Intermittent Side Thruster bow thruster issues

I have a 2003 trawler with side thruster bow and Stern thrusters. I’m having an intermittent problem with the bow thruster. It’ll work Port to starboard two or three times for less than three seconds pulses then starboard it quits. Port is fine. Wait 10 -15 minutes and the behavior repeats itself. Pulses are limited to less than 3 seconds. This happens in all stations and Remote. I replaced the Side thruster interface module but the same thing happens. Stern thruster OK in both directions, Bow thruster good in port but intermittent in Starboard. Any ideas?

Bad relay? There are big relays on or near the motors. Look to see if it’s closing when you move the lever.

Could also be low voltage, do you have isolated thruster batteries, or combined? Have you load tested them?

Usually the thruster relays are built into the thruster. If the thruster works in one direction but is intermittent in the other, it's unlikely a battery issue.

While it could possibly be a relay, they generally work or don't. It seems unlikely that it would repeatedly work for a few seconds and then quit.

The first place I would look is the motor brushes. Near the end of brush life, one of the brushes may not be making good contact on the armature (getting cocked in the holder, chipped, spring tired, etc). The reason it could work in the opposite direction is that the armature is turning the other way where the brush could move to make better contact. I would consider pulling the brushes, blowing the dust (carbon) out, and inspecting both the brushes and the armature.

Ted

Bmarler said:

Bad relay? There are big relays on or near the motors. Look to see if it’s closing when you move the lever.

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I think Bmarler has the answer. I had the same issue years ago. Worked one side and not the other. It was a bad relay.

Rob

I agree with OC Diver. Sticking brushes are a common issue and it's easy to check.

BTW, Sidepower has a great troubleshooting video.

welippisch said:

I have a 2003 trawler with side thruster bow and Stern thrusters. I’m having an intermittent problem with the bow thruster. It’ll work Port to starboard two or three times for less than three seconds pulses then starboard it quits. Port is fine. Wait 10 -15 minutes and the behavior repeats itself. Pulses are limited to less than 3 seconds. This happens in all stations and Remote. I replaced the Side thruster interface module but the same thing happens. Stern thruster OK in both directions, Bow thruster good in port but intermittent in Starboard. Any ideas?

Click to expand...

I had this issue with my Vetus thrusters. It turned out be problems with the switches at the helm station. I was able to take apart the switch assembly and then replace the faulty switch and reassemble. If I recall, the part was extremely cheap, compared to what Vetus wanted for a replacement for the switch assembly.

Sounds like a bad contact or thermal overload.
Corroded contacts create heat and higher amp draw. Most high draw motors have thermal cutouts. Had the same problem with a windlass. Wound up being a corroded contact at the windlass to power cable.

I have experienced the same problem . I agree with OC Diver as far as blowing the commutator section out and examining the brushes carefully. This is easier to do with the thruster removed from the boat and placed on a bench. These brushes on some models are no longer available so be cautious. My brushes were in excellent condition and had plenty of brush length left. The brushes can be visually examined in length without even removing them which is the most cautious thing to do . If removed, be sure to put the same brush back in the same location facing the same direction as it was removed for they do have some wear pattern based on rotation of the commutator. My suggestion is to pull the entire Thruster motor which will allow you to inspect the relays as well. While you have gone to the trouble of removing the Thruster which is no easy job, you can replace the relays if there are old as mine were. After doing this work to mine it works extremely well. Hope thus helps.

I'm seconding either low voltage or the brushes. Measure the voltage at the thruster while operating.

Everyone is assuming (perhaps correctly) that the OP's thrusters are electric motor driven . . . .
I had almost the same situation happen to us, but we have a hydraulic bow thruster. It turned out to be the spool valve for the hydraulics.

It is most likely a loose or corroded connection in one of the plugs in the wiring harness.