Low Voltage - Raymarine Autopilot SG3

[geoffr]

Wondering if anyone has a solution to this problem:

Our Raymarine Autopilot SG3 // ST6002 is giving us "Low Voltage" alarms when I know the voltage to it isn't low as our batteries are being charged. Does anyone know if it gives the same error for higher voltages?

The problem seems to go away in the afternoon after motoring all morning...

[skipmac]

Low voltage alarm only indicates low, not high voltage.


How do you know the voltage isn't low. Are you sure whatever charging system is active is putting out full charging voltage? And if the charging is good have you checked the 12V wires supplying power to the AP? Over time connections can corrode or get loose so voltage at the batteries may not be getting to the AP.


You need to check the voltage at the AP and while it is under load and operating the drive motor.

[kipwrite]

On my B&G autopilot, I was getting low voltage alarm as well, under similar circumstances. Batteries were charged, but I found that when I ran a winch under load, after sailing without charging for several hours, I’d get a ‘low can bus voltage’ alarm on the autopilot display. On B&G there is a setting that allows you to see can bus voltage at one of the displays, and it fell below 11.8 volts or thereabouts, triggering the alarm, under these conditions. I do not know if there is a high voltage alarm in B&G or Raymarine.

After consulting with my dealer, he recommended and installed a power jumper line to add more current to the network near the autopilot, which completely solved the problem. There is a voltage drop somewhere in the network, but this little jumper wire solved the issue. I suppose if the problem returns we’ll chase down the loose connection that’s the underlying cause.

Hope this helps.

[geoffr]

I am measuring the voltage right at the screw terminals on the Autopilot computer, so not likely a wiring problem. Also the low voltage alarm does not seem to be related to the hydraulic pump being driven - IE if I push +10 degrees a number of times the pump works hard.. no error message.

[DeepFrz]

What voltages are you measuring at the batteries and at the autopilot drive both when motoring and when the motor is stopped? If the problem goes away after motoring for a while then that points to low system voltage.

[Snore]

When I purchased my boat I discovered that many of the devices had under size wire. Start by checking the wire size suggested vs what is in the boat.

Next check your connections, a lose or corroded connection can cause an under voltage situation.

My bet is on #1.

[skipmac]

Originally Posted by geoffr

I am measuring the voltage right at the screw terminals on the Autopilot computer, so not likely a wiring problem. Also the low voltage alarm does not seem to be related to the hydraulic pump being driven - IE if I push +10 degrees a number of times the pump works hard.. no error message.

So you are seeing 12.5V or more at the AP? What is the voltage in the morning vs after motoring all day. Is it possible the battery voltage really is a bit low in the am after running lights and house loads all night.



Assume you checked to make sure the wires are tight on the terminal, no corrosion, etc.


What about the output from the computer to the drive unit? If that's good as well then seems like the only thing left is the computer itself.



Last idea, is there an adjustable setting for what voltage is considered low?

[skipmac]

Originally Posted by DeepFrz

What voltages are you measuring at the batteries and at the autopilot drive both when motoring and when the motor is stopped? If the problem goes away after motoring for a while then that points to low system voltage.

I would say this is a strong possibilty.

[geoffr]

In the morning the house bank is down (but well above 12.5), so the Balmar MC-614 will be operating in bulk mode trying to get to 14.9V. I know I measured 14 point something volts when the problem was happening. By the afternoon while still motoring the batteries will be charges so sitting in float of 13.5V

MC-614 settings:
Bulk limit 14.9V
Float limit 13.5V

[svmobert]

It's unclear from your comments what the voltage was when you measured AT the S3 power terminals. Was that the 14V you measured?

Disconnect the power leads from the smartpilot course computer... Cut the ends, stripe new exposed ends and reconnect. Ensure that the wires going into the terminal block are clean and not corroded.

Do the same for the drive unit power leads and the SeaTalk wires. Check and replace the fuses inside the course computer, check for corrosion on the fuses.

Measure the voltage with the autopilot running and drive moving.. Check it at the terminal screws in the course computer, check it at both sides of the fuses inside the course computer. See if the voltage drops when the drive is moving.

[geoffr]

Here is what I was able to measure the other day while motoring:

In the morning:

• 14.80V @ at the terminal screws on the SG3 computer
• 14.82V @ Bus Bars

Just after the low voltage alarm went off:

• 14.85V at the terminal screws on the SG3 computer

While the low voltage alarm was going off:

• 14.86V at the terminal screws on the SG3 computer

At the end of the day (hadn't seen a low voltage alarm in a long time):

• 13.67V at the terminal screws on the SG3 computer

These numbers seem to make sense as my Balmar MC-614 is set with a bulk limit of 14.9 and float of 13.5

I will be wiring in my fluke meter which will report high/low voltage levels so I can be sure I haven't missed a very short drop etc.

I'm still confused because if I am measuring at the screws on the SG3 I can't see how the voltage could be low.... unless its a very brief droop.

[Snore]

Originally Posted by geoffr

Here is what I was able to measure the other day while motoring:



In the morning:

• 14.80V @ at the terminal screws on the SG3 computer
  
• 14.82V @ Bus Bars
  

Just after the low voltage alarm went off:

• 14.85V at the terminal screws on the SG3 computer
  

While the low voltage alarm was going off:

• 14.86V at the terminal screws on the SG3 computer
  

At the end of the day (hadn't seen a low voltage alarm in a long time):

• 13.67V at the terminal screws on the SG3 computer
  

These numbers seem to make sense as my Balmar MC-614 is set with a bulk limit of 14.9 and float of 13.5



I will be wiring in my fluke meter which will report high/low voltage levels so I can be sure I haven't missed a very short drop etc.



I'm still confused because if I am measuring at the screws on the SG3 I can't see how the voltage could be low.... unless its a very brief droop.

These are the symptoms of underside wiring or a bad connection. Static voltages are good, but under load there is a voltage drop. Did you check your connections? Did you check the gauge of the wire?

[geoffr]

Originally Posted by Snore

These are the symptoms of underside wiring or a bad connection. Static voltages are good, but under load there is a voltage drop. Did you check your connections? Did you check the gauge of the wire?

I would normally agree with you, however I only see this problem at the start of the day when the voltage is higher.. which is what is confusing me so much!

The wire is AWG8 which is oversized according to the documentation for the SG3 and Type 2 pump. The run between the breaker and SG3 is perhaps 8 feet. There is no corrosion at all on the wires.

[smac999]

have someone steer the pilot back and forth while measuring and see if the reading changes at all. but those are certainly high. I bet the low voltage alarm is down around 11v.

if you are still getting 14v and the alarm is going off then the computer has an internal fault. or it is actually alarming for high voltage. I would set the reg to 14.4v bulk and see if the problem goes away.

[jamhass]

I'm not on our boat, but I seem to recall that the power connector is removable. Try checking for corrosion there. Also check the internal fuses and their contacts. Doesn't take much contact resistance to cause problems