I'm all out of ideas here. I've searched all over the internet and haven't come up with much either.,

2001 Ford Excursion
Limited 4x4
7.3 Diesel
Front A/C does not blow cold. Outside vent air is warmer than should be. Heat works.
Rear A/C works great.

Steps so far:
started with fuses, all good.
Checked AC coolant levels. Good.
Checked vacuum leak at heater-core bypass, previously patched, nothing found, but not much vacuum, can't find numbers to tell what this should be?
pulled apart the diverter and checked functions, working as it should.
opened blend door and ran the heat to cold to heat, watched the door move. complete close at both extremes. no appreciable air leak.

So what am I missing here? I thought it might be the heater-core-bypass but even if the vacuum line is completely failed or the bypass is open the cab should still cool, just not like it would with Max-AC on right?

 

have you looked at the heater core, and verified it is not plugged up with debris?

when I had my a/c compressor replaced last year, I made it a point, to have the blower motor removed, and inspect the core, these trucks do NOT have a Cabin air filter.

 

And how did you do that short of evacuating and recharging by weight?


Clamp off the heater hose and see if you regain some degree of cooling. Either use a special set of pliers or, in a pinch, a set of vice grips with something padded to keep the hose from being damaged. I used a couple of wood shims. At least, this will keep the air from being heated at all. This does the same thing as the shutoff valve when in MAX A/C. You should have (eventually) manifold vacuum at the shutoff valve but only in MAX A/C.

Um, no. He doesn't have a heater core problem being plugged, either internally or externally.

 

Friends with way cooler tools than me. (did just that)

I didn’t try crimping the hose line yet, I assumed that’s what the vacuum switch did.

One clarification, the heat isn’t coming on unless I move it to heat. But the air through AC or vent is hot.

thanks!

 

You need to check your evaporative core, not your heater core, unless you are mistakenly calling the evap core the heater core. They get plugged up with debris and will cause the exact issue you are having.

 

Got pressure readings?

FWIW, I'd be suspicious of a failed TXV valve....

 

OK.
Condenser coil: Clean/Dirty, able to allow air to flow through, fins not all smashed? this is the coil in the front behind the grill.
Evaporator coil: Clean/Dirty, able to allow air to flow through? This mostly viewable once the blower motor is removed. A heavily obstructed evap coil will mainly cause the coil to freeze over and thus you will loose most of not all of your air movement.
Refrigerant: High and Low side gauges need to be connected to the service ports to read the pressures of suction, and hot gas sides with A/C compressor running at various RPM's. This will give a good understanding of the refrigerant flow.
Compressor: Is it original? They don't last or pump refrigerant forever.
Front orifice tube: Is the strainer/filter clogged with bits of the compressor probably breaking down? All the refrigerant needs to be removed in order open this thingy up and verify.

So you've checked the mechanical aspects of the front system, like the blend and hot/cool blend doors functioning. If the system has never been touched and is all original, than it's probably time for a minor overhaul.

FYI: the TXV (thermal expansion valve) is used in the rear at the rear coil to variably meter the refrigerant to that coil. The front does not use a TXV, but instead the Orifice Tube.

https://www.ford-trucks.com/forums/1...e-clogged.html


Front Evap box with coil, and no blower fan.

 

Condenser coil: Clean/Dirty, able to allow air to flow through, fins not all smashed? this is the coil in the front behind the grill.
>> Clean
Evaporator coil: Clean/Dirty, able to allow air to flow through? This mostly viewable once the blower motor is removed. A heavily obstructed evap coil will mainly cause the coil to freeze over and thus you will loose most of not all of your air movement.
>> Dusty, but clean. I went ahead and hit it with compressed air just to be thorough
Refrigerant: High and Low side gauges need to be connected to the service ports to read the pressures of suction, and hot gas sides with A/C compressor running at various RPM's. This will give a good understanding of the refrigerant flow.
>> 160/60 I think? I'll have to double check with the friend that has those tools.
Compressor: Is it original? They don't last or pump refrigerant forever.
>>I think all parts are original but we can't find any leak. Also the rear is COLD.
Front orifice tube: Is the strainer/filter clogged with bits of the compressor probably breaking down? All the refrigerant needs to be removed in order open this thingy up and verify.
>>Have not checked. I'll try to get the system drained next weekend and look.
One additional issue now. The fan doesn't kick up when you switch to MAX A/C, I'm guessing its either a vacuum leak, or a 22 year old blower motor. Anyone have any input on how to test that?

Thanks!!!

 

Test your fan speeds separately in the vent mode, or any other mode, if they all work low to high, the fan and resistor are probably fine. The change in noise you hear for the MAX A/C setting is from the fan intake being heard inside the vehicle as the recirculate door blocks off the outside air intake path. This changes the fan intake resistance slightly and the sound, no fan speed change occurs. In my pic above, the recirculate door is visible, covered in the foam, it's currently in the non recirculate mode at rest, when in MAX the door moves up.

 

I didn't realize that I thought that MAX added one additional step up from the fan. I just replaced the resistor due to an intermittent no start on the fan and that was the cheaper and easier part to yank out and test.

Thanks!

 

In this pic I'm replacing the blower plenum. This is the backside that mounts to the firewall, the vacuum motor had to be moved over, it operates the recirculate door, which at rest, is in the outside air mode.

 

If the rear is cold and front is warm and you're blend door is operating properly, but you're not seeing condensation coming from the front evaporator, then likely your fixed orifice insert is likely plugged or there's an obstruction in the evaporator. The front and rear systems are parallel systems that split post condenser.