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Old 04-29-2015, 05:00 PM   #1
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AC diagnostic help.....

I have an old Mermaid reverse Cycle system...12K BTU and likely as old as my boat. It was working just fine but recently developed an issue. Just looking for some feedback before I start pulling things apart.

The compressor starts up upon signal from the thermostat. The evaporator coil goes Hot or Cold depending on my selection so I've pretty much ruled out the compressor. Water Pump and circulation are fine.

The problem is the fan does not come on in either manual or Automatic mode.

I can hear the fan relay click when kicked on from the thermostat, but no fan rotation. Occasionally the re-set circuit breaker on the unit will trip.

At this point I'm suspecting a bad or seized Fan motor, though it could be relay contacts.

Anyone have any experience with a similar problem? I'll start my troubleshooting this week...
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Old 04-29-2015, 06:09 PM   #2
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Try hard wiring the fan to known AC source.
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Old 04-29-2015, 06:17 PM   #3
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Quote:
Originally Posted by caltexflanc View Post
Try hard wiring the fan to known AC source.
Or measure the voltage to the fan motor when the relay pulls in. If you have 110V and the fan doesn't run, then....

If you don't have voltage at the relay then maybe the contacts are shot.'

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Old 04-29-2015, 06:30 PM   #4
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Disconnect air duct from blower discharge and see if fan can be rotated by hand.
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Old 04-29-2015, 06:58 PM   #5
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Disconnect air duct from blower discharge and see if fan can be rotated by hand.
Thanks all...
This will be my first step, then voltage troubleshooting..
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Old 04-29-2015, 07:06 PM   #6
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Greetings,
Mr. H. You know of course to try Mr. Ski's test with the power off. If you're going to try to spin it with the power on, use a screwdriver or some non-fleshy object please.
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Old 04-29-2015, 07:22 PM   #7
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C'mon RT. No pain no gain

Honestly though, important safety tip and nice catch
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Old 04-29-2015, 09:02 PM   #8
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Old 04-29-2015, 09:10 PM   #9
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Lol....
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Old 04-29-2015, 09:49 PM   #10
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Fuse in control panel?
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Old 05-05-2015, 04:33 PM   #11
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Just to give you guys an update....Electrically jumpered the motor on the boat (no love).

Pulled the whole unit and brought it home, Pulled the squirrel cage assembly and still no love with the motor when bench tested. Turns out the whole Squirrel cage assembly with motor is $131 on Amazon (Ordered). A Dimensionally perfect drop in. I should get a few more CFM's out of this too as it's a few hundred RPMs higher than the old one.. I guess a good design 25 years ago still is! Should be back in business as soon as the blower gets here..

Disasembly:



Squirrel cage:



The offending motor:



New replacement assembly



Turns out the Mermaid had a hard start capacitor already in place! Now to find a wiring schematic..

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Old 05-05-2015, 05:53 PM   #12
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That capacitor in the box is probably for the compressor. The capacitor for the fan motor is the thing attached to the fan blue wires.

Compressor capacitor is needed to start/run, does not mean it is part of a soft start kit.

Did you try a new capacitor or test the old capacitor?

Did motor hum when energized? That is typical of a bad capacitor.
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Old 05-05-2015, 06:29 PM   #13
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That capacitor in the box is probably for the compressor. The capacitor for the fan motor is the thing attached to the fan blue wires.

Compressor capacitor is needed to start/run, does not mean it is part of a soft start kit.

Did you try a new capacitor or test the old capacitor?

Did motor hum when energized? That is typical of a bad capacitor.
Ski...There are (2) capacitors in the Control box for the compressor. One standard one (seen behind the relay at the bottom left with the zip tie), and a hard start wired in as well just above that in the pic.. The motor does have a separate capacitor, and Yes, I did swap with a known good unit and got similar (no start) results. The compressor starts and runs fine..After 25 years, I think the blower motor just got tired..
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Old 05-05-2015, 10:24 PM   #14
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Got it. Sounds like you are on the right track.
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Old 05-05-2015, 10:55 PM   #15
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Looks like the daytons I use for my engine room blowers.
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Old 05-09-2015, 12:40 PM   #16
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Fixed and tested! Back in the boat tomorrow..
Motor seems much more substantial. Also Used lots of Neoprene padding for noise and vibration control..

BTW, This 20+ yr old Mermaid looks exactly like the current offerings...





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Old 05-09-2015, 08:32 PM   #17
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does the motor spin, hum or get warm?

Older motors, not being used regularly sometimes have a problem with the bearing lube thickening to the point that it can't spin up. If you can start it spinning and it continues, you just need a new blower motor. If no heat, no hum and won't spin if you after give it a spin, then you may have an electrical problem or the blower motor is bad.
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Old 05-09-2015, 10:08 PM   #18
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Looks like you forgot to "dress" the new blower body.
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Old 05-09-2015, 10:50 PM   #19
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Quote:
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or the blower motor is bad.
That was the case. No hum, no sticking...Nuttin

Quote:
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Looks like you forgot to "dress" the new blower body.
Yeah, the old one was slathered in a neoprene coating...Applied pads at all points of contact so should be fine..
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Old 05-10-2015, 01:22 AM   #20
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That was the case. No hum, no sticking...Nuttin



Yeah, the old one was slathered in a neoprene coating...Applied pads at all points of contact so should be fine..
The coating is for more than the contact points. It acts as insulation for both noise and temperature.
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