I have a 99 silverado 1500 v6 (4.3 unfortunately). so I'm having a weird problem with my Heat/ A/C. My fan speed docent work on 1&2 but does on 3,4&5 this may tie into something with the bigger problem that I'm having but Sometimes when I turn on my truck the A/C comes on and is on even when my heat is on high and the window vents are on. when the A/C comes on I can't change which vent it comes out of and i can't adjust the temp. but when i turn my truck off and back on it all goes away and my heat works. just wondering if any of you would know anything about this and any way to fix it. I just installed some Hid low beams but i don't think that would do it. Thanks for reading!