desertrat Posted November 23, 2009 Share Posted November 23, 2009 Just wondering if anyone knows anything about this P>O>S> that's on my rig. Looks like a It seems to be working, but the middle wire seems small for the alternator wire. I think it is 14 gauge. Also, my SLI battery reads 14.64 V while engine is running, but the coach reads 12.64. Wondering if the wires are too small of a gauge and maybe I'm losing volts through the run because of resistance. Looks like it is 12 gauge wire and runs about 10 feet to the coach battery. Just FYI, the reading at the isolator is the same as the coach battery off the posts. Also I'm getting 13.72 V from the alternator to the isolator. I'm trying to make sense of all this. Forgive my ignorance. One photo-The isolator looks like a mechanical relay or solnoid type. I hooked up a spare multimeter to the coach battery and mounted it. I call it my poor mans battery volt minder. Happy Trails By the way, the photo with my finger also shows a finned block about 4 inches high by 2 inches wide. Not sure what it is. Any ideas? Quote Link to comment Share on other sites More sharing options...
Maineah Posted November 23, 2009 Share Posted November 23, 2009 Can't tell what you are pointing at but you have a solenoid type. Where does the black wire go? It looks like it loops around and connects to the other side. Does it "click" when you turn the key on? The alternator is not connected to it, the small wire goes to the key switch and only carries the load for the coil in the solenoid. One wire goes to the truck battery and the other to the coach battery the alternator charges the truck battery wired by Toyota there is and extra wire that goes to one side of the solenoid from the truck battery the other side goes to the coach. When the key is off there is no flow from the coach to the truck battery this keeps it from draining the truck battery. When you turn the key on the solenoid connects both batteries together. So with the engine running you should have pretty much the same voltage on both big terminals they look pretty nasty take them off and give them a good cleaning. They do go bad but seldom make sure it "clicks' when you turn the key on. What you can do is remove the wire to the coach turn the key on and check the voltage on the empty terminal should be real close to the battery voltage watch the coach wire it will be "hot". If you put it all back together and the voltage is still low it's bad inside (burnt contacts)replace it but be sure to get a continuous duty solenoid it looks like a Ford starter relay but it's not don't let them sell you one it will burn up in about an hour. Quote Link to comment Share on other sites More sharing options...
desertrat Posted November 24, 2009 Author Share Posted November 24, 2009 Thanks again Maineah. I'm not with my rig right now, but will see where that black wire goes when I get back home. I appreciate the advise. I thought I read somewhere the middle wire on these isolators come from the alternator, but I can see it goes into a wrap of wires that look stock from Toyota, probably, as you said, to the ignition. It's hard for me to follow some of these wires around on this vehicle because they dissapear under the engine block. I'll check to see if that puppy clicks when the key is turned on. How do you know if an isolator is a cheap one when you are buying it? Should I avoid Kragen auto parts type places? Also, is there a way for me to figure out how much power my alternator is cranking out? It's old with no apparent writing or tags on it. Thanks in advance Quote Link to comment Share on other sites More sharing options...
desertrat Posted November 24, 2009 Author Share Posted November 24, 2009 Sorry, I missed the part about getting a continuous duty solenoid type. I'll look around Thanks Quote Link to comment Share on other sites More sharing options...
Maineah Posted November 24, 2009 Share Posted November 24, 2009 If it was a solid state isolator it would have wires going the the alternator. The black wire is some thing I would like to know about it looks like it just loops around and goes to the other side if it does it defeats the purpose of the isolator. Quote Link to comment Share on other sites More sharing options...
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