safulop

I've had some excess heat intruding into the HVAC system. It always comes from the floor vent only. When switched to center position, the floor vent hot air is shunted to the center vent, and you can feel it coming through the lower section.
When switched to windshield position, the floor vent hot air stream disappears, but still the AC cooling is mediocre at the front, cold in the rear even in 100 degree heat.

I replaced the heater valve to try the quick fix, but this had only a small impact, apparently the old valve was still fairly good.

Trying to figure which vacuum actuator internally could cause this, if any, or what other bugbears. The hood rubber seals look great to me.

-Sean

Jadz928

I'd start with troubleshooting your HVAC vacuum diaphrams. Use this to guide you thru it: LINK

Start with a general system vacuum check at the main line runs into the cabin.

Here it's called line to HVAC vacuum console.

Check for vacuum leak-down on all the HVAC settings (inluding AC on). You will need the ign. on to do this. Pump up to 15 in/hg and see how will it holds. If if falls almost immediately, you will need to diagnose each vac. actuator independently, as shown in the link above.

Another quick check is to tie you heater valve open to see if you have still have heat problems. My guess is you won't, which will lead you to servicing the vacuum system.

Bill Ball

When there is SOME heat, but not full heat, when you aren't calling for it, in my experience this has been a partially leaking heater control valve. It may be getting vacuum and closing as it should but not providing a complete seal. It's certainly worth checking the integrity of the vacuum lines and operation of the solenoids as well as the valve.

Here's a link to John Pirtle's write-up on the vacuum system for climate control:
http://members.rennlist.com/pirtle/svc_act.html

And the heater valve:
http://members.rennlist.com/pirtle/svc_heatv.html

Almost certainly you will find a leaky actuator or two. If they are vent controls, you can temporarliy plug the solenoid vacuum outlet to them to restore full vacuum to the other operations. I think your problem is likelier to be the valve itself.

WallyP

Make certain that the heater valve is not installed backwards - it only seals one way. The black side goes toward the engine. If you look inside, flow from the engine pushes the flap onto the seat when installed correctly, off the seat when installed backwards.

safulop

Well John Pirtle's write-up on the heater valve pretty much explains things. Probably the old heater valve had a poor vacuum *and* was warped. Now the new one is not warped but still has a poor vacuum, so hence I observed an improvement but not a resolution of the problem. I have to do something about the vacuum actuation of the heater valve, pretty sure.

Thanks,

Sean

Bill Ball

If you want to temporarily improve your AC for the summer, you can pop the arm off the vacuum pod on the heater valve, move the arm to the closed position and tie wrap it so it stays closed.

If you think you have "weak" vacuum to the valve, check the ability of all the other actuators to hold vacuum. If one of the others has a leaky diaphragm, then the vacuum could be weak to the working actuators, depending on the settings. Also, the rubber manfold that attaches to the solenoid pack will develop cracks leading to low vacuum.

safulop

A good tip before chasing down wild geese for the "warm AC" problem. Charge the system fully! I had my AC recharged after hunting and fixing all possible vacuum leaks, and it is like night and day. The system will never be all that good when it is not fully charged.