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74 k5 ,just want defrost

BigBK5

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I haven't posted in years,but having an issue. My blazer is factory ac,but i deleted it. I just want defrost for cold mornings for windshield. I dont have a vacuum line from engine to interior. I have the dash mostly apart and heater assembly removed. Do i need vacuum for just the defrost? The vacuum line scenario in my blazer is sketchy at best,lots of loose ends. I marked the ones that were still attached. I just want to be able to defog windshield if needed,im in norcal,and dont drive it much in the winter,or much at all really,lol.
 

flatland

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You might be able to build a set up using one of the small aftermarket heater cores and home built ducting. Mojave, JEGS has a unit, etc. Not sure how to control it unless a solenoid would work for you. My work truck uses a similar setup teed in to the heater lines to heat the bed unit. I can lift the hood and cut the ball valves off for the summer or leave them open to run the water heater coil.
Some of the hydronic/engine heater units people use in campers might be a source for controls or ducting ideas as well even if you aren't using a diesel heater.
Theres always the small electric units for occasional use as well. Not always super effective here with our humidity , ymmv.

Good Luck and let us know what you come up with.
 

BigBK5

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Got it working by lubing up and cleaning the blower motor,hooking back up the vacuum reservoir ball thingy to engine vacuum ,and connected to controller on dash. I blocked off the ac port on the box and defrost works great,i think. Hasnt been that cold here in norcal.
 

Wes Harden

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With no vacuum to the plenum, doors should default to defrost. You will have to have warm/hot engine coolant for it to work
 
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