'89 S15 HVAC Issue

[bcrooms]

Is it common for the vaccum type actuators to stop working on these trucks? I'm more familiar with the electronic type actuators found on the later Silverado trucks.

 

My grandpa's 89 S15 seems to blow most of the cold air out of the floor vents...It does seem to change from dash to defrost, but not matter which mode is selected, the majority is still coming from the floor vent.  On these 90+ degree days it takes a long time for the truck to cool down like this...

 

What should I check first? it seems these older vacuum type actuators and HVAC controls are hard to find replacements for.....unless I'm mistaken.

[dna9656]

Your truck is old enough to have dry rot in the vacuum powered rubber diaphragms, they are prolly leaking. I'd pull the seat out and drop or open the heater box under the dash and replace all the diaphragms.