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Topic: Continuing electrical issues (12 volt side) (Read 747 times) previous topic - next topic

Continuing electrical issues (12 volt side)

A week ago we had to take the coach out for propane (first purchase since 2 January). When we got back I couldn't level the coach. I finally plugged into the power pedestal and suddenly I could level the coach. Normally I plug in while waiting for the turbo to cool and the mercury in the switch to settle down, but for some reason Saturday I reversed my normal practice.

I talked to my brother-in-law (an electronics technician) who suggested two tests. One is to disconnect the batteries while leaving the converter connected. That will provide 12 volts to run things while letting the batteries sit for a while. If the batteries are defective (they are about a year old) the voltage after a day of disconnect will be significantly less than 12 volts. The second test is to turn off the 120 volt power but leave the batteries connected. Check the voltage across the three main circuit breakers. If the breakers are good the meter will show little or now voltage. A defective breaker will show close to battery voltage.

Unless someone can tell me NOT to do these tests, I'm going to try them tomorrow after work. I'll flip off the 50A breaker, then check the three breakers. If all check out I'll disconnect the house batteries and turn on the 50A breaker. I'll check the house batteries' voltage at that point and again after supper. If there isn't a significant voltage drop after a couple of hours I'll check again after work Tuesday.

Re: Continuing electrical issues (12 volt side)

Reply #1 –
David,

Better battery test if these are wet cell batteries is to fully charge them (like overnight) and then use a battery hyrdometer to check the cells (they are under $10 at any auto parts house).  As an alternative, have the fully charged batteries load tested by most any auto parts house.

I would not try to run appliance PC boards off an older converter w/o batteries-- the batteries act as a filter,
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Continuing electrical issues (12 volt side)

Reply #2 –
The converter is new last year.

Re: Continuing electrical issues (12 volt side)

Reply #3 –
Have the batteries been connected and charging all winter? Have you checked voltage at any time? Best would be to leave the batteries charging for a day, disconnect and isolate each one and check for voltage. After disconnecting and waiting a couple of hours, each one should be about 12.7 volts. Was the new converter installed properly? Many times you can go back to the last thing done and find the fault there. Terminal corrosion can also be part of the problem. Use a digital voltmeter to check the voltage while plugged in. If the batteries went flat over the storage period, it could be they are finished. If they were not being charged over the winter but were still connected, they will be ruined them as the parasitic drain will flatten them quickly.

As Brett says, there are a lot better ways to check the batteries/charging system than trying to use the converter without having batteries as a buffer while you check the system. The converter is not a low ripple power supply for the 12V appliances. One spike can ruin a control board.

Check my very old post with the two digital voltmeters I have on the dash. I drive with them on and turn them on almost every time I get in the coach. A glance can instantly tell the health of the batteries, the charging system, etc. The plug in variety for the cigar lighter sockets also work great and for about $3 each, give you a wealth of information. Even if in a controlled storage environment, a coach should be monitored on a regular basis.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Continuing electrical issues (12 volt side)

Reply #4 –
We've been living in the coach for just over a year now, and have been plugged in all the time. I thought I had the problem fixed a couple of months ago when I found a loose connection on one of the auto reset breakers, so I assumed that somehow that connection had come loose again. It was tight. I pulled all the old black tape off of the salesman's switch and checked those connections, too. Again, both were tight. Covered it all up again and started scratching my head.

Re: Continuing electrical issues (12 volt side)

Reply #5 –
Boy, compared to Brett & Pierce & a couple other folks here, I am the last one to give advice on anything electrical but here goes!

I read somewhere, either here on Foreforums or another website that one should not leave the "Boost switch" on while connected to a power pedestal as the house battery could end up "toast". I don't know if that is true, BUT I have lost two 8D batteries in four years.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Continuing electrical issues (12 volt side)

Reply #6 –
David,  Many places such as auto supply stores and tool stores sell low cost battery testers, they are cheap and maybe not very accurate but it takes a load off your mind when you can LOAD TEST your own batteries and not depend on a clerk in a store to do it.
I have a load tester that I think I paid 50 bucks for several years ago and it has paid for itself many times over.
Gary B

Re: Continuing electrical issues (12 volt side)

Reply #7 –
David... even if your charger/converter is new I would not leave it on with no batteries. Disconnect one battery at a time and test it that way. There is a good chance that one of your house batteries has a shorted cell. The hygrometer is the best test of battery condition but I cannot do that in my coach without removing the 8D batteries (no overhead room at all). Yours may be the same. So the "charge overnight, disconnect, let sit for 4 or 5 hours, and then measure voltage with a digital voltmeter" could be the only effective test. I bought a Harbor Freight load tester for under $50 and have used that to discover bad (or weak) batteries.

Battery able connections: corrosion products can build up even if the connections are tight; especially right at the batteries. I would remove them, wire brush the connections (both battery end and cable end), and re-install the cables.

I agree with the advice to not leave the boost switch on. Use one of the several other methods to charge the start battery. I turn the boost switch on and leave it on for 7 hours or so (on in the morning, off at night). My coach is on solar charge only for the house battery systems (for the past 6 weeks). I tripped the breaker for the PD charger/converter; I suspect that my solar charge controller is far better than even the PD unit.

Good luck. :)

Craig

1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Continuing electrical issues (12 volt side)

Reply #8 –
Adding to Craig's post, you can purchase a small, high frequency trickle charger for about $25, plug it in next to your converter and run very short wires to the electrical bus (engine battery lug) just inches away. This way, anytime the rig has shore power, both the house and engine batteries get charged. The boost solenoid uses quite a bit of juice (and gets hot) and in the event of a shore power failure, the boost solenoid will flatten the batteries in about a day.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Continuing electrical issues (12 volt side)

Reply #9 –
Well, I should have quit when I was ahead.

I left the interior lights on, then shut off the 50A breaker on the power pedestal. I put the meter on all three main 12V breakers. All three read 0.00 volts, which meant that they were passing current. About that time the hot water heater kicked on. Hmmm, doesn't that require 12 volts? I crawled out of the basement and touched the handle by the door. The porch light came on. I should have quit at that point.

Instead, I continued with Bob's tests, and disconnected the batteries. Due to some other activities, the batteries were disconnected for about an hour. I had checked the voltage immediately upon disconnecting and again about 10 minutes later. After an hour I was able to get back to the project. Voltage had dropped all the way to 12.87 volts from 13.46. That seems like a healthy battery to me.

I reconnected the batteries - and no lights. By that time it was time for supper, so I just turned on the 50A breaker and quit for the day. There is an RV place just down the road, so I think I'm going to stop in there one of these days and see what they say.

Re: Continuing electrical issues (12 volt side)

Reply #10 –
David,
Not to fear, you're almost there. OK, go back by the bed and look at the 12V electrical panel there. Start checking the fuses there. This is where the juice comes from for your outside handle and water heater. You can see what they do here in the first PDF. The next thing is to open the bay door where the converter is and take the two small nuts off the plastic panel and remove it. The second PDF shows how it feeds the 12V through the coach. The third is a photo of what it looks like under the plastic panel. You can see on the bottom right side of the photo where I connected the trickle charger to the engine batteries and also how I installed the big cable from the solar controller. I used this photo as I don't have one of the entire bus panel but you can compare the schematic to the photo and get the idea. You can use your tester to check for voltage and look at the circuit breakers and fuses. This is also the location of the water pump relay in case your pump ever stops working. Pump is on the opposite side of the coach on ours from the relay. Your 40 footer may have things in a little different location from our 36' but you should be able to find it. Only 12V under the panel so you won't shock yourself. Lots of amps though.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Continuing electrical issues (12 volt side)

Reply #11 –
Thanks, Pierce. You sent me the schematic some time ago, and I've spent quite a bit of time with it. I have had that panel cover off several times. One of these days I'm going to remember to get some wing nuts for it. I also need to get some sort of label maker so I can mark all the red lines.

Now, which lump of black, greasy crud is the ground?