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Advanced Compass Troubleshooting

After following the Autopilot compass calibration procedure to the letter the autopilot will still not produce a deviation value. I am fairly technical is there any advanced troubleshooting I can perform

There are two instances that will cause the autopilot compass to not produce a "deviation" value during the Sea Trial calibration procedure

The first instance will be if the strength and characteristics of the magnetic field around the compass is to high for the pilot to get through the linearization procedure. Make sure that there is nothing around the compass that would influence this field. This would include equipment mounted on the other side of the compass bulkhead.

The second instance is a possible problem with the compass or the compass wiring. You should try to "box" the compass to see if there is an obvious problem. To "box" the compass put the pilot in STANDBY, next swing the vessel a full 360 degrees. Even if the compass is out of phase (out of calibration) you should see a nice smooth swing throughout the entire 360 degrees. A frozen compass heading indicates a problem with the compass input. Double-check your connections. The autopilot will most likely give the same frozen indication even if the compass was disconnected. If a problem with the compass is indicated then this could either be due to the compass, cable or compass circuit in the autopilot. The next step is to test the fluxgate compass using the procedure below.

Raymarine Fluxgate Compass Test (Multi-meter required)

Multi-meter should be set to:

(a) Resistance scale

(b) 200 ohm scale

The following procedure should then be followed:

1. Disconnect the transducer from the system.

2. Connect one multi-meter lead to the red wire and the other lead to the green wire and a reading

as indicated in the test data table should be present.

3. Follow the above procedure for all the color combinations indicated in the test data table.

4. If all readings match those indicated assume the compass transducer is functioning correctly.

Compass Test Data:


Cable Colors




Red to Green

4 ohms

Measurement is taken between the two colors




Red to Yellow

4 ohms

As above

Green to Yellow

8 ohms

As above

Screen to Blue

8 ohms

As above

All other combinations

Open Circuit


You are looking for a short or open. A +or - 2 Ohm reading is allowed.

If this check indicates a fault with the compass then you will be best served by replacing the compass. If no problem is indicated then you should send the compass and the course computer to a repair facility for evaluation.