DC power seems low, lights dim

[scottkeen]

Recently my 2011 Montana Mountaineer 347THT has been exhibiting low DC power symptoms -- the DC lights are dim, the more DC lights I turn on the dimmer they get.

I have a Progressive Industries 50A EMS and it shows that shore power has no errors E-0, 121V on L1, and 122V on L2.

I tried the following to troubleshoot:

Disconnect 50A shore power so I'm running just on the 12V house battery
Lights are extremely dim

Disconnect the battery so I'm running just on shore power and the converter
Lights are dim

I topped the battery water up a bit with distilled water. Disconnected, it was showing 13.28V. The battery is about 5 years old.

I was thinking the problem is the battery, maybe a dead cell (?) because when running off the battery the lights are extremely dim. But when I disconnect the battery entirely so it's not in the loop, the lights are still dim.

Could this be the AC-DC converter going bad? But if so, then why is it that when I disconnect shore power and run just off the 12V house battery that the lights are extremely dim?

Any ideas or suggestions before I call for a mobile RV tech to come out?

Edit: One thing that's really weird, at night when the outside temp drops it seems like the dimming problem goes away. During the day in Texas the outside temp is around 102 degrees. I thought maybe it's my eyes tricking me with sunlight, but the dimming is really noticeable and if I have too many DC lights on, the refrigerator light won't come on and the stove hood fan runs noticeably slower.

[jsb5717]

You're EMS won't help with this issue as it is watching the incoming 120v and is either allowing good current in or would shut it off. This is an internal 12v issue which points to converter or batteries...or both.

I would suspect the converter. I had one go bad in our 2018 with all interior lights dimming. It's pretty easy to check the voltage it's producing. You can pull the cables from the batteries and check with a volt meter there or at the unit itself once you gain access to it.

When connected to shore power the converter can run your 12v systems with or without good batteries. However, bad batteries can eventually over-tax the converter and damage it. Also, a bad converter can damage good batteries (as it did on ours). So I would also have the batteries load tested.

Have you converted all of your interior lighting to LED? That will help reduce the draw on the 12v system. It won't help your current issue but would be a good idea going forward.

[C&P RV]

Check the main ground connection to the frame. Could be corroded a small amount which would impact the power flow.

[scottkeen]

Originally Posted by jsb5717

I would suspect the converter. I had one go bad in our 2018 with all interior lights dimming.

Thanks.

I just disconnected the house battery and plugged it into a battery charger -- it's showing 12.5V only!

With the house battery disconnected, and running DC straight off the converter the DC lights are so dim in the RV they are barely on. I try and turn on more than 2 DC light switches and the lights won't come on or are flickering. This is with the battery disconnected.

So maybe the converter is bad? Or as you suggested, a bad battery overtaxed the converter and the converter is bad. Maybe both the battery and the converter are bad?

Ugh.

Yes, all my lights were swapped out to LEDs 5 years ago. Everything was working fine with the lighting for the last 5 years until just the last few days.

[jsb5717]

Sounds like a converter to me. If you have a good battery charger you can try connecting that to the battery leads and see if that brightens up the lights. That can help short-term. I wouldn't do that long-term but would also show that the system is working and that the converter is bad.

Even if you disconnect the batteries the converter should adequately run your 12v systems. it's not a good long-term solution either but can prove a bad converter. If connecting a battery charger makes things work correctly then I'd be replacing the converter. But get those batteries tested as well just to be safe.

[scottkeen]

Originally Posted by jsb5717

Sounds like a converter to me. If you have a good battery charger you can try connecting that to the battery leads and see if that brightens up the lights. That can help short-term. I wouldn't do that long-term but would also show that the system is working and that the converter is bad.

OK.

I tested the leads going to my battery and they show only 0.58V. Yikes, that sounds low.

So now I have...
1) the battery connected to the RV.
2) my external battery charger connected to the battery, and showing that it's charging the battery and the battery is now 12.7V (was 12.5V)

The lights are bright again!

So this all points to the converter gone bad as you suspected. The fact that the battery is charging (was 12.5V now it's 12.7V hooked up to the charger), I hope that means my battery isn't totally dead and also has to be replaced. I don't know how to replace a converter or what to get, so I'll probably have to call the mobile RV tech.

Thanks for your help.

[Carl n Susan]

Originally Posted by scottkeen

....I topped the battery water up a bit with distilled water. Disconnected, it was showing 13.28V. The battery is about 5 years old....

13.2 is normal after effect of the converter having just charged the battery. You need to wait 15-30 mins to let the battery equalize and get an accurate voltage measurement.

Originally Posted by scottkeen

....I just disconnected the house battery and plugged it into a battery charger -- it's showing 12.5V only!...

12.5 is the normal State of Charge (SOC) for a battery. That is a very good voltage.

It sounds like the converter is working putting out 13.2V to the battery and the battery is in good shape with 12.5V when disconnected. The reason for the dim lights has to be elsewhere. The suggestion to check the ground connection (battery and frame ends) is a good one.

Here are step by step instructions for finding a problem in the 12V system. It is intended for situations where there is no power. It may not help where you have power but low voltage. If all this checks out with good 12.5+ voltage readings then look at the power distribution system (aka fuse panel). Check for loose connections and that the wires are all tight in their respective sockets.

• The converter is part of the power distribution panel -Ensure the CB for it is On
• There are Reverse Polarity Fuses on the converter which protect against connecting a battery backwards. - Ensure they are not blown.
• Check the output voltage at the converter. - it should be in the 13.5V DC range.
• The power then runs to the Disconnect Switch in the Convenience Center. - Ensure the Red Key is in the position where it can *NOT* be removed. If removed, this interrupts the power charging the battery. The Disconnect Switch is not know to fail, but you can remove it to check there is power in and out of it just to be sure.
• The power next flows to the group of 50 amp self-resetting CBs behind the battery. We all know about the one that hiccups and interrupts the hydraulic system. That one also passes power to/from the converter and batteries. You want to check it and it's brother (it is in the current flow to the battery) to ensure there is 13>5V on *EACH* side of the CB.
• The last connection is the one from the 50 amp CBs to the batteries. Ensure you have clean connections and the cables are not corroded (watch out for internal corrosion under the shrink wrap).

Somewhere along this path there will be the problem. A simple VOM should find it. I hope this helps.

[scottkeen]

Thanks everyone.

The RV tech that I've hired before for other work came out here and said it was definitely the converter.

I asked if it could be a grounding issue and he said No, it was definitely the converter.

He does a lot of work in the RV park and I've used him before several times. I'm pretty confident he was replacing it if it was necessary.

He installed a new converter and viola the lights are all working again.

[Ram Montana High Country]

Up size the converter when replacing

[DABOO77]

My monies on a bad converter. Acting / sounds just like my symptoms 2 years ago. Replaced the converter and all is good. I like the idea to upsize the converter when replacing, I did. Mine also came with a 10 foot pigtail lead with a small controller I can change charging modes depending on usage / storage situations. I placed the controller in a coat closet out of site but easy to get to.

Just FYI, I have a 2011 fifth wheel and my converter was a separate item from the fuse panel and was mounted behind my steps. I had to remove a panel in the front pass through compartment to access it.

Good luck.

PS,, current batteries seem to last approximately 6 years+/- a year. Probably a good idea to replace the battery also and start fresh.

[Jay Merritt]

5 year old battery in Texas heat - needs replaced

[DutchmenSport]

Read the post I put here: Click here. It's a similar problem as yours and my solution.

[jsb5717]

This thread is already resolved. The OP had the converter replaced and all is well.