2001 AC not cold, blows through defrost under load/accelleration

I have a 2001 Expedition XLT, 5.4, AWD.

If I have the AC set on console and start from a stop or going up hill (high vacuum condition) the AC blows through the defrost.

This used to happen rarely but has gotten progressively worse to the point where the AC doesn't cool at all.

The AC, front and rear, do not blow cold, just cool. Not enough to cool the truck on a hot day.

Any suggestions?

Thanks, Steve.

After work, I pulled the battery and checked the vacuum tank and the check valve. Both seemed ok.

I pulled the radio/hvac control bezel and removed the fan/temp/diverter switch. I have no vacuum at the switch (black hose).

I need to did out my vacuum gauge. Is there a vacuum schematic, how much vacuum should I have?

Does anyone know how the black vacuum hose is routed from the vacuum tank, through the firewall, to the switch? Is there a splice/connection/adapter under the dash? The vacuum line going through the firewall is a different material than the lines at the switch.

Thanks, Steve.

Port Hose Color Function
1 White Air inlet duct door
2 Yellow Floor/panel door
3 Black Vacuum source
4 — Not used
5 Blue Floor/panel door
6 Red Panel/defrost door



VACUUM APPLICATION CHART—MANUAL A/C
Switch Port Color Function Function Selector Switch Position
MAX A/C A/C PNL/ VENT OFF FLR/ PNL FLOOR FLR/ DEF DEF
1 White Recirc/fresh V NV NV V NV NV NV NV
2 Yellow Floor/panel NV NV NV V NV V NV NV
3 Black Vacuum source V V V V V V V V
5 Blue Full floor NV NV NV V V V V NV
6 Red Panel/defrost V V V NV V NV NV NV

V = Vacuum

Item Part Number Description 1 18A318 Vacuum control motor— panel/defrost door
2 18A478 Panel/defrost door (full vacuum position)
3 — Defrost airflow
4 — Side window demister airflow
5 18B545 Temperature blend door (full heat position)
6 19860 A/C evaporator core
7 19A813 Air inlet duct door (full vacuum position)
8 — Outside air inlet
9 18A318 Vacuum control motor— air inlet duct door
10 — Recirculated air inlet
11 19805 Blower motor
12 — Vacuum to emission control
13 — Vacuum from the engine intake manifold
14 19A563 A/C vacuum check valve
15 19A566 A/C vacuum reservoir tank and bracket
16 19B888 A/C-heater function selector switch
17 18476 Heater core
18 18A559 Floor/panel door (full vacuum position)
19 — Floor airflow
20 18A318 Vacuum control motor— floor/panel door
21 — Panel vent airflow

I removed the vacuum line going from the check valve to the cabin.

Put a vacuum gage on the check valve and shut off engine.

No loss of vacuum. Tells me I am good at the engine bay.

Checked the Vacuum line going through the firewall.

Found an abrasion right at the connector.

Cut off the bad piece with a razor blade and installed a new adaptor. $4.95 for an assortment at Auto zone.

Tested switch and everything worked fine.

great job!

thanks for the update, others will learn from it!!

Hey, All. I just want to say thanks for posting this. As Brian said, someone else will learn.

My son-in-law has a 2003 Expo that had the same symptoms. I sent him these pics and he found a disconnected vacuum line near the check valve. Connected the hose and violà! Ice cold again! Good thing, too since it's going to be over 100° for the rest of the week here in north central Utah.