I have a 99 Z-71 Silverado 1500 4wd w/ towing package. The heater only blows cold air. I checked the hoses going into the firewall, one is hot the other is warm, probably from the heat of the other hose. I can not find the valve under the dash to manually open it. Am I going to have to rip the whold dash to get at it, or is there a better soloution?

Thanks

 

Sounds like your heater core is plugged/slugged up. I'd pull the hoses and try to back flush it and see it the blockage might break loose. Might need a new core, if all the controls are working ok.

 

Yeah I second that emotion. Appears to be a stopped-up line. I think a back-flush is the first step too.