Under-dash plastic tube

[89Blazin]

I replaced the heater core on my K5. I put the under-the-dash stuff (vent duct work, control linkage, etc.) back together and discovered a VERY small diameter hard plastic tube danglin under the glove box. Found some sort of device (diaphram?) mounted on the passengerside, where the outside air vents used to be located on older vehicles. It has the same size tube running to it. Cannot find a home for this danglin tube. Anyone know what the tube is for, where it goes, and what that is mounted on the side panel?

85 Burb and an 89 Blazer
One just for fun, one simply for pleazer

 

[Leadfoot]

I would say (without seeing it for myself) that it is your hard plastic vacuum line. The diaphram you saw mounted where the old hand operated vents used to be on older K5's controls the opening and closing of the vents with vacuum. No vacuum and the spring in the diaphram holds it closed, when vacuum is applied it overcomes the force of the spring and it's opened. You need to trace all the hoses until you find the source (coming through the firewall (uses engine vacuum), and all the connections ("T" fittings, diaphrams, etc.).

If you didn't built it yourself, how can you call it yours.......?

 

[newyorkin]

I agree with Leadfoot. What you might try is turning on the a/c or heater and trying every position to see what doesn't work, i.e. when you have bi-level selected, see if it's blowing through the top, the vents, the floor, etc. May be a starting point.

Ratch
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[89Blazin]

Thanks all....heater / defrost, vent, AC all 3 positions....all work. Maybe the vent on passengers side is not opening when in the vent position. I wonder if this small of a vacumn leak would affect engine performance?

85 Burb and an 89 Blazer
One just for fun, one simply for pleazer