I was thinking that I DO need the resistor> please correct me if I am wrong.
Thanks
I tried adding pictures, but I haven't figured that out yet either

[VetteVet]

Unless you made a typo your L and S wires are reversed. The red wire to the old voltage regulator is the sensing wire for the internal regulator and The BLK wire, usually brown, is the exciter wire which goes to the L terminal.

You need the resistor in the L wire terminal and it needs to be at least a 35 ohm resistor and 1 watt in power. Painless Wiring recommends an 85 ohm 5 watt resistor for their conversion. Plenty of guys have used up to 300 ohm 1 watt resistors with success.

I run my conversions like this.




It amounts to the same way you've done it with the jumpers, but I just extend the Brown wire ( in your case BLK) all the way to the L terminal with the resistor soldered inline.
The red, constant hot, wire goes to the S terminal.

If you are lucky you haven't blown one of the phase diodes in the alternator.

BTW welcome to the forums.

[19brownie92]

Thanks, I was thinking they were reversed too, I swapped them in the connector and it still didn't charge. But this was after I had it wired wrong, so a blown diode would be just my luck. Ill pull the alt off and have it tested.
Is the diode something that I can replace, or would I just replace the internal regulator?
Thanks again!!

[VetteVet]

Originally Posted by 19brownie92

Thanks, I was thinking they were reversed too, I swapped them in the connector and it still didn't charge. But this was after I had it wired wrong, so a blown diode would be just my luck. Ill pull the alt off and have it tested.
Is the diode something that I can replace, or would I just replace the internal regulator?
Thanks again!!

You can do either one but until you get it tested you won't know which it is. Your IR can be bad or one of the phase diodes could be shot. I think you would notice more than a 1 volt drop if that was the problem. You have to pull the alternator apart for either one but it is not a difficult job. There are U-Tube videos that are pretty informative. I'll see if I can find one.

This is an AD but I think they are very similar.

https://www.youtube.com/watch?v=dUPRwrbzwAM

[19brownie92]

Thanks for the video link.
I had the Alt. tested today and it is fine. putting out 14.6V
I think I have bigger issues when it come to wiring. I have some parasitic draw, 11.6 volts worth. I know part of it is my EFI control unit, but even when I disconnect it there is still draw.
I went looking under the dash and the large red wire to the ignition has melted insulation on it. Im lucky the whole thing isn't a smoking hole in the garage. Now I am suspicious of what is melted together inside of the harness, causing draw and affecting the Alt.
I have ordered a complete wiring harness and will doing the install this week. I am planning on running dedicated #2 wire from the Alt. directly to the batt. hopefully this with a strong ground and new harness will put me back on the road.
Thanks for your help!! it is much appreciated.