Air only blows through defrost
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Air only blows through defrost
Ok this is my first post. I’ve been working on getting my ac to work again and getting the air to blow out other vents besides the defrost. I’ve been doing lots and reading and watching videos but I’m kinda stumped. Here goes:
2003 f350 v10. The ac seems to works cause the lines in the engine compartment get really cold. The blend door works. I Know the climate control is vacuum drivin but I can’t find a bad hose anywhere. The only leak I have found is there is air blowing from the evaporator core box. Doesn’t seem normal but i don’t know. That’s all I can think of. Any help would be awesome
2003 f350 v10. The ac seems to works cause the lines in the engine compartment get really cold. The blend door works. I Know the climate control is vacuum drivin but I can’t find a bad hose anywhere. The only leak I have found is there is air blowing from the evaporator core box. Doesn’t seem normal but i don’t know. That’s all I can think of. Any help would be awesome
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
How have you determined that the blend door is functioning?
You identified the most common issue, vacuum lines. The most common failure are the ESOF vacuum lines at the wheel hubs. Check those vacuum lines, where they are rubber. Then check the vacuum pump on the fender.
There are some vacuum junctions under the passenger side of the dash. Check those junctions. If you have a brake bleed kit you could manually apply vacuum to the vacuum lines here and that would help you narrow down what the issue is.
You identified the most common issue, vacuum lines. The most common failure are the ESOF vacuum lines at the wheel hubs. Check those vacuum lines, where they are rubber. Then check the vacuum pump on the fender.
There are some vacuum junctions under the passenger side of the dash. Check those junctions. If you have a brake bleed kit you could manually apply vacuum to the vacuum lines here and that would help you narrow down what the issue is.
More Turbo
Joined: Apr 2018
Posts: 551
Likes: 151
From: King and Queen Virginia
I went through this last year on my son's truck. The small vacuum line feeding the dash was bad where it connected to the vacuum tank. The end of the line was dry rotted and split. I also found the lines going down to hubs were leaking where they connected to the hubs. The fitting in hub had rusted down to nothing and fit very loose. Replaced them with 1/8 pipe to barbed fitting (stainless steel). A Mighty Vac be your best friend chasing down leaks in the old tubing. You can Isolate a section at a time.
Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,081
From: St Louis
If 4x4, check for a leaking (cracked) PVH solenoid. Simply cap off or plug the line going to it to isolate from rest of system. It's far more likely to cause your symptom than the individual hub vacuum lines since the lines only have vacuum applied during switching.
Otherwise, inspect the vacuum supply line that goes from under the hood to the HVAC climate control head. The area near the battery is particularly prone to failure.
Otherwise, inspect the vacuum supply line that goes from under the hood to the HVAC climate control head. The area near the battery is particularly prone to failure.
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
If you have manual 4x4 then you don't have vacuum lines going to the hubs. That helps eliminate that at least.
Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,081
From: St Louis
Check and see if he PVH solenoid was eliminated in the conversion or if it's still attached to the vacuum supply. It's a common failure for those trucks where it's still installed.
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Lead Driver
Joined: Dec 2006
Posts: 7,093
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From: San Diego, CA
The 2003 trucks had a vacuum operated valve in the heater line for the Max A/C setting to block off some of the flow through the heater core. The tee for that is under the glove box (I don't remember if there's a panel to remove to see it). I ended up removing the line when I installed my EGT gauges. It's not in the engine bay where it can weather faster but things were stretched pretty tight under there on my truck. Might be worth a look. 
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Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,081
From: St Louis
The 2003 trucks had a vacuum operated valve in the heater line for the Max A/C setting to block off some of the flow through the heater core.
That valve and its vacuum supply line will not cause this problem.
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