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Any alternator guru's out there? FIXED WITH REPAIR

kauzenkaos

kauzenkaos

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I recently purchased an alternator for my 90 k5. After it gets hot it stops charging. I sent it back to the place i bought it from and was told there is nothing wrong with it. I took it to a friend who has a bench capable of pulling 500 amps. We ran it up to 100 pretty easy and as soon as it gets hot it stops charging. We took it apart and tested everything and replaced the regulator on a whim. It works better but still shuts off and after cooling down starts charging again. Do these regulators have overtemp protection. The alternator is a 140 amp max 100 amp idle. From what the guy tells me it has a good 4 strand double wrapped stator and the rectifier is supposedly good with avalanche diodes. Im sure none of this has anything to do with the problem but this whole thing is really pissing me off. Any ideas?
 
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Have you checked voltage at the large lug on the back of the alternator with the engine running? If not then check it when the engine is cold and also again when the engine is hot and respond back with the results.
 
Yeah I I've checked all the vehicle stuff. Battery voltage at lug when not charging. Between 13.9 and 14.6 when charging. I always have power on the key on power wire at the connector. Like I was sayn it does the same thing on a test bench. I'm really looking for internal issues that may cause this mostly because I'm tired of dealing with the people who sold it to me. I really just want it fixed
 
And also to add ambient temp hasn't really played a role because the alt worked great for like 3 weeks at 100 plus degrees and now it'll kick off at 50 or 90 deg just depends on how much load I'm pulling on it to how fast it stops working. At about 2100 rpm it takes less than 5 mins to cool the alt back down to working temp. All of which are way to hot to touch by hand. That's why I'm thinking it may be some type of thermal protection.
 
Most electronic regulators will shutdown at a set temp, but they should not be shutting down under normal operating temps unless they are defective, or not coupled to their heatsinks properly.

Its been so long since I have torn an alternator down, I don't even remember what they use for regulation.
If you see any components other than the diodes that are bolted to the frame or any thick piece of metal, check to see if the bolt is tight, and if there is a small amount of white paste that has oozed out from behind.

Just not seeing the paste is not a guarantee of a problem, lots of companies use custom sized little soft pieces of heat sink compound but it is suspicious.

If it is just going dead suddenly, probably the most likely thing is a cracked foil trace or a bad solder joint.

If the foil trace is cracked, when they heat up, they expand, and one piece slides under the other.
The glue keeps them from making contact.

If you can find it, you can flow some solder across the crack and fix it.

But, if its under warranty, your best bet is to turn on your headlights for a couple of hours, to slightly run your battery down.

Then, drive up to the place with as much stuff running as you can.
That should get the alt good and hot and they can see for themselves that it is not working.
 
Foil trace? I have no idea where to even look. If you can tell me where to check and I'll test it for an open. As for the warranty f-them the place is an hour away and there only open 8 to 5 and I can't take the time off of work. The guy that was helping me out is kinda old and I think he has forgotten more than I'll ever know. The only solder joints I know of we had to unsolder and resolder the stator wires to get the alt apart
 
I just installed a 160 amp alternator and have been watching very close. It doesn't ever shut down even while under extreme heat. If it does it on the bench as well its not a gauge issue. I noticed mine being intermittent when I first installed it, turned out to be the connector on the + side of the volt gauge wasn't tight at the power source.
 
Yea I know it's not my gauge both my trans controller and ez efi have digital voltage readouts. Most of all I can hear it when it's charging has a slight wine to it
 
Ok, I was all set to give you a set of things to check, and request some pictures.

Then I went back and reread your posts. I realize now that I was barking up the wrong tree.

I was assuming that the voltage regulator was shutting down, and I was all set to try to diagnose it over the computer. That was the foil trace I was talking about.

Now I see where you have replaced the regulator. Which I assume eliminates it as the problem.

Trouble is, there is not a lot left.

Either it is getting too hot, which is either an internal short or bad bearings, or something in the windings or brushes is opening when it gets hot.

You have already resoldered the stator wires, so those solder joints are unlikely to be bad.

All I can do from this distance, is to suggest you check each connection you can.
Re-flow the solder on as many as you can, and pay close attention to the brushes.

Its possible that they are sticking in their holders when they get hot. If they are real tight, you might take them out and lightly sand the sides to free them up some.
 
Fordum said:
Ok, I was all set to give you a set of things to check, and request some pictures.

Then I went back and reread your posts. I realize now that I was barking up the wrong tree.

I was assuming that the voltage regulator was shutting down, and I was all set to try to diagnose it over the computer. That was the foil trace I was talking about.

Now I see where you have replaced the regulator. Which I assume eliminates it as the problem.

Trouble is, there is not a lot left.

Either it is getting too hot, which is either an internal short or bad bearings, or something in the windings or brushes is opening when it gets hot.

You have already resoldered the stator wires, so those solder joints are unlikely to be bad.

All I can do from this distance, is to suggest you check each connection you can.
Re-flow the solder on as many as you can, and pay close attention to the brushes.

Its possible that they are sticking in their holders when they get hot. If they are real tight, you might take them out and lightly sand the sides to free them up some.
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Just wanted to say thanks for the info 1st off. 2nd i did forget to mention that we did work over the brushes and housing a little and only because it looked like upon inital assy they had caught the top edge of the housing. Any idea what temps may cause this thing to stop charging? I cant find any type of spec. As much as i hate to admit it im an automotive tech for my whole life and never ran into one like this its really pissing me off.
 
kauzenkaos said:
Im guessing no cauz i have no idea what that is and i dont remember him mentioning that to me.
Click to expand...

The commutator is what the brushes rub against. Many people "clean up" the surface when they are rebuilding an alternator or changing brushes. The problem is that you CANNOT use anything that will transfer metal if so you will short the windings and the alternator won't work.
 
No all that stuff is brand new didnt see any reason to mess with any of that stuff. I got a feeling that this alternator is comming back apart one day this week so ill make sure i check all that. You have any idea on a shut off temp for the regulator.
 
I have NEVER heard of or seen an alternator shut off from getting hot.
 
Yea my alternator finally sh!t the bed. Damn rotor goes open after hot. But at least I can get it replaced now. Just though I'd post an update. Tested that damn rotor everytime I took the alt apart
 
Don't know if anybody else has had as many dead alternators as i have but i finally found the fix. After killing 2 more cs130's I started searching on the internet for solutions and found that a few years of chevy trucks use a similar mount on a cs144 as the factory cs130. I couldn't find a core at any of the parts houses that fit the chevy trucks but found that the cs144 is common on caddys but has the wrong mounts. I took that alternator to our alternator guy and we found the stator was bad. We bought a 200 amp stator (factory 160amps), overdrive pulley, the gm 2 inch 2 foot mount and an upgraded rectifier. Paid $120 for the parts and labor and another $25 for the core to build and haven't had a charging problem for quite some time. I had to elongate one hole removed the rear bracket and switched the position on the key on power wire in the connector. No more dim lights at low rpms or strobing lights when the stereo is turned up.

alternator.jpg
 
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