Fujitsu AST30ABA-W Indoor fan speed issues.

[Raisins78]

Hi.
As above im having issues with 5 x splits.
All 5 were running fine for years untill today, now they still run perfect on low and medium fan speeds, but when they are turned to high fan, the indoor fan switches on and off every second, like clockwork. no codes are showing, and all 5 in this building are doing it which is making me think its not faulty boards etc, cause when does 5 machines all fail at the same time, except a power problem.
Sounds more like a software, enviroment issue.
Has anyone come across this before?

Enviro stats right now...
Outside ambient - 29C
Inside ambient - 24C
Outside RH 89%
Inside RH 63%
Town is pretty much located on the Tropic of Capricorn, so fairly tropical weather.
Pressures, temps on and off, both indoor and outdoor are great, except when fan is on high.
Comp and cond fan both run as normal when on high.
no flashing lights.
no codes.

[cool_tech]

could be a faulty pcb. check to see if all wires are tight. can you take high speed out of fan by cutting wire and putting a connector on it to test if it is pcb or motor. give it a try. i would also look at the humidity could cause pcb problems
lj

[Raisins78]

Same thoughts as me, untill we found all 5 units started doing it, all today. Pretty rare coincidence that we have all 5 Fujitsu's with PCB failures in one building in one day. All other units in this building are Acson and Daikin (17 in total.)

[install monkey]

units in dry mode- indoor fan stops,starts every second-try cooling-snowflake symbol:p:p

[Raisins78]

LOL. no, its on cooling. as above, it runs 100% perfect on med and low speeds, just high speed fan is when the problems occur.

[Raisins78]

ps. went through the units from top to bottom with Fujitsu Tech Support on the phone, tested everything possible inc fan motor winding resistances, sensors resistances etc, voltages, frequency (its on a mine site, so can be different) current etc.
Seems the boards are switching the fan on and off (on high speed only) but no idea why, or why all 5 have gone at once.
I am ordering new boards anyway, and fans, just for the hell of it. Fujitsu arent sure, and have never seen them do this.

These units also run 24/7 as they are in a Laboratory office area's, and this place doesn't close, ever.
always set at 23C, cooling, high. Remotes are removed and kept with us to stop people playing with them, setting them at 18C etc.

[mikeref]

First thought was high ambient and the indoor evaporator sensor freaking out on high superheat. Could be the fan relay has given out. Are a/c,s normally left on high fan speed? Strange that all 5 are doing the same :confused:.

[oldmanriver]

Very strange for all five to go at once- though if they were all running on the same speed setting, its possible a power spike of some sort has damaged the control board in the same way on all boards. Being a mine site powers not always reliable.

[cool_tech]

Is the power fed from a generator? and is there a lot of VSD s on site? maybe just run them on medium speed... job fixed lol

[Raisins78]

Gas fired power station. Just changed a board and motor (ordered three of each) no luck. Still doing it