79 300td ventilation woes--help?

[glassman]

I've read some of the previous threads on this subject, and still have questions, so I apologize for re-covering ground, but...
PO installed ball valves in heater in and out lines, so I assume the vertical temp control wheel in the console is inoperative.
With both valves fully open, Def button pushed, Iget too much heat!
With both valves set about half, temp is toasty...
Def pressed, I get full fan, lots of hot air from windshield Def vents and outer dash eyeball vents, nothing from centers.
If I then select BiLev, Auto Hi or Auto Lo, I still get warm air from outer and windshield vents, no fan(or very low).
If I select any of the above from Off, without first using Def, I get nothing.
I never get any heat from lower or floor vents, and sometimes seem to get cold(very cold, lately) air coming from console/floor area.
A/C seems to work--Blows cold when switched on, windshield and outer vents, no centers, no lowers, etc.

Please, please, please show me the way . Thanks, Glassman

[kerry]

Originally Posted by glassman

I've read some of the previous threads on this subject, and still have questions, so I apologize for re-covering ground, but...
PO installed ball valves in heater in and out lines, so I assume the vertical temp control wheel in the console is inoperative.
With both valves fully open, Def button pushed, Iget too much heat!
With both valves set about half, temp is toasty...
Def pressed, I get full fan, lots of hot air from windshield Def vents and outer dash eyeball vents, nothing from centers.
If I then select BiLev, Auto Hi or Auto Lo, I still get warm air from outer and windshield vents, no fan(or very low).
If I select any of the above from Off, without first using Def, I get nothing.
I never get any heat from lower or floor vents, and sometimes seem to get cold(very cold, lately) air coming from console/floor area.
A/C seems to work--Blows cold when switched on, windshield and outer vents, no centers, no lowers, etc.

Please, please, please show me the way . Thanks, Glassman

You've probably got a bad vacuum pod on the floor vents. It's to the right of the accelerator. Pretty easy to test and fix. Use a Mity Vac.
I think that 79 probably still has the dreaded ACC Servo is that correct? Big ugly pod to the right of the front of the engine with a bunch or wires and vacuum control lines going in. Heater hoses should also go into the bottom of it. If so, the Servo is probably bad is causing the rest of those problems. They cost $$$$$. Get the newer design with the metal case at the bottom.
If you don't have the Servo, diagnostics take a different direction. I assume you have the vertically arranged climate control buttons? If so, I'm pretty sure you have the Servo.

[boneheaddoctor]

Originally Posted by glassman

I've read some of the previous threads on this subject, and still have questions, so I apologize for re-covering ground, but...
PO installed ball valves in heater in and out lines, so I assume the vertical temp control wheel in the console is inoperative.
With both valves fully open, Def button pushed, Iget too much heat!
With both valves set about half, temp is toasty...
Def pressed, I get full fan, lots of hot air from windshield Def vents and outer dash eyeball vents, nothing from centers.
If I then select BiLev, Auto Hi or Auto Lo, I still get warm air from outer and windshield vents, no fan(or very low).
If I select any of the above from Off, without first using Def, I get nothing.
I never get any heat from lower or floor vents, and sometimes seem to get cold(very cold, lately) air coming from console/floor area.
A/C seems to work--Blows cold when switched on, windshield and outer vents, no centers, no lowers, etc.

Please, please, please show me the way . Thanks, Glassman

you have a siezed up Vacuum servo...thats why its acting that way...defrost is default upon failure...with out fixing it correctly or converting the entire thing over to the Euro style..which is beaucoup work you are stuck with what you have now.