[TG] [TG11] A78 7" MFD wifi - failing to detect transducer

[Tom - Raymarine - Moderator]

Hello Darren,

Sorry you've not had a reply before.

The a78 detects the presence of the transducer using a simple 'sense' resistor. The value of the resistor denotes what class of transducer is connected. Because the measurement is so simple, it's normally very reliable.

We have seen sense resistance measurements fail because of electrical noise on the power supply or transducer cabling: in one memorable instance I dealt with, the owner found that his system consistently worked at low speeds but always reported no-transducer once he got above about 5 knots. The cause was very noisy charging voltage from his outboard, and when run off a separate house battery everything worked perfectly. It's worth, then just checking whether the system does the same on an independent battery if possible.

If it does then the next step would be to measure the resistance of the 'sense' line in the transducer cable, and if that checked out ok then perhaps something is making a poor contact inside after that rough trip home. That shouldn't happen and I don't recall coming across it before, but of course anything's possible.
I'll send you the transducer sense resistance check details tomorrow, but if this and the independent battery test check out then I think that you'd need to get the display checked, I'm sorry to say. We have a network of Service Dealers in the bigger population centres around the coast, and a service centre in Sydney.

Regards,
Tom