Help! A/C vent trouble

[Achilles]

Just recently my A/C is only blowing out of the heater ducts. It is still nice and cold but I need the "air" above my feet!

Pulled the dash apart and I see that neither the defrost or a/c flapper is functioning. I can manually open both flappers if I connect a brake bleeder pump to the corresponding vac hoses. But on its own they will not open.

Checked all my hoses to the acuators and they seem to be fine as far as I can tell.

Need some ideas!

 

[TimAT]

If you can make the actuators move when you put vacuum on them, I'd bet the vacuum switch on the control head is bad or the entire system is not getting vacuum.

 

[Achilles]

Okay, thanks Tim. Now what is the control head?

John

 

[TimAT]

That's the lever/switch stuff in the console. All of the vacuum for the HVAC runs thru a rotary valve attached to the lever that changes the mode- OFF-MAX-A/C-VENT-HEAT-DEF.
There's vacuum from the engine that feeds to that valve and it is sent to the actuators depending on what's been selected.
I'd start at the engine- usual point for vacuum source is the right rear of the intake in the runners for cylinders 6-8. Same place the headlights get vacuum, just a different line. Track it back to the control. SOme years use a 1/8 plastic line- they get brittle and break with heat.

 

[Achilles]

I have the 1/8" vac lines and checked all that I could easily see. Had one broken and thought that it was my problem, but not so. I checked the vac lines that run to the consol swtch and I don't feel any vacuum from the incoming lines. I don't know if I should be able to feel vacuum or not - thinking it would be either the black or the green stripe hose.

So I have either a break or a clog in the line somewhere.

Is there some electrical devise that opens to allow vacuum to these lines?

Thanks for your help.

 

[TimAT]

When the engine is running, there should be vacuum all the way to the switch on the control head. Open up the left side of the console, the switch and all the hoses are visible. The connector is held on the switch with a couple of spring washers. gently remove them and disconnect the switch. Start the engine, there should be vacuum at the connector. You'll be able to hear it hissing, and when you put your finger over the connector, you can feel it too.

 

[Achilles]

I have the console and half the dash assembly apart. No hissing and no suction at the air hoses to the switch. So Where ever they get vacuum from is where I assume the problem lies.

 

[TimAT]

Usual place for the vacuum source is the right rear corner of the intake in the runners for cylinders 6-8. Same place the headlights and vacuum modulator for the trans get vacuum. IIRC, there's a plug in the firewall that the vacuum line to the inside runs thru. It's about 1" in diameter, with the line running thru it.

 

[Achilles]

Found the trouble. The rubber plug in the firewall on the right hand side has three (1/8") plastic hoses coming out of it. One white stripe that goes to the heater valve actuator. A green stripe hose that goes back into the cowl that I believe goes to the fresh air inlet inside the lower right kick panel. And a black one that goes to the source of the vacuum. Which in my case are some vacuum T fittings that eventually lead to the intake on the left side.

Anyway, last week while I was trying to diagnose this problem I noticed the white stripe hose was broken. At the time I didn't know where it went to (partly due to its age the white stripe now looks tan), untill I saw another small vac hose that had a broken piece of 1/8" tube inside it. I assumed the two went together and rejoined them. WRONG!

Yesterday, I found that those two hoses both broke off at the rubber plug in the firewall. The other rubber vacuum hose with the piece of plastic tubing in it went to the T fittings where the vacuum comes.

Through a series of splicing some 1/8" tubing into some small vacuum hoses, I was able to reconnect everything to the proper source and everything is working in perfect order.

Now I get to put my dash and console all back together.

Its kind of Mickey Mouse'd back together, but it works. Someday I'll fix it right.

Thanks again for your help Tim!

John

 

[TimAT]

Great! If you get around to replacing all those vacuum lines, I think Willcox or Doc Rebuild has a complete diagram and maybe even a replacement vacuum harness.