Burning plastic smell in air vents and temperature gauge bouncing

Hello, I would suggest trying to determine the actual engine temperature before taking the gauge for granted that it's telling accurate information. 160 would be way too cold for an engine "at operating temperature" - so there's either going to be a cooling system issue or a temperature sensor issue. None of this is going to be related to the burning plastic smell. I would suggest checking the exhaust system under the vehicle to see if there is indeed a plastic bag stuck underneath. It happens! Then it burns off slowly and this smell can enter the cab through the ventilation system. You may also want to check the cabin air filter (if your truck has one) and see if there is debris in there causing the smell. If you would like some advice near you, try a local shop: https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.