In alt.home.repair, on Thu, 12 Sep 2019 03:26:28 -0700 (PDT),
" wrote:

We have a Frederich SM18J30 18000 BTU through the wall AC on the first floor of our small Cape. It has been a work horse for 20 years without any big problems. Yesterday morning I turned the power off (was running all night) and the compressor wouldn't shut off. So now the compressor just stays on and the thermostat has no effect and I have to pull the plug to turn it off. I did some googling and it seems like it is probably a broken relay which makes sense. I am leaning towards replacing it because of its age but it still works well. Not sure if I can find someone to repair it. Finding parts might be a problem. I think most AC repair places around here deal with central air only. Should I break down and get a new one ($1600 is what I am seeing for a similar 18000 btu that fits this opening) or should I try and find someone to repair it? Thanks in advance.

I think you're in very good shape on this one because you know with 98%
certainty which part is the problem, the relay, like you said.

Well, 90% I guess it might be the thermostat, but I gather your
googling made pretty clear it was the relay. Relays can freeze closed
becuase the current going through the contacts can make them stick to
each other.

Open it up and look inside. There might well be only one relay, and the
problem one will certainly be the biggest one if there is more than
one***, with the biggest wires connected (2 of which will go to the
compressor) or biggest leads on the circuit board, and two of the leads
will lead to wires that go to the compressor.

It might unplug, and yoou might be able to get the part through
Frederich, but if it unplugs there will probably be numbers on it to get
the part from the manufacturer or part distributor. Using just the
numbers even if no brand is stamped on it.

With the relay out and an ohmmeter, you can see if the contracts are
closed and if you can get the cover off the relay, you can see with your
eyesif the contacts are stuck.


Even if you can't get the exact part, you can get one that is
electrically identical and if it doesn't just push in, you can solder
the right number of wires to the circuit board and solder the other ends
to the connectors on the relay. The wires can be 8 to 12 inches and the
relay can sit someplace safe, so that if it has a metal case it won't
short anything. You could cover that in electric tape.

I did something like this with my furnace for years. The transformer
built into the control box burned out the first summer I lived here.
Went to an AC supplier and he wanted about 200 dollars for the control
box, and I knew it was just the trnasformer. I asked, Isn't there
something cheaper and he offered me a transformer. 50% bigger than the
original so I put it 12 inches away and mounted it with a screw and nut
to the furnace case. I'm thinking there might not be a good place in an
AC like you have so just stuff it anyplace where it won't short anything
out.

If you can't solder, you can learn in a few mintues or you can find
someone who can.




**My girlfriend, a girl no less, did this when her oven or fridge broke.
The appliance repair man said he couldn't get the part. She got the
part number off the little part and bought it online for $10 and put it
in herself.