Hi,

Just been through the exact same problem. I went to a Dometic agent in Bundaberg who diagnosed the problem.

When you turn on the unit does the little light flash red for a few times. I think from memory it was two or three quick flashes a short gap and the red flashes again.

First up they plugged in a brand new Remote receiver inside the MH. Wasn't that, so it was either of the two temp probes in the outside part.

I had a few problems getting a new temp probe but that was caused by an unfortunate series of events.

Since my unit was three Yrs. old and out of warranty I decided to do the job myself.

I got a new probe after a few hiccups and fitted it myself. Not hard to do but care must be taken with the coolite block inside the unit not to break it. Of course the unit must be switched off and isolated.

The probe slips into a small tube and is connected with a small connector to the circuit board. Then fixed in place with an electrical tie.

I also took the opportunity to clean the fan which was a matter of unplugging an electrical plug and two Phillips screws. I used a toothbrush and some Glen20 to keep it healthy.

I also had to buy some replacement clips to secure the covers together. Almost impossible to take the old two part clips without breaking them. Bought from a car accessory Co. Autopro  Black not white like the original, but no biggie.

I tried replacing one and it still didn't work with the new one so tried the one I changed and left the new one in place.

The original one I took out replaced the second one and hey presto. All OK.

I spent approx. four weeks in Melbourne and ran the unit virtually full time on heating and now back in Qld have used it on cool to test it.

The new probe cost me $106  and the agent charged me $44 to check the system and find the problem.

If you are feel competent it can be done but depends if you feel competent to do the job, and  a head for heights.

Hope this helps

Cheers

Trevor