cucv alternator rebuilding

There are a number of reasons an alternator will stop charging. I was wondering if others that rebuilt their alternator and knew which part failed and the symptoms it displayed before it totally failed. I have had the dash light give off a dull glow that seemed to gain in brightness until it failed and I have had the dash light flicker at higher RPM's that when I applied a draw like headlights or the blower fan would stop flickering. I usually run with the lights on all the time for this reason. I'm thinking this alt may be on it's last legs.
I have seen rebuild kits for sale but I would like to replace only the faulty part. I took one of my bad alternators apart and everything checked out fine. The only thing I couldn't check was the regulator. Is there such a thing as a common failure? or at least one problem part that fails a higher % of the time? maybe the regulator?
Lastly I dug out another bad alternator opened it up and it was built with a different configuration and part from the rectifier to the regulator. Not all CUCV alternators are the same.

Thanks

OH boy dude .. you are going to get soooo hollered at due to the fact that you are asking that question .. you are going to get check the TM'S.. check TM's before any body really answers you question.. and you are going to get check other threads and research first. but any way if it were me rebuilding the alts I would just replace all the parts in there since you have it apart anyways. why put in old stuff with new . like if you are putting on a water pump wouldn't you put upper and lower hose's on ..unless some emergency and you cant .. but any way just my thoughts.. have fun..

What you have described does sound like a bad regulator.

2deuce, I'm as big a cheapskate as the next guy , but I think the rebuild kit sets you back like 40 bucks shipping included, isn't that worth peace of mind for such a critical component on your vehicle?

P.S.Not saying or implying that you are a cheapskate in any way or fashion.

Tough to say, low output could be worn brushes. Jumping voltage could be regulator. IMO, get the rebuild kit and tear them down. Be sure to get a quality kit for an isolated ground alternator.

Cheapskate, maybe I could fit that definition, but I prefer to think of myself as frugal. Why buy parts that you don't need? Then throw away good functional parts because they are not new. I've got probably 6-10 of these alternators that aren't working, $40x6 $240. $400 is as Angel Eyes might say "a tidy sum"(the Good, the Bad, and the Ugly). Anyway besides the bad alternators, the good ones may not stay good too much longer with the symptoms I have. I have read posts about rebuilding and I intended on doing this long ago, but I've waited until I have too, unfortunately.
What I'm worried about and buying a complete kit would solve is having one weak part like a regulator cause something else to fail, but by buying and installing the entire kit you learn nothing.
So far I've bought 3 triple diodes and 3 rectifiers then when they arrived tore apart 2 alternators to find these parts good. So now I'll buy 3 regulators (being frugal on shipping) and put one in and test the alternator. I'll come back and post what I find. I'm going to try to provide what was wrong with each one. And the one that is still charging, but flickering the light in the dash, I'll pull when I get a good alt to replace it and test the parts in it too. Hope somebody beats me to this but in case they don't... I'll be back.

Not telling you to read the manuals but there are test procedures for each component in alternator section of the TM 9-2320-289-34 manual.

The three common failure items are the trio diode, regulator and the rectifier. Majority of the time it is the trio diode.

You can easily test the trio diode and the recitifier. Along with most of the other components. The regulator needs a special tester. Most people do not have access to that.

There are many documents published by Delco Remy over the years on how to test alternators. While they do not address the CUCV alternators they do cover not of the operations.

Another trouble spot is the two wire exciter plug at the alternator. Dirt and grip play havoc with the connection. And all the other electrical connections in the circuit.

I have tested the triple diode, rectifier, field windings and rotor. I can't test the regulator so that is going to be replaced. The plug is dirty a well as the spade connectors. What is the result of the bad connection? Is it a alternator that won't start charging easily? Usually the light on the dash will go out with a slight rev of the engine, but I have had the light stay on until 3K (about) in the past. I would like to find out about cause and effect as much as possible.

Thanks

2deuce said:

There are a number of reasons an alternator will stop charging. I was wondering if others that rebuilt their alternator and knew which part failed and the symptoms it displayed before it totally failed. I have had the dash light give off a dull glow that seemed to gain in brightness until it failed and I have had the dash light flicker at higher RPM's that when I applied a draw like headlights or the blower fan would stop flickering. I usually run with the lights on all the time for this reason. I'm thinking this alt may be on it's last legs.
I have seen rebuild kits for sale but I would like to replace only the faulty part. I took one of my bad alternators apart and everything checked out fine. The only thing I couldn't check was the regulator. Is there such a thing as a common failure? or at least one problem part that fails a higher % of the time? maybe the regulator?
Lastly I dug out another bad alternator opened it up and it was built with a different configuration and part from the rectifier to the regulator. Not all CUCV alternators are the same.

Thanks

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I have had these symptoms on my gen 1 light for a while on my M1031. The other day when it was snowing I was running the wipers at full speed and the defroster on high as well. Then there was a definite burned smell and the gen 1 light stayed on all the time. I checked for voltage on wires to alternator. The 8 gauge wire that is supposed to be hot all the time was not. I moved the 8 gauge wires(the ones with the fusible links) at the 12 volt buss on the firewall by the glow plug solenoid. My alternator wire had a little over 12 volts for a little while and then none again. I pulled on these wires again and one pulled into between the 8 gauge wire and the fusible link. The fusible link itself had not burned but had burned into where is fastened to the 8 gauge wire. This was an old spliced on fusible link that was on the M1031 when I got it. It was not a good connection and was not carrying the correct voltage all the time. I cut out the burned area and put a new fusible link on and all is good. Gen 1 works again and I am not having the flickering or coming on for a while any more. Might want to check yours out.

I like watching you tube and there is a good demonstration there rebuilding and testing a 10si delco alternator. Basically the same as our cucv 27i's. It is worth watching.

If the regulator needs to be replaced, I'd say rebuild the whole thing while you're in there. I'd hate to have to tear it all apart again because the diode trio failed or the brushes wore out and I hadn't replaced them when I replaced the regulator 2 months ago...

Do it right, do it once.

It is funny how we don't have the time to do something right, but we do have the time to do it over again...

I would strongly agree with you cpf240 except that taking the alternator off and on the truck is the most time consuming thing and I would rather save good parts and learn how to be more self-sufficient. I just had my well pump replaced last Friday because the pipes had rusted through. The pump was still running fine, but it had been in there 12 years. I didn't want to risk the pump going bad in the near future so I replaced the running pump with a new$1600 pump and replaced all 400' with new pipe. CUCV's have been around for quite awhile and if your going to drive one you better expect repairs to be needed regularly. Maybe it is just me but I like fixing what needs to be fixed. Others would look at your post and say why rebuild an alternator, why not do it right and buy a brand new alternator. I think alternators for cars nowadays run on that philosophy they can't be rebuilt. you chuck it and put in a new one. I would rather spend 2 or 3 bucks and replace the triple diode than buy a whole kit and blindly replace everything in there.

Thanks Royal, I'll check my connections at the fusible links. In the past I would have thought I needed to pull the alternator if the light came on and stayed on.

I replaced the drive end bearing on an alternator, a few months later the rotor burned out, probably from bad battery terminals. the 1009 had the group 31s from Interstate that have screw posts, I have since then swapped out the failing terminals with side post terminals that are far better than post adapters. yes, original battery terminals were shot.

It has been almost a month, but I finally fixed an alternator and thought I'd post what I found out in the last month. If your gen light is flickering, it is nothing to be concerned with if it happens at higher engine speeds and can be stopped with lights or the defroster being turned on. If you get a dull glow coming on while the truck is running, that is a sign of a rebuild in your near future. This has happened before on other CUCV's I have had, but I didn't know what caused it. This time I checked the voltage when I 1st noticed the glow and it was 13.7 coming from that alternator. As the light got brighter the voltage steadily dropped and that was reflected in the voltmeter. Sometimes the gen light would get bright and sometimes it would go out totally. When the light is out it is charging but not the level it should be. Another thing is when the truck was started the voltmeter would spike toward a heavy charge when the gen light would go out, but then drop down to a much lesser charge on the volt meter, immediately after. I found that the rectifier was bad in this alternator and I tore down two additional alternators and both of them had bad rectifiers too. I'm going to buy some more rectifiers and repair all the bad alternators I have and see what is wrong with each.
One guy that knows his stuff(auto electrics) told me that he has never seen a motorola triple diode fail and quit testing them. Zenith are good too. I think that guys that want to rebuild their alternator and just replace everything with a kit may be throwing out better parts than the new ones they put in, especially if their kit parts are made in china.

I own 2 M-1009s. Rebuilt two alternators...Both on the Driver's side. Both had the rectifier bridge shorted out causing the front battery to drain. On my dash.. the alternator light(#2 if I remember) would stay on along with the Low Oil Pressure light. ??? I make no claim that everything is working as it should. Just what happened to me.