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Marine-AC Topics
Troubleshooting
MTC-IV Control

MTC-IV Control
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Member

bmaw

Rhode Island

posts 5

8:25 am October 14, 2011
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I just purchased this boat with a Lunaire split system and MTC-IV controls.  The air handler will operate when it is turned on at the breaker, however the compressor will not start when turned on at the breaker.

 

The MTC-IV display does not operate with the buttons, i.e. the power cannot be turned on or off.  The lights for heat and cool remain on all the time the breaker to the air handler is activated.  It seems that the control is fried.  Any ideas to verify this?

 

Thanks.
Admin

Steve Pooler

posts 1127

9:07 am October 14, 2011
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Sorry to say that even if we trouble shot what was causing your problem….Parts for that control have not been available for quite some time (many years)

Your option is a upgrade/retrofit to one of the newer control systems which comes with all parts needed such as this one:

http://www.dometic.com/45a5617…..e4a0.fodoc

 

The link above is for the "Elite" keypad…The Passport I/O Compact is slightly cheaper yet has all the same functions.

You can see Retrofit kit pricing on page 8 of the Marine Airrr price book link at the top of any page on this site.

 

Steve~ 
Member

bmaw

Rhode Island

posts 5

9:33 am October 14, 2011
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Is there a way that I can bypass the control to start the compressor to verify that it at least operates before changing out the controls?
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Steve Pooler

posts 1127

9:56 am October 14, 2011
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Sure…But you are taxing my memory when speaking of Luneair service & wire colors…They have also been out of production for many years…

Look inside the MTC IV control box…On the actual circuit board should be labels printed under each wire post…You are looking for the Comp, Compressor, or C-1…Something like that, and it may be a Purple wire if memory serves…

The control only switches Line (or Line 1)

Neutral or Line 2 should not be switched…

If you move that compressor wire over to the Line or Line 1 main power into the box/board (connect it with the Line wire on the board however you can) Then turn on the breaker, and you should get the compressor running…Be sure the pump & fan are running too if you want the system to run long enough to see if it will cool or heat…

 

Steve~
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bmaw

Rhode Island

posts 5

10:14 am October 14, 2011
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The reversing valve does not have to be energized for this to work?  I guess in other words, it will either cool or heat depending on where the valve is stopped when the compressor energizes, is that correct?

 

Thanks
Admin

Steve Pooler

posts 1127

10:30 am October 14, 2011
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That's correct…

In fact…I think I would remove the reversing valve wire from the board to see which it does (cool or heat) in the un-powered/relaxed position…

Again if memory serves…Some Luneair equipment (I think depending on age) would heat in the relaxed position…

This is opposite all other brands…And controls…

If your's heats with no power to the valve coil, then we will need an extra relay to install with the new control…

 

Steve~
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bmaw

Rhode Island

posts 5

10:47 am November 3, 2011
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I've been able to get the system to run in both heat and cool modes, so I now know that the control is NG.  The system is now winterized.  Once spring rolls around, I'll decide what to do with the control.
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Steve Pooler

posts 1127

11:08 am November 3, 2011
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Ok…But be aware they have had a price increase every year for at least the last 5 that comes about January.

Just for my curiosity…Did your Luneair system heat, or cool with the reversing valve NOT powered ? 

 

Steve~
Member

bmaw

Rhode Island

posts 5

6:58 am November 10, 2011
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It ran heat when the reversing valve was energized.
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Steve Pooler

posts 1127

9:23 am November 10, 2011
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bmaw said:

It ran heat when the reversing valve was energized.

Thanks…I'm thinking it must have been the older 3 knob Lunair's that energized the reversing valve for cooling…

It was one of their better features because it exercised/lubricated the valve each time the unit was started in cooling (predominant usage of most systems) and kept valve sticking to a minimum…

 

With digital's…It's done thru the microprocessor by energizing/powering the valve only momentarily before/during startup.  

 

Steve~
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