Help with 12 volt question

traveler · 08-01-2008, 01:27 PM

I have a newly developed problem. First, I have an almost new battery and problems persist even when I connect jumper cables to the battery. So, bad battery not an issue.

I first noticed that the 12v light above the battery compartment was intermittent. Then it failed altogether and new bulb did not fix.

A day or two later all of the lights in the basement and the water hose compartment became inoperable.

There was full voltage to the lights and the associated switches worked ok.

I examined the 12v fuse panel. No red lights were on. Then I established that circuits 2 (motors), 8 (furnace), 8 (awning) , and 11 (hydraulics) did not light up when I pulled the fuse. All other circuits would show a red light with the fuse out.

Voltages on the hot side of the circuits--all of them--was about 13.5 with the fuses in place. This measurement was made on the terminals to the left of the fuses.

Voltages at those terminals dropped to zero with the fuses out on all but circuits 2,6,8,and 11, where it dropped to 11.5 (again without any fuse in place).

I am not sure what motor circuit 2 runs, but apparently the water pump motor is one of them. The water pump works but acts as if it is on low voltage. This jives with the low voltage measurement on circuit 2.

The hydraulics work, but I cannot tell if the hydraulic motor has low voltage.

I realize that this is a confusing set of symptoms, but maybe some of you have an idea about what I can check to further diagnose or fis the problem.

Thanks

BobW · 08-01-2008, 04:26 PM

Most cases there is a ground problem. Check the batteries big ground terminal and the wire that comes from it. The ground terminal connects to the the RV body somewhere and if it's not connected correctly, it can cause all the problems you have. By the way, the voltage still can be high until a load is applied.

jack_diane_freedom · 08-01-2008, 05:26 PM

I have found that I have had to 're-crimp' almost every connection within the battery cabinet and ground connections have come loose and required retightening as well. Go into the battery cabinet and give each connection a gentle pull and twist as they may look secure but they may not be.

Okie · 08-01-2008, 05:29 PM

what Bob says is true. It sounds like a ground problem. If you look at the output of the inverter you will see two legs of black and white cables going out, the black being hot and the white is ground. In my battery box there is also two sets of outputs. Thats why you have half good and half bad. I would trace out all the white lines and try to find the one that has a bad or no connection. You might get lucky and find the white wire with the low voltage on it and trace it out.
Good luck and I hope you get it soon.

Okie

traveler · 08-01-2008, 05:54 PM

Thanks to all. I have to be gone for a few days. I am in Lake George NY for the summer and will chase this issue starting Monday. We live in Montgomery, Texas and do not have to head home until August 25. I should have it straightened out by then, I hope.

Except for the water pump, all other things seem to work ok--especially the hydraulics. Kent tells me that the hydraulic pump is wired directly to the battery. So the hydraulic fuse that is in one of the circuits behaving badly must control the relays and perhaps they work ok on low voltage. The slides and landing legs seem to be ok.

By the way Kent said he had never heard of this problem, but he thought it may be a ground problem too.

I will let you all know how this turns out.

Motor31 · 08-02-2008, 12:05 PM

The hydraulic pump and switch should be on their own cable direct from the battery. That's why they work when the battery isolator switch is pushed in.

You might also check any bundles of 12 volt wires and see if they were clamped so tightly that the wires are broken. Loosen the bundle and wiggle wires in it to see if something comes back on. Look at the wires where they connect into the fuse block and make sure they are tight.

You might also check the master circuit breaker on the side wall of the battery compartment. Look where there are some large wires connected to a silver grey unit. There is a very small black plastic button on the end of it. Push that in and see if it clicks. If it does that acts like a battery cut off as well.

traveler · 08-03-2008, 04:49 PM

Here is a good one. The problem went away! I think that there is a good chance it will return. I suppose intermittent problems are the most complicated.

Nonetheless, I think that all the suggestions made by you guys sound good. There is a loose or shorted wire somewhere and I should try to find it.

One more thing. I have looked for the small button on the battery wire terminal mounted on the sidewall of the battery compartment. Is it possible that I do no have this circuit breaker switch. I understand that the small button is on the short side of the --about 3/4 by 1 and 1/2 inch-- terminal. But I cannot find the "button" I see a small indentation on each end of the terminal (the ends with the mounting tabs), but I discern no button (pop out circuit breaker).

Thanks again.

ponch · 08-03-2008, 05:00 PM

The box that you are looking for is mounted on the right side of the box as you look in. The button will be on the end of the box. button is very small.

Okie · 08-04-2008, 09:41 AM

In some cases there is no button on the little box. There is none on mine. It is just a terminal to connect the wires. Mine is just that, I have had it apart and it is a solid bar terminal. I have no idea what the determination factors are to have one or the other.

Okie