I need some expert help.
After driving about 2 hours this AM, my voltage readings dropped to 12.2V. That is, the dash gauge (confirmed by the VMSpc) and the audix display both went to about 12.2.
Boost switch was not on; inverter was on running 2 laptops; headlights were not on, but had been on for first hour; Aquahot was on diesel with only the bay thermostat on (so two radiators on active); dash heat/defrost on. I believe the batteries to have been fully charged at outset.
I turned on the generator. That brought the audix (house batteries) reading up to the usual 14V or so. When I switched on the boost that brought the dash and VMS up to 14.1V also.
I drove 30 min or so before turning off the boost to see what would happen. Dash and VMS read 14.1V, as they should, until I stopped about an hour later.
Is the 12.2V reading I got the alternator output? If the engine/alternator was off, the dash would read the engine batteries and the audix would be reading the house batteries. But, how could the alternator output be 12.2? Is there a most-likely culprit here?
Thanks,
Mike
2003 U-295
It does appear that the alternator or the voltage regulator that are driven by the engine are not delivering a charge voltage to the starting battery. One easy way to test this is to turn off BOOST and anything that is driven by the starting battery (headlights, dash radio, etc) and measure the voltage at the starting battery terminals; then start the engine and measure again. Be sure you are on the terminal and not on the clamps.
If the engine-driven charging system is working you should see a slow increase in battery voltage over time... a tenth of a volt (or so) every minute or two.
If there is no slow increase then check the house batteries without the boost on. Since the engine-driven alternator will charge both sets of batteries these, too, should either show a full charge (if fully charged) or a slow increase in voltage at the terminals while the engine is on.
If the house batteries increase slowly but the starting battery does not (and remains low) then you probably have either a bad battery or a disconnect in the charging system wiring between the alternator and the battery bank. Check the connections at the battery. Is the battery voltage as measured on the wires the same as measured on the battery terminals? If not, then you have a connection problem.
If you are not seeing a slow voltage increase on either battery bank with the engine running (and the batteries not fully charged) then follow the system back and measure at the alternator output (being careful to avoid getting tangled up in belts and pulleys). This point should read pretty close to the same voltage at the battery terminals. If it reads higher then there is a disconnect between the battery and the alternator. If it reads the same (e.g.: no increase in measured voltage over a few minutes' time) then it seems likely there is a problem with the alternator. These can be checked easily on a test stand at most places that service vehicle electrical systems.
I think I've run through all the permutations here... but if I haven't I'm sure someone will notice and let us know. :)
Good luck,
Craig
Actually, the easiest place to check voltage is at the DIODE BASED ISOLATOR. Check for 14+ VDC at the IN wire from the alternator with the engine running. And around .6 VDC less at the OUT to the house and chassis batteries.
Brett
Thanks for the quick response.
I had checked the voltage at the isolator before I shut down and both legs showed 14+. Unfortunately, I didn't stop and check it when I had the problem; remember that my gauges went back to the proper 14.1 after I had driven a while.
Since then I found a loose connection at the house battery terminal on the isolator. I don't see how this would create the problem though, since the alternator is reading (regulated by) the voltage from the engine batteries and that connection at the isolator is solid. Both battery banks seem fully charged and the isolator seems to be working properly.
Thanks a lot for your help.
Mike
2003 U-295
Well... as luck would have it, our weekend camping trip was canceled for two reasons... the first was that the campground was not open as the web page suggested and second our house AND engine batteries were clearly not charging while we were driving the 68 miles to the (closed) campground. We had also discovered that the service station where we tried to re-fill our propane tank (1/4 full) had no way to connect to our tank and the propane distributor (Ferrelgas) was closed on Friday. Running the generator charges the batteries (even the engine batteries with BOOST on) but we were low on propane. So we turned around and drove the 68 miles back home and got there just before dark. It's a free camping spot with electriicity!!! We plugged in, made dinner, watched a movie and went to bed.
Ahh... the joys of motor homing.
So my question is... where is the diode isolator on a '93 U225? Is it the assembly mounted on the bulkhead forward of the battery bank with the circuit breakers?
Craig
The isolater on my former 93, U225 was behind the drivers side rear wheel mud flap. It was an aluminum veined box with several large battery cables and was bolted to a piece of sheet metal along side of the boost solenoid. Open the back bay door on the drivers side a look up and to the left.
Be aware that a failed diode based isolator can be wired around to get you home. Just connect all cables/wires to one terminal.
Be sure to mark where they came from and return them to their original location when after you turn off the engine.
Brett
Kent... that is exactly where I found mine; thanks for the tip. I can't see any obvious problems but I did discover that there is zero voltage at the alternator where the large red cable terminates. There are four terminals on the diode isolator; does anyone know where they go (nothing is marked). There is also a small solenoid. I am wondering what purpose the solenoid serves in the system. Normally zero voltage at the alternator would make me pretty suspicious that the alternator itself is faulty but with all these diodes and solenoids in the circuits (and no schematic) I am not as certain. On my pickup with the same engine (but different alternator) I have 13vdc at the alternator... but no diodes/solenoids.
Anyone know where to buy a replacement alternator if it comes to that?
Craig
When you checked for voltage was the engine running? With the engine running there should be around 14 volts at the large red positive terminal on the altenator and if it has a small red wire going to the regulator on the altenator it should have battery voltage on it and that is what excites and measures voltage for the regulator. the isolator terminals has one that goes to the house batteries. the center terminal should be from the altenator which you should be able to determine by the voltage and one of the terminals goes to the chassis batteries. the fourth terminal I think has a jumper to one of the other terminals on the isolator
Yup... the engine was running... zero volts to the large red connector on the alternator. I did not measure the voltage to the small red wire. I'll recheck this tomorrow with the information on the isolator. Thanks for the info. But it does look like alternator to me right now... interesting in that it looks like a relatively new alternator too.
Craig
I believe the 4 terminal isolator is made for a dual alternator system. I think FT used them because they are larger and can handle more amps. On my coach the two center terminals were jumpered together with the alternator connected to one of them. The two outside terminals were connected to house and chassis batteries respectively.
Craig, Any good alternator/starter shop can bench test your alternator in just a few minutes. Please be aware that FT uses 4 wire alternators and some shops are not familiar with them. FT can provide you with a wiring diagram probably. These good shops can also rig a common GM "J" Frame alternator to work as a four wire in an emergency, I have one as a spare that cost me two hundred bucks.
IMHO Alternator problems are mainly caused by charging into batteries that are depleted or very low in voltage. My practice is to use boost switch for a few hours to see that chassis batteries are charged before starting, that way the alternator is not stressed in trying to charge battery after depletion from starting effort. This may not be a scientific explanation but in practice it has worked for me.
Gary B
Gary... thanks for that tidbit... I had not known they were 4-wire alternators. I'm sure I can find a shop around here somewhere that can test the alternator. Not especially looking forward to removing it. If someone catches me in the act I'll have to marry the engine. :P
If all my joints bent properly it wouldn't be too bad.
Any idea what that solenoid below the diodes is for? I was kinda hoping that was the problem. :P
Craig
Craig, Not sure about yours but in general you will find TWO solenoids near Isolator, One is starter solenoid and the other is the boost solenoid. Test is easy, if it won't start suspect start solenoid, if you turn boost on you should hear a click on one solenoid. IN A PINCH if solenoid is bad you can jump terminals with your jumper cable ( one of them ). OR you can connect both heavy cables together to get home. Also newer solenoids will have two small posts, if so all you have to do is run a ground wire from one post to a reliable;e ground.
When removing an alternator tape off or otherwise insulate each wire and cable as you take them off and mark them. Nasty burn can result if you ground the positive cable and if you reverse them on install you can fry a new alternator.
ON EDIT, Four wire alternators are also termed EXTERNALLY EXCITED.
Gary B
One of the two small terminals must have voltage when ignition is on and no voltage when ignition is off. If voltage is missing, alternator output voltage will be zero. The 'other' small terminal is connected to start battery and will always have about 12.6-volts.
Craig, sending this drawing may help some in identifying the wires.
Thank you, Bobby!!! That diagram is a great help! It appears that there may be no exciter voltage. I'll recheck it today.
Craig
I had to wait for the weekend so the DW could help me; she turned the ignition key on and off (and started the engine once) while I checked voltages.
There is 12.2vdc at the alternator's "ign" post when the ignition key is turned on. But when the engine is started there is still no voltage at the output of the alternator.
Unless there is some other issue I don't know about, I'm thinking that the alternator is defective and needs to be replaced or rebuilt. Anyone have an "alternative" theory? Is there a voltage regulator somewhere that could account for this?
These are Leece-Neville alternators (externallye excited) and I've found a 4833LGH alternator for $319 on eBay. It's rated at 185amps. This alternator has mounting ears 180-degrees apart (12 o'clock and 6 o'clock). It's hard to see the arrangement on my Cummins but it looks like it's the same. Any ideas?
I'd hate to parcel out $319 (plus shipping) only to discover that it's something simple. On the other hand, I'd have a spare alternator, at least.
Craig
Craig,
My advice would be to call Leece-Neville and ask for the name of the nearest authorized alternator shop certified by them.
We have a different alternator, but that is exactly what I did. They recommended a shop near us-- all they do is overhaul alternators-- have 6 employees doing just that.
Generally less than 1/2 the price of a new one and no shipping. New bearings, brushes and fix whatever is wrong with the electrical part (such as diodes). Could it be something more major-- sure, but not real likely. Certainly worth them checking it out for you.
Brett
Brett... that sounded like a great idea and so I launched into a search for Leece-Neville's home site. There are tons of Leece-Neville distributors and resellers but I couldn't find any reference to their home site or factory authorized repair facilities. So I just called a local shop and they agreed that it was the alternator and probably a blown diode.
So I'll have to remove the alternator. This should be fun. I think I'll hire a local mechanic off craigslist to help since crawling around over and under the engine bay is no longer my cup of tea. Worth hiring a young guy to do that. One ad says he just had his first kid and needs the extra bucks.
I do need to get the alternator off so I can decide whether to get it rebuilt and re-installed or just buy a new one and use the rebuilt one as a spare.
Thanks for the help... and if anyone knows the mounting details of the alternator on the Cummins 5.9L 1993 U225 engine that would be handy.
Craig
I had an intermittent problem with my alternator and finally found the self resetting circuit breaker for the exciter voltage was going bad. It would go off and on and finally failed completely. $3.00 later and a few minutes to replace the circuit breaker and the problem is solved.
Craig, I believe the alternator on my 89 GV was probably the same or very similar to the one on yours. It exhibited the same exact issue you're having. 0V at the + terminal. I had a rear engine radiator so removing the alternator wasn't nearly as enjoyable as the side radiator rigs. Anyway, I decided before pulling the entire alternator I'd replace the voltage regulator since that's just a couple screws. Bingo, worked like a charm and was much cheaper. Think it ended up being $20 - $30 or something like that.
Good luck!
Benjie
Benjie... yes... the rear radiator makes removing the alternator a PITA. Does anyone happen to know where the voltage regulator might be in a '93 U225? I'm willing to give that a try. :)
Thanks,
Craig
Craig, it's on the alternator - Removal and installation of the 102200 Voltage Regulator (http://www.beamalarm.com/Documents/removal_and_installation_of_the_102200_voltage_regulator.html).
FYI... I believe Leece Neville has a new PN for it, but if you take it off and take it to any alternator shop they should be able to match it with a new one. At least that's all I had to do with mine!
In my opinion, it is always better to rebuild my existing alternator to eliminate problems trying to match up which replacement to use. But it is important to find an 'old fashioned' alternator/starter rebuild shop. Every part can be easily replaced and the total will be less than a new unit. We have had ours rebuilt several times. Last year's rebuild, I asked for a voltage regulator that has an external screw driver adjustable voltage regulator, which has helped keep charging voltages in line during 100 degree days.
I also ran a new circuit breaker protected voltage sense wire directly to start battery bank from our inverter panel.
The DW and I spent 3 hours taking our U225's alternator out this afternoon. The job was complicated by a previous owner rounding off the heads on the pivot bolt and nut. I finally just hammered one size smaller impact socket onto the nut and put the air impact tool on it... spun it off faster than I thought it would.
The alternator is a Heyr and there were only three wires connected to the unit; a negative wire (black), a positive out put wire (big thick red) and the red wire from the isolator. However, examination of the Hehr troubleshooting documentation it appears that the alternator was wired correctly enough to run (even though the battery sense was jumpered to the field excite (where the ignition wire was connected). Both of these have to have +12vdc in order to run.
Off to the electrical shop tomorrow for a bench test.
Craig
You might take a look at this:
Alternator alternatives (http://www.foreforums.com/index.php?topic=15183.msg91342#msg91342)
I've been very pleased with the performance of this retrofit. Newer alternatives have better/larger bearings per Leece Neville.
Chuck
Chuck... thanks for the link. The Hehr that was on our U225 is kind of cool in that it has all the contacts for various configurations right on the unit. Just jumper across to change it. No drilling into the regulator.
I found that someone had jumpered the battery sense to the field excite (which comes from the ignition contact at the isolator). Info from Hehr says that both of these have to have +12vdc "at all times" when the alternator is running. I am not at all convinced that this was a good idea but maybe it works...
Since the alternator only had three wires connected (one to the negative, one to the postiive and one from the sense to the isolator) I don't actually know where the original "battery sense" wire from the batteries is. I'll have to look at the harness more closely.
The alternator was dead when we put it on the test rack. I explained to the tech how it was wired and he said he understood that configuration so that was ok. We're sending it to Spokane to see what needs to be done. It's either the regulator or the diodes. Bearings seem ok.
When I get it back I think I'll eliminate the strap between the battery sense and the field excite and wire up a real battery sense instead. I wonder if turning the ignition off (which cuts off the 12vdc battery sense) hasn't caused the field to collapse too quickly and blown the diodes.
Or maybe it's heat.
I'll keep everyone posted. These seem to be on-going problems and a newer, more heat-resistant, unit might be the answer.
Thanks again for your info. :)
Craig
Craig, That 4th wire should be to an IGNITION ON source. Mine is wired to the hot wire at the rear engine start panel. If you go there be sure that the hot wire to the alternator is well clear of any heat source or other point where it can ground.n Don't ask how I know that. Its embarrassing. :-(
Gary B
Gary, thanks. I understand about the "don't ask me how I know" stuff. Theoretically, the fourth wire is connected to an ignition on source... but it's from the isolator. When the ignition is turned on both of those contacts are hot... however they are both from the isolator.
I don't understand why a battery sense voltage couldn't be from the same source as the ignition voltage... but a constant voltage to the battery sense might be important if it keeps the field from suddenly collapsing and blowing the diodes. Since the ignition on voltage stops as soon as you turn the ignition off, then there is no voltage to the battery sense when the alternator is slowing.
This may make no difference at all. But the Hehr technical documentation specifically says that the jumper to the field excite (which is where the ignition on voltage goes from the isolator) should be removed and a wire from the battery (a battery sense voltage) connected to that post. 12vdc is 12vdc no matter what route it takes to the alternator but sometimes the removal of that voltage can cause problems.
Solar panels are lots easier. :P
Craig
Whooooops.Sorry Craig, I was referring to a Leece Neville, I had to replace my Hehr Powerline and then I had to rewire it. I should have read post closer.
Gary B
Craig, I'm not up on the Hehr alternator but unless it's self excited I expect jumpering voltage sense to excite will make it drain current when the engine as off as the alternator is always excited. You might want to check on this. Jumpering will work on almost any alternator but they've been known to be battery drainers.
Chuck
Chuck... the jumper is from the hot ignition connection to the battery sense connection. Since the ignition connection only comes on with the key there is no drain. But the documentation says to *not* jumper those two and, instead, sense the battery voltage direction. This would, of course, mean that there would always be +12vdc on that connection (which is, I think, the way the FT coaches come from the factory).
Since we know that the previous owner was having alternator problems I wonder what caused mine to fail and whether it was that jumper.
And Gary... the Hehr is supposed to be wired up exactly like a Leece Neville. At least according to the documentation I found on the 'net.
Craig
Chuck, The original Hehr apparently was factory wired but when I put the Leece on I had to add a wire. There are so many variations on these coaches that its really hard to apply a one size fits all fix.
Gary B
Gary, you got that right. And when it comes to alternators the selection is immense also, some models are superseded several times with tech notes for changes to each revision. Really, after thinking about it, it seems like they need not one but two sense circuits, one for each battery bank. I have a hard time thinking that charging a battery bank should kill a 160 amp alternator but I can see it being a problem if you're sensing coach batteries and charging house batteries (boost switch on.) At that point you've got an unbalanced load with the alternator in the mix, sensing a hybrid voltage. There's also the problem of gel/agm/wet cell batteries, different styles in the two banks each with different charge profiles.
I can see charging a gel battery bank putting a hurt on the alternator.
Chuck
Your remarks make perfect sense. Many of us have two different types of batteries between the coach and chassis units. We've upgraded the shore power circuits in order to protect our batteries but have forgotten that we should probably do the same thing to our engine-driven charging systems as well; especially when we can drive 12 to 16 hours a day occasionally (well, some of us).
Right now I'm wondering whether it might be a good idea to have a way of turning the engine-driven alternator off while driving in sunshine with roof-mounted solar panels (and the boost switch on). My MPPT controller for the solar panels is vastly more sophisticated than the regulator for the alternator. This would help control heat buildup in the alternator and also protect the battery bank.
Craig
Craig, Some one here has done just that by adding a switch to take the alternator out of the circuit when desired. I can't find the post right now but do a search on alternators and maybe it will pop up.
Gary B
Chuck,
You're always charging both coach and chassis battery banks with the alternator through the isolator. Starting the engine with deeply discharged coach batteries is an easy way to overload a 160 amp alternator. To make matters worse, turn on the boost switch to compensate for deeply discharged chassis batteries, and you have a recipe for alternator failure on engine start-up.
One reason many FT owners run the generator (boost switch on) for 30 minutes before starting the engine after they've been boondocking for a few days.
Craig