I've read several books that mention heat is dangerous to your detector.
I work for an electronics manufacturer and I'm not sure I believe this.
Some facts;
Recommended maximum operating temperature for most consumer electronics including digital cameras is about 105F and recommended storage is a maximum of 120F.
Cars in the sun on a 100F day, reach 160F with the windows closed. Car trunks are slightly cooler (140F).
Car radios last longer than the cars they are installed within.
LCD displays may not work properly when heated over 50C (122F) until they cool down.
All batteries lose their charge faster when hot, even when not in use.
Extreme heat may soften the potting compound in the detector coil and let the wires in the coil shift affecting the coil's performance.
Plastic can melt at what temperatures? At the low end, PVC (polyvinyl chloride), melts at 212 °C (about 414 °F). Teflon®, which we use to coat cookware, is polytetrafluoroethene - PTFE, and it melts at 327 °C (about 621 °F). Teflon wire does not melt at soldering temperatures.
For alkaline batteries (the most common kind of household battery), putting them in the freezer will extend their shelf life by less than 5%. And cold batteries can't be used immediately -- you have to wait until they've warmed up to room temperature first. If you need those batteries for a flashlight in an emergency, this could prove problematic. When stored at room temperature, alkaline batteries retain 90% of their power, and the average shelf life of alkaline batteries is five to seven years.
For NiMH and Nicad batteries (often used for electronics), storing them in the freezer might be more practical. These kinds of batteries lose their charge after a few weeks when kept at room temperature. But they'll retain a 90% charge for months if you store them in the freezer. Just like alkaline batteries, you'll need to wait until they've warmed up before using them.
But;
Printed circuit (PC) boards and components are heated to 500F to melt the solder used to attach the components.
After the components are attached, epoxy may be added to the completed PC board assembly and is cured at 260F for one hour.
The finished units containing the PC boards are cycled with power applied at 130F for 24 hours. This helps to weed out components that are likely to fail (infant mortality).
BOTTOM LINE - I keep my detector in my trunk for extended periods of time during the summer and don't have any concerns.
