Traveling with roof vents open?

I'd say dollar bill test failed you.
It might still leak air where you tested with the bill.
Or, could be another leak source between the back of fridge and inside the camper. Sometimes the space heater is open to the wall cavity and possibly the fridge cavity.
Be concerned, as stated, that fumes are coming in.

The roof vent is a bigger hole, otherwise both vents are at the same height and into the same wind so should pull air out the same, but the bigger one might win the tug-o-war.
If you pull air out of the camper vent, then maybe you do not have airflow up the chimney above the fridge - air comes in the side fridge vent and exits the inside roof vent. The air at the chimney might be stagnate.
Fridge needs air to move over the fins to be able to cool properly.

Consider putting in a 12 volt DC fan behind the fridge. Either at the roof to suck air out, or below the fins to directly blow air over the fins.
There are switches that will automatically turn on/off the fan when temps get high, so you never have to think about it. This could solve the problem and also help cool fridge on very hot days. Switches are about $12.

Years ago, heading westward across the Great Plains, ie, INTO a strong headwind, I noticed that my vent kept opening all by itself. I would close it, and next pit stop, it was open again. Evidently the vibration of traveling along with the high wind speed (wind speed plus speed of trailer) caused the vent to open. I used a bungy cord on the crank handle to keep it closed temporarily.

I then installed a MaxAir vent cover. It not only prevents rain entry when the vent is open, it also ended the vent opening itself when headed into a strong headwind.

I can see how the vacuum drawn on an RV with that vent open could interfere with the operation of the burner on a refer on propane.

jplante4 wrote:
Propane fridge? Could be altering the airflow over the roof changing the flow through the chimney.

Perhaps installing or removing a vent cover might improve the situation.

jplante4 wrote:
Propane fridge? Could be altering the airflow over the roof changing the flow through the chimney.

This would be my vote also, I would also check to make sure that the seal around the trim of fridge to cabinet is good as that could be drawing air away from the fridge chimney.

Propane fridge? Could be altering the airflow over the roof changing the flow through the chimney.

The fridge compartment should be sealed from interior space.
Your situation brings concern not only about fridge getting flow of warm air, but also the possibility of CO from the burner entering the living quarters.
Check your seals.

zcookiemonstar wrote:
Your vents being open could be causing the fridge to not vent properly. For hot air to vent out air has to come in some place and that is probably the vent from your fridge.

Great point, that would kill the cooling for sure.
Thanks

Your vents being open could be causing the fridge to not vent properly. For hot air to vent out air has to come in some place and that is probably the vent from your fridge.

Very odd. Never had that problem...