HVAC controls

[Dave MacArthur]

Does anyone know what might be wrong with my HVAC controls? No matter what position the selector switch is in I am stuck on Defrost. I tried a search but didn't come up with anything. It seems much harder to get search results now.



Thanks for the help,



Dave

 

[Archive]

There is no control for HVAC. He has been out of control for years! (Nowell, just kidding).



I remember a few posts on this problem, but this new search thing has me baffled. I don't remember the solution. Was it vacuum related???

 

[Macmc01]

Vacume

Sounds like you have lost vacume to the ductwork. There was a TSB to put in a check valve near the pump because of oil "burbing" into the line. Does you truck have vacume assist brakes??

If it does then the problem is in the duct control or vac pod, If you dont it could be from the pump on.



Hope this sheds a little light.



Mac

 

[LEEH]

Dave, I had the same problem on my 96 RAM. This happened shortly after I took it to the shop for other work (having the temperature sensor located bebind the engine replaced for the third time). Apparently, the vacuum hose from the engine to the heater controls was disloged and dropped down onto or very close to the exhaust manifold. Naturally, it melted and the heater controls went to the default setting of defrost. This happened on one of the hottest days of the summer when my spouse and I were on a hard pull up a mountian towing our 5er. Tempers were frayed and my faith in the Dodge fell a notch or two or three or - - - - - .



Check out the vacuum hoses to the heater controls and you will probably find the problem.

 

[Oasis-3]

Vaccume System

My 96 did the same thing and was fixer under a recall then the warnty was uped to 10 years on the vaccume system.

hope this helps

Cliff

 

[danandamy]

I did a search on this last night. Search under this forum, keyword "vents", no date limit and you should get something. Anyway, I'm having the same problem on my wife's pickup. Of course, everytime I go to work on it it starts working, which makes it imposible to diagnose the problem. What I found this morning was the vacume line was kinked pretty bad going into the little controler that actually moves the arm on the vent door itself. You will see it if you lay on the driver's side floorboard and look up toward the middle of the truck. It's a silver can looking chingasie. Straightened it out and everything seems to be working. However, I have a feeling the real culprit is going to be the selector switch itself, we'll see.

 

[Dieselnerd]

Guys, you need a new actuator or as Mopar calls it, diaphragm sub-assy P/N 04720279. This is located on the left side of the heater box and I was able to change mine by just taking off the dash panel under the steering column. The service manual would have you take out the center panel too but it's not really necessary. When this actuator fails the default position is DEFROST. It usually starts out intermittent and eventually quits. The rubber inside gets eaten up by oil in the vacuum lines. This part will fix it, I changed mine several years ago and it never failed again.

 

[Missouri Mule]

Dave,



I had similar problem with mine during warranty period also had recall done sometime after problem occured.



In my case I think it was main vacuum line (but could of been any paper work did not specify) any way this vacuum line was pinched. They followed service manuals procedures for pinched lines I have not had any probelms since then.

There are a couple of actuators that move doors in different positions. I believe each actuator has two lines to it but mite be one.

On the switch when you select a position vacuum is sent to the corresponding actuators, usually two vacuum lines to two differnt actuators.



Look for broken/pinched/Leaking/ unplugged lines going to switch first from pump. Pull a line off at switch see if there is oil collected in it if so the vacuum check valve went bad on line out of vacuum pump.



Switch control knob has retainer ring on it(maybe clip) if that has broken knob will turn but not the inside switch. Knob will turn easier than before problem.

 

[Deezul1]

96 was the last year for vacum assist brakes and the recall was for 95-96 trucks with bad seal between power steering pump and vacum pump. oil in the vacum lines which caused rubber break down. It sounds like a bad vacum leak, maybe a hose came off, usually when a hose comes off it is right after some service work and somebody bumped it

 

[Dave MacArthur]

Thanks for all the info. I will check it out today. I haven't had/done any work on it recently. It wasn't intermittent, it just didn't work one day.



Thanks again,

Dave

 

[kcv67]

Warranty

Oasis-3 How difficult was it to get the dealer to warranty the vacume control problem?

 

[Dave MacArthur]

Thanks to everyones help it was fixed in less than 10 minutes. The vacuum line had dropped out of its' holder and burned in half on the turbo. I just shortened it a little by cutting the burned section out. It works fine now. Will replace that piece of vacuum line with the proper length soon.



Thanks again,



Dave



p. s. Everyone should make sure that their vacuum line is not hanging down (runs just below the cowling in the engine compartment in front of the base of the windshield).

 

[GSchlegel]

Once again you guys are on top of everything. Today my vent controls went south. The defrost will work and the foot level vents work, but when I tried to get the A/C out the dash vents, it instead sends the air to defrost. I ran a search and came up with nothing. I then go to the 2nd gen. forum to ask for help and here it is!!!!! From the above posts, I suspect either a loose vac. line to an actuator or a faulty actuator. Vac. pump seams ok since the cruise worked perfect on todays 300 mile run. If there are any other suggestions, I would appreciate hearing from you. Thanks for the help.

Gene

 

[Deezul1]

GSchlegel

Your 96 has the vacum pump seal problem recall. I went through that with my 96 and the dealer replaced all the AC controls, cruise control servo and everything else in the vacum system caused by oil contamination. The recall is #720 and there is a 7 year unlimited mileage warranty on the vacum components damaged by oil. My 96 did the same as yours so maybe the dealer can pick up the tab on this for you. Check Dave Fritz's web page for the recall info, I believe it in the links or maybe some one can post the address.

Good luck

 

[jsimpson]

I'll take in my 94 that I bought this week and see if the dealer will pick up thye tab!

 

[Extreme1]

jsimpson, please post your results, mine doesn't have the checkvalve.