Before spending any money, there is likely a simple fix. The thermal switch may have come loose from the heat sink fin it is mounted to. These thermal switches must have a good thermal connection to the temperature of item they are monitoring. If they don’t have a good thermal connection, rapid cycling occurs. Here is why: when the switch heats up, it switches on the cooling fan, and the fan will begin to cool the heat sink, but the thermal switch will first rapidly cool down, given it isn’t reflecting the actual temperature of the heat sink. In this case, the switch opens and turns off the fan, however the heat sinks isn’t actually cool enough yet. The thermal switch heats up again, etc. etc.
The solution is to assure a good thermal connection to the fin or area it is connected to. Assure that the fin is flat. The best thermal connection can be made by applying some silicon heat sink compound. It is a type of thick (typically white) grease that transfers heat well. Apply a small amount between the switch and whatever it is connected too (heat sink fin shown) to assure good heat transfer. This solved my rapid cycling issues. Look for “Thermal Paste Grease Compound for Heatsinks”. Should be about $6 for a small tube.
Not exactly related to the rapid cycling, but in the same circuit, I upgraded the fans and did a little improvement to the systems air flow. Originally there was one small fan mounted to the back of the refrig pointed toward the heat dissipating fins. Without to much more discussion a fan out in the open air can create a circular air flow which reduces its efficiency. I added some pressboard plates with holes for the new larger fans I used and also added some air guides to assure the air flow hit the fins.
Happy RV’n
I am sure he has already spent the money if he was going to considering the post is 11 years old. but you bring up an interesting issue and solution if that is the issue, might be worth starting a new post and copy that into the DIY section.
