OK, had another thread going, but I managed to make it confusing. Car only blows Cold Air (from AC cold). Heater valve works properly and opens/closes from controls. Checked all 4 vacuum solenoids (9V jump), they work fine. Servo motors that operate blend doors(heater core/evaporator) work fine if jumped with a 9V battery. Checked all connections, unplugged, cleaned re-plugged. Checked all grounds with OHM meter, all are no resistance. Apparently not receiving any instructions from controls. Anyone have an idea what is happening here?

 

When you say checked all connections, does that include thermostat to ECU? And does the thermostat actually give a sensible output? And did you check for shorts between wires e.g. thermostat wire pair, not only continuity? Ditto temp control wheel? If all are OK then if pussible try your ECU in someone elses car (a damaged ECU will not damage sensors or solenoids). If all is still well try patching into the thermostat and temp control inputs to the ECU (while battery disconnected) feeding the ECU. Then monitor inputs with a digital voltmeter or even better laptop with an USB oscilloscope. If you can beg or borrow an ECU you could try that but any wiring faults you have missed could toast it, even without your knowing ......

 

I knew it was going to go this direction....darn,darn,darn,darn,darn!!!!

 

Per, may turn out to be heater valve after all. Valve is operating from vacuum, but return line is only about 10% as hot as source and other hoses. Thinking maybe valve failed internally and failed closed, maybe corroded away. After all, this particular vehicle sat up for 9 years and is only recently running again. Let you as soon as new heater valve gets here and i install (sure as heck not going to the trouble of pulling things apart without replacing it). Thank you and all the others for trying to assist so far. My education on HVAC is now much better than I ever wanted it to be :-)

 

Per,
Wasn't the heater valve, replaced it. Vacuum all the time. I have individually checked every vacuum solenoid (all work), check electric blend door motors (they work), fans work. System seems to think I am calling for full AC all the time. Will not respond to Air/Heat slide nor will it respond to the Temperature control (potentiometer). any guesses???

 

Hi Meeither,
Well I cannot help you yet, but am delving into the insides.

Have rebuilt the fans and controls that were not blowing/controlling correctly, but now have an issue with the blend door actuations. I think the top is working but the lower always blows cold air even though I can get hot out of the sides when set to hot and can get cold out of the center now.

So, question, do you know how to best approach the AC controller removal. How much of the dash do I need to pull to remove it? It seems that the lower servo is underneath the controller that seems held in with a couple of simple screws, one of which I can get out.

Appreciate any advice from your exploits.

 

Drop the panels under the glove box, 4 screws I think. Take the cheek piece off the passenger side (US) (front of console), 2 screws that hold the vent on. If you are talking about the piano shaped ECM, you will need to access from the front, thus necessitating taking the "ski slope" out and front panel where radio is (I think I am right here, has been a while since I did this). However, it more than likely is blend doors from what you are describing and the blend door motors are located on the passenger side (US) and can be tested (use a 6 volt battery and make sure they are disconnected from harness first) fairly simply without removing any of the console. Getting them off is a Bear though just because of access. If blend door motors are functioning properly, then go to connections and clean them all on the ECM, slide control, and vacuum solenoids (4) before you assume the ECM is bad. Don't see many bad ones (I have a known good one for $100.00 if you need it, but I don't think you will need it). My bet is connections, some are tiny and tedious to clean, but clean them, re-connect them and see if it resolves your issues.

 

Well Much better thanks to your guidance. Cleaned contacts and while there, managed to get to both the blend doors and motors and validated their operation. (Nice high quality motor in them too). While off, I removed the fan fuses and manually turned the blend doors and validated that the control unit drove the blend door motors and that the feedback pots provided feedback. In manual temp mode, the motors were active until the blend door was in the right position to direct air to either center vents (COLD) or elsewhere. Found that with both fans operating, and on cold, quite a few bits of non-British metal (foam) was blown to the center vents. Guess there are some seals that are not as good as they should be. Much more air also available with both fans blowing and the ducts connected properly. Some past person failed to reconnect correctly.
After also replacing the heater valve with the Ford plastic equivalent, I only have hot on hot and good cold on cold.

The only issue I have not yet fully resolved is the center temperature bias. Seems that It needs to be in full face warm to have a moderate temperature in the side vents, while the feet are quite warm. If I move to mid or cool, then the side vents are quite a bit colder than the feet. Seems as though it may be set wrong or partially open.