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-   -   I have vacuum but cannot switch from defrost (http://www.ramforumz.com/showthread.php?t=73602)

Xtremehumpdog 02-06-2011 02:38 PM

I have vacuum but cannot switch from defrost
 
Hello all,

I have read the forum regarding this topic and the general consensus seems to be Vacuum and the check valve on the line into the cab. My check valve works correctly and I have 20" of vacuum at idle. My blend door operates correctly, heated mirrors work, and the selector knob will shut off the air. The knob will only turn off or on with the Defroster vents, it will not engage A/C as well. I took the switch out and saw the vacuum lines. If I have 20" at the firewall does that mean my switch is bad? Haven't priced one at the dealer yet but I could imagine the cost.
Thanks,
X

RamTech 02-07-2011 09:17 AM

It could be a problem with the actuator itself. Check this out:

A/C HEATER CONTROLS
  1. Connect the test set vacuum probe to the HVAC vacuum supply (black) tube in the engine compartment. Position the test set gauge so that it can be viewed from the passenger compartment.
  2. Place the a/c heater mode control switch knob to each mode position, one position at a time, and pause after each selection. The test set gauge should return to the 27 kPa (8 in. Hg.) setting shortly after each selection is made. If not OK, a component or vacuum line in the vacuum circuit of the selected mode has a leak. See Locating Vacuum Leaks below. CAUTION: Do not use lubricant on the switch ports or in the holes in the plug, as lubricant will ruin the vacuum valve in the switch. A drop of clean water in the connector plug holes will help the connector slide onto the switch ports.
LOCATING VACUUM LEAKS


WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN AN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
  1. Disconnect the vacuum harness connector located between the a/c heater control and the HVAC housing under the instrument panel.
  2. Connect the test set vacuum hose probe to each port in the HVAC housing half of the vacuum harness connector, one port at a time, and pause after each connection. The test set gauge should return to the 27 kPa (8 in. Hg.) setting shortly after each connection is made. If OK, replace the faulty a/c heater control. If not OK, go to step 3.
  3. Determine the vacuum line color of the vacuum circuit that is leaking. To determine the vacuum line colors, see the Vacuum Circuits chart below. Disconnect and plug the vacuum line from the component (fitting, actuator, valve, switch, or reservoir) on the other end of the leaking circuit. Instrument panel disassembly or removal may be necessary to gain access to some components. Refer to Instrument Panel System for the procedures.
  4. Connect the test set hose or probe to the open end of the leaking circuit. The test set gauge should return to the 27 kPa (8 in. Hg.) setting shortly after each connection is made. If OK, replace the faulty disconnected component. If not OK, go to .
  5. To locate a leak in a vacuum line, leave one end of the line plugged and connect the test set hose or probe to the other end of the line. Run your fingers slowly along the line while watching the test set gauge. The vacuum reading will fluctuate when your fingers contact the source of the leak. To repair the vacuum line, cut out the leaking section of the line. Then, insert the loose ends of the line into a suitable length of 3 millimeter (0.125 inch) inside diameter rubber hose.
https://w05.dealerconnect.chrysler.c...S/80c2c22c.gif

Xtremehumpdog 02-07-2011 06:52 PM

I got as far as verifying vacuum after the check valve going into the cab. I will have to test the individual lines at the distribution block in your write up. Let you know what I get.

Xtremehumpdog 02-08-2011 06:48 PM

Ok update. I checked for vacuum at the switch and had nothing. Chased it back to the distribution block underneath the dash and still nothing. I removed the glovebox to try and chase the black line coming into to the cab and then got sidetracked. I ended up removing the top of my dash since it was broken into a million pieces. So needless to say that's project #2. I am hoping to find that black supply line tmr.

Xtremehumpdog 02-12-2011 03:34 PM

Ok so I chased the vacuum line through the firewall under the wiper cowling. It goes into a reservoir box and ends there. Does anyone know if there is suppose to be a T off going into the cab? The dealer down here doesn't even know. Starting to think I am crazy as I cannot see where it would actually enter the cab. Please advise.

Xtremehumpdog 02-14-2011 07:06 PM

Anyone? It's pretty bad when the dealer doesn't even know.

RamTech 02-14-2011 07:26 PM

There should be a vacuum supply line going into the cab on the passenger side firewall. It looks a bit like a washer fluid line and has a small check valve in it.

Xtremehumpdog 02-15-2011 07:30 PM

I followed that one into the wiper cowl and it ends into a reservoir. Am I missing another line to find?

Xtremehumpdog 02-20-2011 01:53 PM

1 Attachment(s)
Found this. Tested this line with a vacuum hold tester and low and behold it is the supply to the climate control unit. Can someone please take a pic from behind the glovebox as you can see by my pic it plugs in somewhere but can't seem to find it. Thank you

GTyankee 02-20-2011 03:16 PM

if you youtube heatertreater
there are many videos that people have submitted, as they chased down & located their own climate control problems

you may see something in there


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