I've had the truck back from it's lastest trip to the shop... Before the air vents contols worked. Now, it only blows on the windshield (defrost position)... both hot & cold. I think this is a vacume line. I don't know where this runs but I bet it's damaged or fallen off.I'd really like to have my truck worked on & not have new problems when it comes back.Russ

i had the exact same thing in my ford rangerturns out when i changed a leaky intake gasket a vac line was touching the egr tube.i was driving on the freeway with AC on full blast and bam...only thru the defroster.a coupler and reroute solved my problem.

There is only 1 vacuum line that come off the vacuum pump and head over to the passenger side. Now there is a spot near the exhaust that is possible ot melt the vacuum line and also sometimes it comes apart at the vacuum pump...

Thanks Guys,I've not been home, I need to get a peek under the hood & trace the lines back to the pump & see if they got dislodged somehow. Seems logical since it's just back from the shop.Russ

Edited November 22, 200916 yr by flagmanruss
cause Russ can't spell

I haven't been up to doing mechanic work lately & the Ciris has been getting the attention. Back to my heater / defrost problem. I think this is different that the other heater thread we have active, because I can control the amount of heat, just not where it goes. I gotta admit it is baffling why they used a vacume control for one & electric for the other!Russ

I haven't been up to doing mechanic work lately & the Ciris has been getting the attention. Back to my heater / defrost problem. I think this is different that the other heater thread we have active, because I can control the amount of heat, just not where it goes. I gotta admit it is baffling why they used a vacume control for one & electric for the other! Russ

So if you got DEF mode only then you have vacuum loss. Then you just check the vacuum lines from the vacuum pump towards the cab. The vacuum line enter the cab at the passenger side firewall. Cold to Hot controls is the stepper motor on the passenger side floor board. If you lay on the floor and look up at the bottom of the HVAC towards the trans hump you'll see the stepper motor. Common to break the plastic link or burn up the motor.

OK, I managed to get up under the hood (without falling, no longer to be taken for granted). I traced the tiny vacume lines from the pump to the check valve along the edge of the cowling, to the firewall, very high up. No sign of damage. No rodent damage (though plenty of acorns). What else runs on the vacume pump? The only thing I can think of is the engage/disengage on the front axle. I could not see the routing on that line. I seem to recall it going to the transmission first then to the axle. Crawling under will be another day.Russ

Hmmm... Well does the 4WD engage? That would give a clue...

Mike,I had CTD out today. Runnin nice. Had to shut her off at the drive up squawk box... Could not hear me to place an order.... LOL! I tried the 4WD. This truck always does the crab hop on tight turns (on gravel) in 4wd... and yup, it still does. So the 4WD is engaging so that big vacume line is ok. On the lack of heat diversion... Back to the drawing board... Dang, weather turning colder... I need some heat besides blowing in my face. Like I said before, I think I traced the small vacume tubes along the edge of the cowling to the firewall... no sign of damage (I was half expecting mouse damage). Russ

Edited December 5, 200916 yr by flagmanruss

Ok... Then I would pull the dash bezel and pull out the control switch for the vacuum and check the controller for function I know your going to have to get creative with tubing but I would use a piece of tubing and go from port to port seeing if the vents change. I would also measure the strength of the vacuum...

Drove CTD again today. Funny thing... even though back in 2WD, it kind of felt crabby on a sharp corner, like front axle was still driving. My 01.5 has the front axle center section disconnect. Question: Does the vacume engage the center secion or disengage? I'm gonna have to crawl under the damn truck. (Crawling under is easier than getting out... ) In Short, I'm not sure that the front axle vacume line is intact. It'd be better to view all of that before taking anything apart.I can see the line from the front axle runs up inside the passengers fender. I'll have to track it. Is the control built into the tranny or some relay point? Not today it's raining & prediced to go over to snow. Russ

More resarch on the "CAD"... Center Axle Disconnect. The dash light switch is triggered by the sliding sleeve which engages the RIGHT front shaft & wheel. So if the light is ON, the axle has actually engaged. If the light goes out (and mine does) then the axle has disengaged. In other words, it's working. While those lines can still stand checking, it reduces the odds of that being the source of the malfunction... it may help to know the vacume line routing.In my research the CAD valve on the transfer case can get grunged up but is responsove to cleaning. This is in relation to engagement issues.Earlier years had a recall for lack of a check valve allowing engine oil to contaminate vacume accessories.I think I need to scout under the truck to ensure the larger exhaust has not interfered with a vacume line somewhere. So I'm back to inspecting the air duct control door & the mechanics inside. Russ

Edited December 6, 200916 yr by flagmanruss

Strange part about you vacuum problem I think it going to be in the cab... Being the axle seem to be working for the most part... But the vents might have a bad vacuum motor? Something jaming the door? :confused:

How does one get to the vacume motor & door?

Ummm... Errr... Ummm... full dash removal most likely... But I might get lucky and be able to fish ro remove stuff and see in to them...:confused:

Leave the porch light on, I'll be over! Ha!I'll let you know what I find.Russ

On my Mom's 96 there was a box of BB's dumped on the dash by the previous owner and the BB's went every where. 2 BB's got stuck in the vacuum motor for the fresh air/recirculate door. It wore a hole in the diaphram and cause it to behavor wildly. When the BB landed in the right spot it would seal the hole and allow the door to work. Then if the truck hit a bump and BB moved then the door wouldn't function. The sad part was the vacuum motor cost $80 bucks from the dealer and required the dah to be pulled loose enough to slide the passenger side against the seat to get just enough room to replace the motor... Still a afternoon project...

I read a bit on 12V aboout the speed control which is vacume operated... mine works as does the CAD. So this pretty much means it's in the heater box. I've not been able to get out to look at it. It may have to wait until I save up cash to get it done.Russ

Shoot... I wish you lived a bit closer to me... I be more than happy ot look into it... But alias I'm a good few thousand miles away... After looking back over the older post of the thread... Is it possible a mouse built a nest inside you HVAC system jamming the doors? Or make ate a vacuum line under the dash? :confused:

It's certainly possible that a mouse found it's way in. I don't think it's a damaged line outside the cab. I did have to have the A/C pulled apart & to replace the evaporator a few years ago. It was very costly. I have the underneath of the hood hinges packed with SS steel wool (pot scrubber) to keep mice out & I've seen no sign of them. I have not been successful in keeping mice out of the Cirus & I have had to evict mice & clean the heater core by removing the fan / motor assembly & working through the hole. Russ

I want to tie this thread to a new thread... I'm hopeful this will solve my issues... I have ordered the ungraded part. I hope it is this easy. Russ http://forum.mopar1973man.com/showthread.php?p=5416#post5416

Edited December 17, 200916 yr by flagmanruss
add order