Deb,
Long again but to tell it accurately, it needs words and lots of them.
Being a longtime and now retired engineer, I tend to go deeper into the details than most but most any RV/home owner can do this also as it so simple. Such as another very helpful action to find air leaks or lacking insulation fast or things heating up or being colder than they should be. It's easy with the use of an infrared temperature gun right off a store's shelves. They are extremely accurate. So many uses for home and RV's including checking tire temps when you pull into a rest area so you know instantly where tires problems are likely to come from. Checking of the hub center also tells you when the bearings are getting/going bad, need grease, or there's increased friction occurring for any reason such as a brake surface drag happening. Low pressure in tires creates excessive tire sidewall flexing which then creates heat buildup and the flexing and heat destroys tire structures fast, and the heating increases as speed increases, overloading tires and on which side, hot blacktop road surfaces that heats tires considerably, and other causes. You have to adjust your found results as to which side has had the hot sun (when it's a factor) constantly heating as that side can be 10-20+ degrees hotter than the shade side. Tires are black and absorb so much of the sun's heat!
Who wants a blowout or shredded tire and wouldn't you want to know about a problem BEFORE failure happens? Works on vehicle tires also. They can be purchased in many places, big box stores, Harbor Freight, Northern Tool, Lowes, Menards, Home Depot, and so many more and the price will vary greatly. I bought 2 new ones a couple years ago for $19.97 each just to keep in our 2 tow vehicles since any trailer or the TC won't be going anywhere without the motorized vehicle! Have another infrared gun in the home i've had for years and been been using.
For use in your RV "after" you sealed the obvious leaks etc you've found, the temp outside the RV needs to be either hotter or colder outside than the remp inside by at least 20 degrees or more. In cold outside temps, you heat the inside up to at least 20 degrees higher than outside for a min of 24 hours. 30+ degrees and 48 hours even works better and the infrared reading differences are more vivid and accurately found. Close every window and door tightly. Open one ceiling vent that has a good exhaust fan such as ventline etc for best results. If there's no exhaust fan, i've used a 14" or 16" square box fan against the vent hole blowing out. It must cover the entire 14 X 14 hole. Lots of ways to keep it tightly up there so you don't have to hold it up. Clamp it up with 2 telescoping or spring loaded shower rod adjustable rods holding on opposite corners with the other end in the shower base or the floor or a chair seat or a table or a secure solid riser buildup. I have even loosened 2 of the cross corner screws in the ceiling vent plastic housing and twisted simple steel wire around the screw and then twisted the other end around the box fan outside rim. Endless ways to hold it up there! The fan creates a sucking action to draw outside cold air in even the smallest leaks, cracks, or voids and forces cold air into the insulation voids so it gets colder.
After the RV temps are truely stabilized, let the exhaust fan run for about 5-10 minutes and yes the heat/furnace will turn on and that's good as the heat is required. Keep the fan going and go around and point the gun at every corner and scan. Do every outside wall/window/door etc, along the entire floor, the ceiling, around every appliance, vent, in every cupboard and closet, and pinpoint the higher cold readings. You'll probably be surprised where some are and would never suspect it! Will even show you where insulation voids are or do not fully fill the hidden space behind. Be sure to write them down on a sketch made of the RV or home so you don't forget where some are. Now you'll know where attention is needed even after you thought you sealed all the leaks. It's the known as the standard Weatherization Testing Proceedure and it's so accurate. Works for hot air leaks and cold air leaks.