Toyota Repair: overheating, rad cap, engine temp

Question
my 1994 toyota truck overheats when i put the climate temp selector to hot. It
cools back down as soon as i move the selector to the cool side. The idle is
unusually high when its cold outside and low when its hot. When the idle is
low, it feels like its going to stall so I adjust the idle up to compensate. Its a
v4 auto with 155k miles. The thermostat was replaced 6mnths ago. Any help
will be greatly appreciated.

Answer
Hi Eric, I do not understand if you have engine overheating or gauge problem. It sound like electrical problem. You still have to verify you engine temp with regular thermometer. And then you can know if it is electric problem. Just be very careful when opening rad cap when hot (you can burn yourself)Cover the cap with thick cloth and release pressure slowly.