Water pump causes led lights to flicker when on Battery

dougrainer wrote:

1L243 wrote:
I measured voltage coming back through the ground from the dinette light in the slde out. I dont think that is normal. My experience has been that power going to ground usually blows a fuse or melts a wire. But in this case nothing seems to be affected by it.

I have 38 years working on RV's and a LACK or LOOSE ground will not cause a fuse to blow or melt. There is no path for current. Doug

I agree with that statement but in my case to track down the problem, I found two issues. A broken ground bolt on the frame of the trailer which fixed the pulsating light issue when on water pump power only

AND

10.8 volts of power coming from the dinette light into the GROUNDING block bolted to the floor behind the converter.

In my experience power transferring over to the ground side can blow a fuse but it's not. In fact I can't find it doing anything at this point because everything is working.

If I had access to the wiring of the dinette light I am sure I would find the issue that's causing the power to ground but I have no access.

1L243 wrote:
I measured voltage coming back through the ground from the dinette light in the slde out. I dont think that is normal. My experience has been that power going to ground usually blows a fuse or melts a wire. But in this case nothing seems to be affected by it.

I have 38 years working on RV's and a LACK or LOOSE ground will not cause a fuse to blow or melt. There is no path for current. Doug

I measured voltage coming back through the ground from the dinette light in the slde out. I dont think that is normal. My experience has been that power going to ground usually blows a fuse or melts a wire. But in this case nothing seems to be affected by it.

1L243 wrote:
Problem solved!

I was checking the 12 volt grounds behind the converter. There is a grounding lug screwed to the floor for additional 12 volt grounds. I had checked them for tightness earlier but this time I decided to pull each one out to check for broken wire. Some had more than one wire going in the grounding clamp.

I pulled the one that had the water pump going to it along with two other wires and when I went to put it back I got a spark. I separated the 3 grounding wires and found that one wire coming from the overhead light in the dinette slide had 10.5 volts going to it??

There is no access to the wiring above the slide so I went under the slide and was checking the harness when I discovered a grounding lug from the battery to the converter was not connected to the frame. The bolt had broken. I refastened the ground lug and the water pump would now work without flickering the LED's.

The dinette light grounding wire is still getting feedback but at this point it does not seem to be affecting anything. The light works and fuses are not being blown???

Why would a fuse blow from a bad or NO ground? Because that is NOT a short. Overload or short will cause a fuse to blow, but NOT lack of ground or loose/bad ground. Doug

Problem solved!

I was checking the 12 volt grounds behind the converter. There is a grounding lug screwed to the floor for additional 12 volt grounds. I had checked them for tightness earlier but this time I decided to pull each one out to check for broken wire. Some had more than one wire going in the grounding clamp.

I pulled the one that had the water pump going to it along with two other wires and when I went to put it back I got a spark. I separated the 3 grounding wires and found that one wire coming from the overhead light in the dinette slide had 10.5 volts going to it??

There is no access to the wiring above the slide so I went under the slide and was checking the harness when I discovered a grounding lug from the battery to the converter was not connected to the frame. The bolt had broken. I refastened the ground lug and the water pump would now work without flickering the LED's.

The dinette light grounding wire is still getting feedback but at this point it does not seem to be affecting anything. The light works and fuses are not being blown???

1L243 wrote:
Today I checked battery connections, water pump connections and connections at the converter power supply. All seemed fine.

The trailer is a 2017 and has two new batteries. I installed a battery monitor inside the trailer wired directly to the the batteries.

When on battery and running cabin led's and the water pump the voltage drops about .08volts on the monitor. The lights only flicker when on battery they don't flicker when plugged into 110.

Have you determined if the lighting and water pump are on the same fuse? If so, depending on how the traier is wired, the LEDs may be seeing more voltage variation than your battery monitor is showing. Also how far is the water pump from the power panel and also from the pump switch?

The actual instantaneous voltage variation also may be larger than your battery monitor is showing due to the transient high start current pulled by the pump motor as it pulses on and off. You might be able to reduce the flickering by connecting a large (> 100 ufd) capacitor across the pump power and return to provide some of the surge current.

GordonThree wrote:
The battery monitor isn't going to react fast enough to show you what's going on. Your eyes and LEDs are much faster than the monitor.

What does the dealer or manufacturer say? Is this a problem for you, or just an annoyance?

Open up a light fixture and attach a multi-meter in parallel with the power leads for the fixture. Turn the light on, and watch the meter closely while someone else operates a faucet somewhere. What numbers are you seeing?

I try to avoid the dealers for repairs unless absolutely necessary.

I imagine if your were dry camping and someone was using the shower for several minutes the flickering would be pretty annoying.


I checked the voltage at the light and there is a significant voltage drop.

Measured at light fixture
LED lights off 12.67 v (no water pump)

With only one LED test light on...12.48 v (with no water pump)

With only one LED test light on 10.88 v (water pump on)

I spoke to a guy who just bought the same trailer and his lights don't flicker..

I have rechecked all the connections from the water pump to the converter and found noting loose???

It is a new trailer and I did not discover this little problem until after I added some TV's (they should not be related as they are not connected to 12 volt and were pre wired), second battery and battery disconnect switch (I have disconnected both and problem still exists) Battery monitor(goes directly to battery not connected to trailer system)

http://www.mouser.com/ProductDetail/United-Chemi-Con/E36D500LPN103TA67M/?qs=sGAEpiMZZMtZ1n0r9vR22eR2bRpDnYLenEFVrOOgPd0%3d



Image data wrong. Link is to a 10,000uf electrolytic capacitor. Uses 2 10x32 terminal screws. One + and one -

Connect + to power wire going into pump. Connect - to chassis negative wire at pump. Two wires, one red and one black. 2 10x32 ring terminals and a pair of "T-TAP" pinch on terminals.

Observe polarity that + goes to positive. This ends all lighting fluctuations forever. I've QUIETED many a Shur Flo pump as well as cured flickering lights by adding a capacitor. Cost, installation are negatives although very minor. Advantage: No snipe hunts.

The battery monitor isn't going to react fast enough to show you what's going on. Your eyes and LEDs are much faster than the monitor.

What does the dealer or manufacturer say? Is this a problem for you, or just an annoyance?

Open up a light fixture and attach a multi-meter in parallel with the power leads for the fixture. Turn the light on, and watch the meter closely while someone else operates a faucet somewhere. What numbers are you seeing?

Mine will do the same thing if I take the 2 gallon accumulator out of the pluming. I know the new shurflo pumps are suppose to operate fine without one but they eliminate this problem and keep the pump from cycling so much. I will never have an RV without one. I disconnected it due to a leak in the plumbing but reconnected as soon as I found the leak and fixed it.

Sam