52 l85

[Geoff Weeks]

Here is a simple test you can do.

Get a test light, connect one end to a good ground, turn on the ign switch and touch the other end of the test light to each field terminal. It should light on one and not on the other. If it lights on both, you have a bad ground, if the doesn't light on both, either you have a bad regulator or it is set -up different than mine and regulates the ground side of the field (not likely, but can't rule it out.)

 Anything more and we are going to have to get deep into testing stuff that is hard to explain over the .net.

[Angelo]

The one field wire went to bolt on rectifier I made replacement wire and fixed that. The other went to the F on my regulator and I ran a new wire between them as well. So both of those are replaced. 

[Angelo]

Gonna have the alternator gone thru and cleaned up by a shop. When I opened back where field is there was a lot of dust and junk. It spins free with no noise hopefully it comes back good. Now I think I need to replace rectifier too it’s 42 years old. Anyone have one or know how to replace it with something else that can work? Frame to motor ground is good and cleaned up some other wires I didn’t like the look of. 

[Geoff Weeks]

Replacing the rectifier is going to be a problem. There are remote rectifiers with a fan, as an assembly, but you are looking at several hundred dollars, and will not look like original.

 I think it is time to make the choice, original or retrofit?  Nothing wrong with the original alternator, but the rectifiers are not the best, it was all that was available at that time.

 A replacement modern alternator, can equal or exceed what you have now, and all in the same footprint.

 I think I would either leave it be, or replace with a modern unit.

Like I said, I have the same set up, only difference is your field is 12 volt and mine is 6 volts.

 If you go with a modern unit, it would eliminate the divorced regulator, the new ones are all self contained.

 So in short leave it as it is now, I  wouldn't open it up unless you detect a bearing problem. The brushes and brush holder can break easily when you try to remove. Last I checked, they were still to be had, I have one stuck/broke one in my alternator and purchased are replacement brush holder. My brushes looked ok so am not going to replace.

 The other option, is to replace. Your choice.

[Angelo]

I understand what you are saying. If rectifier is bad could that cause my overcharging? The Regulater is replaced all grounds cleaned and checked, field wires clean and check out. Not sure what else could cause the 18volt overcharge. I appreciate all your help so far

[mrsmackpaul]

Test the rectifier before changing it

Simple to test

If it was mine and it's not

I would stop just guessing and start testing things

To me there's a lot of guess work going on

The alternator is working, we know this as it's over charging so leave it be 

The rectifier is working, your getting DC from AC so leave it

The regulator isn't working 

It needs a reference to know what voltage to regulate at

Do you have voltage at the regulator 

And yes replacing the alternator is the easiest way to solve this with a modern type

But this should be easy to fix

 

Paul

[Angelo]

I’m trying my best to learn and figure this out. I’m asking so I can learn. I’m not just guessing, I’m asking from people who have way more experience than me. I’m doing this work alone in my back yard and don’t have endless money on hand to hire people. I appreciate the help everyone has gave so far 

[Geoff Weeks]

This is how I understand it:

It was working fine, then it went to 18 volts, then the regulator was changed, then it stayed at 18 volts. If this is not the sequence than let me know what is.

 Two regulators being bad, is not as likely as one.

 There are resistor cards under the base of the regulator that cut the field current in stages. If one of these has failed it can not do its job.

 So there may be other reasons the regulators can't keep the alternator under control.  Wiring and grounds are chief among them here.

 If it was working, then went to 18 volts, and the regulator was changed, and it went back to working for a while, then went back to 18 volts, then there are other suspects.

 The regulator works much like a single pole double throw relay. The top contact provides full battery voltage to the field. the field is connected to the movable contact. When the contact is neither touching the bottom or top contact, the field is fed power through the resistor cards, at a center tap. when the relay pulls all the way in and the moveable contact is touching the lower contact, the field is shorted to ground (no field current).  In practice, the center contact is always dancing between the three positions, sometime touching the top sometime the bottom and most of the time in the middle, all based on the voltage supplied to the relay core.

 If one or more of the resistor cards are burnt too much current get to the field.

If the regulator isn't well grounded, it may see only 11 volts between it and what it is attached too, even if the battery is seeing 16 volts, the regulator thinks it needs to raise the voltage when it really need to cut the voltage.  This is what I mean by poor ground.  The battery is often grounded to the frame, but the engine and body are often mounted in rubber bushings, so if you don't have good ground bonds, the voltage the body sees may be different than the voltage the engine sees, which may be different that what the frame sees. Good ground bonds are essential.

 If the field current is too high, because of a short in the field, or a 6 volt field being used as a replacement sometime in the past, because it looked right and fit, it could be burning the resister cards in the regulator, A check of the field current might give some answers, but I don't have the spec's.

 There are an awful lot of unknowns at this point. If you are working by yourself and aren't well versed in how to check these things, (often times it is much easier to show you than tell you how to run the checks) I would seriously have you consider a modern alternator set-up.

 There is also the rectifier situation, If you read the Wiki link I posted you will see that type of rectifier suffered from shorter life span and releases toxic fumes when it fails. I would hang onto the old set-up for show, but would suggest going with a modern unit for operation.

 When I get time, I am going to look into making a rectifier mount that will accept modern Leece Naville  diode blocks, to mount on the rear of the alternator case, such that the cooling fan in the front of the alternator draws air over the diodes before it enters the rear of the alternator. The mount not only must hold the rectifiers blocks but also be electrically insulated from the alternator case, as well as being sturdy enough to take the vibration and heat in use. It must also protect from falling wrenches and such during maintenance. In modern alternators they are mounted inside the rear cover with insulating washers and feed throughs on the rear case.  There isn't room for them inside the alternator case, I checked.

 

[Angelo]

Thank you for response. I have braided ground straps from frame to motor. And frame to body. And they are in really good shape. I used dremel tool with wire brush and cleaned all terminals on alternator, regulator, battery and ground connections. Replaced field ground between alternator and rectifier, replaced field wire between alternator and voltage regulator. When I turn ignition on you can hear voltage regulator click. Starts right up then voltage climbs to 17-18 volts within a few seconds.

[Geoff Weeks]

On 9/30/2023 at 2:48 PM, Angelo said:

New voltage regulator installed. All terminals cleaned and still charging at 18volts. Any one have a clue has a leece Neville generator on motor. Idols at 14 volts soon as into pedal goes to 18volt 

this seams to imply that it  was 18 volts before and after the regulator was replaced. Is that so?

That would point to other problems

Are you sure of your volt meter?

[Angelo]

Two different volt meters so yes. Everything was fine. Was driving home from show when it happened. Changed voltage regulator and it’s still happening 

[doubleclutchinweasel]

I curious about the resistors.  Their exact job is to reduce voltage.

[Geoff Weeks]

2 hours ago, Angelo said:

Two different volt meters so yes. Everything was fine. Was driving home from show when it happened. Changed voltage regulator and it’s still happening 

Ok, this suggests it is not the voltage regulator if changing it did no good.

On to testing the rectifier as if shorted it could put a high ac spike into the system giving a high reading. Meter reads the ac.

Normally you would drain the battery (with a shorted diode) with the engine off, but the main relay in the reg prevents this as it disconnects the battery from the rectifier when the ign is off.

 Turn the ign on (should hear a click in the regulator) then take a test light, one end on a good ground, and probe each of the heavy ac output wires from the alternator (NOT the heavy DC wire to the reg) and if the light lights, the rectifier is shorted.

2 hours ago, doubleclutchinweasel said:

I curious about the resistors.  Their exact job is to reduce voltage.

Resistor resist current flow, there job is not to reduce voltage, voltage drops when you try and pass a current through the resistor but how much varies with the current (load)  Also were are talking massive wattage so any resistor would be huge and the energy wasted would be in the form of heat.

Edited October 4, 2023 by Geoff Weeks

[Geoff Weeks]

modern replacement for the rectifier:

https://bermantec.com/shop/products/alternators-spare-parts/prestolite-leece-neville-alternators-spare-parts/leece-neville-rectifier-regulator-1111ca/

Add shipping and import duties (couldn't find one listed in the US)

all comes to much more than a one wire modern 100 amp replacement.

Here is another but shown "sold out"

https://hdpsi.com/collections/33hd-series-external-rectifier-models

https://hdpsi.com/pages/external-rectifiers

Edited October 4, 2023 by Geoff Weeks

[mrsmackpaul]

I probably came across a bit harsh

That wasn't my intention 

I'm trying to just get you to not just start changing things and fiddling and making it worse

I have worked on a lot of plate rectifiers over the years, worked on a lot of generators and alternators, mainly on the electrical side of things

It is how I got my start in the world as a young man, so I do have some idea what I'm talking about

Goeff is very switched on, listen to what he is saying

I tend to stay out of giving advice on electrical things like this as everyone else has plenty to say and people that don't understand things can get very confused 

Your ground (which by the way, is what I think is wrong) wont be a wired connection as such, at least I doubt it will be, it will most likely be the connection that the regulator or what ever is faulty is attached to

So I was taught as a apprentice, and still use these princables

Always prove the fault before changing anything 

Prove the bad connection before undoing things and cleaning

Prove the faulty rectifier before tampering with it

Prove the faulty alternator before sending it off to be reconditioned  

By doing things this way you teach yourself actually  gind the fault

If don't prove things your only guessing and potentially making the problem worse and waisting time and money

Anyway, good luck and I'll stay out of this unless asked

My only advise is to prove the fault before changing or adjusting anything 

 

Paul

 

 

[mrsmackpaul]

5 hours ago, doubleclutchinweasel said:

I curious about the resistors.  Their exact job is to reduce voltage.

I have just the right hand side of this hanging on the office wall to explain to the apprentice about things like this 

 

Paul

[Angelo]

I appreciate your input very much. Changing a motor is nothing to me. Some wires and I’m lost. Took me a while just to understand positive ground because everything I’ve ever learned was opposite. I’m eager to learn and care for these rigs for the future

[Geoff Weeks]

39 minutes ago, mrsmackpaul said:

I have just the right hand side of this hanging on the office wall to explain to the apprentice about things like this 

 

Paul

Love that drawing, never seen it before.

 I was very careful to say ground and not negative, because it doesn't matter to the vehicle which polarity but some items may care. The basic operation is the same regardless of which battery terminal is connected to the frame, or if none are and everything uses two wires (like in marine).

It is very possible that the rectifier is bad, but it wasn't the 1st place I'd leap without other indications. This system is a bit odd, as it disconnects the battery from the outlet  (DC side) of the rectifier when the ign is switched off.

Electrical can be hard to explain over the internet to someone who is not well versed in how the system works. Often easier to show then tell. Even harder (for me anyway) to learn solely from a lecture or text (likely why I didn't do well in school) then having my hands in and someone showing me how and why.

[mrsmackpaul]

You need a test lamp, very basic old school type

And a analog multi meter, nothing fancy, not digital

If your not experienced a digital meter can lead you up the garden path very quickly 

This way when Geoff or someone else asks a question you can give a positive correct answer on exactly what you are looking at 

 

Also a couple of leads with alligator clips 

And if the budget can stretch a few more dollars, a set that plugs into your meter

Now remember the golden rule, "always test the tester on a known supply" 

So test the test lamp on the battery, then test it on the ground your going to clip alligator clip to from the test lamp

Once ground is established amd proven then test what ever it is with the probe

Once found a reading that's a bit sus, recheck the tester encase the ground or tester has changed

You don't need flash test gear and 99% of your faults will be found with a test lamp, thats all most workshops had back when this fire truck was built

So keep it really simple 

Geoffs your man here, he is much much better with words than I am

Paul 

[Geoff Weeks]

I call a test light my "optical volt meter".

[Geoff Weeks]

3 hours ago, mrsmackpaul said:

 

 

Your ground (which by the way, is what I think is wrong) wont be a wired connection as such, at least I doubt it will be, it will most likely be the connection that the regulator or what ever is faulty is attached to

 

 

Paul

 

 

Paul,

 electrically you are correct, but in this case the "grounded" side of the field is wired to the DC output of rectifier. A heavy ground wire carries both the output and the field ground path.

I think the reason for this,is these are (were) sold as an upgrade to what the chassie mfg had. Mine is wired (and looks to have a complete original wiring) to the DC output on the rectifier also. This allows Leece Neville to pre-wire the kit, and which ever side of the rectifier you ground (positive for positive ground, negative for negative ground) the system will work with the same supplied voltage reg. No need for positive and negative regulators and no re-wiring by the end user.

 It was a trait of Leece Neville's that carries on to this day. While Delco and many others produce separate positive and negative  ground units, Leece Neville made theirs neutral, and you ground the output terminal for the vehicle polarity it is being installed on. It means, unlike Delco's and others you can't use the case directly for a heat sink on the "ground" side. Both in the old selenium rectifier and on modern  diode "bricks or blocks" are isolated from the surrounding metal, and in the case of the old selenium rectifier, they put a whopping big relay in the output so the battery and rest of the trucks electrical system is isolated from the rectifier when the engine is off.

 Makes for a simple "kit" but looks a bit odd.

Edited October 4, 2023 by Geoff Weeks

[Angelo]

So can I use a 3 phase block rectifier that’s rated at 100amps 1600 volts to replace the rectifier is that shows bad ?

[Geoff Weeks]

9 minutes ago, Angelo said:

So can I use a 3 phase block rectifier that’s rated at 100amps 1600 volts to replace the rectifier is that shows bad ?

Has it tested bad?

[mrsmackpaul]

7 minutes ago, Geoff Weeks said:

Has it tested bad?

This is important Angelo

I think it won't of tested bad as the voltage is coming thru okay

However Angelo you can test the rectifier easily even with just a test lamp

Remember on the other side of the world so don't think I'm been rude if I dont answer as I'm asleep when your awake

 

Paul

[Geoff Weeks]

15 minutes ago, Angelo said:

So can I use a 3 phase block rectifier that’s rated at 100amps 1600 volts to replace the rectifier is that shows bad ?

You could but I wouldn't.

PIV (peak inverse voltage rating) should be 2.7 x the max forward voltage for a minimum,  Most will go a fair bit higher when selecting a diode. Why not use a 1600 volt rated? Because the higher the voltage rating the more the voltage drop across the diode, so where a 100v PIV may have  .5- or 1 volt drop across in the forward direction, a 1600 volt would be much high drop. Although as a percent of rated voltage the drop may remain the same, at  lower voltages the forward drop may present a problem.