How to use your meter to check the compressor in a mini split.
This right here is an outdoor unit for a mini split.
This is the compressor.
You can measure at the plug to check the windings of the compressor,
but it’s better to actually check at the windings
or the terminals of the compressor.
So we’re gonna use our needle nose
to take the three connectors off of the top of those terminals,
off the top of the compressor.
We had a bad inverter board
and we found out that there’s no Thermal paste used on the IPM
or the Intelligent Power Module.
And that IPM is directly connected to a heat sink
and that keeps it cool during operation.
If there’s no Thermal paste,
then that will cause the inverter board to overheat.
So this is a rotary compressor.
It’s three phase. All mini splits have this.
And if you can see right here are the windings.
So we got those three terminals right there
and they are right there.
So we’re gonna go from each terminal to the next
and I’m gonna show you like this one, two.
Now let’s check the reading on the meter.
Should be the same for each one.
I’m gonna go to the next terminal. I,
I did this one. Now I’m gonna go from this one.
So that was like
um, U to W,
U to V. Alright,
so that one’s 2.1. And then we’re gonna check from the last Winding
or the last terminal to the.
So to check from each terminal to the next terminal,
2.1 for each. So they all read the same.
If one of them reads different,
that can indicate the windings are bad on the compressor.
So for the. The actual terminals,
you can see on the inverter board,
it says U, V,
and W. So we just went from U to V,
U to W, and from V to W.
Now we’re gonna take another measurement,
and we’re gonna go. We got our meter on, homes.
It’s still on ohms. And we’re going to read from, uh,
the windings to ground.
So now set the meter back up
and go from each winding like this to the copper.
And then if you have a reading,
which it looks like. We don’t have a reading,
let’s go to the next one. We don’t have a reading.
Let’s go on the next one. We don’t have a reading.
So I’ll show you what I did with my meter right here.
I had one lead on one of these terminals like this,
and then I had one lead on the copper.
It looks like our compressors not shorted to ground,
and all the windings read the same.
Now, on some mini splits,
the outdoor fan motor, because it’s BLDC,
and it’s three phase. On some mini splits,
you have three windings, right,
for your three wires going to your plug.
From your plug to your outdoor Fan this motor,
we can read the exact same as we did with that compressor.
So we’re going to take and measure ohms,
and we’re going to go from the red to the yellow wire,
which could be indicate. Could be 1 to 2.
Looks like we got about jumping around a little bit,
but 76
and then we’re gonna go to 2 to 3,
which is yellow to blue.
About 76. And then from 1 to 3,
which is red to blue. 76.
All the windings read the same.
Same thing for measuring to ground.
1 winding to the ground. Looks like we got
no measurement.
So the outdoor fan motor
and the indoor fan motor in the wall mount air handler
are the exact same. They’re BL DC,
brushless DC, and they’re 300 volt DC motors.
And they’re three phase. So
should be able to measure those windings
the exact same as the compressor.
And if you have a shortened compressor,
then it can cause the inverter board to have issues as well.
But I think the reason the inverter board went bad on this one
is because we had no Thermal paste.
Also an indication inverter boards bad is turning the board over
or taking it out
and then taking a look at everything visually to see if maybe the, uh,
Moss Fetts have some damage.
There’s some burn marks on the IPM.
Maybe there’s a transistor that’s burnt.
Maybe there’s a fuse. There’s fuses on the Board that can be checked
and if they go bad you have to replace the whole board
unless you want to solder on a new fuse.
This is how to check a compressor and a BLDC fan motor on a mini split.