delco remy alternator arching and glowing

John Zicha

PCS Member / EMT / PARAMEDIC
As I'm getting everything working on the 1970 Cadillac Superior, just tonight the first post on the top of the alternator started glowing out of nowhere. I shut the car off and disconnected it and started the car back up. The other two began to slowly get hot also. When I disconnected all three the car batteries will not charge from the alternator. I was under the belief that these were all AC outputs to go to an inverter or something like that. That is originally what was hooked up to it but I disconnected that. Any idea why it would start barking and glowing out of nowhere? It's a delco remy 40dn 1117140.
 

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Yes I have more than an idea. Your alternator is toasted, and possibly beyond repair! You should have removed the fan belt, not the wire. Had you done that, there is a remote chance that you might have been able to salvage the alternator. When you removed the wires, that was the kiss of death. I know first hand how difficult it is to source the components for this alternator, since when my car was being transported they turned off the batteries before they turned off the car. They blew out all the positive diodes, and they are next to impossible to buy. I lucked out, and found them at a shop in Los Angles that used to do these type of repairs. They have since gone out of business. There are 3 positive and 3 negative diodes, a rectifier, rotor, and stator, and assorted smaller parts inside of that case. Even finding someone to work on it today, is almost impossible, since most of the people that knew how learned the trade 50 years ago, and have since retired. If I were in your shoes, I would find an electrical shop that can wire in a modern type alternator. It won't be inexpensive, but at least if it gets destroyed, a replacement can be had.
Oh... if you are wondering what happened, my guess would be that either the battery switch was in the off position, or the battery cable was loose, and not making a good connection. The other explanation would be that the battery shorted out, or has a shorted cell.
 
Quick and dirty google gives a lot of info on the Delco 40DN series.

1st generation pretty much copied LN engineering with a remote rectifier box, but of course GM just had to louse that up shoveling the diodes inside the case where they couldn't cool. It made for a lot of work for ladies at Delco on Lyell Ave, where Monroe Ambulance now has their barn.

If the windings and slip rings still have integrity it is possible to build a rectifier/regulator pack that lives outside the alternator with far superior components to those that were hammered into the case.

Good info on the Antique Construction site
http://forums.aths.org/PrintTopic155330.aspx

Before panicking, I'd crank the car up and determine the AC side of the alternator.
 
I replaced the alternator with a brand new internally regulated one. Jumped the wires together from the old external regulator and works beautifully. That is until I put lights on and then it squeals like a pig. Shut the lights off and the sound goes away. Belt tension is great. Would I be better off getting an alternator with an external regulator and using the regulator that's in the car already? Would the alternator squeal if it is underpowered? The new one is only 75 amp at idle and goes up to 100 amps max. Any ideas?
 

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The reason its going off when you put the lights on is you are increasing the load or there is a short in the lighting system somewhere (doubtful). When the load goes up the alternator compensates by charging more thus it pulls harder on the belt and squeal results. Double check your belt tension and pulley size on the new alternator is it correct for the belt you are using if not this will cause what you are getting under a heavier load. BTW a 100 amp alternator ain't exactly heavy duty.
 
The reason its going off when you put the lights on is you are increasing the load or there is a short in the lighting system somewhere (doubtful). When the load goes up the alternator compensates by charging more thus it pulls harder on the belt and squeal results. Double check your belt tension and pulley size on the new alternator is it correct for the belt you are using if not this will cause what you are getting under a heavier load. BTW a 100 amp alternator ain't exactly heavy duty.

Yep....it wasn't tight enough. After tightening it, it works perfectly. As of 100 amp not being heavy duty, I'm aware lol. I got it for a good price and when tested it's at 90 amps at idle and when it kicks up it's actually 118 amps. Nothing special is connected to it now. I removed the inverter for the back and getting rid of the heat/AC blowers for the rear also. So it's basically just headlights and the Emergency lights for if it's a parade. If that doesn't handle it, I can always get one that puts out more juice.
 
Nothing draws current until you turn it on. Leave everything alone, in case you eventually find a correct alternator. Once you start taking things apart, they will never be put back correctly later on. Many items are fused, so all you need to do is remove the fuse, and tape the fuse to the wire. Remember, that this car is going to outlive you, and the next person to own it, might not agree with what you have done, but would agree with what the body builder built it as.
 
Yep....it wasn't tight enough. After tightening it, it works perfectly. As of 100 amp not being heavy duty, I'm aware lol. I got it for a good price and when tested it's at 90 amps at idle and when it kicks up it's actually 118 amps. Nothing special is connected to it now. I removed the inverter for the back and getting rid of the heat/AC blowers for the rear also. So it's basically just headlights and the Emergency lights for if it's a parade. If that doesn't handle it, I can always get one that puts out more juice.

Nothing draws current until you turn it on. Leave everything alone, in case you eventually find a correct alternator. Once you start taking things apart, they will never be put back correctly later on. Many items are fused, so all you need to do is remove the fuse, and tape the fuse to the wire. Remember, that this car is going to outlive you, and the next person to own it, might not agree with what you have done, but would agree with what the body builder built it as.

John, I have to agree with Paul. It is very difficult to put these cars back together again the way they were. I am glad to see an agency that actually cares about its historical vehicle! However, I don't understand what appears to be a need to rush - is there any event coming up? Unlike "normal" cars, and many antique fire engines - these cars were hand-built and there is often little in the way of documentation. Many parts books, online resources, and perhaps even the advice you receive here may be wrong or unavailable!

I will again echo what Paul said about us just being caretakers. Perhaps authenticity won't matter to you, your members, or the public at this moment - but the missing headliner/etc. you described in another thread may on its own cause you quite a bit of grief to replace. As opposed to the regular cars many are used to, each professional car is unique. The components may be custom to that coachbuilder for several years, just one year, or perhaps even just your car! I would personally hestitate to remove/replace, if historical preservation as a "museum piece" is your goal. I would most certainly not throw anything away. As Paul says, many things can be disconnected if electrical is your concern.

If you have already removed the inverter - I do have a need for one. If you chose to dispose of your original alternator, I am also interested in it.
 
John, I have to agree with Paul. It is very difficult to put these cars back together again the way they were. I am glad to see an agency that actually cares about its historical vehicle! However, I don't understand what appears to be a need to rush - is there any event coming up? Unlike "normal" cars, and many antique fire engines - these cars were hand-built and there is often little in the way of documentation. Many parts books, online resources, and perhaps even the advice you receive here may be wrong or unavailable!

I will again echo what Paul said about us just being caretakers. Perhaps authenticity won't matter to you, your members, or the public at this moment - but the missing headliner/etc. you described in another thread may on its own cause you quite a bit of grief to replace. As opposed to the regular cars many are used to, each professional car is unique. The components may be custom to that coachbuilder for several years, just one year, or perhaps even just your car! I would personally hestitate to remove/replace, if historical preservation as a "museum piece" is your goal. I would most certainly not throw anything away. As Paul says, many things can be disconnected if electrical is your concern.

If you have already removed the inverter - I do have a need for one. If you chose to dispose of your original alternator, I am also interested in it.

I removed the original generator and leaving it our "parts bin" Maybe I can have someone rebuild it at some point. I wanted to get an alternator in so we can drive it in and out of the bays when we need to and while we're working on the rest of the car. As for the inverter- that went in the garbage because it was destroyed and rusted away (sorry). I'm a VERY impatient person, so taking my time is going to be a chore on it's own, but I'm working on that also lol. Thanks for the input!!
 
I removed the original generator and leaving it our "parts bin" Maybe I can have someone rebuild it at some point. I wanted to get an alternator in so we can drive it in and out of the bays when we need to and while we're working on the rest of the car. As for the inverter- that went in the garbage because it was destroyed and rusted away (sorry). I'm a VERY impatient person, so taking my time is going to be a chore on it's own, but I'm working on that also lol. Thanks for the input!!

The one thing you need most (after the money to do the project) is patience, and a lot of it!! You ever hear the old saying "good things come to those who wait", truer words were never spoken regarding pro-cars. Take a deep breath and relax, you'll be surprised at the results. We've owned our '64 for 4 years and still have some things to do, but it all seems to happen eventually. As long as it runs and drives SAFELY, you've got it made.
 
For anyone who happens to be looking for one, I was able to find someone who knew exactly what I was looking for. Leece Neville 4800 is basically a new version on the Delco Remy that was in the car originally. Just modernized with an internal regular etc. Just ordered one!!!
 
I'm a VERY impatient person, so taking my time is going to be a chore on it's own, but I'm working on that also lol.

I can relate. I tend to be pretty impatient myself, I see the car and I think of all the things that need to be done and I try to do them all immediately. I need to work on that myself, being impulsive can be a problem of its own
 
This was the alternator that was on my ex military 72 CB. The DOD had them in there contract. That one was externally regulated. At that time I don't think there was the other option.
 
It's internally regulated. You can get an external one if you want. They have a ton of options. Leece Nevile 4800 series alternator.

Where did you order your from and how much did it run you if you dont mind me asking? I may be in the market for one soon. My searches turned up $400 - 800
 
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