FAP 7002 burns out when overriding autopilot

[Balaou]

I have an older Navpilot system with the FAP 7002 processor. Now for the second time the FAP 7002 has somehow burned out when I inadvertently overrode the autopilot for a few seconds. Both times the system blew the 25 amp fuse when I initially overrode the autopilot. When I replaced the fuse, both times it gave me the "drive unit is overloaded" error message when I replaced the fuse and tried to re-engage the autopilot. And then after getting that error message a few times, both times it started just immediately blowing the fuse when I tried to engage the autopilot. Both times the only fix was to replace the FAP 7002, at which point it was instantly fixed, so the "drive unit is overloaded" error wasn't the actual problem.

I can't believe that the system would be designed so that just overrriding the autopilot would blow the entire processing unit. I opened up the unit both times and the 2 internal fuses were not blown and there was no obvious damage. Does anyone have any tips for resetting the FAP 7002 when this happens without having to replace it (these units are getting hard to find!). It would also be nice to avoid the problem in the first place, as it's easy when things go south quickly to forget the autopilot is on and try to turn the stearing wheel.

 

[DannyAtSowilo]

I also have a FAP7002 and this has never happened me - so it is not super common.
And if it has happened with two FAP:s i suspect something else.
I would assume it is like the error code says, you have a problem with your drive unit that is overloading the FAP:s.
Mind you that fuses are often slower (metal need to get hot and melt) then the electronics so a sudden spike will kill electronics before the fuse is blown.
And that is my intial guess: When you override the unit a spike is generated.
What drive unit do you have?
What exactly did you do when you "overode" the autopilot?

 

[Balaou]

I also have a FAP7002 and this has never happened me - so it is not super common.
And if it has happened with two FAP:s i suspect something else.
I would assume it is like the error code says, you have a problem with your drive unit that is overloading the FAP:s.
Mind you that fuses are often slower (metal need to get hot and melt) then the electronics so a sudden spike will kill electronics before the fuse is blown.
And that is my intial guess: When you override the unit a spike is generated.
What drive unit do you have?
What exactly did you do when you "overode" the autopilot?

Override means I tried to turn the wheel left while the autopilot was trying to turn it right. Basically someone cuts in front of you on the ICW and you try to turn the boat away without remembering to disengage the autopilot first. The reason I don't think there is a problem with the drive unit is that it worked fine for many hundreds of hours before and after replacing the FAP7002, and the error was resolved by replacing the FAP7002 both times with no other drive unit errors ever showing up under any other circumstances afterward. I am thinking about putting in a 15 or 20 amp cb with the idea that a few nuisance fuse replacements are worth not having to find a new FAP7002 in the Bahamas on no notice or having to pay $1,500 for a spare.

 

[DannyAtSowilo]

Override means I tried to turn the wheel left while the autopilot was trying to turn it right. Basically someone cuts in front of you on the ICW and you try to turn the boat away without remembering to disengage the autopilot first. The reason I don't think there is a problem with the drive unit is that it worked fine for many hundreds of hours before and after replacing the FAP7002, and the error was resolved by replacing the FAP7002 both times with no other drive unit errors ever showing up under any other circumstances afterward. I am thinking about putting in a 15 or 20 amp cb with the idea that a few nuisance fuse replacements are worth not having to find a new FAP7002 in the Bahamas on no notice or having to pay $1,500 for a spare.

I assume your drive unit is based on an electrical motor. Anyhow your Override prevents the motor from rotating as it should. Correct?

An electrical motor is suposed to be able to rotate. If not a (very) high current can go through it.
If the FAP try to start the motor when someone hold the motor still with counter stearing I think the end result is an ugly electrical spike.
I think the spike will both kill the electronic drivers of the FAP and a bit later melt the fuse.
After this you have to either repair the FAP or get a new.

Conclussion: Override by putting the Autopilot in Standby first.

Btw: A fuse is mostly ment for protecting you from a cable fire - A lot of electronics are to sensitive to be protected by something getting overheated and melting. So if you want to try with another fuse the critical thing would be speed.

 

[Titanic II]

Navpilot 7xx should be on its own 30A breaker/fuse...nothing else connected to that breaker.

The reversing motor can be test independently by connecting directly to the 30A breaker bypassing the FAP7002. Reverse the +/- leads to move the motor both ways to make sure it does not pop/blow the breaker/fuse.

To override the Navpilot quickly I suggest adding the accessory SAFEHELM 2 https://furunousa.com/en/products/safehelm2. This way as soon as you input control on the helm it will kick the NavPilot 7xxx into STBY.

 

[Balaou]

Navpilot 7xx should be on its own 30A breaker/fuse...nothing else connected to that breaker.

The reversing motor can be test independently by connecting directly to the 30A breaker bypassing the FAP7002. Reverse the +/- leads to move the motor both ways to make sure it does not pop/blow the breaker/fuse.

To override the Navpilot quickly I suggest adding the accessory SAFEHELM 2 https://furunousa.com/en/products/safehelm2. This way as soon as you input control on the helm it will kick the NavPilot 7xxx into STBY.

Thank you, Safe Helm was exactly what I was looking for.