thermastat goes crazy

[Gary Rose]

hi i am a new owner of a 2000 356 when i turned on the heater this morning it worked normal for about 10 mins then the thermostat started to climb temp to 125 and the heater would turn off and a/c would turn in it is 58° here so i shut it off let it sit then it worked ok for a short while then it did it again. any suggestions, does it sound like a control unit problem on the wall? i take it that is where the thermostat is right ? help

[Viper]

Gary, post the brand and model you have as it will help people reply to your specific model. Newer vintage control panels have the temp sensor built into them. It could be that you have a bad sensor.

[Gary Rose]

cmp16k marine air systems thank you Viper

[Cooler]

Gary, are you sure the temp is displayed as 125, or is that an error code informing you of the reason for failure. I have the same unit, and discovered they need a lot of air flow around them to function properly. If you have any storage near the unit, clear that out and let that unit breath. er

[Gary Rose]

Well the reading is all over the place it will be at 51 then just start claiming slowly and will go above 125 , I did clean out the strainer before this happened so i am wondering if it has an air bubble in it but it is pumping water out both sides ob the boat. Is there a wat to bleed out the unit?????

[Cooler]

I don't know a lot about these units. When you cleaned the strainer, did the very top reseal itself, or did it leak a bit? it needs to be tight and sealed, but sometimes a challenge to get it to fit just right. The heat cycle of the unit does not require as much water flow as the cooling cycle. If you have a lot of air circulating around the unit, then I would think I would follow Viper advice and focus on sensor. Call Dometic, I understand they are very helpful. Do not know if there is a way to bleed out a bubble, but if you are getting good discharge flow, that should not be the issue. er

[tomschauer]

Its not a water flow issue. Check the connection at the back of the control and where the controller plugs into the a/c unit. They should be telephone type plugs. Un plug them and re plug them. If that doesn't work, try switching the controllers and see if the problem moves to the other unit. If it does, you need a new controller (thermostat), if the problem stays with the same unit, most likely a control board.

[Gary Rose]

So when you say controller you are talking about the one on the wall right ? Just clearifiying

[Gary Rose]

Thanks To all I figured it out it was the wall unit. I have 2 units in this boat so i swapped wall control units and now works normal. The rear unit has another problem it runs for a short while the shuts off and has an HHH code on the wall controller so ant ideas let me know. Thanks Again

[tomschauer]

HHH, should be a high pressure fault. Most likely a seawater flow issue, if in cooling mode, low airflow if in heating mode.