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itstony
16-08-2012, 07:37 AM
Guys,
Just wondering if anyone has a view on a fault I found.

Checked the R-B-W cables for resistance when disconnected on the compressor and had a posative reading.
Reconnected and ran the outdoor unit while monitoring the three and found all were reading output voltage while the fan was running.
After a short time it was identified that the W would drop its voltage and phase.

On seeking advice it was deemed to be a board fault and due to cost or a new board would not be economical.
Two units were replaced.

What I would like to know if anyone had a theory on what would cause this.
It did appear that when the fan or unit was calling for a step up. Trying to find what else might be causing this came up against a blank?

install monkey
16-08-2012, 10:22 PM
some units put voltage to the windings to generate heat in the compressor to keep the oil warm-instead of a crank case heater- usually an inverter pcb will start a compressor with around 170v ac then ramp up if ok, as for droppin a phase would be possibly breakdown in the diode bridge -there are ways for testing this

itstony
17-08-2012, 06:16 AM
Yes, that is about what the tech-dept said. Once the unit was being asked to ramp up, that was finding the fault. As you know, it seems in nobodies interest as a whole to either be interested or prepared to invest time and find out why, hence "Replace the board", which is uneconomical.
This kind of attitude does not produce tech minded people, just installers.

Good reply, thanks.