canman47 Posted July 8, 2014 Share Posted July 8, 2014 I have a simple solenoid type battery isolator. After draining my coach battery I put the voltmeter on the isolator and found that it was close to 14V going in and only 11 on the coach battery side. I expected it to be the same on both sides since when the solenoid is energized it just connects them together. Is there something I'm missing or is there excessive resistance in the isolator? When I disconnect the coach battery I get 14V both sides. Solenoid was pretty hot. Is that normal for heavy charging? Quote Link to comment Share on other sites More sharing options...
canman47 Posted July 8, 2014 Author Share Posted July 8, 2014 Sorry, accidentally posted twice and can't find any way to delete a post. Quote Link to comment Share on other sites More sharing options...
linda s Posted July 8, 2014 Share Posted July 8, 2014 Gone now Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 8, 2014 Share Posted July 8, 2014 Yes they do get hot it's normal it's the windings inside holding relay on.Your coach battery dead? Quote Link to comment Share on other sites More sharing options...
canman47 Posted July 8, 2014 Author Share Posted July 8, 2014 My battery is new but as I posted on another thread the pump switch is draining my battery. Not the pump but just the switch being on drains the battery very quickly. Quote Link to comment Share on other sites More sharing options...
5Toyota Posted July 9, 2014 Share Posted July 9, 2014 short somhow somewhere cant find rewire bypass etc Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 I have a simple solenoid type battery isolator. After draining my coach battery I put the voltmeter on the isolator and found that it was close to 14V going in and only 11 on the coach battery side. I expected it to be the same on both sides since when the solenoid is energized it just connects them together. Is there something I'm missing or is there excessive resistance in the isolator? When I disconnect the coach battery I get 14V both sides. Solenoid was pretty hot. Is that normal for heavy charging? If there's 14 volts on one pole and 11 volts on the other - the contacts inside the relay have high resistance. That is assuming the terminals on the outside are clean. Time for a new relay. In regard to heat? The low-draw relays designed for continuous use get warm - not hot. The ones made for the job of being on all the time only draw around 1/4 to 3/4 of an amp @ 14 volts. The intermittent duty relays that draw 2-5 amps to close DO get hot when left on all the time. That's why they are sold for part-time use and not full-time use like with a battery-combiner setup. What relay do you have? The more amps they draw to close - the more heat they make. You need something with a closing-coil rated at 13 ohms or more. Surplus Sales has been selling continuous-duty Trombetta relays for $18 . Great deal. They usually sell for over $60 each. I bought half-a-dozen of them. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 9, 2014 Share Posted July 9, 2014 My battery is new but as I posted on another thread the pump switch is draining my battery. Not the pump but just the switch being on drains the battery very quickly. Ah how is that? The on off switch? Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 Ah how is that? it's just a micro switch in a plastic housing. It recirculates exit water into the inlet and has a trimmer-screw adjuster on it. That screw can be turned in far enough so the pump constantly pumps water back to itself and never fully shuts off. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 9, 2014 Share Posted July 9, 2014 If there is 11 volts on the coach side of the relay the coach battery is dead or there is a bad connection to the coach battery. If the coach battery is charged that is what should register at the isolator post or something pretty close regardless of the relay being on or off. This is not to say that the relay is good it is possibly bad what you should have is climbing voltage as the battery charges but your coach to isolator voltage should be the same if it's not the isolator will not charge the battery. The path of least resistance is all ways going to be the truck battery. The relays get hot even if they carry no current it is a magnet coil it is less than 100% efficient the heat is efficiency loss. A non continuous duty relay will fail in less than a day they nearly burnt up a fire truck here in town using one. Quote Link to comment Share on other sites More sharing options...
WME Posted July 9, 2014 Share Posted July 9, 2014 Just to check things unplug the water pump and see what happens. Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 Not all intermittent-use relays will burn out in a day. I've seen Ford-type starter relays with 80 watt coils on RVs used as isolators that worked for years. Just ran very hot and drew a lot of power. I'm sure much depends on the make of the relay, air-flow to cool it, actual constant amp draw on switch contacts, etc. Sometimes when they burn up the problem is the contacts making heat and not the closing-coils. As far as all of them getting hot? Guess we need to define "hot." I've got a full-time relay on two RVs -both with 6 watt closing coils. I can drive all day long and they only get warm to the touch. I used to have a 40 watt continuous and it got so hot you could not keep your hand on it very long. Quote Link to comment Share on other sites More sharing options...
Vanman Posted July 9, 2014 Share Posted July 9, 2014 I replaced what I think was the original isolator relay on my 91 Dolphin a few years ago, (really rusted and looked old) with one I got on amazon was supposed to be a Tekonsha. Looked exactly like the old one, but new, draws 605 ma steady coil current, across made contacts zero ohms and under heavy charging current had a voltage drop of .06 VDC. Which has suddenly blossomed up to .2+ VDC. Tapping it whilst on can vary the drop from .2+ all the way up to .5+. I'm not happy about buying another one of these so am shopping for a better quality replacement.BTW the new relay, like the old one had absolutely no markings on it anywhere.vanman Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 I replaced what I think was the original isolator relay on my 91 Dolphin a few years ago, (really rusted and looked old) with one I got on amazon was supposed to be a Tekonsha. I assume you have something like this. I won't buy from Cequent anymore (Tekonsha) simply because they do not post detailed specs on their products like relays and battery-combiners. I'm not even sure how much they actually make anymore. I don't really care who makes what but I DO want specs on something before I buy. Cole Hersee sells pretty much the same relays with a lot more info. I assume you've got a metal-can full-time relay with a .685 amp coil draw, 85 amp @ 12 volt full-time contact rating, and a 125 amp contact part-time rating. I think the Trombetta full-time relays for $19 at Surplus Sales are good deals. Proven to be well sealed since they come standard on many Western snow plows. The Trombetta is more rugged and has a full-time contact rating of 150 amps @ 12 volts and a surge rating of 800 amps @ 12 volts. Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 I forgot to include the photos. Quote Link to comment Share on other sites More sharing options...
zero Posted July 9, 2014 Share Posted July 9, 2014 Relay temps. I tested my "big" Trombetta relay which draws .8 of an amp when first engaged. Left it on for 5 hours while 80 degrees F outside. Then we used the Toyota for a 2 hour trip. When left on for 5 hours with the RV parked - the relay housing got to 88 degrees F - i.e. 10 degrees hotter then the ambient air temps. Then after doing 2 hours of highway driving, the relay housing was 185 degrees F. Note the rest of the engine compartment was 137 degrees F. So the relay got 48 degrees hotter then the environment it was in. Yeah, more then anyone needs to know about under-hood relay temps. But now - I can cite degrees F instead of saying "warm" or "hot." Quote Link to comment Share on other sites More sharing options...
Vanman Posted July 9, 2014 Share Posted July 9, 2014 I called the phone # on the Tekonsha PDF and got a "tech" at Cequent. Could only tell me they are made in Mexico, no other info. I like the idea of a simple relay, but want one of high quality so I'll give the Trombetta a look. Have you ever checked the voltage drop accross the contacts while charging? I tried to get an ohmage reading on mine and lowest I could get after many tries was 69 ohms other times was triple digits sometimes the meter (digital) would just flash around different levels so it's toast. When the last one died I was getting a coupla volts accross it !! vanman Quote Link to comment Share on other sites More sharing options...
zero Posted July 10, 2014 Share Posted July 10, 2014 I called the phone # on the Tekonsha PDF and got a "tech" at Cequent. Could only tell me they are made in Mexico, no other info. I like the idea of a simple relay, but want one of high quality so I'll give the Trombetta a look. Have you ever checked the voltage drop accross the contacts while charging? I tried to get an ohmage reading on mine and lowest I could get after many tries was 69 ohms other times was triple digits sometimes the meter (digital) would just flash around different levels so it's toast. When the last one died I was getting a coupla volts accross it !! vanman I've had virtually no voltage drop. I know because I have two volt meters on-board for the cranking battery and the two house batteries in back. When the engine is running and alternator charging - all are the exact same voltage. I'm not saying that the Trombetta is of any superior quality as compared to others with same amp-carry ratings. It IS, however, made with proven weather sealing since it's used on snow plows working out in the weather, uncovered.. It also has large high-current-capable contacts. For any brand relay -the lowest cost models use copper contacts and that's what this $19 Trombetta has. For more money, you can get silver-alloy or silver-tungsten-carbide contacts. I've never felt a need. I've had no issues with what I'm using. The silver-tungsten-carbide contact relays like from Cole-Hersee cost around $50. From Trombetta around $75. If I was carrying a lot of amperage I'd get the silver version. But when only switching 30-50 amps - the copper has been fine for me. Quote Link to comment Share on other sites More sharing options...
zero Posted July 10, 2014 Share Posted July 10, 2014 I guess I should add that my rear batteries are fully charged. I.e. very little amp-flow through the relay. Obviously - the voltage drop across the relay can change when there's a big demand and amperage gets up near the limits of the contacts inside the relay. I've checked mine at 50 amps @ 14 volts and there was almost no drop. That when the relay was new. I won't know now if it's changed over time until I run the rear batteries down a lot and then start the engine. That's not something we do often. We drive by day and camp at night. One night of having a few fans running, lights on, and a few hours of watching a 32" LCD TV and DVD player doesn't run them down much. The only big draw I have on the batteries is when I use the microwave oven which is not often. Quote Link to comment Share on other sites More sharing options...
canman47 Posted July 12, 2014 Author Share Posted July 12, 2014 Still not sure if the isolator is bad or not. The coach battery is charging so maybe just leave well enough alone. I disconnected the 2 battery connections and started the engine. Seems to me there should be close to 0 ohms across the terminals when the closing coil is activated but I read infinite. Maybe the start battery lead needs to be connected to power the coil? Anyway when running with slightly discharged coach battery there is a .12 voltage drop across the isolater. Normal? Quote Link to comment Share on other sites More sharing options...
canman47 Posted July 12, 2014 Author Share Posted July 12, 2014 By the way I've read reviews of Tekonsha relays being sold on Amazon that are Chinese counterfeits that have blown apart creating dangerous short circuiting. Quote Link to comment Share on other sites More sharing options...
canman47 Posted July 13, 2014 Author Share Posted July 13, 2014 Still not sure if my isolator is failing. It's charging the coach battery so maybe just leave well enough alone. But as I said when the coach battery was pretty low I read 14 volts on the start terminal and 11 on the coach terminal. To my simple thinking if it's just a set of contacts then it should read close to the same on each side minus a tiny voltage loss through the contacts but not 3 volts. Am I wrong? With the batteries fully charged there's only a tenth of a volt loss. Quote Link to comment Share on other sites More sharing options...
burberry Posted September 5, 2014 Share Posted September 5, 2014 i'm fairly new here (and new to RVs in general) so i wasn't sure if i should jump in with my problem or start a new thread. if it's the latter, please let me know. i've been told that my battery isolator is bad, and i've thought about replacing it myself. i've done little DIY projects on the rv and some cars, but i am always hesitant with new things, so i wanted to get confirmation that i'm actually looking at the right thing and replacing it with the right thing. is this my isolator? i have no idea what i'm doing here but i want to learn! Quote Link to comment Share on other sites More sharing options...
linda s Posted September 5, 2014 Share Posted September 5, 2014 It says Toyota on it. Don't think that's a battery isolater. Linda S Quote Link to comment Share on other sites More sharing options...
zero Posted September 5, 2014 Share Posted September 5, 2014 i'm fairly new here (and new to RVs in general) so i wasn't sure if i should jump in with my problem or start a new thread. if it's the latter, please let me know. i've been told that my battery isolator is bad, and i've thought about replacing it myself. i've done little DIY projects on the rv and some cars, but i am always hesitant with new things, so i wanted to get confirmation that i'm actually looking at the right thing and replacing it with the right thing. is this my isolator? i have no idea what i'm doing here but i want to learn! That is your windshield-wiper motor. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted September 5, 2014 Share Posted September 5, 2014 Follow the cable from your engine battery positive post. That should lead you to your isolator. Quote Link to comment Share on other sites More sharing options...
canman47 Posted September 6, 2014 Author Share Posted September 6, 2014 It's very close to the wiper motor and usually gets it's signal from the same wire. Usually silver can with 3 wires. Quote Link to comment Share on other sites More sharing options...
burberry Posted October 5, 2014 Share Posted October 5, 2014 there's no "can" type thing - that's what i've been looking for, but i did find this on the drivers side right up against the wall. it's made by leisure components and it has posts for main battery, alternator, and auxiliary battery, which leads me to believe it should be it...right? i can't be further off than i was with the windshield wiper motor! Quote Link to comment Share on other sites More sharing options...
WME Posted October 5, 2014 Share Posted October 5, 2014 BINGO... Also the little box on the firewall with 1 wire is a self reset circuit breaker. Quote Link to comment Share on other sites More sharing options...
burberry Posted October 5, 2014 Share Posted October 5, 2014 Awesome! Now the question is...with what do I replace it? I'm going to pick up a multimeter and test it just to make sure it's bad, but I feel pretty confident that it is. should i pick up something like this or replace it with a something like this? i'm all ears as far as type and brand recommendations! i only have one house battery, a 12v, in addition to my starting battery. thanks so much. Quote Link to comment Share on other sites More sharing options...
WME Posted October 5, 2014 Share Posted October 5, 2014 The solid state one you have is basically diodes, easy to check with an ohm meter. The relay one will provide a higher V to the batteries when its new. As the contacts age they can loose more V. A diode will drop .7v for its life span. Quote Link to comment Share on other sites More sharing options...
Maineah Posted October 6, 2014 Share Posted October 6, 2014 It will be a bit involved to go to the relay type. The wiring for the alternator has been changed so that it will work with a solid state device. What year is your MH? It can make a difference in what style isolator you use if it's new enough it will require a 4 post isolator. It kind of looks like who ever was fooling with it did not have a clue how it works. The wire from the alternator should be landed on the post marked "A" the battery leads will be on post 1 and 2 it really does not matter witch one usually truck on one and coach on two. Now if your MH is new enough it will require a 4 post isolator. The 4 post will have an "E" terminal that will need to connect to some thing that has power when the key is turned on. The little box WRE noted is a circuit breaker to protect the wiring from a short circuit it really should have two one for the front battery the other for the coach wiring. Either type of isolator works fine but switching from one to the other is not a simple task so you would be better off using the type you all ready have. Quote Link to comment Share on other sites More sharing options...
zero Posted October 6, 2014 Share Posted October 6, 2014 For me - a relay is the best way to go. No constant voltage drop and for the money, a lot more amp-carrying capacity. Mine is hooked so it can send 60 amps of alternator current to the back when wanted. A low-draw continuous-duty relay can be had for $25. Then you have to decide how you want to hook it up. One way is to just hook it into the ignition circuit when the the ignition key is "off" , front and back batteries are separated. 'When the IGN is "on" they are connected and both get charged. One thing I do not like about this setup is this. Lets say you camped for a night and ran your "house" battery down a lot. When you turn the key to start the engine - the front full-charged battery is instantly hooked to the "house" discharged battery. Usually not a problem but I prefer to put a manual cut out switch in to. Then start the engine, let the front battery recover, and then flip the switch and let the rear battery charge. Another way is to use a voltage-sensing module hooked to the relay. This way no wiring is needed to energize it. When you start the engine - it first sends all the charge to the front "cranking" battery. Once it is fully charged, the front connects to the back and then they all the batteries charge. When you turn the key off, they separate. One slight warning. On some brands - the batteries, front and back stay connected - even with the key off until the front battery voltage drops to below 12.7 volts. No harm in that. These are called "smart" relays. Winnebago has been using them OEM since the 80s in many RVs. Cole Hersee, Power Stream, and several other companies sell "smart" relays. Power Stream also sells just the voltage-sensing control module for $28 and this way you can buy the relay separate if you want (that's what I did with my Toyota). On my 1988 Toyota Minicruiser - I wanted to ability to send a full 60 amps of charge current to the back when needed. For one thing, it helps run my microwave oven when just run from batteries. I put a 150 amp rated relay under the hood (cost $18) and added a Manson "smart" module to control it (cost $24). Have #2 copper cable running from front to back with a large circuit breaker on each end . Not what everyone needs but works great in our rig. Quote Link to comment Share on other sites More sharing options...
burberry Posted October 6, 2014 Share Posted October 6, 2014 It will be a bit involved to go to the relay type. The wiring for the alternator has been changed so that it will work with a solid state device. What year is your MH? It can make a difference in what style isolator you use if it's new enough it will require a 4 post isolator. It kind of looks like who ever was fooling with it did not have a clue how it works. The wire from the alternator should be landed on the post marked "A" the battery leads will be on post 1 and 2 it really does not matter witch one usually truck on one and coach on two. Now if your MH is new enough it will require a 4 post isolator. The 4 post will have an "E" terminal that will need to connect to some thing that has power when the key is turned on. The little box WRE noted is a circuit breaker to protect the wiring from a short circuit it really should have two one for the front battery the other for the coach wiring. Either type of isolator works fine but switching from one to the other is not a simple task so you would be better off using the type you all ready have. mine is a 1987 toyota sunrader i actually did see a little box like that next to the starting battery on the opposite side under the hood. as for the one you can see - there's a wire floating around that's disconnected from the other side of that circuit breaker...i don't know if i should reconnect it or not, or why it's undone to begin with. Quote Link to comment Share on other sites More sharing options...
Maineah Posted October 6, 2014 Share Posted October 6, 2014 If it's a 87 it will need the 4 terminal isolator. You got some strange stuff going on there. See if you can trace the center wire on your isolator back to the alternator. Quote Link to comment Share on other sites More sharing options...
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