Heater no longer blows hot. It's only an issue a few days out of the year down here but on those days I'll really want it. When dial the heat to hot I still get a lot of airflow but it's just cold.

A/C still blows cold. MAX seems to have some kind of issue but regular A/C works fine.

Anyway I was poking around and I saw some kind of actuator under the dash between the ashtray and glovebox. Seems to activate when A/C or MAX is selected.

There is another actuator under the hood at the firewall but I was not able to get it to actuate. It appears to have a vacuum line and the vacuum line is crumbling so there'll be no vacuum pulled by it.

Could this be my heater problem? Or just a distraction? I also see a crack in the housing where the shaft goes down into it.

Thanks all,
Marshall

 

After reading my own post the answer seems obvious that I need to replace the vacuum line and maybe the actuator at a minimum. Hopefully it isn't too big a pain.

 

That white vacuum hose was the first to go on mine. I have replaced all of them since. I think I used 3/32" rubber.

 

That white vacuum hardline to the underhood Recycle<-->Cowl Air Intake vacuum motor is the only vac hose I have had to replace on mine. Not only did it crumble out in the open where it could be seen, but also crumbled two inches or so back inside the harness that it comes out of. I unwrapped the harness a ways to cut back to get good solid line. I got same size hardline at O'Reilly Auto in the "Help" product line out on the floor. I used a small length of rubber vacuum hose as a hardline to hardline connector on the harness end.

That solved my heater/AC control problems, but the problem I had was where the air came OUT of, not of no heat or no A/C.

If the 1996 EB trim level HVAC system is still like my 94 XLT, a manual system, no ATC, no electronics, then the temperature blend door is controlled by a wire cable direct from the temp ****. Easy to move the temp **** back and forth and feel the blend door and cable resistance. Could look under dash to see if the blend door crank is moving with ****, too.

At least in my 94 XLT, even a total HVAC vacuum system failure would not prevent heat from working, just where the warm air blew out of (defrost or panel vents or floor).

If your 1996 is like mine, then I would also be feeling both heater hoses after it is warmed up to check for a plugged heater core. Also, if low on A/F can create an air pocket in the core, though harder acceleration will usually force some A/F through with a gurgle.

Back to the vacuum motors, no need to replace unless they fail the test. You can check vacuum motors easily. Particularly if you have a Mity Vac! Or can use the finger method - disconnect vac hose, push in the plunger all the way, put finger or thumb over the vac port on the motor, then release the plunger. If good, the plunger will come out some, then stop, until you release your finger off of the port, to which it will go out the rest of the way. A bad one, with a hole in the internal rubber diaphragm, will come out all the way even with your finger over the port.

For many years in Ford-Lincoln-Mercurys, there was one vac motor under the dash that was a dual-diaphagm motor. It has two vac ports. Vacuum on one pulls it in part way, then vacuum on the other pulls it in the rest of the way. Can still test diapragms by hand, just less movement per finger-plugged port. IIRC, the dual-diaphragm vac motor was used for Panel vs. Floor selection, but it has been a while...

 

I just replaced the hardline from the underhood device point to about 2 inches back in the harness with the rubber hose.

I wasn't able to see the door move, but I can feel the resistance change as I move the temp control **** and feel the force of the airflow change.

That's a good clue. Thanks.

I'm thinking this may be where my problem is. A long while back I refilled the radiator with water and not coolant. I paid for my ignorance with corroded freeze plugs which failed (as did the water pump) and lead to a loss of coolant. Freeze plugs have all been replaced but maybe there is a pocket of air in the radiator and/or there is corrosion plugging the heater core.

I really appreciate the detailed info. Thanks for taking the time!

Marshall

 

Have heat! Not great, but a definite improvement.

Took the heater hoses loose at the engine end (leaving firewall end attached) and ran water through the heater core. I probably did it wrong as I alternated directions, but what was initially clogged started flowing. Was really red/brown. When it was finally as clear as tea I replaced the water with coolant and reconnected the hoses.