CUCV alternator symptoms, diagnosis and fix.

i learned today that the only differnce between civvy and cucv alternators are the rectifers. the cucv ones have larger mounting holes than the civvy ones to allow for the insulators to keep the alternators isolated. in a pinch you could enlarge the holes on a civvy one i believe. another good parts source if you are in the oklahoma city area is Oilfield Ignition, located at nw 2nd and classen. they are very helpful and knowledgable about the 27 si, cucv alternator.

the only differnce between civvy and cucv alternators are the rectifers

Click to expand...

This is incorrect.

Yes, a case grounded alternator can be made into an isolated alternator(not easy to find the parts).

i am sorry my info may not be correct, when i purchased parts for mine today, rectifier, brush rack, regulator, bearings, diode trio. the only part number that was different was the rectifier. upon examining the two rectifiers side by side that only difference was the mounting hole, to allow for the insulator. the parts source i gave carries the correct parts, i will post the part number for the rectifier tomorow.

Your forgetting the ground stud and isolators(not in a case grounded alt).

I use the same rectifier , as for a regular alt.(the isolation tube/sleeve fit.

Maybe 1stSarge can clarify or comment on this. He sells kits.

thanks doghead, i did not know about the ground stud. and thanks for all your informative posts, i have successfully done your starter relay mod a few months back.

All Parts for Alternators, as well as Stater relays and all parts for the glow plug system are easly had at CUCV Electric.com. They are members here and there is no shipping charges and the prices are great. I have used them several times and they are great to work with!!!

When we are saying “mounting hole” I am assuming that we are talking about the square cavity where the ground stud passes though the rectifier.

With that in mind, I put a micrometer on all of the ones I have - old and new, and there was a size difference.

Of the 6 old ones (stock) that I have here, the width of the cavity measured out at .243 inches to .236 inches. So the argument that some are bigger might be true, but I don’t think this is an actually measuring spec, I think it is simply a manufacturing tolerance as the difference is only 7 thousandths of an inch based on my samples here.

All other hole dimensions are identical +/- .002 in (old and new).

The heat sinks on the rectifiers are mass produced by an extrusion process, and then cut apart. The main difference between models are the diodes. I really have a hard time picturing an assembly line setting up two different extrusion systems. That would be an extraordinary amount of re-tooling to gain .007 inches.

Other than that cavity, I cannot see any other dimensional difference between the 6 old ones and the new ones we sell.

On the part numbers, there are at least a half dozen different rectifiers that will fit the 27si. The one we chose to sell is the heaviest duty one. So there could easily be different part numbers from one alternator to the next. Of the 6 that I have taken out of CUCV (stock) alternators there were three different part numbers.

Subscribing to print this out at home!

ok i got a question the #1 alt on drivers side. isnt working according to the tests in this thread but i have another wire im not sure about.

my alt has the ground wire the red hot wire the 2 wires in the plug (one red and one brown) and then another little brown wire that has a push on style connector on it.. what is that wire for and is it one of those brown wires that you all were talking about in the testing phase if so when is it supposed to have voltage and how much?

brianc613 said:

ok i got a question the #1 alt on drivers side. isnt working according to the tests in this thread but i have another wire im not sure about.

my alt has the ground wire the red hot wire the 2 wires in the plug (one red and one brown) and then another little brown wire that has a push on style connector on it.. what is that wire for and is it one of those brown wires that you all were talking about in the testing phase if so when is it supposed to have voltage and how much?

Click to expand...

I think you are describing the output for the tach buffer connection that goes to the diagnostic port.

cpf240 said:

I think you are describing the output for the tach buffer connection that goes to the diagnostic port.

Click to expand...

ok i just wanted to make sure it wasnt supposed to get volts to it while it was key on engine off for testing. thanks

Gotta ask the questions!!!! I have a no gen 2 light issue. heres the story. Cleaned the dash and the light stopped working... I know by looking at the Volt meter #2 is not working. It does not light up before start. I have a new relay in under the dash, was done with the dog head upgrade. checked for 12 volts at alternator and have power to big red wire and to the plug, but no exciter wire voltage with key on!! Where do I start looking. One member said to change some 10 fuse at the fuse block. All fuses are in working order. Is there a fuse link popped. I have tried looking through the TM's but have not found anything positive there. Please any answers or questions are welcomed. Thank you!!!!

Oh and the light bulb in the dash is good also...sorry

mudman said:

Gotta ask the questions!!!! I have a no gen 2 light issue.... It does not light up before start.

Click to expand...

TM 9-2320-289-20 2-59
5.1. GENERATOR LIGHT DOES NOT COME ON WITH KEY IN “ON” POSITION BEFORE ENGINE IS STARTED
Step 1. Trace all circits from generator to generator light in instrument panel (including
fuse, bulb, arm relay}. (See wiring diagram F-11)
If circuits are good, replace alternator.

I'm finding there is a problem with the light in the dash after all. After checking it with a test light, the test light comes on but not the bulb. Checke the conitnuity in the bulb and it is good.I believe the socket is bad and not making a contact on the other side of the cirsut board. so I'm in the middle of pulling the dash out and getting a good look at WTF.!! The board looks to be good. Must be the socket I will tryanother socket in that hole and see!!

Well, I have been having the classic signs and symptoms of Gen1 going south. Read lots of the threads on diagnostics and fixes, ordered a rebuild kit from CUCV electric, got the TMs printed out and was rocking and rolling this afternoon.

Got to the point of pressing out the bearing in the frame and heard a sickening "POP" from the frame. Cracked. Toast. Hosed. UGH.

Off to ebay to hunt for alternator frames. Bummer.

Other than that, thanks to all the Steel Soldiers wrench turners that made this whole operation pretty darned simple.

Driving on...

The mystery fof the Gen 2 light!!

Well I must say I learned a lot today. I now know that, in order for the gen 2 light to work, you must first have the exciter wire and the power wire (two wire plug) plugged into the Alternator before checking anything else. I could not get the power togo through the light. I had power to one side but it would not go thoughh and light up the light (%^$%*&^&). So being the person I am I took the whole dash apart and into the kitchen I went. I put all new lights in 194 for gen 2 and 168 for the rest. The gen 2 light socket was a little funky, so got a new one from Napa.
So this morning I got out to mount the dash back in. Ah but first I plug it in to see if gen 2 light working.....^&^%##@%&&, it is not!!! So I back track from yesterday and find that I did not plug the wires back in to alt 2 so, I plug them in and back to the dash I go, low and be hold the &^&^$%$@#$&%%*& gen 2 light is working. Power to the exciter wire and all is good in the hood.

Moral of the story is....If you are having a gen 2 light problem and suspect the light bulb it self, retace what you have done, before you totally disasemble the whole ^*(*(&^ thing and find out you have done soemthing stupid. I'am now an expert on gen 2 light, dash boards, printed circuts, 2 wire plugs, trouble shooting light bulbs, and cussing

Thank you for reading my rant!!!! Long live the the GEN 2 LIGHT!!!

This may be the best help I've found. I think I need alternator rebuilds and now I know where to go. Awesome!

This site is great been alot of help, my gen 2 went bad took it to the local alternator repair shop he claim it's a positive ground took it home put in truck still not charging. Was he right or should I take it back to him and have put a negative ground on it?

rolcam said:

This site is great been alot of help, my gen 2 went bad took it to the local alternator repair shop he claim it's a positive ground took it home put in truck still not charging. Was he right or should I take it back to him and have put a negative ground on it?

Click to expand...

Both GEN1 and GEN2 are, in stock form, isolated ground alts. Only GEN2 MUST be an isolated ground alt. Perhaps he meant that it was "positive ground" in that GEN2 takes its ground reference from the output of GEN1? Was GEN2 tested? Was it rebuilt? Rebuild kits can be bought from places like CUCV Electric.