I have a 1999 dodge ram 1500 4x4 5.2l.
I have the "wild vents" syndrome where my vents at throttle switch to defrost.

I have done the following to locate/fix the problem but have some questions to get me further....

1. checked ALL vacuum lines with a vacuum pump. ALL lines hold vacuum except for the very thin vacuum line that goes through the firewall behind the glove box into the heater core housing area. This line holds vacuum for no appreciable time. Line does not seem to be damaged going into the firewall.

2. Installed the ram TSB fix for "wild vents" A 35mm cannister looking check valve/vacuum reservoir at the line before it enters into the firewall.....This helped the problem and allowed me to accelerate mildly before I lost enough vacuum to switch to defrost. It also recovered a little quicker but did not fix the problem anywhere close to acceptable.

3. disconnected the GREEN vacuum line that goes to fresh air door vacuum controlled pump behind the glove box. (it was the only easily accessible vacuum line I could get to. while I can see/feel the vacuum line coming into the firewall from the engine compartment, I cannot get to it easily to trouble shoot it.) I observed the following..
-While my vacuum tester is connected to the green tube with the ignition switch to on but engine not running, AND the defrost/vent switch on max a/c; I get a quick vacuum loss until about 4" of vacuum, then a pretty good hold for about 30 seconds. Then I lose all vacuum and it switches to defrost.
- With the engine running, I get normal vacuum at idle on the green vacuum line under max a/c, but a loss of vacuum on this line on every other switch setting and it goes to defrost.
-switching the defrost/vent switch while the engine is running to different settings seems sluggish but it does switch.

My question are (sorry for so many):
A. should I expect vacuum hold on the line going into the firewall to the climate control system?
B. How can I test the defrost/vent vacuum switch? I tried to pull off one of the colored connectors, but it seemed like I was going to rip the tubing in half so I stopped. Can I unscrew the two nuts on the back of the switch to disconnect the connector and isolate/test each port? If so, what am I looking for? This step is VERY important to me because it keeps me from ripping my dash apart further if necessary.
C. If my testing of the defrost/vent switch turns out that the vacuum problem is somewhere else, where/how do you recommend I look/test?
D. could my problem be corrected by installing another check valve/vacuum reservoir inline or make-shifting my own much larger vacuum reservoir?

Thank you for your help with this issue. I hope my trouble shooting makes it easier for you to give me an accurate diagnosis.

 

I saw another thread about this involving vacuum check valves.
Try a search

 

Thanks for the reply, but I have already done several searches and replaced all check valves. I have identified an issue with no vacuum hold on the line that comes into the firewall for the climate control system. My problem is somewhere else other than the check valves.

 

I have now disconnected the yellow vacuum line from the vacuum actuator and applied a vacuum to this line. It will not hold vacuum. I have then connected my vacuum pump to the actuator and applied vacuum. It will hold vacuum. This has eliminated the possibility of a vacuum actuator leak. I now need to find where the yellow vacuum line goes and trouble shoot it from this point.

Any help would be greatly appreciated!

In the mean time, it looks like I can "engineer" a block of some sort to the end of the stem on the actuator to always allow full air to the dash ducts until I can isolate the problem :-)

 

wow new people are catching on DO A SEARCH!

 

I DID do a search. SEVERAL searches. I have also, in GREAT, SPECIFIC, AND CLEAR AS CAN BE DETAIL; told you what I have done, trouble-shooted and fixed. FYI, Every single search points to a vacuum check valve or the "wild vents" solution (Which is a check valve and a very small vacuum reservoir, which I have also done as per my original post.)
Or a vacuum line broken in the engine compartment, or a vacuum line broken under the battery, or a vacuum line broken to the supply of the CAD 4x4 switch....ALL of which I have clearly trouble shooted and singled out to NOT BE part of the problem.

I may be new to THIS forum, but I do not deserve this kind of treatment from YOU. Why don't you actually read my post (you would clearly see I am not a NOOB and have done my homework) and help me instead of saying "go search?" I know that it is probably a vacuum leak somewhere between the firewall and the actuator switch and I am TRYING to get some first hand experience to this issue and am SUPPLYING detailed information to help someone that is willing to HELP ME trouble shoot the problem so I do not rip the entire dash out only to find out that it is a simple vent switch problem/replacement.

OR if it is not......................... how to; where to; should I go............to fix the problem.

I am glad to help you get your 94th post by rediculing me. I am happy to be of some "assistance" to you...

 

Dude, give it some time. First of all not everyone has logged in a read your post, so not everyone has tried to help you yet. Secondly, slow down, you can't expect your problem to be solved in one day. Remember Rome wasn't built in a day. Third get a Haynes manual it may give you some information that you have overlooked, and fourth, and most importantly, always remember, we are ALL a bunch of smart asses around here, so if you intend to stick around, get ready for ribbing, it's part of life on this forum. I would say something to to be a smart ***, but I'll give you a free pass this time

 

Doesn't the yellow line go to the control switch on the dashboard? Sounds like the switch could be bad or the test you are doing is faulty , because when you pump the vac pump you are sucking air the opposite direction of it's normal flow. The check valves, switch's and other components are designed to flow one way.Try hooking the vac gauge to that yellow line,start the motor and see what vac you have without pumping the vac pump. BTW, if you tested the rest of the vac lines like you tested the yellow one, depending on which end of the hose you were testing, one end you tested right and the other end you were sucking in the wrong direction. The way you did it , would be fine if you were just testing the hose itself for leakage and had the other end of the hose disconnected and blocked off.

 

ok mahicks3322 sory dude i was kinda a D*ck but didnt mean it, had a ruff day an just went off on some people an shouldnt do that cause their are alot of good helpful people on here , so im sorry dude an everyone here i gusse i will just go take a drive for a while.

 

No need to apologize to me. I don't think, LOL