12V -side question

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12V -side question

November 21, 2014, 05:17:15 pm

My house batteries are showing well over 12 volts when not connected to the charger, but for some reason I have no 12 volt in the coach. Also, my inverter has started turning itself on automatically. When I reconnect to shore power the inverter causes the lights to flicker. Also, after that happens I can't get any readings on the old Audit system. That seems to continue until the shore power is disconnected and then reconnected.

Another symptom that may or may not be related is that my boost switch doesn't seem to work anymore. We're parked for a week or so, so I have time to poke at a few things. Any suggestions as to where to start?

Re: 12V -side question

Reply #1 – November 21, 2014, 05:20:55 pm

David,

"A little over 12 VDC" is not any good if you are plugged into shore power and the inverter/charger is working. Should be 13.0-13.2 VDC in float (once charged) and up to mid 14's in bulk mode.

Check voltage at the chassis battery as well.

If battery voltage is too low, there is not enough power to pull the boost relay in.

Re: 12V -side question

Reply #2 – November 21, 2014, 05:24:05 pm

Brett, I had over 13 volts at the batteries with shore power disconnected but engine running. Should I disconnect shore power, engine off, and then check battery voltage?

Re: 12V -side question

Reply #3 – November 21, 2014, 05:26:46 pm

Yes, with engine running, the alternator should charge both battery banks.

Turn off the engine and let it sit a few minutes, then check voltage before plugging in. Surface charge will dissipate quickly, leaving a fully charged battery reading 12.7 VDC.

Plug in. If inverter/charger is working (assume that is what you have), voltage should go right up to 14 VDC, then drop off to low 13's after the batteries are fully charged.

Re: 12V -side question

Reply #4 – November 21, 2014, 05:31:25 pm

if you are looking for the actual battery level of charge, 1st remove the surface charge.

Re: 12V -side question

Reply #5 – November 21, 2014, 05:39:36 pm

David,

Are you saying your 12vdc lights are not working except when your inverter is plugged in?

Pamela & Mike

Re: 12V -side question

Reply #6 – November 21, 2014, 05:44:42 pm

David, I'm not sure where your main 12v switch is (ours is in the front step well) but make sure it is on. Mine got switched off accidentally once, half hour of panic later Susan asks the obvious, "Is that 12v switch on?" Good for her.

Roger

Re: 12V -side question

Reply #7 – November 21, 2014, 06:09:20 pm

We had our disconnect switch accidentally turned off when loading things into the coach. That was a real scramble for a bit. Electrical problems are always so troublesome, just have to be calm and start running thru the could be's. Process of elimination. Stay calm and have a great day ---- Fritz

Re: 12V -side question

Reply #8 – November 21, 2014, 06:44:40 pm

Main 12V disconnect switch (salesman's switch) is by the door and is turned ON. The interior 12V lights don't work unless we are plugged into shore power. I suspect that the inverter has something to do with the problems, since it is now behaving differently than it did this summer. Weather permitting, tomorrow I'm going to crawl into the basement and turn the inverter off with the main power switch rather than with the remote. Then I'll see what happens.

Re: 12V -side question

Reply #9 – November 21, 2014, 06:49:57 pm

David,

Check to see if your unit has the main breaker tripped that is hid in the hole in the top left hand side of the service bay. I have a pic. that I will post if I can find it so you will know what to look for. On our '92 we also had a main line fuse between the battery and the 12vdc panel in the basement.

Pamela & Mike

Re: 12V -side question

Reply #10 – November 21, 2014, 07:34:19 pm

David,

Here is the breaker that I am talking about. It just took a while to find the pic. this is off our '92. In fact this is the same location on our '97.

Pamela & Mike

Re: 12V -side question

Reply #11 – November 21, 2014, 10:36:40 pm

Our coach has three 90-amp 12-volt large round circuit breakers that are mounted next to each other near the top under a white removable bay wall cover.

Two of the breakers are automatic reset. One is manual reset with the reset button located on the back of the breaker. To reach the backside reset button, Foretravel drilled a hole in the bay wall so the reset button can be reached from the other side of the wall. The photo shows this manual breaker reset.

One of the wiring diagram sheets shows what is under the white cover.

Re: 12V -side question

Reply #12 – November 21, 2014, 10:48:05 pm

To me it sounds like one of your house batteries has gone bad. To properly check them you will have to completely disconnect them from each other and the coach.

Re: 12V -side question

Reply #13 – November 22, 2014, 09:56:38 am

Well, thanks to PamelaMikeBarryCindy, I've crawled all over our coaches and never noticed that reset button!
jor

Re: 12V -side question

Reply #14 – November 24, 2014, 04:30:56 pm

To get back to my original question: why do I not have 12vdc unless I'm plugged in? I had noticed the hole but didn't connect it to the electrical stuff on the other side of the wall. I tried pushing the button, but it didn't move, so I'm assuming that it probably is okay.

I'm plugged into 50A, and just tried starting the generator. Flickering lights, but otherwise nothing. I suppose the next step is unplugging and disconnecting batteries, then checking each one. That may have to wait for a bit until I warm up some. The temperature may be 40, but so is the wind.

Re: 12V -side question

Reply #15 – November 25, 2014, 01:55:02 pm

Maybe an inline breaker between your converter and the batteries. I know that you replaced your converters, so maybe could have a bad connection somewhere. Sounds like your converter is not charging the batteries. Also might have a broken connection there close to the batteries

Re: 12V -side question

Reply #16 – November 25, 2014, 02:17:14 pm

Red, I'm starting to wonder about that, too. I just disconnected everything, and both house batteries were at 12.96 volts, measured separately and disconnected. I didn't crawl under the coach, but I'm wondering if the isolator may have something to do with this. Since I have power when plugged in, obviously the 120VAC is being properly turned into 12VDC. Since the batteries show full charge I would assume that they are, in fact, being properly charged when plugged in.

I'm thinking that my next test will be to leave the 12v stuff on and flip the 50A breaker, then check the batteries. Jo Ann can tell me how quickly the lights give out.

Re: 12V -side question

Reply #17 – November 26, 2014, 08:15:01 am

David,

Your 300 may be different and I hope im not making myself a fool with this explaination and you may already know this.

This is how I understand the electrical systems operation. If I am a fool, be gentle as I am corrected, I only want to understand

The 12v system is a stand alone system. The charger-inverter, solar or engine, charges batteries. The isolator only works with the engine, 110v does not hook to the isolator.(this was my concern) Solar controller and charger hook directly to the battery.

The shore power is completely seperate to your 12v system except through the charger.

If you had an inline fuze tripped, you would not have any lights, since their dim or flicker it makes me think of an intermittent issue, like a loose or corroded connection.

Our 88 had the same issues flickering, gen no start. Turn on the power lights were back on. As it turned out the salsman switch and a couple loose battery connections were the cause..

Hope this helps

Re: 12V -side question

Reply #18 – November 26, 2014, 09:21:27 am

John,

Here is another thought to go along with your insight on 12 vdc. If your inverter/charger can't see a battery it can go crazy and cause the lights to flicker. Depending on where there is a bad connection, cable, or complete battery failure will determine if this condition will occur. If you run some of the inverters without a battery for it to fill the inverter can be damaged.

Pamela & Mike

Re: 12V -side question

Reply #19 – November 26, 2014, 09:41:33 am

I've become a bit confused after all the suggestions. Do all your interior lights work fine UNTIL your inverter is turned on? Is the inverter also the charger? If both of those are true then I would suspect the inverter/charger.

If both house and start battery banks are fully charged you may not see any reaction from the Boost switch. I had to replace my boost switch a month ago, however... there was no increase to start bank when I was on shore power and turned the boost switch on.

Craig

Re: 12V -side question

Reply #20 – November 26, 2014, 12:45:47 pm

Quote from: wa_desert_rat – November 26, 2014, 09:41:33 am

I had to replace my boost switch a month ago, however... there was no increase to start bank when I was on shore power and turned the boost switch on.

Craig

Where did you get the replacement boost switch, have a part number? I need to replace the ether start switch with a normal on off switch.

Roland

Re: 12V -side question

Reply #21 – November 29, 2014, 12:32:14 pm

It is nice and sunny today, with temperatures in the upper 50's to lower 60's, so I decided to see what I could see about my electrical problem. Since a couple of other questions got added into my original thread I decided to start a new one.

ALL house 12 volt circuits work fine as long as I'm plugged in. As soon as the 120VAC goes away, though, all house 12V stuff is dead. The two house batteries were new less than a year ago, and show 13.87 volts while plugged in. After about 15 minutes of being unplugged they showed 12.6 or so.

The generator starts from the house batteries, and it will not start even when plugged in. When we get ready to leave Monday morning I'll try jumping it from the Jeep.

The light on the boost switch does not come on, nor does it seem to make any difference whether it is turned on or not.

I crawled under the coach to look at the isolator. It has three large terminals across the top with two smaller ones between them (L s L s L) and what look like two solenoids in the lower right part, two automatic resetting circuit breakers and a couple of plugs in the lower left part. Since I was by myself then I couldn't trace all of the wires, but it looks like the far left large terminals go to the house batteries. Does this make sense, and does it sound right?

It appears to me that the two chargers/converters are supplying the proper current to the batteries and coach stuff when plugged into 120VAC. Somehow, though, the batteries are not able to provide current by themselves. On the other thread someone mentioned the reset button that is accessed from the utility bay. I tried pushing it, but nothing moved, so I'm assuming that it didn't need resetting.

My thought at this point is that after lunch I'll shut everything off again, disconnect all batteries, crawl back under the coach and take off each connection on the isolator, clean it up, and retighten it. If that doesn't solve the problem, what should I look at next?

Re: 12V -side question

Reply #22 – November 29, 2014, 04:09:04 pm

Could it be that the terminals on the 12v disconnect switch (the one in the stairwell) are corroded?
Might also check the main 12V breakers (or high current fuse - not sure what your coach has) to see if there's voltage across them (should be zero) Breakers get weak or fail over time.

And, of course, there's always the question of whether all the grounds, particularly the high current ones, are still good. Any connections exposed to the weather may need to be tightened or removed and cleaned.

Are you measuring the house batteries directly on the battery terminals? Might measure voltages with cables disconnected from the batteries after the surface charge dissipates (~1/2 hr), then measure current draw between ground cable and battery terminal with things in the coach turned off.
If voltages are still low after charging overnight and immediately removing the cable, I would suspect the batteries.

Re: 12V -side question

Reply #23 – November 29, 2014, 04:15:29 pm

I'm back from crawling around under the coach. All connections were good. I cleaned off the top of the isolator and found what I believe is a brand and model number, Powerline PL1-190-3. I searched for that and found PLI-190-3, so I looked at it. The picture showed a much smaller isolator, with only three terminals on it.

We're scheduled to head back home Monday morning, and then head to Stillwater Wednesday morning. I'm thinking that maybe I ought to call Foretravel Monday morning and have them send a new isolator to the church in Stillwater. Does that sound reasonable? Maybe I should have them send all of the other things on that panel, too, so that while I'm underneath changing the isolator I can just do all of it and not have to crawl under again.

Any EE people here?

Dave, yes I have been measuring right on the battery terminals. It seems strange that I have 12V when plugged in, but not when not plugged in.

Re: 12V -side question

Reply #24 – November 29, 2014, 04:20:59 pm

David, Does your coach have a transfer switch ? Some coaches have two, seems funny that 12V is available on shore but not on batteries, disconnect somewhere. Sorry can't be specific.
I would start with a voltmeter from pedestal ( including cord ) to isolator to inverter thru transfer switch. Got to be some point where current is not flowing.
Good luck.
Gary B

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