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What Am I Looking At Here? - A/C & Vacuum Line T/S

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  #11  
Old 05-22-2018, 04:02 AM
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Originally Posted by YourMileageMayVary
Moparite,

Thanks for the drawing. This is the diagram that actually caused me the greatest confusion between what's actually installed in my truck, as seen in the photo in the OP, and what's supposed to be there. On the basis of this diagram, I was about to go in and change out the downstream check valve; I stopped when I noted the reality/diagram mismatch.

Another day of rain is keeping me from pulling the cowl and looking at what's going on there.

@HeyYou, if that mini reservoir/check valve assembly was supposed to help with wild vents, it wasn't working well at all. Have had the wild vent issue since I had the truck, but only recently did the blower doors stop working altogether.
Originally Posted by HeyYou
Check it and see if the check valve in it has failed.
Actually that check valve is right. It's in a TSB for the dealer to install that check valve. It does have a little reservoir but that is the correct check valve how that line only.
 
  #12  
Old 05-25-2018, 12:30 PM
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Happy Memorial Day to everybody! Update as fol:

It is indeed a check valve, Mopar part 4677204. Check valve has been verified functional.

It is inline upstream of the vacuum supply for ventilation control. The line that branches off from the T connection is for the cruise control (which, as expected, doesn't work either). Thus, odds are really good that this was the source of my problem.

Now to the business of finding the firewall penetration and repairing and replacing vacuum lines.
 
  #13  
Old 05-26-2018, 06:28 PM
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Cap this line and see if the cruise control works. What year and engine are your truck? If you have 4wd, it also gets vacuum from that line. Have you replaced the plenum gasket yet? It's a huge vacuum leak if it's bad.
 
  #14  
Old 08-05-2018, 01:42 PM
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So, my work life has been absolutely miserable since I last posted.

At least the internet filters at work let me access this site today.

Since I've last posted, here's what I've learned:

- The ginormous check valve is working properly.
- I obtained a hand operated vacuum pump to verify where the vacuum leak might be. Connected to the cruise control reservoir (located under the cowl), I was able to draw 25" of vacuum, with a 4" drop over 10 minutes. Probably not there.
- I was unable to draw any vacuum using the line to the HVAC system. Next step is to chase the leak inside the cab.

Sometimes where not to look is as good as knowing where to look.

More to follow.
 



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