Re: Alternator Reply #25 – July 17, 2012, 04:10:01 pm It has been wired this way for two years and two vacations with no apparent harm and I didn't know enough about it to be worried until I noticed my batteries were in boost mode all the time. We never dry camp so it didn't become apparent. The Delco they put on in Jackson has a ground, sense and POS output...so three wires total. I'm still looking for what happened to the forth wire that should be present on a Foretravel (according to FOT). The output post on the Delco is the one that needs 7.5V to start putting out (but only for an instant). They jumped the sense post (which comes from engine battery side of isolator) creating a condition just like when the alternator is running only getting power from the engine side of the isolator instead of alternator output and feeding it to the center post...which is the problem...boost all the time. I really need to find the missing forth wire (12V hot when ignition is on). Maybe the auto electric shop will buy my Delco and sell me the correct four wire one and it won't be too painful. I going to see what he thinks the next time I'm over at the coach. Right now the alternator is out and no risk of magic smoke. Quote Selected
Re: Alternator Reply #26 – July 17, 2012, 06:45:41 pm No. On my Delco (which is the wrong alternator), the excite is on the main output post (self-exciting). Without the isolator, as on a big rig, there is always voltage on the output post as it is connected directly to a battery. A self-exciting alternator needs 7.5V to be present on the main output post to start putting out. The sense post is next to it. Now, the sense post is, on newer Foretravel units, directly to the engine battery side of the isolator according to James T. On older ones like mine it is supposedly on the starter (I think) but the schematic for the 92 U280 that Pierce posted shows the engine battery side of the isolator also so I'm not sure other than it has 12+ volts all the time and is reading battery voltage. On the correct alternator, according to FOT, the DUVAC post (which in different applications has different functions) is for the sense wire. Foretravels do not use a dual voltage arrangement but they do use the alternator that is capable (DUVAC). Then there is a wire and a post for 12V when the ignition is on (for external excitement). There is the main output post (+) and the negative to engine block. Four wires total on a Foretravel alternator. Big rigs all use a three wire set up. The guys in Jackson cut my wire that was off the ignition and taped it up (I think). This afternoon I found a wire in a run of wires right by the alternator that obviously was cut or spliced and taped up. I tested it and it only lit the test light when the ignition was on. I have two choices: buy a correct new alternator and wire it as above or run a wire from the engine battery side of the isolator with a solenoid like the boost solenoid that activates when the ignition is on and take that to the main output post on my Delco alternator so that when I turn the ignition on there will be greater than 7.5V present so that the alternator begins to put out. The sense wire will go to the sense post with no jumper as it should. The POS and NEG connections as normal also. I am going to clear this plan with the auto electric shop. It is what the Delco tech told me to do to make their alternator work and to interrupt the loop which is defeating my boost switch that the Jackson truck shop created with that jumper between the sense and output posts. They needed 12V to the output post so they got it the easiest place available...on the next post with the sense wire to the engine side of the isolator where there is always 12+ volts. Quote Selected
Re: Alternator Reply #27 – July 17, 2012, 07:02:57 pm Dwayne... if that red wire goes hot with the ignition key then that's the one you want for the 4-wire setup.If you decided to keep the system factory-original (more-or-less) you can always find a Leece-Neville (or equivalent) on eBay. Here is one link to a 160A unit for under $200: LEECE-NEVILLE NEW ALTERNATOR 2800JB | eBayA search for "hehr series 25 powerline alternator" was disappointing but maybe I added too many words. A search for Leece-Neville was more productive. I don't think it matters much where you get the constant +12vdc for sensing as long as it's constant and not a lot of voltage drop. Anyway, you already have that connection. I'm pretty sure that the red wire with +12vdc with the ignition is the other one you need.So for about $200 you can get back to where you were.BTW: What happened to the original alternator? They keep it and give you the Delco instead? Craig Quote Selected
Re: Alternator Reply #28 – July 17, 2012, 09:18:50 pm The Leece Neville is a much better alternator than the Hehr powerline, IMO. I worked on motorhomes for a lot of years and most have Leece Neville on them Quote Selected
Re: Alternator Reply #29 – July 17, 2012, 09:27:17 pm Dwayne, You might take a look at this link, it describes exactly the problem you're having with the Delco and how it was fixed. And, it was on a Foretravel. replacing a Leece Neville alternator with a Delco | Prestolite NewsChuck Quote Selected
Re: Alternator Reply #30 – July 17, 2012, 10:20:26 pm Wow...Chuck...that sounds just like my saga. I am stunned that this battery / isolator system is so poorly understood by so many supposed professionals. At least I now know what needs to be done or what I can probably get away with to fix it. Yes, Craig it is a red wire and it was sticking out just a little from the plastic tube holding a bunch of wires. When I saw the electrical tape I had a good feeling. For $200 bucks I might as well do it right and keep the Delco for an emergency. Yes, they kept the old alternator which I now realize was really dumb on my part. I assumed an alternator is an off the shelf part and every backyard mechanic can hook one up. WRONG! I've made the comment in other threads that only someone with a lot of aptitude or a lot of money should own one of these things and this is another case in point. The main thing for most of us on this forum is to understand that if your alternator fails you can't go just anywhere to have it fixed and it is unusual enough that you will have to educate yourself on the unique set-up and be very proactive with regard to the repair. Trucks have a direct connection between battery and alternator and the newer alternators all self-excite with voltage from the battery being present on the alternator output post. Our coaches don't work this way. I don't know if this is a common to all coaches or if Foretravels are unique but the truck shops won't have a clue and an RV guy trying to tell them that they don't know how to wire an alternator probably won't go over well. Quote Selected
Re: Alternator Reply #31 – July 17, 2012, 11:10:07 pm Quote from: Dwayne – July 17, 2012, 10:20:26 pm I've made the comment in other threads that only someone with a lot of aptitude or a lot of money should own one of these things and this is another case in point. The main thing for most of us on this forum is to understand that if your alternator fails you can't go just anywhere to have it fixed and it is unusual enough that you will have to educate yourself on the unique set-up and be very proactive with regard to the repair. No one can be an expert on every facet of motor homes. This is the real value of this forum and of having Foretravel in business in the same place with many of the same people. I read the other forums and I'm just astounded at the level of misinformation out there. Basically, it's every opinion counts just as much as one from someone who actually has a clue. At least here we don't have to try to figure out who is knowledgeable and who isn't. Essentially, every member is knowledgeable about something useful; or at least is observant enough to give out clues.However, at least in electrical systems, as over-the-road trucks get more sophisticated in the area of living quarters - and as trucking companies crack down on running 500hp engines just to keep a heater or a/c going in the condo - the level of expertise among the mechanics will increase. A lot of these trucks are not much different than motor homes when it comes to the "house".CraigIt Quote Selected
Re: Alternator Reply #32 – July 17, 2012, 11:20:16 pm Dwayne, it answered a lot of questions for me too when I was in the alternator phase. (!) Anyway, as a plug for Leece Neville/Prestolite, their tech support and online forum was very helpful and their alternators seem to be of first quality. And, as a really big plus, they actually give modification instructions so you can take one of their standard alternators and convert it to a DUVAC alternator if you're wanting to save some cash. That's the route I took, and posted the info on this forum a couple months ago. Not many mfgs do that sort of thing anymore. Chuck Quote Selected
Topic: Alternator