A/C problem

Trying to figure out where to start, Clifford has factory A/C, when I turn it on, it only blows from the defost vents. I was told that is the default when it is low on freon, but I check and gauge show it is good. Vacuum hose appears to be good also. Suggestions on where to go now? Thanks and hope everyone has a great 4th of July.

Defrost is the default when no vacuum is applied to the doors in the HVAC system.  Typically the problem is where the vacuum line goes through the firewall.  You can see that in the upper left of the illustration below on the line that is called 17543.

The line seems to get brittle and then it breaks close to that grommet where it goes through the firewall.  So check that out and let us know what you find.

I was doing something under the hood and dash and my HVAC system was working 1 min and not the next?
As Gary said the vacuum line broke inside that pass through.

If you look inside in that area you will see where that vacuum lines come through.
A little farther inside you will see where that engine bay lines meet the HVAC lines and plug together.
With the motor running and you pull that plug apart you should get vacuum on the engine bay side of the lines. No vacuum at that plug you then will need to track down why.

Now if you do have vacuum at that plug and moving the HVAC controls dose nothing, still on defrost, then you may need to look into the "broken door hinge".

BTW what gauges did you use that said the AC system was charged?
Dose the compressor run when you have it on AC and it is blowing cold out the defrost?
Dave ----

Ok, the vacuum hose going through the firewall appears to be ok , but I will check again first thing in the AM. The compressor does not come on unless I remove the pressure switch and jump it, then it comes on.  Right it's just me so I am not sure it works when the compressor is on, but will have help tomorrow. I used the gauge that the freon can, planning on getting the adapter for my "real" gauges tomorrow also.  After 40+ years I am going to try to replace all the vacuum hoses. If the hinge door is broken, what is the best way to access it?

Gary, in the diagram, there is a small hose next to hose# 17543, it is broken, it is a hard plastic hose. I  can't find any referance as to what it is/for or what it is connected to. Any ideas?  Thanks

If you mean the one called out in the illustration below, that goes to the recirculate door.  It closes in Max A/C but not in Normal A/C, so if you put the control in Normal it shouldn't have a problem.




The illustration below is from the 1985 EVTM, which you can find at Documentation/Electrical/EVTMs/1985 EVTM and then go to the A/C Heater section.  It has more, including testing.

majorfa05 wrote

Ok, the vacuum hose going through the firewall appears to be ok , but I will check again first thing in the AM. The compressor does not come on unless I remove the pressure switch and jump it, then it comes on.  Right it's just me so I am not sure it works when the compressor is on, but will have help tomorrow. I used the gauge that the freon can, planning on getting the adapter for my "real" gauges tomorrow also.  After 40+ years I am going to try to replace all the vacuum hoses. If the hinge door is broken, what is the best way to access it?

It sounds like you may have 2 issues going on here.

First is to get the controls to work to change the air flow from defrost to floor & vents.
This way when the control is set to defrost / floor / vents the air will go where it is wanted.

Once that is working the AC system may need re-charging based on the need to jump out the psi switch to get the compressor to run.
Now do you know if the system has been changed to 134a or still has the R12 in it?
How long has the system not worked? This will tell you what you need to do to get it running and blowing cold again.

If it has been changed to 134a that is good as it will be a little less work.
If not you will need to figure what charge is compatable with R12 with out a flush and oil change.

If been down for a long time the dryer should be changed out. I would also pull the orifice valve to see if it has any junk on it. If it does then you will need to find where it came from and replace that part or the whole system and flush out what has not been replaced.

Some say you will need to replace the hoses and others say you dont?
I did only because my system had been open for 4 years and was a mix & match to get the system together other wise I would of reused the old hoses.

I also replaced the dryer, age & open to long, and condenser, hole, flushed the evap.
Added oil as needed and pulled a vacuum. When it held vacuum for an hour I charged it, n134a, and was blowing cold. Then the first leak showed up. I have had 3 leaks, 2 caused by me and this last one I will fix this weekend a fitting I never had apart.

Vacuum never showed the first leak, new o-rings, I forgot to tighten a fitting.
This last leak I will pull a long vacuum and let it sit to make sure it has no more leaks as I am getting tired fixing this AC system!
Dave ----

I'm thinking you may have a blend door issue. This is not uncommon with our vehicles. In fact, expect it. I repaired mine a couple years ago and the link below is the route I went. You should at least inspect that door. If it's never been repaired, I'd wager it is your problem.

https://www.ford-trucks.com/forums/1486377-how-to-repair-the-ac-vent-door-hinge.html

another part in the system that is a potential is the vacuum selector switch. it is literally a switch in the heater control assembly in the dash which routes vacuum though different ports then on to different vacuum motors to change air flow through the different duct positions. a black plastic body with an amber colored plate and a transparent rubber connector mounted to it, with a red electrical plug off the end. these can (will) degrade over time with enough heat and will either warp or leak vacuum but can also get very brittle and the lock tabs which hold the two halves together can break off allowing them to not seal either.

Thank you sir, great info.

Mmmmmm   saw it but didn't check it Thanks I will try that next off day.