Marco UP6/E pump and MASS+ light

Scott SV Tengah

Hi all,

I've been using the Marco UP6/E pump for domestic water for almost 6 months now. I've been quite happy with it. I regularly check the Mass- and Mass+ switch on my A54 to ensure no electrical leaks.
This evening, I checked and got a Mass+ light, clear and bright. Luckily, I was able to quickly isolate it by turning off the freshwater water pump on the 24v circuit breaker panel. The only way I could get rid of the Mass+ light was remove the bonding wire from the pump body. Do you know what may cause the Marco pump to all of the sudden create continuity between + and the pump body? 
I had a small leak from the watermaker hoses so some salt water got on the Marco pump, but could that cause a short somewhere and cause the pump body to be + energized? 

As an aside, had some issues with the smart sensor positive lead (between smart pressure sensor and pump itself) keeping the Amel 24v panel freshwater pump light on permanently. We couldn't figure it out so I just moved on and dealt with the 24v panel freshwater pump light being on all the time. Has anyone else using the Marco pumps figured out how to wire this so the Amel 24v panel light only comes on when the pump is being operated? Also, to test to see if this was causing the Mass+ fault, I cut the wire. The 24v panel freshwater pump light obviously is no longer on, but the Mass+ light remained.

Any thoughts on the Mass+ light or getting the Amel 24V panel freshwater pump light to work properly with this pump would be appreciated!

A54 #69 Tengah

Bill Kinney <greatketch@...>


Salt water is almost certainly the cause for a short circuit between the pumps electrical supply and the case and hence the bonding system. The other, less likely, possibility is accumulation of carbon dust from worn brushes. 

The solution is to disassemble the motor, clean with fresh water, dry, spray with CorrosionX, and reassemble. 

Bill Kinney
SM160, Harmonie
Mayaguana, Bahamas

Scott SV Tengah

Thanks Bill, you're likely right.

But I am going to reach out to Marco to see what they say. I wanted to open it but the manual clearly states that the warranty becomes void if I try to service it!

Duane Siegfri


I had the same issue (masse light) with my Marco UP3E pump.  I would be very interested in what you may have learned.. 

I also removed the bonding wire from the pump to solve the problem.  However, a year later the pump stopped running in a place I could not easily replace it.  I disassembled the motor and found the motor brush wire was completely corroded and had fallen apart.  I'm guessing that the corroded wire was touching the case???  As a temporary repair I soldered in a new brush wire, but I don't expect it to work for long. 

I'm not sure what caused the brush wire to corrode.  Only one of them did, the other was fine.  Now I need to replace the pump and I am not sure I want another Marco pump.  The cause of the corrosion could be external to the pump I suppose.  There were not any leaks wetting the pump.  The only thing I can think of causing the corrosion was the plumbing fittings I used.  They were advertised as 316 stainless steel, but they are corroding internally like mad.  I'm replacing that plumbing with Pex, plastic fittings and stainless pinch rings.

Wanderer, SM#477

Alan Leslie

We have a Marco pump on Elyse and don't have it connected to the bonding system.
As I understand it the bonding system as far as pumps etc go is only applicable to those items in contact with salt water.
Regarding the 24V indicator panel light, we have the original wire connected to the red wire between the smart sensor and the pump.
The green light on the panel comes on when the pump cycles and goes off when it stops.
Our pump has been installed now for 2+ years and we have had no issues with it.
Elyse SM437