answersLogoWhite

0

air pockets in the cooling system, start by bleeding the lines, plus there is a bypass for the heater core when you have the a/c turned on, or your heater isn't on, this fluctuate between makes and models. but i would go to YouTube and look up how to bleed coolant lines, and that should make it easy for you.

User Avatar

Wiki User

13y ago

Still curious? Ask our experts.

Chat with our AI personalities

DevinDevin
I've poured enough drinks to know that people don't always want advice—they just want to talk.
Chat with Devin
RafaRafa
There's no fun in playing it safe. Why not try something a little unhinged?
Chat with Rafa
ProfessorProfessor
I will give you the most educated answer.
Chat with Professor

Add your answer:

Earn +20 pts
Q: What causes heater not to get hot in 1999 gmc truck?
Write your answer...
Submit
Still have questions?
magnify glass
imp