Interesting generator configuration

Lin · July 31, 2008, 05:29:50 PM

We are at a campground up near Idywild, CA. These little trips are great for taking a look at little bus problems that do not require anything heavy. With that in mind, I decided to see why my "Not Gen" light stays on. I know that the current at the battery is 27+ volts at a high idle with the headlights on, so I was not concerned that the alternator was really not working. Anyway, following advice in earlier posts here, I went looking for the Discharge Relay and found it just where it is supposed to be. Since it is a normally closed relay, I propped it open and, sure enough, the gen light went off. "Great," thought I, "all I need to do now is replace the relay." This is a little more difficult than it sounds because the air filter obstructs the opening of the rear panel. Anyway, I got the idea that I should check to make sure that the wire from the generator was connected. Now this brings us to the interesting configuration. There is only one wire attached to the alternator. It is obviously not the original type of anyway. Although I have not investigated it thoroughly, I have known this all along. It is only the size of a normal Delco automotive alternator, and I have assumed that it may be only 100 amps or so. But I did not guess that the system had been reconfigured.

As far as the generator light goes, I am guessing that it will be easier to just put a voltmeter on the dash and forget about the light. However, I am curious about how this is wired. On a one wire system, does that wire (maybe a 10 or an 8 at most) just go directly to the batteries? I also noticed that the belts are a bit loose. I aired the bus up to see if there was some air system that tightened the belts, but they were just as loose as before.

gus · July 31, 2008, 08:29:38 PM

Lin,

I found on my 4104 that after the installation of a truck alt plus a bunch of other elect alterations involving rectifiers and relays that the original bus wiring system didn't mean much. 27v at the battery sounds normal to me.

My original "Charging" meter does all kinds of weird things but I just ignore it and use my self-installed voltmeter as my reference. My alt sounds as if it is the same as yours and is a 105a, all I will ever need.

I highly suspect that your charging light fits into the same category.

NJT5047 · July 31, 2008, 08:36:56 PM

One wire alternators have B+ to the alternator all the time.
That sounds like someone has modified the system and just left the 'relay' lead and relay in place. No harm. As you state, the batteries are being charged.
That's what I'd do. Remove the offending light wire and install an LED voltmeter. Ebay, $10 bucks. No joke. I've got them in my EV. They work great. Be sure and look for correct DC range readout , and 24Vdc (or 12Vdc) control voltage. LED meters come in all sorts of control and readout voltages...AC and DC too. Blue or Red color. I'm gonna get some more for my house voltage. I've got an LCD monitor panel that works fine, tons of info, IF you want to get up in it's little face and read it. The big Chinese meters can be read from the rear of the bus!
The only functional difference in 'one wire' and 'ign controlled' alternators is at what RPM charging begins. Ignition controlled alternators charge at idle. One wire alternators generally charge at a little higher RPM...they turn themselves off when idling...or at some lower RPM.
You have all the alternator you need as long as the OTR AC isn't functional.
I'd recommend tightening the belts. As you described, some coaches have an air cylinder that tensions belts. Not sure about alternators on early belt driven unit. Gear driven units use an air controlled relay (the one you're looking at) to cut off charging and AC when the bus isn't aired up.
AC units usually have air tensioners.
JR

Lin · August 01, 2008, 10:44:06 AM

JR

So you prefer the LED voltmeter, which I assume is digital, to analogue? It seems that would be the easiest to do it. I was wondering though, if I could energize the discharge relay directly from the alternator, or would I just be asking for trouble. Another thing, does this one wire alternator have a built in voltage regulator, or is my old voltage regulator still part of the system? I have the wiring diagrams, but I guess they are just for nostalgia in this case.

Len Silva · August 01, 2008, 11:57:22 AM

If it is a one wire alternator, then it is self regulating. There would need to be a field connection for an external regulator to work.

DrivingMissLazy · August 01, 2008, 01:35:43 PM

I believe I would control the one lead connection with a relay that would close when the oil pressure switch closes. This would definitely remove the voltage from the alternator. The relay would have to be able to carry the full current of the alternator output.

Richard

NJT5047 · August 01, 2008, 07:43:09 PM

Quote from: Lin on August 01, 2008, 10:44:06 AM
JR

So you prefer the LED voltmeter, which I assume is digital, to analogue? It seems that would be the easiest to do it. I was wondering though, if I could energize the discharge relay directly from the alternator, or would I just be asking for trouble. Another thing, does this one wire alternator have a built in voltage regulator, or is my old voltage regulator still part of the system? I have the wiring diagrams, but I guess they are just for nostalgia in this case.

I agree with Richard and Len. Your external reg isn't functional. And the field relay is about useless. It serves no purpose. Your alternator charges anytime it's spun at 600 RPM, or thereabout, or greater.
I like the LED guages because they read down the 100ths. Probably not dead-on accurate, but the results are repeatable. Analog guages are OK, just don't jump out at you when there's a problem.
LED guages may have to be covered at night, depending on where you mount them.
Your alternator may have a port for an idiot light. If so, you'll have a blank spade connector recessed on the back of the alternator. If so, you could jump from the idiot light terminal, using the old relay wiring, shunt the relay to the dash light, power up the light, and you'll have a functional idiot light for the alternator.
If you mount an LED voltmeter in the dash, you'll know readily when it isn't charging...don't need an idiot light really.
I've got a 12V and 120V dc LED meters in my EV. The 12Vdc unit monitors the chassis battery. You can see the brake lights working, turn signals, everything has a 'footprint' in the LED. After a bit, you can spot a burned out tail light bulb!

The only downside to cheap LED guages is they are not dampened. They move around constantly. But they show what's going on. Can be a distraction if this would bother you.

Cheers, JR

Lin · August 01, 2008, 09:25:54 PM

Thanks for the info. I like the idea of the LED voltmeter, but may try to set up the telltale too if the alternator has the spade connector you mention. It is not really accessible to even see without removing the air filter. Since we are at a campground, I do not want to be appearing to be doing too much. Aside from their policies, it gives bus conversions a bad image. I will attack it when I get home. I would like to see what alternator it is anyway and may want to have a spare if it is reasonable. I have a feeling it might not be easy to get in a pinch.

The current gen telltale is always hot and is grounded by the discharge relay which leaves it on all the time. If the alternator has the telltale connection (I don't find the term "idiot light" a real confidence builder), I could just re-task the existing wire to be the hot from the alternator to the light and let the light ground at the dash.

The old voltage regulator is still hot, and I guess there is no real reason, other than avoiding future confusion, to do anything with it, but do you think I could just remove it and cap off the wires?

NJT5047 · August 02, 2008, 08:43:27 AM

Yeah, that's thinking outside the box! Retasking the 'no gen' light' may accomplish what you want.
Most charge indicator lights are powered from the dash to the alternator, where a voltage imbalance turns the light on or off. When the alternator powers up and generates more voltage than the dash light is supplying, the light goes out. If the alternator output drops below the dash light supply, it becomes a ground and the dash light illuminates.
If no alt terminal, a guage of some sort will be your only real charge indicator.
Unless you wish to sort out a relay that opens at some predetermined voltage such as 25 volts. That sort of electronics is beyond my meager learnings. I'll bet there are plenty folk on this board that can describe exactly how to do a voltage sensing relay circuit.
There are also auto switching relays on the market.
HTH, JR

gus · August 03, 2008, 03:21:44 PM

I'm confused about what an LED gage is?? Is this actually a digital gage we're talking about? An LED is a light so I don't understand how it can be a gage?

My Leach-Neville truck type one wire alt comes on at low or idle rpm and charges at idle. Although it does not charge at as many amps as it does at highway speed it is well above battery voltage.

Didn't know such a thing existed until I bought it last year from an alt repair shop in OKC.

NJT5047 · August 03, 2008, 05:01:32 PM

Yeah, digital meters. Here's a link to one of the LED meters. There's various versions, with voltage range, amp ranges, control voltages, and read-out colors. These are old fashioned technology. But they are much brighter than LCD meters.
Dakota Instruments manufactures a really upscale set of LED automotive meters. They are way expensive. But Dakota doesn't cover the various voltage ranges found in most RVs. These cheapo Chinese units are almost give-away. $8 to $14. bucks. They are available for almost any application. They are not automotive fare, so only electrical readouts are avail.
Try this link: http://cgi.ebay.com/3-1-2-Green-LED-Digital-Volt-Panel-Meter-DC-200V_W0QQitemZ370073902709QQihZ024QQcategoryZ25411QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
If the link doesn't work, and you want to see the meters, just type in "LED dc meter" into the Ebay search and you'll see hundreds of the things.
I've bought several, and even though they are shipped from China, they get here as quickly as from most US shippers.
I've been thinking about buying some for my house monitors in the bus. I'm using several in my EV and they've worked well for some time now.
They are large and easy to read...day or night. They are a little too easy to read at night.

Leece-Neville one wire alternators will charge at idle. Powered (3 wire) alternators such as Delcos found on automobiles with electric radiator fans charge at a much higher rate at idle without overdriving the alternator.
Depending on the load, single wire alternators must be 'overdriven' to charge enough amps when used on diesel engines. Smaller driven pulley, or larger diameter drive pulley solves the idle charge rate problem. Not a problem for a low RPM diesel engine, big issue with a gas engine that could spin the alternator up to 8+ grand.

JR

Lin · August 03, 2008, 05:39:23 PM

JR,
I looked at the link and some others. It seems the thing to watch for will be getting one the can use a 24 volt power supply aside from having the proper range. It looks like some might be a bit overpowering at night. I don't see much of an issue with poor or no charge at idle. I don't think I idle that much that it would drain the batteries since OTR air and heat have been removed.

NJT5047 · August 03, 2008, 06:01:45 PM

Lin, I agree with all of your statements. Your alternator is fine as it is.
And the meters are quite bright.
The meters could be operated on 12V from a center tapped source thru a 24V relay so that they work with the ignition master. They operate on mA, so the load is negligable.
A 0-50Vdc range with 12V control would work without issues. You probably have 12V in the dash already for radios, CB, backup cam, etc.
You could directly wire one of the volt meters into your 12V system (don't need a relay) and leave it on all the time without running your batteries down any quicker than the self-discharge rate.
The only purpose for such a meter would be to monitor charge output while using the bus.
If your alternator fails, you'd notice the failure quickly with a digital volt meter.
JR

gus · August 04, 2008, 09:29:31 PM

My Leece-Nevill One wire alt was a direct replacement for the old three wire type, same pulley size. All I did was bolt it in, attach the battery cable and ground cables.

My analog voltmeter works just fine with its well marked range colors. I could see no reason to mess with a more expensive and fragile digital.

My main objection to digitals is that they flicker back and forth between very minor voltage fluctuations and drive me nuts. Digital tachometers are even worse.

If you really need a warning of some sort a low voltage light is the best way to go.

Len Silva · August 05, 2008, 05:23:58 AM

Speaking of voltmeters......Eagles have an interesting hookup, not sure about other brands. The Eagle runs the voltmeter lead all the way back to the batteries through a relay controlled by the ignition switch.
This way, you are looking at the battery voltage and not the voltage taken from a point up front, which would include whatever voltage drop there may be.

Len