AC diagnostic help.....

[Heron]

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...

 

[caltexflanc]

Try hard wiring the fan to known AC source.

 

[DavidM]

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.'

David

 

[Ski in NC]

Disconnect air duct from blower discharge and see if fan can be rotated by hand.

 

[Heron]

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..

 

[RT Firefly]

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.

 

[CPseudonym]

C'mon RT. No pain no gain

Honestly though, important safety tip and nice catch

 

[RT Firefly]

 

[Heron]

Lol....

 

[Capt.Bill11]

Fuse in control panel?

 

[Heron]

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..

 

[Ski in NC]

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.

 

[Heron]

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..

 

[Ski in NC]

Got it. Sounds like you are on the right track.

 

[N4712]

Looks like the daytons I use for my engine room blowers.

 

[Heron]

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...

 

[stubones99]

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.

 

[Capt.Bill11]

Looks like you forgot to "dress" the new blower body.

 

[Heron]

or the blower motor is bad.

That was the case. No hum, no sticking...Nuttin

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..

 

[Capt.Bill11]

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.

 

[Heron]

The coating is for more than the contact points. It acts as insulation for both noise and temperature.

Bill...
Ironically the whole system is quieter now and blows more air to boot!
I think the detail I took on reassembly of the cage and seawater coil with contact point insulation etc. seemed to help. The Cage seems of thicker steel too which dampens some. This squirrel is Whisper quiet!
On the other insulation issue, I'm not sure 1/16" of "dressing" makes a whole lot of difference. It's a 12K unit in a relatively small boat. Cycled on and off nicely today with smooth start-up and my new Honeywell Home type thermostat held temps perfectly. It used to be quite loud on start-up. ..Job done for just a few bucks, Happy camper here!

 

[Forkliftt]

That looks like the same Mermaid I recently installed. If you got a good product- why change it??


1983 Present 42 Sundeck
Twin Lehman 135's

 

[Heron]

That looks like the same Mermaid I recently installed. If you got a good product- why change it??

Yup...Their offerings today look just like this one installed 20+ years ago...

 

[Capt.Bill11]

Bill...
Ironically the whole system is quieter now and blows more air to boot!
I think the detail I took on reassembly of the cage and seawater coil with contact point insulation etc. seemed to help. The Cage seems of thicker steel too which dampens some. This squirrel is Whisper quiet!
On the other insulation issue, I'm not sure 1/16" of "dressing" makes a whole lot of difference. It's a 12K unit in a relatively small boat. Cycled on and off nicely today with smooth start-up and my new Honeywell Home type thermostat held temps perfectly. It used to be quite loud on start-up. ..Job done for just a few bucks, Happy camper here

Hey if it works, that is all that counts.