Hydramaster 4.7 CDS Help

Diego-

New Member
Dec 22, 2020
2
0
1
Real Name
Diego Julio
Hello,
I recently bought an older Hydramster 4.7 CDS. Everything works great except it doesn't pump in water from the fresh water tank. and in these cold days I need to use the water on board. When I turn the machine on and turn the switch on for the fresh water pump the light doesn't even turn on (at Panel). I also can't hear the pump working. The pump is directly wired to the inside of the panel. How can I distinguish if this is a bad pump or an electrical issue?
 

SRD

Premium VIP
Nov 6, 2010
5,823
4,502
113
midwest
Real Name
Spencer Dawdy
Business Location
United States
Continuity and power check from hot on panel switch to hot on pump if you have both pumps bad. If your pumps one with a microswitch vs an internal bypass check the mucriswitch 1st
 

JDARNOLD

Active Member
Jul 31, 2012
338
131
43
60
Real Name
Edward Arnold
Business Location
United States
Hello,
I recently bought an older Hydramster 4.7 CDS. Everything works great except it doesn't pump in water from the fresh water tank. and in these cold days I need to use the water on board. When I turn the machine on and turn the switch on for the fresh water pump the light doesn't even turn on (at Panel). I also can't hear the pump working. The pump is directly wired to the inside of the panel. How can I distinguish if this is a bad pump or an electrical issue?
 

JDARNOLD

Active Member
Jul 31, 2012
338
131
43
60
Real Name
Edward Arnold
Business Location
United States
When you say older, how old. When you look in the water box does it have a float like a toilet bowl, or does it have two switches one above the other. If you have the two switches the pump is wired to the switches through a relay. when both switches are down they turn on the pump and when both are up the pump cuts off. It could be the relay, the switches.
 
  • Like
Reactions: SRD

CarpetConveyor

New Member
Jun 6, 2022
1
0
0
Real Name
Nick Jones
The problem with using a 12v fresh water pump, is how the water box manual float and the demand pressure switch on the 12v pump work together. The water box float opens and closes to rapidly or the float flows water at a low gpm which is something these 12v pumps switches do not like, creating the 12v pump demand switch to overheat which temporarily makes the pump stop working till the switch cools off. Over heating this switch multiple times will destroy the demand switch eventually which is the problem. These pumps are designed to run approx. 3 gallon a minute or more like a house/rv faucet and the water box float limits this gpm, to less then half a gallon per minute at times which causes the demand pressure switch to over heat and stop working.

There are multiple ways to help with this. 1. Accumulator tanks, create passive pressure that is designed for this issue but not always perfect. 2. Or you can use a limited bypass hose to flow and circulate water back to you fresh water tank so the pump is always flowing water. 3. Or you can just run the 12v pump directly by bypassing the demand switch function. You can do this by changing 12v electric wires directly to the motor and always running the pump motor constantly which works good a long as a alternator is powering it. 4. Another thing that they do not make yet, that would allow the demand switch to work right, is a differential float in the water box. A differential float closes when the tank is full but opens after the tank has emptied a certain amount or a bit lower then full. Not just on off rapidly like the floats they sell now and always have sold. Someone needs to make this differential float soon.
IMG_20220606_084205625~2.jpg

This picture is where they use differential float in large water tanks but they do not make it for smaller tanks like truckmounts have. Again someone should make and sell this.

Using a garden hose directly, you will not see these issue.