I used work light with a plastic cover to cover the 75w bulbs and just laid them into each compartment. The I placed a $9 wireless sensor in the compartment away from the bulb so I could monitor the temps from inside the coach. It has worked so far in the 2 compartments I did this to. However, the compartmen where the water heater is froze before I realized I n eeded to do it too.
Did you put a 75 watt bulb in the area above the propane tank where the water pump is. Don't look like much room????. How did you do it. I put a 40 watt bulb in a drop lite under the tank drain vale area and that helped when it was 23 degrees here in Richmond Texas where I am wintering. Just curios how you did it.