platinummaker

The patient is a 72 small block coupe. Started hearing alternator bearing noise growling at me louder and louder and decided to change from stock to a CS 144-140 amp alternator. Changed over pulley, added EC82 connector from Napa Auto parts to adapt old alt 2 plug output to new alt, and we're plug and play. Connected battery back up and started car and noticed voltmeter reading slightly over 12. Took trusty meter out and confirmed no voltage other than battery voltage coming from alternator output regardless of rpm. Rechecked connections and figured I got a bad alternator. Went to parts store and got another one....and same result. The alternator is originally for a 95 C4. I know that I couldn't have gotten 2 bad alternators in a row and am pulling my hair out trying to figure out what's wrong. The old alternator was actually charging fine before replacement. The resulting extra scotch intake is not providing any insight. Can anyone please provide some coaching points before I totally run out of scotch.
many thanks
Dave

gkull

With the key off do you have 12 volts to the red power wire terminal on the side of the alternator

SI67

It's St. Patrick's Day. You should be drinking Irish whiskey.

Probably the insight you were looking for..

carriljc

Check the connections on the EC-82 harness. Last time I thought my alternator had gone bad it was the terminal connections between the old 12 Si harness and the new harness.

Take it apart (take a picture of it so you put it back together properly) and ensure that all the ends are making good contact. Ensure you have good continuity from one end to the other.

Here is a link to ensure that the EC-82 harness is the appropriate one for your vehicle: https://www.corvetteforum.com/forums...post1561071452

You can also have the new alternators tested before you leave the store....

Mooser

A very outside change but worth a look.
Did your EC-82 actually have the resistor on it?
I bought two of them (one from NAPA and the other from CC) and neither had the required resistor. Rumor was there was a bunch on mis-boxed one floating around...
Anyway, remove the conduit around the wire and make sure there is actually a resistor heat-shrunk to the wire, don't go by the part number on the box
M

SH-60B

Add a ground wire from the case to the engine block. Sometimes paint/ dirt/ corrosion insulated the mount.

Kacyc3

Probably not the insight he was looking for, but the one he needed..

mbb9674

Might also want to check the pins the wires on the adapter are going to on the alternator I think it needs the “I” and “L” terminals for the voltage regulator to kick on. I bought a PICO adapter and had to swap over a pin. I found this from an old post when I was looking at upgrading:

carriljc

You're going to love it once you get it working. Great upgrade.

platinummaker

Thanks to all for the resolution of my attempted CS144 alt upgrade. Mooser per your suggestion, checked resistance of the EC 82 and came out with 50 ohms, so figured we were right where we were supposed to be on that. Took alt back to Oreilly's and it checked out healthy. That left wiring. Per MBB9674's illustration and explanation, clarity on who does what. Closer inspection of the connector from the harness that went to the old alternator revealed a broken wire just inside the connector that was held intact only by the insulation. Replacement of old connector with insulated spade terminals and we are off to the races with over 14.5 volts at idle and plenty of amps to play with. Carriljc I love it already! Now I will be upgrading relating wiring to heavier gauge as per previous recommendations from this forum. Thanks again!

Mooser

Glad it works out for you. The ability of the CS144 to produce at lower rpm (when I actually need the electric fans) is it's biggest bonus. I'm still waiting for GM to make a smaller version but it's not looking good so far
M

Big2Bird

I would not drive that car until the output wire is enlarged.

caskiguy

Thanks for info guys !