Autopilot Revenge

[sandpiper10471]

I recently replaced my water pressure pump. Now, if I am on autopilot (Raymarine 4000) and I turn on the water, the boat takes of hard to starboard. Somewhat disconcerting to say the least.

I don't believe this is an issue of current surge or depletion as I have also tested it at the dock on shore power. Besides, the water pressure is running off four new Trojan 105's. More likely it is some kind of radio wave interfering with the fluxgate compass (which is not even close to the pressure pump) or the head unit.

Any ideas on what is causing this? How to resolve it without swapping out the pump or leaving the water pressure off?

 

[tomgrigsby]

Might try one of those radio noise suppressors we used to put on our cars back when we had AM radios. You can probably still get one at an auto parts store. Either the pump is electrically noisy, or the new one draws more of a startup load than the old one did. Is the pump on the same breaker as the AP, or do they share a ground? (make sure your grounds are good and clean)

 

[Manny]

Does the ST4000 require a ground like the X-5? If so is the AP grounded to the battery or a ground plate below the water line? It may be interference and you may have to rethink the ground... It may not hurt to contact Raymarine for guidance.

 

[Bill Roosa]

Check your power and ground wires to the water pump. They SHOULD be running together to cancel out any magnetic field they generate when the motor runs. If they get separated or follow different paths you can get a fairly large magnetic field (that extends to infinity).
ALWAYS run power cables in pairs!
OR
The ground on the AP head/controlbox/motor is poor. Poor grounds allow noise into circuits which can play the devil with electronic equipment.
OR
You could have gremlins and they got into the water during the daylight hours.