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AC + Heater vacuum valve question.


ben_2_go

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The past couple weeks, I noticed that my AC isn't getting as cold as normal. Broke out the tools and average 40 psi low side and 160 psi high side. Compressor cycles on about every minute or two. All of this is at idle with the engine at normal operating temps, ambient outside temp around 91F, and humidity around 80%. Driving on the highway at 60 it takes 20 to 30 minutes for the AC to get cold. I thought I'd try the heat just to see. Why the hell not? No heat. The temp coming through the vents stayed the same, not cold but not warm. I'm guessing around 60-ish.



Until now, my truck has never failed to put out cold air within five minutes after turning on the AC. Outside temp never seemed to matter much. Since the heat side fails to return heat, I'm wondering if the heater valve has failed inside and is half open preventing the AC from cooling the truck completely. I know the blend door would have to be completely open for full heat. Maybe that's my problem. I hope not. I don't have the time or place to pull the dash out, at the moment.


01 2.5L auto, in case no one looks to the info card or sig line.
 
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adsm08

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This sounds like a blend door issue, not a heater bypass valve.
 

ben_2_go

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Do you know if it's electrically actuated? I haven't used the heat in so long, it may come down to corrosion on the connectors. I'll look more into it this weekend weather permitting.
 

ben_2_go

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I did some diagnosing last night. The control panel is sending vacuum to the heater valve all the time, even when set to cold. Can the control panel be repaired or is the vacuum ports somewhere else?
 

Macneil87

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Any fixes as of yet?


Sent from my iPhone using Tapatalk
 

ben_2_go

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2WD
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235-75-R15
My credo
None at all.
Any fixes as of yet?


Sent from my iPhone using Tapatalk



My AC manifold gauges turned out to be bad. I still found a leak in the bottom of the evaporator. Corroded right through. I found it while replacing my blower motor and resistor. I'm not pulling the HVAC box off the firewall until next spring to fix it. I dunno why my manifold gauges went bad. It's a quality set. They have been good, but have set in their box on a shelf for a few years since I last used them.



The heater issue was behind the control panel for the heat/AC. Had a leak behind the controls, cracked vacuum line. I cut the vacuum line and used a rubber vacuum line coupler I bought from Assvanced Auto to fix it. Surprisingly, it wasn't hissing like a pissed off snake.
 

kimcrwbr1

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When your done with the guage set you can purge the lines with nitrogen it is the oil that will break down the rubber orings. If you use air pressure be sure and use a water filter. A single drop of water will destroy the compressor by producing acid.
 

ben_2_go

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Joined
Aug 24, 2007
Messages
322
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330
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63
Location
Third rock from sun
Vehicle Year
2001
Make / Model
Furd
Engine Type
2.5 (4 Cylinder)
Engine Size
2.5 Scrap
Transmission
Automatic
2WD / 4WD
2WD
Tire Size
235-75-R15
My credo
None at all.
When your done with the guage set you can purge the lines with nitrogen it is the oil that will break down the rubber orings. If you use air pressure be sure and use a water filter. A single drop of water will destroy the compressor by producing acid.



I'm up on all of that. Thanks for the reminder. The system will need a rebuild. The evaporator has a bunch of pinholes in the bottom of it from sitting in moist (love that word moist:haha:) debris. A lot of debris was inside the box. So much so that I couldn't tell where the bottom of the evaporator was and where the box began. This truck used to run around the coal mines and gravel quarries in the high mountains of SE KY. My GF was a night watcher up there for a few yars.
 

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