When heater is on truck almost stalls

[Mytwogrls]

When I have my heater or ac on my lights dim and trucks idle goes really low(almost stalling). It gets worse as the truck warms up. As soon as I turn the heat off it is fine. Any ideas? I just change the pcv valve and the cracked elbow

 

[Rick]

I would look for a vacuum leak. Check the vacuum lines that attach to the heating and ventilation system.

 

[Mytwogrls]

Checked all vacuum lines no leak! When the idle goes down I noticed that the a/c pump is trying to engage! It only does it when it is the engine is warm! Any help would be appreciated .. Thanks

 

[1Aauto]

welcome to the site

Tony