Help with Mini Split Debug
Can anyone help with debug of a mini split problem ?
MSZ-FE18NA/MUZ-FE18NA, Single Head, Hyper Heat
I have had a long list of frustrating experiences with local service folks over the years. After one $400 Mitsubishi “diamond star” service call that failed to resolve the problem, I am resolved to at least have some idea of what the issue is before having another tech out.
Here are the symptoms:
Compressor runs. Inside air handler runs. Front panel lights show that the unit is active and heating/cooling. The air coming out of the air handler is the same temperature as the air going into the air handler (no cooling or heating happening).
In AC mode, the liquid connection (the small tube) gets very cold (frosts up) while the suction connection (the larger tube) remains at ambient temperature.
In heat mode, the suction connection (the larger tube) gets very hot while the liquid connection (the small tube) remains at ambient temperature.
I have to assume that this is the result of a stuck valve or lack of actuating voltage to a valve but which valve and what can I do to verify that this is what is actually going on ?
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Replies
https://www.mitsubishitechinfo.ca/sites/default/files/SH_MSZ-FE09_18NA_OBH542B.pdf
Dunno if there is anything in there that might help
Replacement pair is around $3k shipped, so might limit repair options
BTW, in 14 years the only failure I have had among 3 was very similar, both units operating, no hot or cold air, no blinking lights
It was low on refrigerant, tightened a fitting, all good for years since
Did you get a diagnosis of the problem for $400?
What does the work order say they did?
Consider disputing the CC charge.
Are the tubes still hot and cold when they get to the indoor unit?
Did they check the pressures?
Seems to me the tubes would not be getting hot or cold as described unless some refrigerant was flowing and that disproves your assumed faults.
Most likely failure is always a leak and the symptom you described sounds consistent with a leak and low charge.
Walta
You are low in gas