one more stupid stock-truck vacuum question...

jcc

jcc

Member
lightning vacuum.jpg

see the golf tee?... what's that vacuum line to? truck idles better with it plugged, must be a leak somewhere,... but everything still seems to function in the cab (heat, floor, mix, defrost etc),... i know you guys will know. Thanks in advance.
 
HVAC blend door. The tee is stuck in the source connection, so no way for there to be a vacuum leak there. Looks like the nipple below it has a cap on it. That's the vacuum source.
 
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^^^What he said. The blend motor likely started leaking and causing driveability issues that they solved by doing that.
 
...that's what i thought it was for, but i swear that blend door is moving... oh well, i just pretty much leave it on floor anyway, not ripping the dash off any time soon. Thanks!
 
-is the blend motor easy to change out on the Lightning, i looked around but it didn't pop out at me,... i know some are impossible w/o removing the dash
 
There are actually 3 blend doors with vacuum actuators, the outside air (Max AC) is the one you can see under the passenger hood hinge. The other two are inside the housing and control the panel/floor/defrost blend doors.

BTW, it should fail in defrost mode since from a safety standpoint that's the most import mode, so I'm not sure why it would always be on floor with that line disconnected.
 
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After thinking about this a little more, isn't the temp blend door on these cable operated? Since that is on the checked side of the check valve that may just be another reservoir. The line that goes into the wire loom on the left of the golf tee is the one that supplies the HVAC.
 
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i see the blend actuator under the hinge, that one is crusty, but not leaking, there's one in that black housing in the engine compartment (behind the golf tee, lol??) right where the vac line goes in,... i'll have to take a look in there

thanks again!! ...maybe i'll get my golf tee back yet!
 
Before you get in there, look under the dash on top of the housing. I honestly can't remember where they're located and if I'm remembering my '93 Lightning or my '02 Blazer (the only two vehicles since my '83 Rabbit I've had to mess with blend doors/heater cores on). Getting old bites!!
 
-interesting, that tee'd off vacuum line goes to an accumulator box, which was fine, no leak there... but the vacuum Check Valve was faulty,... let vacuum through in both directions (intermittantly), $10 on Amazon
 
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