defroster/heater problem

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My 96 has a problem with the heat selector switch. The defroster vents will not shut off
no matter where the selector is placed the windshield vents always have air coming out. When the selector is in the off position there appears to be a vaccum leak coming from behind the dash.
Thanks
Joe D.
96 3500 dually Red/Black waterfall paint,JRE stg1 plate,K&N,no muff. ,pyro/boost guages,Alcoas,Weston CPS step bars.

 

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I had the same problem with my truck,but what I found was that the selector knob itself was broken on the back of the knob where it fits onto the selector switch. These knobs are plastic and like anything else made from plastic can break. I made an emergency repair with some monofiliment fishing line. Just wrapped it around the broken area and kept pulling it tight - it's still working.
Bob Ellithorpe

[This message has been edited by Bob Ellithorpe (edited 12-19-2000). ]

 

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Joe,check the knob like Bob says,the switch may be stuck in-between two positions. If that isn't the problem check to see if a vacuum line behind the switch has come off. The knobs on both my trucks have broken,when it happened again on the 2500 I super-glued a 1/4"long piece of copper tubing over the broken barrel to reinforce it,no more problems. A new knob is less than $10 from the dealer,the parts guy told me these knobs and the clips for the visors are his most commonly sold parts for these trucks.

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95' 25004X4,AT,Driftwood,Banks Stinger,Warn fender flairs and running boards(Play truck)95 3500,5 speed,Driftwood,Banks&Phscotty,34,000 GCVW apple and tractor hauler(work truck)

 

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Also check the vacuum motors that control the airflow doors. There are a couple under the dash above the diesel pedal. I had one on my 96 that went bad and caused the same thing you described. There was a recall for an oil check valve to be installed due to oil contaminating the vacuum system and causing problems like this. That may apply also if it hasn't been done.

Bob

 

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The recall # is 720 I believe. Lots of info on Fritz's Ram page. The recall is what it took to fix mine when it was doing that, it involves all vacuum components.

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96 SLT Laramie CC 5spd, 3. 54, no muff, no cat, 5"turn down tip
. Member NRA/USPSA

 

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If it turns out to be the heater actuator ($37 fm mopar, pn 4882286) you can replace without taking dash & ac/heater sys apart, but you need a special short ratchet that uses screwdirer bits to remove the screws (#2 phillips) that hold it in, since vertical clearance to head of screws is about 1. 25 inches. I can provide more detail if needed.

Andy Raiha

96/2500/4x4/4. 10/5sp/cc

 

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chrgr446 you read my mind!
I was just getting ready to post the same problem.
My '96 only blows out the defrost vent also. I can turn it off and it will stop, but any other position and all air come out the defrost. My feet never get warm darn it!

 

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Wow, you guys got the same thing huh?
Mine quit blowing out the panel vents a month ago. When I put it on panel it blows out the defroster.
I'm glad someone mentioned this. Now I know where to start at.
Thanks to this site I'm learning about this diesel p/u better than the trial and error system. Thanks guys and TDR.
Ron

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97 3500 dually, ext. cab p/u,5sp,3:54,245/75R16,
straight pipe,105k mi. Ron

 

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How about when you select the defroster only and it comes out the defrost and the floor or if you select the defrost and floor it comes out of the floor only? Basically it comes out of the vents that are one selection below what you have it set at. Knobs are fine and the vacuum recall has been performed.

Paul

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'96 2500 ext. cab, LB, 4x4, 5 speed, 3. 54, TST 280 cam plate, AFC spring kit ,pyro and boost gauges mounted on A-Pillar, tinted windows, 16x8 Eagle alloys series 1219, 285/75R16 Durango A/T's, stainless steel rocker panels and alluminum stirrup steps

 

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When my system started acting up, I found that the actuator was not going through its full range of motion. It was two stage. The first worked, the second did not. After I replaced it I took it apart and found residual oil (undoubtedly left over from pre-recall days). Changed it out and had no problems since. I used my service manual to identify the lines and pulled them checking for vacuum until I found what was not working. LOL!

96/2500/4x4/4. 10/cc/5sp

 

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Flatlander:
Had the same thing happen to me with the oil thing but then had it come back. I found the vacuum line had falled onto the engine and melted into. First thing I would do is check all vacuum lines and go from there.
Just an idea.
Good luck. Preston #ad


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96 3500 Black 5 speed turbo diesel, SLT, with US Gear overdrive, Rhino liner, Reese 15,000 lb. fifth wheel hitch, US Gear de-celarator exhaust brake, muffler elimination kit, Amsoil lub. , with other goodys on the way.

 

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Had the same problem with mine, would blow air out the defrost vents no matter where you set the knob. Had to replace the vacuum motor in the dash which was contaminated with oil.

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1997 2500 Ext Cab 4X4,5 spd,3. 54's,Pac brake,Rancho 9000's,Centerforce clutch,K&N airfilter,Missing Cat,Isspro gauges,and #11plate(280hp/680tq)AFC medium spring

 

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No air out the dash is the lowest vac control motor under the dash just above the kick panel. IF your truck was ever on the recall list all vac systems on the unit are covered under warranty 7 years --unlimited milage. Even if you weren't the org. owner.
Just stop by any dealer and ask if your ser #
was on the recall list. That includes the brake booster and cruise servo. Pop off the hose at the vac control and look for sign's of oil. If a recall was preformed correctly all items were to be checked plus- replace the hose going to the unit.
My defroster is doing the same thing now,and i was there when they installed the check valve and replaced the dash vent control and i know the never checked any thing else. --This time they will.

 

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I move around every 2-3 yrs & don't have the luxury of establishing good relationships with dealers, besides warranty work does not seem a priority. I really don't want them working on my truck anyways. I would rather buy the parts, fix it myself, and learn more about my truck. The one time the dealer touched it (vacuum check & fuel sender), my truck almost got set on fire from all the (gallons) of diesel fuel pumping out of incorrectly installed fittings. I do NOT need the dodge shaft to worry about, warranty or not. Whew I feel bettttter now!

Andy Raiha

 

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On my 96 there was a pinched line behind dash. The service adviser did mentioned that a lot of selector knobs were at fault because or clip that holds them on.

I would check vacuum lines/connections for pinches or leaks if you have only one selection(selector knob is OK).

Flatlander, Check to see if the vacuum lines are in right order on back of switch or lines going to actuators are correct. I rember some one posting this same problem but don't remember the fix.

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Bill Thomas
Missouri Mule - 96 Wht 4X4 ST CC,5 spd, 3. 54, 8 ft bed, 1 ft high cheater boards.
99 Freightliner bl/wht FL60 ISB-5. 9 24v,215 hp,520 tq,6 spd, 3. 59 nsr,16 ft box, 19. 5 tires,Wt/gvw 11,000/23000