[DG] [DG] AH4000 control unit replace

[KariR]

I have an old AH4000 Wheel Drive autopilot which has served now 26 years. In later years it has suddenly switched to stand by and now the last year it totally stopped to work after a while. However, after a day or more it starts to work again for a while! I have checked all wire connections and have not find any failures. I believe that the control unit has now fulfilled its duty and needs to be replaced. The old unit is not anymore available to buy and thus I have thought to upgrade it to a newer one. The drive unit itself seems still to be ok. I would not like to spend money to buy a completely new system so I wonder if the newer Raymarine control units are compatible with the old AH4000 wheel drive unit?

[Derek - Raymarine - Moderator]

HI KariR

Thank you for your enquiry.

The replacement control unit for the AH4000 was the ST4000 and sadly this is discontinued too. the current replacement for this is the EV100 part number T70281, this kit includes all the electronics required, but not the drive unit.
Regards
Derek

[KariR]

Hi Derek,

Thank's for your reply. I may look after the ST4000 in second hand shops. On the other hand, does the T70281 kit work well with the old drive unit? I'm interested in connecting the autopilot to my chartplotter.

I may have now a third possibility: I found that one of the Darlington transistors regulating the power to the drive unit is broken (short cut between B and C). I'm just waiting for a new transistor and after replacing the old one the control unit may work again? Anyway, this is a cheap try (less than 1 €/ transistor + delivery costs). This failure with the power may explain the earlier sudden drops from auto to stand by and the final stop of working, where I found that the control unit gave only 0,1 V to the drive unit. (However, in this case no possibilities to connect to the chartplotter.)

Best regards,
Kari

[Derek - Raymarine - Moderator]

Hi KariR

The T70281 will work as well with the older drive as it will the new one, just bear in mind you are connecting old mechanics with possibly a fair amount of wear and tear to new electronics and so may compromise operation and reliability.
Thanks
Derek

[KariR]

Hi Derek,
You are right! I just fixed the control unit but that did not help because the drive unit does not work properly! I noticed that the motor works well only to one direction. At the other direction it gets stuck. I may try to repair this too, but as you say, it seems to be best to by a totally new system. Is EV100 what you would recommend?
Regards,
KariR

[Derek - Raymarine - Moderator]

Hi KariR

The EV100 Whellpilot is the one we would recommend assuming your vessel weighs less than 7500kg fully loaded and kitted out ready for sea.

Regards

Derek

[KariR]

Thanks Derek,

The EV100 seems to be my new wheel pilot, if I can't anymore fix my old one. However, I still try to replace the old defective motor with some new one, if I will get it low-priced. You know, I have become attached to my old so many years faithful servant.

Best regards,
KariR

[Derek - Raymarine - Moderator]

Hi KariR

Good luck,

You are welcome

Thanks
Derek