Hey guys, I would really appreciate some help on this issue before I just start throwing money at it.

I've got an '05 Excursion with a power stroke. The front climate control is digital and the rear is the manual dials (obviously). The front A/C blows cold and hot while the rear will only blow cold. If the A/C is not on, the rear will blow cold air from outside. When we go on trips, the FRONT air will slowly fade away until I get no air out of the front ducts. The rear air will continue blowing strong, but only cold. This usually takes about an hour to an hour and a half of driving. I have to pull over, turn the truck off and let it sit for a bit, restart and get back on the road.

I have had an issue with the front climate head where it wouldn't respond and I had to turn the headlights off, spin around three times, wait, then turn the headlights back on and the head came back to life. I've also recently replaced a dead vacuum pump.. with an O'Really's pump that I am suspicious of being a dud. Or could it be the blend door actuator going dead? What would that have to do with the rear? Or is it multiple issues?

I really appreciate any help. I was going to start with the blend door actuator, but I realized I'm just throwing parts at it with my level of understanding here.

Thank you!

 

mine is an '02 4wd, but the vacuum pump has failed twice in 3 years.

I suspect because of a leak in the rubber hoses, causing it to run all the time.

they aren't built for continuous duty, only 15-30 seconds until the canister is purged...

as of today, mine is dead again.

 

only problem is the symptoms don’t seem to match a dead vacuum pump to me

 

So for the rear, it's completely mechanical, and the damper doors are rheostatically controlled. The rear system has no access to outside air. One of the damper door foam insulation wraps , I can't remember which one either blend, or temp, will come unglued and prevent that damper door from fully operating. I've posted pics about this before.

 

I agree, vacuum can be the problem. there is a vacuum hose from the pump to the cabin, try putting a manual pump on it and see if stuff activates.
Also, the control head issue is a bug in the electronic systems, turn headlamps on and off 3 times, a known problem.
Check to see if the fan is blowing after that hour of driving, Evaporator may be frozen. If that is the case there is a switch on the side of the accumulator that needs to be replaced, super simple job.

 

I ripped apart the whole side of my excursion yesterday to get after the blender door. It’s there. It’s on the track with the actuator. The actuator works. The rear still blows cold air.. any other ideas?


The blower still blows.. just no air comes through. I’ll just for leaks.. maybe get a higher quality pump..

 

So an update and bump for this.. don’t have money to just throw parts at this so I would really appreciate help!

replaced the front actuator cause it did seem to never get totally hot. Now.. the front runs ONLY blazing hot with the new actuator. The vacuum pump is running fine, I watched it move through all the positions then turn on and turn off.

could this be the a/c head unit? I have the digital one. Or is there a relay or something?

thank you!

 

You are going to need to narrow some things down.

Things to keep in mind:
1. The blend doors are not vacuum operated-neither front or the rear.
2. There is a heater bypass valve, which IS vacuum controlled in the engine bay. It should turn off the heater cores when on max AC. if this valve is working, it will open and closed depending on the set temperature. If you do not see it moving, I would recommend closing it and putting a zip tie to keep it shut and see if you get a difference in temperature. if that works, you may have a vacuum leak, but the tubes are no longer available, and you will have to find vacuum hose that you can try to fit, but the Ford hoses are extremely small. Technically the blend doors are working. You shouldn’t see much difference anyway so I suspect your blend door may be stuck. You said you changed it. It’s the one mounted on the top side of the front AC, accessible behind the glove box. You should be able to see this move as you change the temperature settings.


3. On My Ex, a previous owner disconnected the rear heater core in the passenger front wheel well. I would run the heater at full. Get the truck up to temp, and see if the heater lines under the truck heading to the rear are hot. Something like this may explain your rear teeth issue. My lines were cracked and had to be replaced so I used heater hose and retrofit it.

4. The rear blend door actuator is on the backside of the AC enclosure against the fender. If you snap the panel off you can access it with a stubby screwdriver/small wrench to remove. There is foam wrapped around the door, but you’d have to remove the whole rear AC unit to repair the foam.

give these a try and report back.