Gulfstream Greg Posted June 26, 2014 Share Posted June 26, 2014 About 30 miles into a trip battery icon and transmission over heat light started coming on intermittently at first then eventually stayed on. Thought it was strange that the trans high temp also lit up. Pulled over and ran some voltage checks. Note that I am using a solid state isolator. At idle I had 14 volts on all the isolator terminals including the exciter terminal.But after increasing rpm the lights would come back on and voltage would drop to nominal battery voltage. Luckily we were convoying with two vehicles and made a run to a nearby auto parts store and got a new alternator. 30 mins later it was installed and I had a 14 volt charge. So off we went. Some time later I realized that my charge gauge (tach dash) was looking like it was on the low side. A few miles further and the needle dropped even lower. So I found another spot to do some investigating. I now had no voltage on the exciter terminal. The power feed to that exciter terminal is fused and I found the fuse to be blown. Replaced the fuse and it blew again. So I had to move the alternator cable to the starting battery terminal and the alternator was happy. Since we headed to a rv park with shore power I was not worried about charging the coach battery.. So I have to eat crow because sometime ago I said that solid state isolator's never die. I have not investigated the isolator to see exactly what failed. The exciter terminal appears to be shorted to ground. I have searched high and low for an actual schematic of the isolator internal components but have had no luck. Quote Link to comment Share on other sites More sharing options...
Maineah Posted June 26, 2014 Share Posted June 26, 2014 About 30 miles into a trip battery icon and transmission over heat light started coming on intermittently at first then eventually stayed on. Thought it was strange that the trans high temp also lit up. Pulled over and ran some voltage checks. Note that I am using a solid state isolator. At idle I had 14 volts on all the isolator terminals including the exciter terminal.But after increasing rpm the lights would come back on and voltage would drop to nominal battery voltage. Luckily we were convoying with two vehicles and made a run to a nearby auto parts store and got a new alternator. 30 mins later it was installed and I had a 14 volt charge. So off we went. Some time later I realized that my charge gauge (tach dash) was looking like it was on the low side. A few miles further and the needle dropped even lower. So I found another spot to do some investigating. I now had no voltage on the exciter terminal. The power feed to that exciter terminal is fused and I found the fuse to be blown. Replaced the fuse and it blew again. So I had to move the alternator cable to the starting battery terminal and the alternator was happy. Since we headed to a rv park with shore power I was not worried about charging the coach battery.. So I have to eat crow because sometime ago I said that solid state isolator's never die. I have not investigated the isolator to see exactly what failed. The exciter terminal appears to be shorted to ground. I have searched high and low for an actual schematic of the isolator internal components but have had no luck. It's nothing but diodes Greg. The "E" terminal diode keeps the the battery from back feeding the IGN. with the key off. The alt. need to see 12 volts at the "B" terminal to start the charge cycle so the "E" sends the ign 12 volts to the "B" through the diode and it blocks the return flow to the "E" so you can turn the truck off! Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted July 2, 2014 Author Share Posted July 2, 2014 It's nothing but diodes Greg. The "E" terminal diode keeps the the battery from back feeding the IGN. with the key off. The alt. need to see 12 volts at the "B" terminal to start the charge cycle so the "E" sends the ign 12 volts to the "B" through the diode and it blocks the return flow to the "E" so you can turn the truck off! Yes but what kind of diode? The e terminal is now a direct short to ground. Quote Link to comment Share on other sites More sharing options...
zero Posted July 2, 2014 Share Posted July 2, 2014 . At idle I had 14 volts on all the isolator terminals including the exciter terminal.But after increasing rpm the lights would come back on and voltage would drop to nominal battery voltage. You've got me confused. The only "exciter" terminal I know of is on the alternator. Not the silicon rectifier-type isolator. That is unless you've got some contraption I've never seen before. The simple isolators used on many RVs are just a couple of silicon rectifiers that split the alternator charge between to batteries and do not allow backwards flow of current (to prevent discharge). An "exciter" it just what it sounds like. It energizes or "excites" something. The alternator has an exciter circuit and cannot work without it. A simple rectifier-isolator does not. Power just comes in at one point - and comes out in two places. If you had a relay-type isolator -then that does have what you could fairly call an exciter terminal. That is the terminal that makes the relay close when it gets power. In regard to rectifier isolators failing? I've seen many fail. All it takes is one surge over the rating and they are toast. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted July 4, 2014 Author Share Posted July 4, 2014 You've got me confused. The only "exciter" terminal I know of is on the alternator. Not the silicon rectifier-type isolator. That is unless you've got some contraption I've never seen before. The simple isolators used on many RVs are just a couple of silicon rectifiers that split the alternator charge between to batteries and do not allow backwards flow of current (to prevent discharge). An "exciter" it just what it sounds like. It energizes or "excites" something. The alternator has an exciter circuit and cannot work without it. A simple rectifier-isolator does not. Power just comes in at one point - and comes out in two places. If you had a relay-type isolator -then that does have what you could fairly call an exciter terminal. That is the terminal that makes the relay close when it gets power. In regard to rectifier isolators failing? I've seen many fail. All it takes is one surge over the rating and they are toast. Here is the schematic. Typical normal isolator for toyota. http://toyotamotorhome.org/forums/index.php?app=gallery&image=997 Quote Link to comment Share on other sites More sharing options...
zero Posted July 4, 2014 Share Posted July 4, 2014 Interesting. I've never seen one before on a Toyota RV but obviously, I've not seen them all. Those rectifier-based isolators were very common on vehicles with internally regulated Delco alternators. E terminal on the isolator got hooked into the excite circuit for the alternator. My 88 Minicruiser came OEM with a three-pole rectifier-based isolator with no "E." Same with my Chinooks. I gave up using them on anything long ago. Seen too many failures and also do not like the voltage drop across the rectifiers that they all have. I've yet to have a single failure using a relay instead. They come in "dumb" versions that just come on whenever the ignition switch is on. Also in "smart" versions that only connect the front and rear batteries after the front (cranking) battery is fully charged. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 4, 2014 Share Posted July 4, 2014 Toyota alternators require 12 volts to the "B" terminal in order to charge know as a 4 wire isolater system. The isolator blocks the B+ to the to the "B" terminal on the alternator and with out that signal it will not charge. The "E" (exciter) terminal is connected to keyed +12 volts same type a connection that would run a solenoid. The diode allows the the power to flow to the "B" + from the "E" but not back other wise you could not turn the truck off. If your "E" terminal is shorted the diode most likely has gone to ground inside the isolater.. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 4, 2014 Share Posted July 4, 2014 The diagram you posted Greg a simple diode could be added between the ign and the "B"+ on the alternator and then a 3 wire isolator could be used. But no matter how it's done the "B" terminal has to see 12 volt before it will charge. The isolater 1 and 2 terminals are blocked to the the "B" terminal on the isolater other wise in essence the batteries would be joined at that point so with out the "E" terminal terminal diode there would be no B+ at the alternator so basically the isolator is nothing more than a heat sink with 3 diodes. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted February 4, 2015 Author Share Posted February 4, 2015 OK here is an update. I am finally getting around to replacing my isolator. I am moving away from the diode type to this http://www.carid.com/pac-audio/pac-audio-accessories-16830926.html Opinions are welcome as I will not have it in my hands until some time next week to install. Quote Link to comment Share on other sites More sharing options...
Totem Posted February 4, 2015 Share Posted February 4, 2015 I would go with one of these: http://www.waytekwire.com/item/80066/?gclid=CJjCm8rQyMMCFcRQ7AodKgcA-Q and then in your rig's dash run two voltmeters (led or LCD digital in any color) in through the firewall to your rig. 1.) its cheaper 2.) you get an exact real time display of your rigs coach and main truck voltage in volts instead of some kind of led bar guage thats red or green. Once i put in my dual voltmeters all electrical problems in my rig ceased. I know exactly when an alternator gets fritzy and or can watch charging progress on the coach; Just my opine. I posted a youtube video on this setup in here somewhere. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted February 4, 2015 Author Share Posted February 4, 2015 There is a voltage drop across diode isolators. The diode isolator is what blew up taking out my alternator. I do use voltmeters to monitor voltages both in the cab and in the coach. I think the idea of the PAC multi color led is more of a status and warning system. But the different colors do represent specific voltage range states. A yellow led high voltage is 12.4-11.5 volts. I think 12.4 is considered 80% charge, 11.3 and below is considered drained. So yes to better evaluate battery state a volt meter is an vauluable tool. My coach panel is just a little bit custom. Here is a pic The panel is fed by 6 ga. wire directly from the coach battery, More info on the panel here http://toyotamotorhome.org/forums/index.php?app=gallery&image=3221 Quote Link to comment Share on other sites More sharing options...
Totem Posted February 4, 2015 Share Posted February 4, 2015 omg, thats awesome! ^ its like the flux capacitor meets steam punk,I love it. diode isolators are your term for solid state isolators right? On the unit you are considering, whats with the crazy wired and fuse box that displays battery condition on the isolator you had a link to? -So its a solenoid type isolator with another box to measure batteries? seems like extra $ for something your panels do much better job of. As far as voltage drop on the solid state (diode) isolator; its very very tiny and yes mine also blew my alternator when my fridge blew it also...you are so right; its a weakness in that type of setup. Still, I do like the voltage and current regulation that the solid state provides that solenoids do not. generally speaking when solid states fail its something else that's drawing on them that's the cause. Personally I find the alternators that these toyotas use ( stock) to be very very fragile and their voltage regulators will get spiked really easily. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted February 6, 2015 Author Share Posted February 6, 2015 Yes a diode is a solid state device. Normal relay type solenoid isolators just work off of the ignition switch run side if wired correctly, Correctly means on the run circuit and not the ignition on circuit. When the ignition is in run position the solenoid gets power and closes or energizes. The pa-sprc200 monitors the alternator side voltage and when it drops down to a certain state (11.5 volts) disconnects the coach battery. It's really just a fancy solenoid that can monitor the voltage state. One thing it does do is not energize until the engine is running. Must see the higher voltage on the alternator side I guess. As I stated above about correct wiring of any solenoid it is important that the coil side is wired to the run circuit and not the ignition on because if the starting battery goes bad and the coach battery gets connected during a start that high amperage the starter needs could burn up the wires on the coach battery side. Quote Link to comment Share on other sites More sharing options...
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