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JNewberry 05-12-2019 02:51 PM

DUVAC Alternator
Hi, new here. I have a 2003 Endeavor 40' motor home. I replaced the Leece-Neville 160 amp alternator some time ago but have had an issue ever since with chassis batteries draining when parked for more than two days. As I repaired a few unrelated systems (ignition switch, leveling pin pad, oil pressure sender) I have been trying to isolate problem. I have been disconnecting the chassis battery switch when parked. So, from the disconnect there is a big red wire that feeds fuse panels up front. Guessing problem was there I disconnected each fuse panel and observed voltage drop of 1/2 volt per day. The only other wire is a "DUVAC" fuse wire that goes to alternator. With this fuse removed, chassis voltage stays up. I am wondering if the rebuilt alternator was not wired for DUVAC. I hate the thought of pulling it again as I removed it previously to have it tested and it was OK. Found DUVAC fuse was blown back then. Anyone here sharp on this?

Old Scout 05-12-2019 03:10 PM

...typical DuVac wiring config has two large + and - wires; and two small wires--one for the battery sense and one for the ignition...not sure what happens if you reverse the two small wires?????

JNewberry 05-12-2019 03:17 PM

Thanks. Will crawl under and check wiring tomorrow. I bought the replacement at a truck supply so need to check with them too. I read coaches use DUVAC and trucks don't on same alternators. Something to do with rear engine/long wire runs to front on DP's.

Old Scout 05-12-2019 03:23 PM

...think using a DUvac system has more to do with when it was popular to use a battery isolator to control battery bank changing---alternator can't sense voltage thru the diodes in the old style isolators....

153stars 05-12-2019 03:43 PM

Is it discharging at same rate or matching with the house batteries.I found a jumper between the positives on diode type isolator. Probably because was bad and or alternator upgrade.It was recommended to dump isolator and get a modern marine isolator / combiner that charge house batts when chassis is full. Can do boost as well replacing boost solinoid and doing the job of both.

bluepill 05-12-2019 03:48 PM

Here is some good basic info. on wiring for the DUVAC series.

JNewberry 05-14-2019 05:21 PM

OK, so what I thought was the boost solenoid must be the isolator. There is a 3 (small wire) gismo labeled isolator delay wired to this solenoid. The solenoid if energized would connect house positive to chassis positive. To answer another question, only the chassis batteries discharge. I also noticed on my alternator there are three terminals for the signal circuit. I am connected to the center. If I remember I called the truck supply where I bought the rebuilt and asked them to look at my old one to see which terminal had marks from connecting. The alternator diagram shows connected to left terminal but does not show the pos/neg cables in right place either. Yesterday when I turned on the chassis battery disconnect I got everything on that you would get with key in RUN. Even with ignition switch removed and disconnected. Alternator diagram shows a relay that I think could cause this but cannot find any plug in relay that turns everything off when pulled. Anybody know where this relay is? Other than that I would have to have a dead short between battery and ignition wire from switch. Coach has been parked here in desert for a long time and was parked two years at an RV dealer on consignment before that.

JNewberry 05-15-2019 12:23 PM

OK, the little light over my 68 year old brain came on this morning. The "short" that appeared mysteriously the day I only looked at wires showed up then because it was the next time I turned on batteries after checking alternator the day before. I shorted something in the alternator when I pulled the DUVAC fuse while it was running. IGN wire energizing through alternator from the DUVAC wire. Pulled fuse and back to normal (dash board not lighting up). I think it is going to be an expensive lesson.

JNewberry 05-29-2019 09:29 AM

Thanks again to all that tried to help. I found on Amazon a new exact replacement alternator and my battery drain issue is resolved. No more rebulds for me. And price was $250, free shipping. 5 ,years ago I paid $227 and drove an hour for the rebuilt.

CountryB 05-29-2019 12:12 PM

1 Attachment(s)
Sounds like you have it worked out ...

Here's a basic diagram on the DUVAC and connections to either the Delco 28SI alternator or Leece Neville. With the LN you need to be sure there is a "remote sensing" terminal on the alternator as it is an option on some models. The Delco includes it as standard.

JNewberry 05-30-2019 11:48 AM

Thanks. I had a generic diagram but my Endeavor is wired a little bit different. The Isolator is a solenoid. The positive lead to alternator is connected to the starter positve lead. From there a larger cable goes to chassis batteries. Then a lead from chassis batteries to one side of solenoid and one lead to other side from house batteries. And a small "isolator delay" module to solenoid coil. What really threw me is I replaced the alternator with a rebuilt, wired it wrong at first and blew two fuses. Then my battery drain issue started. I removed that alternator and returned it to the truck supply house. They had it tested and claimed it was working fine. I reinstalled it and mistakenly assumed the drain was some other component wired to chassis batteries. I used the coach like this for a couple of years, disconnecting the chassis switch if I was parked more than two days. I'm going to sell it (hopefully) now and did not want to pass this headache on to a new owner. By the way, this coach was on consignment two years but I found it on their back lot and nobody knew why it was there. The sales manager that thought he could sell it easily had been fired and my fault for not checking on it sooner. Anyway it was parked closed up through two high desert summers. Checking out everything, everything with any kind of electronic control did not work. I managed to fix everything except the back up camera system by unplugging and plugging back in. This worked for heater, a/c's, microwave, and refer I needed to reset a thermal cut out added by Norcold recall in 2011. If anyone has similar issue (No refer operation with steady red light on thermal cut out clamped to coil in outside unit) you reset by placing a strong magnet over the red light. Another weird thing, my leveling system was not working and I was ready to order the $600+ new style pin pad. Now that I replaced the alternator and voltage gauge, the leveler works. Although it could be intermittent and waiting for a prospective buyer to be here to let me down.

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