I am posting for my husband Mark:
Approximately a month ago, our leece-neville alternator with a DUVAC signal input went out. Simultaneously, our tach and our engine compartment fan quit working. Then after we replaced alternator the tach started working and the engine compartment fan started working however, the engine compartment fan would not shut off and the tach would only work if the running lights were on. So i proceeded to find what controlled the engine fan. (originally, the engine compartment fan would run for 30 minutes after shutdown which told me that it had to be an off-delay timer relay.)
I was able to find the off delay relay controlling the electric engine compartment fan. It is initiated by the output of the alternator charging terminal that goes directly to the center post of the isolator. The current problem is that there is always 12v at this output even when the engine is turned off which also drains the battery over time. I have determined that this voltage is bleeding through the alternator from the duvac sensing wire. So I thought this new Alternator was defective and put on another new alternator and got the same results. So I am thinking these newer alternators from this manufacturer are wired differently than the original ones. OR - there is another relay somewhere that is in the DUVAC wire circuit that interrupts its continuous connection?
Can anyone verify one or the other. Maybe look on your motorhome and determine if you have continuous 12v at the charging port of the alternator and continuous 12v at the DUVAC port of the alternator with engine off.)
(My second issue is the tach - when the engine it first started, the tach works fine. After about one to two minutes it quits working. But if I turn on the running lights, the tach works. Thoughts?)
We have a 1996 Beaver, model 38’ emerald marquis with a cat 3176B engine.