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psneeld 07-16-2012 07:03 AM

Air Conditioner Problem
 
Scenario - Approximately 20 year old split unit, reverse cycle 16500 btu MarineAirrrrr unit in main salon. Water pump died a month back and was replaced in kind. Water pump and new cycling issue may/may not be related. Unit now runs fine for 5-10 minutes, 65 degree air blowing, 50 degree coils, with 90 degrees in cabin.... then compressor cycles off but trips nothing with fan still blowing. It has come back online after a period of time but most of the time I've just turned it off after the compressor has shut down.

The refrigerant low side is between 70-80 psi when the compressor is running.

The control unit is the old style 3 knob off/on, fan speed, thermostat.

Any ideas? Didn't see anything in the troubleshooting manual.

Thanks!

Keith 07-16-2012 07:14 AM

Is the cooling water flow good outside the boat and is the water warm? You might have gotten some gunk in the heat exchanger when you changed the old pump out. Might just try hooking up a water hose to the circuit and blowing it out.

RickB 07-16-2012 07:31 AM

Is it a true "split" with the evaporator in the air handler?

What is the refrigerant?

What is the discharge pressure?

psneeld 07-16-2012 08:05 AM

Quote:

Originally Posted by RickB (Post 94282)
Is it a true "split" with the evaporator in the air handler?

What is the refrigerant?

What is the discharge pressure?

Kieth...water flow is good

RickB...yes true split
R22 still (at least PO didn't re-label)
Don't have a full guage system...

RickB 07-16-2012 01:20 PM

Quote:

Originally Posted by psneeld (Post 94284)
Kieth...water flow is good

RickB...yes true split
R22 still (at least PO didn't re-label)
Don't have a full guage system...

The suction pressure sounds within limits, it would be interesting to know the discharge pressure just to confirm. Is there a large temperature drop across the condenser with regard to gas in and liquid out?

I would check the compressor current draw and see if there is an internal problem with the motor. Check the air handler as well to see if the fan motor might be drawing too much current. It doesn't sound like a refrigeration issue per se.

psneeld 07-16-2012 04:10 PM

Quote:

Originally Posted by RickB (Post 94332)
The suction pressure sounds within limits, it would be interesting to know the discharge pressure just to confirm. Is there a large temperature drop across the condenser with regard to gas in and liquid out?

I would check the compressor current draw and see if there is an internal problem with the motor. Check the air handler as well to see if the fan motor might be drawing too much current. It doesn't sound like a refrigeration issue per se.

I'm thinking controls or processer board somehow too...nothing is tripping a breaker...the compressor just stops compressing....everything else normal.

RickB 07-16-2012 04:28 PM

Try leaving the power on after it quits next time and see if it restarts on its own then quits again. I don't know if the logic board will permit that kind of start though, do you have to go to the thermostat to start the unit each time after a power loss like when changing from shore to onboard power? If not and if it restarts after taking a break, I would consider the compressor overload safety switch as likely suspect.

psneeld 07-16-2012 04:33 PM

Quote:

Originally Posted by RickB (Post 94380)
Try leaving the power on after it quits next time and see if it restarts on its own then quits again. I don't know if the logic board will permit that kind of start though, do you have to go to the thermostat to start the unit each time after a power loss like when changing from shore to onboard power? If not and if it restarts after taking a break, I would consider the compressor overload safety switch as likely suspect.

thanks...I'll be taking a look there as there is no logic board that I know of...it's the old neanderthal system...on/off, fan, thermostat. Even the pump runs all the time the unit is "on" but not compressing.

may look into control updates just to break into the 21st century...might be all that I need..:facepalm:

RickB 07-16-2012 04:39 PM

What is the model number and vintage?

psneeld 07-16-2012 04:53 PM

:whistling:please don't scold me...she has seen her service life...

model says C16H marine air...looks original as the ser number starts with year the boat was delivered "87"....

that's off the unit plate...don't have any other documentation.

RickB 07-16-2012 04:57 PM

Quote:

Originally Posted by psneeld (Post 94386)
... please don't scold me...she has seen her service life...

I like old stuff ... I have a lot in common with most of it.

psneeld 07-16-2012 05:05 PM

Quote:

Originally Posted by RickB (Post 94388)
I like old stuff ... I have a lot in common with most of it.

true...and it looks like she has life in her...just a weird pattern of operation for the limited number of reasons why it would kick off.

RickB 07-16-2012 05:15 PM

I tried to find a schematic but your unit must have been built before the printing press was invented.

Look on the compressor casing for a "Klixon" type switch, probably held on by a wire clip. If there isn't anything then it might be inside the can.

If you are ambitious, when it quits next time, ring out the compressor power leads and see if you get an open. Ring it out before it quits next time so you will know what to expect.

If that doesn't get you anywhere, hot wire the compressor and fan and see what it does. At least you can eliminate those items.

psneeld 07-16-2012 05:20 PM

Quote:

Originally Posted by RickB (Post 94398)
I tried to find a schematic but your unit must have been built before the printing press was invented.

Look on the compressor casing for a "Klixon" type switch, probably held on by a wire clip. If there isn't anything then it might be inside the can.

If you are ambitious, when it quits next time, ring out the compressor power leads and see if you get an open. Ring it out before it quits next time so you will know what to expect.

If that doesn't get you anywhere, hot wire the compressor and fan and see what it does. At least you can eliminate those items.

Thanks...right down the road I was headed...just posted to see if some other poor slob did all my homework for me first...:D and found something easy and simple...you know the stuff that never happens for me...on a BOAT nevertheless!

Forkliftt 07-16-2012 05:23 PM

Quote:

Originally Posted by psneeld (Post 94382)
thanks...I'll be taking a look there as there is no logic board that I know of...it's the old neanderthal system...on/off, fan, thermostat. Even the pump runs all the time the unit is "on" but not compressing.

may look into control updates just to break into the 21st century...might be all that I need..:facepalm:

PS, there is an adjustment for the thermostat on the old dial units. If it has reverse cycle heat like mine you should feel a "click" from cool to off and then another "click" as it goes from off into heat. Off should roughly be in the center of the dial. If this is not the case, with the breaker off of course, remove the knob (two flat head screws) and you will see a small hole on the face as I recall. Use a flat long small screwdriver to reach in there and turn the screw slightly till you hear it click. It could be in or out- so consider this a disclaimer:). Another possibility is the high pressure switch is failing. Mine also did this. Check your electrical schematic. It is mounted beside the compressor in the high pressure line.

bluebyu 07-16-2012 05:27 PM

When the compressor "turns off", is it still running, but unloaded?

I have a vintage 1984 Marine Aire, the thermostat is bad, it always keeps the compressor unloaded.

From memory, there are 2 solenoids, one for reverse cycle, one to load and unload compressor.

Hope this helps.

psneeld 07-16-2012 05:49 PM

Quote:

Originally Posted by Forkliftt (Post 94400)
PS, there is an adjustment for the thermostat on the old dial units. If it has reverse cycle heat like mine you should feel a "click" from cool to off and then another "click" as it goes from off into heat. Off should roughly be in the center of the dial. If this is not the case, with the breaker off of course, remove the knob (two flat head screws) and you will see a small hole on the face as I recall. Use a flat long small screwdriver to reach in there and turn the screw slightly till you hear it click. It could be in or out- so consider this a disclaimer:). Another possibility is the high pressure switch is failing. Mine also did this. Check your electrical schematic. It is mounted beside the compressor in the high pressure line.

thanks..a real possibility...just not hot enough to get too anti- Buffet and tear into her just yet!:socool:

psneeld 07-16-2012 05:50 PM

Quote:

Originally Posted by bluebyu (Post 94401)
When the compressor "turns off", is it still running, but unloaded?

I have a vintage 1984 Marine Aire, the thermostat is bad, it always keeps the compressor unloaded.

From memory, there are 2 solenoids, one for reverse cycle, one to load and unload compressor.

Hope this helps.

no... the compessor stops running...

Forkliftt 07-16-2012 09:16 PM

Quote:

Originally Posted by psneeld (Post 94404)
thanks..a real possibility...just not hot enough to get too anti- Buffet and tear into her just yet!:socool:

No need to tear very far. Believe it or not, I pulled my thermostat loose this weekend and grabbed a couple of pictures with my iPhone so now I can share. A marine AC tech shared this with me once when mine acted up. As I recall, all you need is to remove the knob as one picture shows. Then notice the springs and brass colored adjustment screw in the other pic. As you adjust it, it changes the spring tension on the small round part the capillary tubing enters.
http://www.trawlerforum.com/attachme...16e49d9528.jpg
http://www.trawlerforum.com/attachme...733ada9516.jpg

psneeld 07-17-2012 09:08 AM

Thanks Forkliftt!


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