desertrat Posted January 30, 2011 Share Posted January 30, 2011 So, I don't have pictures yet, but on my 1988 Horizon, I have a solenoid type battery isolator. Where it sits, there is a single wire running from the back side of the isolator to a small (maybe 1 1/4" x 3/4") black plastic box which has two connector tabs, (male spade type) one at each end. One labeled batt, one aux. The coach battery wire runs from the Aux side of that part back to the battery. I broke one of the tabs whilst taking everything apart to clean isolator connections. Rode my Honda trail 90 to the auto parts place where the guy told me it was the same as a bus fuse. I bought the replacement part which also had Batt and Aux labeled on it. It was a standard 30 amp gizmo with 2 posts on it., but it was made of metal, not plastic. I installed the new part, changing the connectors from spade type to ring type. With everything clean and installed, my rig wouldn't start. Just a click. I yanked the new part out, soldered the old one and reinstalled it. Bessie started right up. I don't know what that small plastic part is. Anyone know without photos? To confuse you more, some of the wires also go to a 3"x3" metal box with fins on it. I have no idea what that is either. I'll post some pics in a few days. When I get home, I'll have to check and make sure the coach battery is charging. I guess I do that by testing Volts while the engine is running? I guess there is supposed to be an audible click in the isolator when key is turned on too. Thanks in advance Steve Quote Link to comment Share on other sites More sharing options...
Maineah Posted January 30, 2011 Share Posted January 30, 2011 Pictures would really help sounds like you got two things going on. Quote Link to comment Share on other sites More sharing options...
Lee & Joan Posted January 30, 2011 Share Posted January 30, 2011 Yes, check the voltage with the engine running, should be 13.8-14.7 range when running and 12+ something when not charging. Quote Link to comment Share on other sites More sharing options...
dayoff53 Posted January 31, 2011 Share Posted January 31, 2011 I don't know what that small plastic part is. Anyone know without photos? It's a circuit breaker. Inside the little box is a thin, flat piece of metal that bends if it gets too hot and breaks the connection. Then, when it cools down, it straightens out and makes contact again. I had one that was all busted up, so I could get a good look at how it works. They come in different amperages - should have a number on it. You can get replacements (identical shape - material and/or color may vary) for about $5 (20 amp) or more at you friendly RV shop. Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted January 31, 2011 Share Posted January 31, 2011 The thing with fins is could be an isolator. The other as someone said is a circuit breaker, they come in metal and plastic housings.. It should only be on the coach side. As far as not starting if its just on the coach side it should not have caused a problem. Sounds like you have something else going on. Disconnect one side of the little plastic box and do another start test. And yes some pics would help. There are two types of isolators. One is finned, it is a solid state type. 3 large and 1 small connector? The other looks like a power transformer (silver or corroded grey) you would see on a telephone pole but in miniature. Two large connectors and one small. Quote Link to comment Share on other sites More sharing options...
desertrat Posted February 2, 2011 Author Share Posted February 2, 2011 Thanks everyone for the input. At this point, my rig starts. Looks like my solder job worked, but my new coach battery only gets up to 13.2 volts when I accelerate the engine. I wonder if the wire that leads from coach battery to isolator needs to be a thicker gauge. I think it's about 10 or 12 gauge now. Not sure how far that run is, but it's at the front part of the sofa area. I have photos of the mystery part. dayoff53 said it's a circuit breaker. I feel he's right. The new part I got that didn't work was a 30 amp Buss Fuse, standard 2 post type. I guess I really am ignorant, as I don't know the difference between a circuit breaker and a fuse. Also, when I had the new Buss Fuse installed, thats when my rig wouldn't start. Put the repaired, old circuit breaker in, and she started right up. My isolator is a 3 post type, old, and I'd like to replace it, but have no idea what to get. In the photos, you will see the red wire on the battery side (is this the wire from alternator. I can't follow it as it dissapears in a wiring harness), the yellow wire from the fuse box, and then the other red wire jumps over to the mystery part. From there, the other side has the wire from the coach battery. The black wires go to a toggle switch that are involved in the solar panel charging. The box with fins on it is not hooked up to anything RE: the isolator. I thought it was, but my mistake. Sorry for the long wind and confusion. Quote Link to comment Share on other sites More sharing options...
Lee & Joan Posted February 2, 2011 Share Posted February 2, 2011 That sure does look like a circuit breaker on the cabin side of your isolator solinoid. It should not have mattered weather you had a fuse or the breaker in there. The fuse just blows once and it is done for life, while the circuit breaker can blow over and over again, it just resets when it cools down. Both of them are there to make sure that too much current does not pass therough them and thus the wire and everything after them. Both are rated in Amps of current. Amps are like electric volume while volt sare electric pressure. Think of the wire as the hose and electricity as water in the hose, more amps = more water volume, more volts = more water pressure. The circuit breaker says "this much volume and no more (or I will cut off the entire flow)" Quote Link to comment Share on other sites More sharing options...
Derek up North Posted February 2, 2011 Share Posted February 2, 2011 Will just add that some circuit breaker have to be manually rest. Quote Link to comment Share on other sites More sharing options...
Maineah Posted February 3, 2011 Share Posted February 3, 2011 Any parts store will have them they are 30 or 35 amp breakers they are cheap just get new wire ends and cut them off you'll probably never get them clean enough. They also should have the solenoid be sure they give you a continuous duty solenoid. It does not much matter what side the bigger wires are on one goes to your coach battery and the other on goes to the truck battery (at least in some method it might take a detour) both of the wires will be hot so be careful not to touch them to ground. The smaller wire goes to some thing hot when the key is on. The extra wire looks a bit scary if nothing is connected I think I would remove it. Your big wires look to be a #8 wire it should be fine that's a stock size it will carry more amps then the breakers will. Until your coach battery charges for awhile you voltage might be a bit on the low side. You might pull the tape off where the red wire goes it maybe connected directly to the truck battery if so that's a good thing if not now would be a good time to do so (it really should have a breaker also as close to the battery as possible) . Quote Link to comment Share on other sites More sharing options...
Gulfstream Greg Posted February 4, 2011 Share Posted February 4, 2011 When charging a battery with a low charge the current going into the battery will be high and the voltage low. As the battery becomes charged the two will cross each other with low amps in and a higher voltage. As everyone has said, that little black box that you soldered is a circuit breaker on the coach circuit. It should not affect being able to start the engine. In another thread I mentioned disconnecting that breaker and try your start test again. Also a note, continue here with any updates, Please don't start a part 3. I will be merging your original thread into this one. Quote Link to comment Share on other sites More sharing options...
Maineah Posted February 4, 2011 Share Posted February 4, 2011 I looked at your pictures again I think what your extra wires are for is an isolator by pass maybe they had a plan to start the truck with a weak battery or to charge both batteries at the same time with a solar arrangement not a swell ideal if the rest of the stuff is no longer there if you forget about the switch you may end up with a dead truck battery best to let the isolator do it's thing. Quote Link to comment Share on other sites More sharing options...
waiter Posted February 4, 2011 Share Posted February 4, 2011 Yah, I was trying to figure out what is on the isolator solenoid. I see a black wire on each side, where do these black wires go? JOhn Mc Quote Link to comment Share on other sites More sharing options...
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