The alternator is not charging the engine battery, is putting out .76 VDC and it's exicitation/sense voltage is zero. The attached photo shows a loose terminal that looks like it came off a circuit breaker, which has 13.6 VDC on both sides of it, near the isolator.
Questions:
1. Does anyone know what this wire does? or Where it is supposed to go?
2. Could it have been disconnected on purpose? Of so, why?
I just purchased this 1997 U270 three weeks ago, so I am a newbie at diagnosing it's issues. The isolator has 13.6 VDC on two legs. The rig is on shore power now. The alternator and isolator connections are dirty but tight. I tried reconnecting the terminal, thinking the nut just backed out and slipped off and got a small spark. I am too presumptive and impatient. The loose terminal shown has zero volts on it.
Thanks for your help.
The wire should have a number on it after you peel back the black chafe protection. If you have the wire schematics, you can trace it that way. Or perhaps someone here could look for you if schematics are not available.
Tim,
First thing to do is find out why zero on excite/ignition hot and sense wire. Without them, you are not asking the alternator to do anything.
You can spend a little time tracing them, but don't get carried away. Too easy to run a new excite from any ignition hot source in the engine room and new sense wire from any chassis battery side of isolator. Just make sure to isolate both ends of the old wires before driving.
One of those wires goes to the AC fan on side panel opposite the cooling fans. It could be that one and maybe removed if AC is not working???
Do as Brett said and run a new sense wire to Alt' then run engine and check middle lug on Isolater to see if you then have 13+ volts.
JohnH
Lucky I found the schematic diagrams for the 1997 U270, attached. The wires will be traced tomorrow. I have a feeling that I caused the problem by screwing in the breaker panel in front of the navigator's chair. It was loose and fell down, so I raised and secured it. However, in the process I warped the breaker panel and perhaps disturbed a connection or cracked the Ignition Exciter breaker. Time will tell.
As far has the loose wire in the first photo, it is connected to the sense terminal of the alternator and the remote engine start stop switch. I am not sure why it would draw a lot of current.
Some wiring diagrams related to the alternator.
Tim, the exciter wire does not go thru a breaker it is from a 12v ( with ign on) source direct to the terminal on Alt.
JohnH
I think these years were known for having the alternator excite wire going to the breaker that runs the A/C condensor fan and the remote start relay. It's shown on the lower left quadrant of img 4705 labeled "Isolator board". There have been threads about this in the past and how it's caused problems.
I think following years, FT took the sense (and maybe excitation?) to a more direct location. I think the alternator on my '98 built in sept '97 is self excited because it doesn't charge until I rev to about 1400rpm or so after starting.
My 96 does the same as yours Krush. build 4810.
I deserve a public flogging. The ignition +12 volt source breaker was blown and would not automatically reset. It's no wonder, the alternator was drawing 16 amps from the IGN terminal. This test partially melted the insulation on my ammeter test wires. Upon further tests, the IGN and SENSE terminals are practically shorted together inside the alternator with a resistance of about 2 ohms between them. I have the alternator off the rig, Unipoint model number ALT-0050 and am looking to replace it with something reliable.
Any advice?
I think that a better choice is have a dedicated breaker/fuse near the start battery bank and to run new dedicated voltage sense wire from the alternator directly to the start battery bank area. Sharing a breaker on the isolator panel is not a good idea, and picking up the start battery voltage at the isolator panel can be problematic.
Here are the facts regarding the $170 remanufactured Wilson alternator I just installed. I purchased it from NAPA, since it was identical to the previous owner's unit, which worked fine on a recent 2700 mile trip:
1. Wrong Alternator installed (ALT-0050)
The previous technician installed a one wire alternator and connected the AC output of the alternator (yes, some truck alternators output Alternating Current for some truck accessories) to the DC Ignition input, causing damage / an open circuit in the IGN circuit breaker. Fortunately, Foretravel included several spare breakers, including the correct 6 Amp Ignition circuit breaker.
2. No Excitation
The alternator I installed today needs momentary +12VDC excitation to produce voltage, otherwise it measures .76 Volts DC!
The current Foretravel circuitry has a diode-based battery isolator, so the alternator does NOT receive 12VDC directly. I could jury-rig a solution by installing a momentary push button switch to excite the alternator.
3. No remote sense
All batteries will not be fully charged since voltage sensing is at the alternator output not at a battery. There is a .6 volt drop across the isolator, so the alternator regulator will not make up the shortfall. The charge voltage will only be 13.8VDC at the batteries.
4. Shall I order the correct DUVAC alternator, with the right connections?
This model appears to have the sense and IGN terminals: New 160A Alternator Duvac RV motorhome 2824LC 90772 A001090772 A0012824LC | eBay (http://www.ebay.com/itm/NEW-160A-ALTERNATOR-DUVAC-RV-MOTORHOME-2824LC-90772-A001090772-A0012824LC-/141456188923)
5) Cost, long term
If the alternator does not charge the batteries fully, their life may be shortened during boondocking or long runs without shore power, thus costing more frequent replacement of the batteries and/or running the genny.
Tim,
I would go with option 4 and one of the smart isolators that are now on the market. You might even look at a manual operated switch that takes the place of the isolator if you want a manual system.
According to the spec. sheet that alternator will work for this application and it has the correct mounting.
Pamela & Mike
The U270 came with a 130 amp alternator and a160 amp isolator, if you upgrade to a 160 alternator you will have to upgrade the isolator at the same time.
The alternator that you are looking at is a Leece-Neville KNOCK OFF, the add says not made by Leece-Neville.
Tim,
The choices are to get an alternator (or wire the current one) for an external sense wire connected to the chassis battery side of the diode-based isolator.
OR
Dump the diode-based isolator for either a manual switch such as a marine Perko ON-OFF switch with alternator output and chassis battery to one lug and house battery to the other. Switch can be mounted at the foot of the bed.
OR
Replace diode-based isolator with a relay-type isolator with no voltage drop.
SOLVED!
I unfastened the sense lug from the $170 Wilson remanufactured alternator and connected it to the Foretravel standard sense terminal. Viola! The alternator voltage increased to 15.23 Volts and both engine and house battery voltages were 14.36 Volts. The quiescent (engine off) current demand from the sense line is 3 milliamps, so it will not drain a battery. See the photo for the voltage measurements.
Perhaps in the future, after adding solar, lithium batteries and an improved isolator, I will look back and laugh about this awkward but workable lead-acid solution. Thanks to the forum, led by wolfe10, for providing an intelligent sounding board.
Tim, is that isolator voltage at eng idle or at 1000 RPMs?
The cruise control held the engine at 1000 RPM.
Here is a photo of the old, dangerously-wired alternator showing the the ingition and sense output lines connected to the alternator's AC (Alternating Current) output. Output to output equals SMOKE! This alternator was probably ordered and wired in a big hurry because a self-respecting shop would have ordered a direct replacement DUVAC type alternator.
The photo is blurry, but it shows the above two connections to the AC output of the alternator. Originally I thought they were the sense and ignition inputs, but all three terminals on top of the alternator are the same: AC output. These connections are used for certain fleet trucks.
I've never seen an alternator like that, but it gives me more ideas I pondered before. That's 3 phase variable frequency output. I wonder if that could be wired into a VFD to make 60hz. Voltage could be cranked up to reduce wire size and save the headache of the inverter/huge alternator combo that some do to run roof A/C while driving down the road.
I have been following this thread because I to lost my Alternator. I had it rebuilt and I reinstalled it. The White wire appeared have got to close to the alternator got hot and melted. I rewired and could not get the alternator excited. I found a 15 amp fuse in the dash that was blown. The wire is white and as soon as I replaced the fuse the alternator was putting out almost 15 volts. The batterys are down and I believe thats the reason for the slightly higher voltage. I will recheck when batteries are recharged and the alternator should be at about 14.6 volts. The a other problem now is my frig wont run on 12volts. Could there be a fuse blown if so where should I look? I'm told the frig needs 13.5 volts to run on 12 volts. Any comments would be appreciated.
No, the refrigerator PC board, igniter and gas valve are happy with 12.0 VDC or above.
And, you really don't care what voltage is at the alternator. It is ONLY on the battery side of the BATTERY ISOLATOR that matters. That is where the sense wire is connected-- chassis battery side of isolator. Because approx. .7 VDC is lost across a diode-based isolator, alternator output is boosted by that amount.
Thanks for the quick response Brett, What should that voltage be at engine idle.
Boost up to 1000 RPM. Read at the chassis battery and also at the house battery. Should be in the low 14's.
Brett,
When I use the cruise control to move mine to fast idle, I think it goes to about 1200 rpm. Is that too fast? Is there a simple setting to change it to 1000? What would that do to my slow idle, which I *think* is in the 600-700 rpm range?
Thanks,
Trent
I am not Brett, but your VIP Smartwheel cruise controls should work like this in regards to setting the fast idle; Turn the cruise on, tap the "Resume" button, RPM's go directly to 1200RPM. Hold the button instead of tapping it, RPM's rise gradually until you release it and then stay there. If you tap the "Set" button instead of the "Resume" button, RPM's go immediately to 800RPM and stay there until canceled or subsequently raised using the "Resume" button. If the RPM's are higher than that, say from initially tapping the "Resume" button, holding the "Set" button down the causes the RPM's to gradually decline until you release the "Set" button and then the RPM's stay there until you cancel, release the parking brake, apply service brakes, or put it in gear... which of course also applies to any fast idle state that was invoked using the cruise control. Tapping the "Set" button while idling faster than 800 RPM's while drop the RPM's immediately down to 800RPM. Our coach's normal idle is a very stable 700RPM (plus or minus 2 or 3 RPM on the VMSPC)
Don
Trent,
1200 is fine. My point is that when checking the alternator output, you want the engine RPM above base idle.
I checked voltage at Alternator and at engine batteries. 15 volts at bothe locations. The volt meter on the dash was going back and forth between 14 and 15 volts. It has never done that before.
If you have the OE, diode-based battery isolator, it is not possible to have the same voltage on alternator side of the isolator as on the battery side, as you loose approx. .7 VDC in the isolator itself (turns into heat-- hence all the aluminum fins to dissipate the heat).
If you don't have a diode-based isolator, let us know how yours is wired.
Brett, thanks for your help. I believe the isolator is original. Would I be able to tell by looking at it. With my Primus system its very cluttered and very dirty. I will look at it and try and take a picture.
Brett, here is some info that hopefully helps you, help me. First per Foretravel it is a diode isolator. Here are some readings I took today. First engine battery 13.17 volts engine off. Alternator Pos. 1.02 volts. Neg. 0. exciter 0. Sense wire 13.04. Isolator left conn.11volts. center. 4.9 volts. Above all with engine off. Engine running at 1200rpm battery 14.2-15.3. Alternator pos 13.99-15.4. neg.0 Exciter 3.5 volts Sense conn 14.1-15.3. Isolator center 13.2-15.7. left 14.49-15.11. right 14.89-15.11. Volt meter fluctuates between 14 and 15 volts at idle. At 1500rpm stays at 14 volts. Engine at idle lumbers along with voltage change and so do 12 volt interior lights.
First, that is quite a range of voltage with engine at steady 1200 RPM. Since your "Sense conn 14.1-15.3" reading at the alternator sense terminal is not only wide-ranged, but 15.3 is dangerously high, you could have an alternator/regulator problem. That reading, which is/should be the same as at the chassis battery bank should be in the 14.0- 14.2 VDC range-- yes, a tenth of a volt plus or minus is fine.
And, this will give a reading at the B+ terminal of the alternator and the center lug of the isolator (the large-gauge wire connects them (read same number on each end) of about .7 VDC higher as you loose that amount to heat in the isolator.
But, first, I would verify that connections at alternator, isolator and batteries are clean and tight and than the batteries are in good and not deeply depleted condition, as these can affect readings.
Further, if the isolator is failing, you can bypass it to further identify the problem.
With engine off and chassis battery disconnected for safety, remove at the isolator three wires:
Wire from alternator B+
Wire to the chassis battery
Sense wire
Being very careful to not allow any to touch any metal (ground), use a bolt to connect all three. Now reading at B+, at your jerry-rigged connection and at chassis battery should all be in the 14.0-14.4 range.
Thanks Brett, I will disconnect the engine batterys and clean before reattaching as they are dirty. While disconnected I will disconnect and clean connections at the isolator. Those connections are very dirty and rusty. As stated earlier The connections are hard to get to. And I will very careful not to short across any ground. Maybe the connections are adding resistance to cause voltage to be high. I cant thank you enough for your help.
I forgot to mention I will try the bolt method to see if voltage will come down.
The only safe way is to make sure you are not connected to a shore line AND disconnect BOTH battery banks from the RV.
Trent
Well here is an update on my progress. First I disconnected both the house and engine batteries. I then crawled under the coach to access the isolator. I removed wires one lug at a time cleaned them with electric parts cleaner and steel wool. Then applied dielectric grease and reattached and tightened. I found several to be somewhat loose. I then restarted and found the voltage still fluctuating. I have three optima red top batteries that would charge but I didn't know how old there where . I removed all three batteries and called optima to fine two batteries eight years old and one was nine years old. I took them to the local car quest and had them load tested. I have two failed batteries. I will pick up three new batteries Saturday and install . I am hoping this solves my problem. Brett and those on this thread thanks for your suggestions. I may be slow but I don't give up.
Well my problem still exists, I installed three optima red tops this morning. I measured 12.3 with engine off. When I started the engine my voltage is still high at the battery 14.8 at 1200 rpm. Also inside the coach a clicking sound was comming from the dash behind the dash air box. When I turned on the fan the clicking stopped. Dash lights appear bright and flicker. My next step is to remove the alternator and take it back to where I had it rebuilt. I believe the problem maybe the votage regulator. Any thoughts?
Before doing anything else, fully charge those new batteries. 12.3 is close to 50% discharged.
If on shore power, hit boost switch so that the inverter/charger will charge the house bank and the boost solenoid (yes, assuming it is working) will charge the chassis battery bank. VERIFY with voltmeter.
You should also see the amp rate of charge go way up when the boost switch is turned on.
Only after everything is back to "the way it should be" would I do any more!
Ok I have left the coach with a battery tender on. It should charge at a slow rate. I will check tomorrow afternoon.
How many amps does the battery tender put out?
How many amp-hrs in the chassis battery bank?
I.E. "can you get there from here".
The advantage of the inverter/charger with boost switch is that it will start in bulk mode and as as voltage rises/amps decrease will automatically drop voltage.
Most battery tenders do not have the needed to bring up large battery banks discharged to 50% capacity. They are great (and designed to) MAINTAIN only.
Its a 2 amp. I do have a larger charger I can put on with auto shutoff.
Good, because a 2 amp charger and several hundred amp-hr battery bank 50% discharged won't get you there!
Brett, I took my 10 amp charger and replaced the battery tender. This charger will reduce amps as batterys charge and then go to a trickle mode. Thanks again.
Well Brett, here the latest reading take this morning after the new batteries got a full charge. Engine off, engine batteries 12.69 volts. House batteries 13.70 volts. Engine running at 1300 rpm, engine batteries 14.52-15.02, house batteries 15.22-15.27. Alternator 7.90-15.23. Very strange.
Yes, sounds like an issue with the voltage regulator and/or alternator.
Thanks Brett, next step is remove and return to rebuild shop.
Well first let me say Thank you Brett for staying with me on this issue. Now I took the alternator back to the rebuild shop and bench tested it. An of course its perfect. Upon reinstalling I discovered in my earlier haste to install, I installed the excite and sense wires in reverse. Pretty dumb huh. Now that its installed correctly, the voltages are as follows at 1200rpm Engine batteries 14.04v. House batteries 14.24v and Alternator 14.98v. No fluctuation . All is well I have clean terminals at the isolator, new engine batteries and a rebuilt alternator. I can only that shop rates around me are $145/hr. I don't mind spending money on items but labor money can saved by listening to the help offered on this forum. Many thanks again.
Glad you got the wiring sorted out.