toshiba rav 460 indoor coil freezing up

[fridgefixer]

i am having problems with a tosh rav460.The customer reported poor performance in cooling mode.On arrival i found one side of the coil completely iced up blocking air flow the check codes where showing 01 08 and 01 09.The suction valve on the outdoor unit and 3/4 of the compressor was also iced up as there was no air flow through the indoor coil and liquid was making its way back to the compressor.I removed the drain bung turned the unit over to heating to clear the ice and drain away the water. I set the unit back to cooling at 21 deg C and watched the unit cycle on and off normally about six times.I also checked that the TA probe was cutting off the compressor by dipping it in ice water and cutting back in by holding it in my hand it ran ok.I also checked that the drain and pump was functioning normally. I recovered all the refrigerant (R22) and recharged it to the factory spec of 3.8 kg so i do not think it is a gas shortage or overcharge problem the pressures were 230psi / 50psi the ambient about 25 deg c. 2 days later it has come back in same fault could this be a intermitant fault on the indoor pcb. sugestions gladly received. thankyou.

[frank]

Check that the controller has not been put into "test" which will override the stat and give the symtoms you describe. Just found exactly the samre problem with a Tosh wall unit. This only applies to the pencil type controller.

Frank

[herefishy]

50psi? .... 26degF S.S.T.? Is this an air conditioner... not familiar with Tosh R460....

[frank]

fridgefixer

The first part of the fault code refers to the number of starts the compressors has requested based on the hexidecimal format. The second part, i.e. 08 or 09 refers to the fault.

08 refers to the "reverse change temp" - you need to check the operation of the 4 way valve or the TC senser (Coil sensor)

09 refers to 2 different things

1 - No change in the indoor unit temps - compressor not pumping/klixon tripped/crossed wiring

2 - Frost condition - Gas Charge/Pipe blockage/Indoor air flow/TC sensor/cross wiring

Looking at this problem from a distance I would suggest that the TC (coil sensor) is at fault

Frank

[Argus]

Frank is absolutely right. From the fact that you have 2 coils, I deduce that it is a cassette. This an old unit, since Tosh stopped making R22 kit some years ago in favour of HFC's.

The problem, if it recurs intermitently, is probably caused by overcondensing - ie the unit operates at low ambient temperatures in cooling.

The 09 code signifies a period of time where the coil sensor (TC) does not sense a change in temperature. Once the coil picks up frost, the problem persists.

Very often this fault is caused by over condensing, especiallly at the pressures you mention (50 psi, which will give an evaporating temperature on R22 about - 3 or 4. The TC sensor goes into fault mode below -2, ( if my memory serves me correctly). The ambient temperature rarely goes above 25 deg in the summer, in the UK, never mind in May!

Check that you have an adequate form of condenser fan speed controller, as a low internal loads at intermediate seasons and low outside ambient can give these symptoms.

Tosh incorporated a fan speed control in the outdoor unit from about the mid 90's. A 460 may be prior to that.

You can check the sensors very easily by looking at their centre value, which is 10k ohm at 25 deg - as the temperature goes up, the resistance falls, but it is not linear. Tosh should be able to provide a temp / resistance gradient.