[TG] [TG11] st4000+ control unit voltage

[timpa]

I have a st4000+ that wont operate the motor drive due to low voltage.

To bypass any possible wiring, battery or voltage drop problems I looked at the rear of the control unit and tested directly with a multimeter. A multimeter check of the control unit shows 12+ volts into it (the "12v" terminals) from the battery OK. When I engage the autopilot the "drive" terminals only show an output of 5 volts briefly then falling quickly to less than 1 volt.


When I bypass the control unit and feed 12v directly into the motor it works fine and can turn the wheel.

any thoughts would be appreciated.

[Tom - Raymarine - Moderator]

Hello timpa,

The drive output from almost all of our pilots is what's called pulse-width modulated (PWM), which means that the drive voltage is pulsed at a high frequency (tens of kilohertz) in order to provide more control over drive movement than a simple 12V would give. The pulses are actually 12V, but a multimeter is too slow to be able to pick up the peaks and only shows an average voltage. 5-6V is a normal voltage measurement for the drive output of a 12V pilot.

If the pilot's putting out ~5V average (0 - 12V pulsed output) and the motor's not responding but does to a direct 12 supply, then perhaps counter-intuitively that's actually a sign of a worn and failing motor. You can check this by connecting a different 12V motor or something like a 12V car indicator globe or incandescent nav-light globe to the ST4000's output in place of the pilot motor. I suspect you'll find that that other load works ok. I've seen failing motors work on direct 12V and not work on pulsed pilot output many times, and it's always been a motor problem rather than a pilot problem. If it were a pilot fault then you'd almost certainly see a flat 0V on the drive output.

Regards,
Tom

[timpa]

Many thanks Tom, I reckon you have nailed it ! The motor was soaked and "brought back to life" so I think its the culprit. Can I get a replacement anywhere ? Is the same motor used on the MK11 etc... or do I need a model specific to suit the ST4000+ ?

thanks again

[Tom - Raymarine - Moderator]

Hello timpa,

Is the drive you have wheel or tiller? If wheel, is it the black Mk1 or grey Mk2? Both wheeldrive versions were supplied with ST4000+ electronics at different times. Similarly, if it's a tiller drive, standard or GP?

Part numbers and availability, at the time of writing:
Mk1 (black) wheeldrive motor: part N012, no longer in stock here in Australia but I see that there are a handful overseas. If you place an order via your local dealer, we can likely get one in time, but personally I wouldn't invest much time or money in a Mk1 drive as it's probably pretty worn throughout; I'd replace with Mk2 wheeldrive, part E12093.
Mk2 (grey) wheeldrive motor: part A18086, in stock
Tiller motor, standard: part Q114, in stock
Tiller motor, GP: part A18013, limited stock

You can order any of these from Raymarine dealers, if you're happy to fit it yourself, or a Raymarine service dealer or service centre can fit it for you.

Regards,
Tom

[timpa]

Thanks Tom,
its a black wheeldrive so i will replace with the MK2 (E12093). I take it the MK2(grey) wheeldrive (A18086) isnt compatible ?

thanks again

[Tom - Raymarine - Moderator]

A18081 is the bare drive unit without fitting accessories, E12093 is the drive with torque restraint bracket, spoke clamps etc. (A18086 is the motor spare from within the Mk2 wheeldrive.)
The Mk1 and Mk2 drives have different fittings (we designed out problems with the Mk1 fittings in the Mk2), so you need the fittings. E12093 is the part you need to replace a Mk1 wheeldrive with a Mk2.

Tom