VIN vs Onboard 12v - Tacho Signal

[JabawokJayUK]

Hello all, Is it expected behaviour to lose the tacho signal on a 4-wire fan if you switch from the onboard 12v to VIN? on OUT3/4 on the DUET 3 Mini 5? I am using 24v 4 wire fans for a circulation system and if I use the 12v, I get a tacho signal, but if I switch to VIN, I lose the tacho signal.

Many thanks

[T3P3Tony]

@JabawokJayUK do you have a fan datasheet?

[JabawokJayUK]

@T3P3Tony sure, I am using a pair of these: https://publish.sanyodenki.com/San_Ace_E/book/#target/page_no=60

[JabawokJayUK]

@JabawokJayUK specifically: 9GA0624P6G001

[dc42]

@JabawokJayUK no that's not expected. Have you left the fan connected to OUT3 or OUT4 and just moved the jumper on the Duet from the 12V position to the VIN position?

[JabawokJayUK]

@dc42 yes. the fan is on OUT4. the jumper is set to VIN.

[dc42]

@JabawokJayUK I've checked the specifications of that fan. It should be compatible with the Duet, provided that you have wired it correctly to the Duet.

[JabawokJayUK]

A further point of clarification:

OUT3 is connected to a 12v water pump, but only the PWM & Tach signals are connected. +12 is direct from an external PSU.

OUT4 is connected to the 24v FAN (all 4 wires).

Neither device shows a Tach signal when VIN is selected. Both show a tach signal when 12v is selected.

[dc42]

@JabawokJayUK please provide a phot or photos showing how you have connected the four colour-coded wires to the fan connector on the Duet.

[JabawokJayUK]

@dc42 it's printing at the minute, so I don't want to go poking around the wiring. I will take a good look at the wiring later, and if I find an obvious issue, I won't reply to this thread! The fact it is not expected behaviour at least points me in a good enough direction to continue debugging.

Thanks for the assist.