PhilOien

Hi Brett, thanks for your rapid response. I was curious if anyone had any experience with the different voltage drops across the 2 isolator channels. I have a 1996 Country Coach Magna with a Leece Neville alternator with the "sense" lead as you mention, and everything has worked automatically for years, until recently, when the inverter started shutting down. The house batteries are about 10 months old, and the engine battery (San Diego, so I only use one) is only a month old, but the problem started about a month after I replaced the house batteries. I do almost exclusively "dry camping" and like to recharge things when underway. I also prefer to keep things automatic, because automatic means I don't have to remember to isolate when it's needed. I put all the troubleshooting details in my post to maybe assist others in their own troubleshooting. I'm a DIY for most things (I like to put money in the fuel tank, not Techs' pockets), and this gremlin is a new one for me, and I've been a professional mechanic for 25 years with a electronics technical school diploma foundation. I know PowerLine doesn't actually manufacture the diodes in the isolator (a semiconductor company does) so I'm inclined to see if I can take apart the isolator, even if it means I destroy the isolator in the process (it's not working right, anyways) to discover what's going on. I'm guessing that the isolator is two banks of diodes in parallel and that possibly one bank has had one or more , but not all of the diodes burn out, not short out, causing the forward resistance to increase and thereby increase the voltage drop. I don't know what's going on, but like I said, I was just curious if anyone has any experience in this area.

I have this same problem with my house batteries overcharging, and my engine battery not whenever the engine rpms are above idle. I noticed the problem after my inverter (Heart Interface 2500) started shutting down from an over-voltage condition when we were underway, and the a/c outlets stopped working. I've checked the voltages at the batteries with the hi-idle on and the engine batteries were at 14.4 and the house batteries were at 16.2 upon arriving home after a trip (all fully charged). I removed all the batteries from the coach, and removed all the wires from the isolator terminals. I checked the isolator, a Powerline 190 amp, with a multimeter that has the diode check function. With the meter positive on the center terminal, the forward biased voltage drops were 0.453v and 0.481, and with the meter negative on the center terminal, the reverse bias was infinity, so the isolator checks good with this test. However, I wanted to test the isolator when it was carrying a charge current, so I split my house batteries into 2 banks, with a common negative, and the positives run with some identical 10 ft. 2 ga cables with ring terminals to the outboard terminals on the isolator. I attached a separate 2 ft. 2 ga cable with a ring terminal on one end and a lead post terminal on the other end to the center terminal of the isolator. I tightened all the connections, and hooked my big portable charger/booster up to charge the 2 banks thru the isolator; each thru a separate diode bank of the isolator. Both battery banks (6v golfcart) were at 12.88 volts to start. There was an immediate difference in applied voltage between each bank, and it increased as I went from low to medium to high to start on the charger charge settings. I measured the voltage drops across the 2 diode banks, and they were 3.2v and 2.2 volts when on high. There is at least 1 volt difference in the voltage drops across the diode banks, so to assume that whatever the alternator is putting out is applied equally to both banks is incorrect. My isolator works, but probably has a problem (as the original poster was thinking). The link above to the Hehr website doesn't work from my iPhone. The server cannot be found. I'd like to troubleshoot the isolator before I buy a new one, or get something better, since the price is the same.