Being fairly new to rving I am having a problem diagnosing a problem I have.

I have a 1988 Southwind that I am trying to determine why the house batteries are not charging. I thought that the house batteries were bad, only 15 months old Group 27, while on a trip when the generator quit while running down the road. Not knowing what was wrong I replaced the batteries. They only lasted about 7 days of traveling before the new batteries were mostly dead.


I checked the voltage at the battery isolator relays and the voltage coming from the alternator was 14v but the out put was only 11v, which is the volatge of the house batteries. Should I be looking at the battery isolators that are controlled by the isolator. I have attached a file with what the wriing looks like.I hate throwing money at the problem so any help is appreciated.


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Jim, Sorry, I just cant follow the picture or schematic well enough to diagnose the problem based on it, but can only tell you the obvious and what you likely already know. The nominal voltage of a good and charged lead acid so called "12 volt" battery should be 12.6 volts. Also, its obviously impossible to charge them with an input voltage (from engine alternator or the RV's 120 VAC/13 VDC Converter/Charger) less then that, and you need at least 13 to 14 and a bit over, while if its only 11 thats actually going to DISCHARGE your house batteries (hook a 12 volt battery to 11 volts and current will discharge flow OUT of the battery NOT into it as required to charge it). I take it the RV uses mechanical isolation relays (versus solid state isolators) such that when the engine is running the house batteries are effectively in paralell with the engine battery so they get charged along with the engine battery via the alternator at an approximate 14 or so volt level. THIS FOR SOME REASON ISNT GETING ACCOMPLISHED. Then when setting and hooked to shore power the RV's Converter/Charger keeps the batteries at a float charge level.

If a person were there armed with a schematic and voltmeter it may be posible to figure why your house batteries are only seeing 11 volts AND THATS THE PROBLEM but its tough to fix the problem over the net. Try to track it down keeping in mind the goal is when you turn the engine key on the isolation relays should latch in and place the house batteries in paralell with the engine battery so they all get 14 charging volts. A loose connection or bad ground or a minor short may well be the problem.

Sorry I cant help more

John T retired Electrical Engineer in Indiana
Our 1987 tiffin house batteries are charged very little by genny and or shore power. We keep a small solar panel trickle charger and put this out in the sun when camped to keep the batteries topped off. We also use an electric trickle charger if camped out in shade just in case.

PS, One more thing, you may want to measure is the voltage drop (if any) ACROSS the solenoid (its 2 big in and out terminals) when its latched in !!!!!!!!!!!!! Ideally there should be no or negligible drop across its closed contacts (when its conducting current) buttttttttttt if the contacts are burned or carboned or pitted such creates internal resistance and a resultant VOLTAGE DROP which could explain the downstream batteries seeing 11 volts versus 14 required for good charging!!!!! This assumes the RV uses isolation solenoids to tie the RV batteries up in paralell with the engine battery when the keys on so they get charged via the engines alternator. if it uses solid state diode type isolation devices then Id have to re think this...........

John T
Hopefully this THANKS gets to all that replied to my post.

I don't believe that the solonoids are getting the pulse to open from the battery isolator relay.
Since I don't have a schematic on the wiring I am sure how to trick the solonoid to open so I can see what piece is really bad.
If you would contact the Fleetwood company, provide the year, model, and VIN of your rig, they will email you complete wiring diagrames (as .pdf attachments) of both the 110 volt and 12 volt circuits. They are fairly quick to respond.

Just for an exercise in under-dash contortionism, have you checked the fuse in the circuite that sends 12 volts from your ignition terminal to the #1 relay?

Sorry I missed your response and am so late in responding. I have 14 volts on one set of terminals and 11 volts on the others. It seems like the solonoids are not opening properly so I may be missing the control input. I uploaded pics of the two sets of solonoids and isolator.
OK - I think that you are going to need create an actual electrical schematic so that there is something to diagnose - otherwise this will just be guess work. However, I would think it likely that you have 3 relays - one that controlls the activity of the other two. These relays, which you are calling isolators, function when voltage is present across the coil terminals. Since you are reading 11 volts on the battery side of both secondary relays, it would indicate that the primary relay is not functioning. You need to check the voltage going to the primary coil input terminals to see if it is getting 12 volts when the key is turned to ignition.

Sorry for the delay in responding. Thanks for you input.
I have checked all of the fuses and they seem to be okay.
What I am not sure of is how does the control voltage gets the solonoid to open to send the voltage to the batteries. I seem to have four solonoids and an isolator, see attached file.
I see that James mentioned Fleetwood, I thought I did inquire to them with no help. But I will try again.
Hi Jim,

You should have a conductor (wire) that is energized when your ignition is in the on position that connects to the + terminal on the primary (master) relay. When this terminal gets 12 volts (more like 12.8 +) it completes the coil circuit, which closes a set of contacts inside, which connects a circuits(s) that energizes secondary relays. Without an actual circuit drawing it is very difficult to know what iz and what izn't functioning. Not easy!





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