Hi Joe~

Sounds like the SMXII controlled unit/s have bad compressor triac/s (solid state relay)

To test this…Make sure the SMX is off (No Fan running) Then go to the engine room & see if the compressor & pump are running…If they are…Shut off the breaker….Don't run the systems till you get replacement triac/s as they will likely ice up which is not good for the compressor…Either that or cycle off the unit with the breaker till you get the part/s…You really don't want it/them running without the fan/s

The replacement Triac part # is A-548 and sells for $40.00 ea…Two screws & 3 wires (push on) each to replace…It looks like a black half of a Domino and is fastened to the inside of the box with the circuit board in it…Wires should be Black, Purple, and a smaller Yellow….

Note: I wasn't clear on if you have one or two SMXII's…One Compressor Triac (A-548) per SMXII…

Steve~

Joe~

I can have a few sent to you, but it may be quicker/easier for you to use this dealer locator to find them locally…They are a commonly stocked part.

http://www.dometicenviro.com/d…..hp?l=water

If you don't have much luck there let me know…You can call me thru the Contact Steve link (at the top of any page here) with a CC #

Steve~

Thanks Steve, will test tomorrow while at the boat,

Joe

Post edited 4:54 pm – June 13, 2011 by Steve Pooler

joesig said:

Steve,

I performed the test as you suggested by lifting the yellow wire off the Triac and the compressor & pump come on when I turn the breaker. I located a new Triac locally and installed it on the main cabin unit. The compressor now cycles off and on when reaching the set temperature. I noticed that the water pump also shuts off & on with the compressor. Is this correct?…Yes Joe…With Cruisair (different than Marine Air) the pump output is wired directly to the compressor circuit…I also performed the test on the forward  cabin unit and found the Triac bad. I left the boat to pick up another Triac and will install it tomorrow morning.

Thanks for your help,

Joe   

Glad to help Joe…But now it may be time to consider why you had 2 triac's fail…

Do you, or have you had water flow problems ?

This can cause High amperage draw & thus triac failure…

Oh…Almost forgot to mention…Don't forget to use the little white tube of thermal heat transfer paste (that comes in the triac package) on the back of the triac…It helps it transfer it's heat to the box to keep from burning itself up…Also make sure the mounting screws are tight so that it can properly transfer that heat…

Steve~

joesig said:

Steve,

I am trying to figure out why both Triac's went bad, also. They were not working when I purchased the boat about 2 years ago. I remember when I was looking at the boat down in FL the previous owner did not turn the AC units off when switching to generator power or back to shore power, maybe this contributed to the failed Triac's...Actually that's fine with SMXII controls…Especially if you go into the program mode of the SMXII & set Compressor Restart delay on each at at least 10 seconds apart (10 & 20 seconds) so that they don't start together…This allows the gen or shore to stabilize before A/C load is applied…The SMXII also hits the reversing valve before a power interrupted start to equalize system pressures instantly (so they don't start against head pressure)…I have good water flow and just to be shure about six month's ago I replace the March AC- 5C pump (I think thats the number) It was old and a little rusty and seamed to run a little hotter that what I thought it should run. It really pumps a lot of water…Have you ever had the system acid flushed ?…It may be time for it…Even though you have good flow, you could have a hard water scale build up inside the water coils acting as an insulating blanket & preventing proper heat transfer to the water…Similar to a dirty radiator in your car… 

With three units on the boat and one of them still with the rotary knobs, if I have all three units running the water pump will stay running even if the other two with SMXII controls cycle off...This is normal for the manual controls and how they were originally wired…That can easily be changed though…I haven't tryed this yet but I think that is what will happen. Normally only the two units with the SMXII controls will be in service unless I have guests spending the night.

Yes, I did use the white paste on the back of the new Triac and tightened the bolts good.

Thanks again for your help.

Joe 

That March pump is good for 48,000 Btu if the units are not too far away, or mounted up on the bridge…

Add up each units rating to get your total Btu…

Remembering that even if you don't run the added system that it still takes it's share of that pump's capacity

 

Steve~