A/C trouble shooting

[Allan Frey]

[FONT=&quot]I have a Marine Air brand system, heat and cool, which started making a new interesting sound that I have not seen described in any trouble shooting info. It is a Marine Air model VRP-16K with a passport 2 control. So far, the heating, cooling and fan work fine and there are no alert codes displayed.[/FONT]
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[FONT=&quot]When I arrive at the boat and turn on the system for cooling, there is a fast tapping sound (~6 per sec) for about 30 seconds. Then the tapping sound slows and ends in the next 20 to 30 seconds. The tapping sound is not due to the fan; if I start the system in fan only mode, the fan turns on and I do not get the tapping sound.[/FONT]
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[FONT=&quot]After the initial tapping sound, I don’t hear it again, even though the compressor is cycling on and off.[/FONT]
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[FONT=&quot]I have not been able to start in heat mode because the interior of the boat is too hot for the heat to come on, so I do not know if it would occur then.[/FONT]
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[FONT=&quot]If I turn off the system and leave the boat for a few hours, there is no tapping sound when I start it. If I turn it off and come back the next day, I’ll have the tapping sound when I start it.[/FONT]
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[FONT=&quot]Is some part of the system going bad, and if so, what?[/FONT]
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[FONT=&quot]Thanks[/FONT]
[FONT=&quot]Allan[/FONT]

 

[MSter]

allan, Just a WAG, but my bet would be a check valve pulsing open and close as the refrigerant gas is pushed through the system. Until the gas gets up to pressure the check valve is opening and closing on each pulse from the compressor. Once fully up to pressure and /or temp the check valve will remain open.
alternately it's the compressor telling you it's working !
Mike Sterling

 

[kloudie1]

Sounds kinda like a compressor mount might be a little weak..a kind of low order harmonic that goes away when the pipes get hot/cold.. Ya might try grabbing the top of the compressor with a rag (so ya don't get burned, the rotary compressors get hot) and kinda pull or push to see if the noise changes..

 

[Bill Roosa]

things contracting as they come down from hot soak temp to normal operating temp????? Kinda like a car exhause manifold "ticking" after you turn it off only in reverse.

 

[Allan Frey]

Things contracting, Bill...
would seem to be a possibility, except for one fact. The tapping sound at start-up did not occur during the decade that I used the system prior to this season. This is part of what makes it so interesting.

Allan

 

[Bill Roosa]

So I'm thinking that something has become lose so before it just stressed up and now it is sliding (badly) across the connection.