A/C starts and immediately goes to "heat" (red Icon)

[GFB]

Hi

My AC unit is acting up. When I turn it on, it runs its diagnosis and immediately goes to "heat", not cooling (which the temp setting says it should).

This is new and sudden and no codes show up on the (small) display.

When we lower the temp to force it go to "cool" it immediately shuts off.

It is a Marine Air Systems by Dometic model 7055 (I believe, tag is worn).

Anyone have any ideas what this might be?
Thanks in advance

[tomschauer]

See if you can find the programming manual. Sounds like it is in the heat only mode, not the auto change over mode.

[GFB]

Thanks, I'll try to find it online, the manual itself is very basic and no real help...

[bud37]

I had the same one....it takes a little fooling with to get all the sequences how you want them. Now that said, was this operating as normal and now it is failing to heat only, where as before it went to cool when the temp was set low enough.

Have you tried resetting it, just turn the main 120 off , wait a short bit then put back on.....those buttons can get depressed by accident because of its location.....good luck, its getting hot....

[GFB]

Thanks, tried the on off trick etc. Might be the code thing as mentioned, I'll try that first. Found the programming manual/guide online...

[GFB]

Final update: Turned out to be a code problem. If you press the start button for 5 seconds and do nothing I understand (I think) that the code turns to HEAT automatically. I reset it to Other which is both heat and cold. Worked.