Autohelm 6000 Bowing a Fuse

[ErikFinn]

My Autohelm 6000 is blowing the 5Amp fuse. I bought the boat recently and have never had the Autopilot working so far.
The system has two control units (indicating unit inside at the nav table, non-indicating unit outside at the helm).
When I switch the power on on the main control panel for the AP, I get the beep for a few seconds (nothing at the display) and then the 5 Amp fuse blows, the 40 Amp fuse is ok.
To me this would imply a bad connection somewhere, and I've replaced the connections from the linear drive unit to the course computer (corroded) but no improvement.

To eliminate a possible fault at the outside control unit can I just cut of the wire and see if there is improvement? Or do I have to remove connections at the course computer?

Anyone had similar issue? Any tips on where/what to check???

[Capn Dan]

If you have a Type 100 or 300 computer, the 5 amp fuse protects the Sea Talk (ST) circuit. There are two sets of ST terminals on the computer. Remove both sets of ST wires from the computer and power on the AP. If the fuse still blows, the problem is in the computer. If it does not blow, start connecting back the st wires, one head at a time, and see where the problem is.

[joemac4sail]

Worth checking is the circuit board in the cable junction box. Its attached to the computer. I found that the circuits had degraded over time (1992 model) and had developed micro cracks in the copper circuits causing intermittent faults, like blowing fuses and cutting out. The board was removed and repaired in 2008 and the Autohelm has been working fine since.
Regards Joe

[ErikFinn]

Originally Posted by Capn Dan

If you have a Type 100 or 300 computer, the 5 amp fuse protects the Sea Talk (ST) circuit. There are two sets of ST terminals on the computer. Remove both sets of ST wires from the computer and power on the AP. If the fuse still blows, the problem is in the computer. If it does not blow, start connecting back the st wires, one head at a time, and see where the problem is.

Thanks for your post Capn Dan,
the Course Computer I believe is "Type 2, Z051", about 20+ years old system; are the Type 100 or 300 computers a newer system and would your procedure apply to my system? I'm not sure but I think the "ST" came after the "Autohelm 6000"?

[ErikFinn]

Originally Posted by joemac4sail

Worth checking is the circuit board in the cable junction box. Its attached to the computer. I found that the circuits had degraded over time (1992 model) and had developed micro cracks in the copper circuits causing intermittent faults, like blowing fuses and cutting out. The board was removed and repaired in 2008 and the Autohelm has been working fine since.
Regards Joe

Thanks for your post Joe,
would these cracks be something I would be able to see with a naked eye, or how did you spot yours?
Where did you have your board repaired? I understand Raymarine has no parts anymore?
Regards,
Erik

[Capn Dan]

The early non ST would be similar. Remove the 4 wires that go to the control head and power up.

I am not familiar with a 5 amp fuse on the early 6000.

Where is the fuse located?

Joe is correct about the cracks. The solder joints tend to crack where the db25 connector attaches to the circuit board. You can not allways see them. If you remove the connector board from the box, just heat each joint with a fine tip soldering iron until the solder remelts.

I repair older autopilots if you can't get it sorted out.

[joemac4sail]

Disconnect the wires, not forgetting to label their position and then take out the circuit board . A good electronics guy should be able to repair or replace the board. Before I found the problem I sent of the autohelm computer to ray marine to see if it was the problem and I received it back with a clean bill of health. I had the feeling that they over specked the computer when they built it originally ( just a feeling on my part). Joe

[ErikFinn]

Done some more troubleshooting but had trouble uploading the pics from phone to laptop (I hate computers, lol), here is a photo from the AH6000 Installation and operating Handbook showing the fuse and the DC power supplies:

[ErikFinn]

Here is picture of the scenario when the fuse does NOT blow; I removed the connector unit (the small box in the picture) from the course computer and had the "Electronic Power Supply" (see pic in my previous post) connected to the connector unit, as evidenced by the 12.5 VDC on the multimeter display-
In this picture I also have the fluxgate and the control units attached. It didn't matter what devices were connected to the connector unit and the fuse would NOT blow, as long as the connector unit was NOT connected to the Course Computer. (see the end of the Course Computer with the pcb sticking out on the left of the pic.)

[ErikFinn]

The connector unit is connected to the course computer; the 5 Amp fuse blows.

[ErikFinn]

The connector unit is connected to the course computer, with or without the "Heavy duty Power Supply" and the "Output to Motor" cables connected; the 5 Amp fuse blows.

[ErikFinn]

I also tested the Linear Drive Unit by applying 12V to it directly and it seems to work ok, the clutch engages and disengages and the arm moves both ways with full movement.
So with all this info I believe the fault MUST be in the course computer, what say you?

[Capn Dan]

Here is the problem with the way you tested. When you remove the connector box from the computer board, you have disconnected power to the control head and the computer.

Connect the terminal box back to the computer. Remove the control head wires (A3 in your pic), remove the fluxgate and rudder reference wires. Now all you have is the power wires into the terminal box. Power it up and if the fuse blows, the computer board has a short. If it does not blow, add the control head wires first (A3) and power up. If the fuse blows, the control head has the short. Same for the compass and RR.

[ErikFinn]

Originally Posted by Capn Dan

Here is the problem with the way you tested. When you remove the connector box from the computer board, you have disconnected power to the control head and the computer.

Connect the terminal box back to the computer. Remove the control head wires (A3 in your pic), remove the fluxgate and rudder reference wires. Now all you have is the power wires into the terminal box. Power it up and if the fuse blows, the computer board has a short. If it does not blow, add the control head wires first (A3) and power up. If the fuse blows, the control head has the short. Same for the compass and RR.

Thanks Capn Dan, I think I tried that as well but just to be sure I'll try that again tomorrow.

[ErikFinn]

Originally Posted by Capn Dan

Here is the problem with the way you tested. When you remove the connector box from the computer board, you have disconnected power to the control head and the computer.

Connect the terminal box back to the computer. Remove the control head wires (A3 in your pic), remove the fluxgate and rudder reference wires. Now all you have is the power wires into the terminal box. Power it up and if the fuse blows, the computer board has a short. If it does not blow, add the control head wires first (A3) and power up. If the fuse blows, the control head has the short. Same for the compass and RR.

Capn Dan,
I removed the control head wires, and the fluxgate wires as per the pic below, leaving only the "Electronic Power Supply" connected to the connector unit, and the connector unit connected to the Course Computer. The fuse blows when I switch on the power on the boat's main electric panel for the AP.
Was this the setup you were looking for?
(BTW, the polarity of the brown and blue wires IS correct, I checked for that, the previous owner did not use the correct color coding for the wires... )