Hitachi ras-6hg8e fan not running

[Glennprice]

Hi there this is my first post
I been working on a hitachi twin fan ras 6 hh8e condenser, it is a twin split and a heat pump, it displays a fault code 02 on the wall mounted controller. Which is an outdoor safety device is active, when the unit is switched on compressor runs and one fan runs, after about 3 mins then fan stops and the compressor carries on running , according to hitachi this is normal, then condenser coil gets very hot and trips on high pressure, but this doesn't happen everytime, sometimes only one fan kicks back in and there's not a problem, speaking to hitachi helpline they reckon the pcb is gone and one of the relys aren't working properly that's why only one fan runs and it only kicks back in sometimes,
What do you guys think?

[Greek_engineer]

Look at sensors or it may be the pcb.

[Glennprice]

Yes they told me to order a señor with the pcb but I couldn't see what señor brings the fan motor in

[al]

Run the second fan off a high pressure switch, run at high speed. way cheaper than the PCB. Is that a r22 unit?

Also check if there is a capacitor fitted to fan, change that first.

al

[install monkey]

had the same issue with a set free unit- alarm relay coil was week- kept alarming on 02 error, usually theres a fan speed controller pcb,bypass it so fan runs at full tilt to see if this cures it

[Glennprice]

It's a r407c unit only not inverter, I've tried running both fans by swapping them around on the pcb and both fans work but only one will run, only one pcb on this unit

[install monkey]

has the pcb got the 3 adjustable pots- set increase the minimum speed and decrease the set temp

[Glennprice]

Don't think it has any adjustments but shall have a look

[Glennprice]

Thanks for your help people

[install monkey]

http://www.mediafire.com/view/?qi1pgdbwine2ef8 service manual for thermistor values and 02 diagnostic flow chart

[Glennprice]

Brilliant thank u

[Glennprice]

Do u know which sensor brings the fan on ? As the only sensor this unit has
Thm7 which is outdoor air temp
Thm8 which is pipe temperature
Thm9 which is compressor temp
That's it :/

[install monkey]

cond fans controlled via control hp switch labelled as ps(c) connection pcn2 on pin 1,3 pin 5 crankcase htr(on main pcb) technical info and wiring diagrams http://www.mediafire.com/view/?959ry6hxokl4dbt
Do u know which sensor brings the fan on ? As the only sensor this unit has
Thm7 which is outdoor air temp
Thm8 which is pipe temperature
Thm9 which is compressor temp
That's it :/

[install monkey]

ps c pressure switch will control fan fans at low speed ,ps h on pcn5 will run hi speed, check winding resistance on all fan tappings,and also the fan thermistor ito1 and it02 test at the 6 pin fan plug cn20,21 pins 4 and 5 for continuity when not powered or 240 in,out on a fan that's not running

[Glennprice]

Pressure switch ?? Is that connected to discharge pipe work from compressor? So in theory if that wasn't working I could disconnect them from the pressure switch join them together and fan should run ?

[Glennprice]

Because there's 2 pressure switches on the pipe work one for high pressure and the other to bring the fans in when pressure rises to a certain point?

[install monkey]

by the look of it, if you joined the psc wires together then that should run the fans in low speed, by joining psc and psh should run both fans in high speed-wiring diagram is vague as it goes back to the pcb , but it does show yfan and yfon as 2 relays- they could have worn contacts or be sticking

[Glennprice]

Yes hitachi helpline said sounds like worn relays as sometimes fan runs and sometimes it does not, some they said replace pcb and thermistor but I'm confused as what thermometer they want me to replace as none are really relevant :/ problem is this unit is in a gym customers cancelling membership cus parts for this unit take 7-10 days so just trying to make sure I've ordered right part but ATM sounds like it might still not be the pcb :/

[install monkey]

Thermistor for the outdoor temperature (THM7)
When the outdoor ambient temperature decreases to -8°C
or a lower temperature during the cooling process, the
compressor will stop. Resistance values of the thermistor
are shown in Fig. 10.3. 35kohm at 0deg 20.5kohm at 10deg and 8kohm at 30 deg (hold the sensor)

Thermistor for the defrost operation
(THM8)
The resistance values of this thermistor are the same as
the resistance values of the thermistor for the outdoor
ambient temperature. cant find any info on fan resistance

[panchovaz]

Problably the fan winding is getting blown, maybe you can try separately, good luck.

[Glennprice]

I've tried the fans separately and they both run with no problems sometimes the unit will run all day no problem so doesn't look to be a problem with the fan that's why I'm hoping its the pcb or the pressure switch that brings the fans in, next time I am back there is to replace the pcb

[install monkey]

on hi and low speed?

[Glennprice]

Hi chaps I would like to thank you all for ur help from the beginning of this forum , I would like to let you know that the fault was the pcb and after replacing it today no faults have appeared as of yet and both fans now run n change speed as they never before .

[install monkey]

yay!- reassuring when u fit a part and it works;)