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wildbill
Dodge Dakota
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8/17/2005
14:55:36
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 Subject: AC/heater only blows out defrost vents
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97 Dakota all of a sudden started only blowing out the defrost vents on all position settings. Anyone have a vacuum diagram or suggestions on how to track this down? I have traced the AC/heater control vacuum lines to the passenger compartment firewall, but can not find the vacuum on the engine side.
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uh bill?
Dodge Dakota
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8/17/2005
18:34:38
| RE: AC/heater only blows out defrost vents
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the problem is in the switch itself, it is vacumm operated, as you have already figured out, but the "O" rings inside that seal the vacumm from different positions has dry rotted, the easiest, but most expensive fix is to replace the dash switch.
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Dan M
Dodge Dakota
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8/18/2005
06:54:46
| RE: AC/heater only blows out defrost vents
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uh ..'uh bill', I would not say that is the definitive answer.
If the vac line for the HVAC controls is not connected to the vac system in the engine compartment, the controls won't work. On my 95, the vac line from the HVAC controls connects in behind the throttle. When mine was not connected properly, I could not switch the HVAC controls and my cruise control was ~ 5 mph lower then where I wanted to set it.
Bill - you are going to just have to spend a few minutes tracing the vac lines. Start with the vac lines coming out of the your "softball" bolted to the firewall. You should find an hose with an open end. On My 95 the vac line enters the engine compartment where the heater core is (drivers side) not where the evaporator core is (passenger side). If yours is routed out the passenger side, it may be elswhere instead of behind the throttle body.
- Dan M
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wildbill
Dodge Dakota
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8/18/2005
16:25:19
| RE: AC/heater only blows out defrost vents
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Can anyone tell me where on the engine the vacuum line for the HVAC attaches? I have the 3.9 V6 in a 97 Dakota.
Does anyone know where I can get a vacuum diagram?
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uh Dan
Dodge Dakota
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8/18/2005
17:03:15
| RE: AC/heater only blows out defrost vents
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if what you say is what you think to be true, then you are terribly wrong, If the vacumm line is not connected to the vac system then he would not be getting air out of only the defrosters he would mostly only get air out of the dash vents as that is the default when the vacuum is non-existant as the door that directs the air to either vents, floor or defrost output is is spring loaded to default to the dash outlets. But of course you knew that before telling me I was wrong, which I ain't. and you are right which you ain't. Right?
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Wildbill
Dodge Dakota
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8/18/2005
18:34:26
| RE: AC/heater only blows out defrost vents
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The default on my system when there is no vacuum, is to come out the defrost vents.
I have no vacuum to the back of the AC/Heater control, thus no vacuum to the door vacuum motor.
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Dan M
Dodge Dakota
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8/18/2005
23:39:00
| RE: AC/heater only blows out defrost vents
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"uh Dan" wrong answer there again spanky. Thank you for playing, please drive through.
wildbill, I don't know where you can get a diagram for what you are looking for. I have a subscription for alldatadiy.com but that diagram in there only shows which color hose connects where in the cab, not for connecting under the hood. Maybe someone who has the tech manual from dodge can tell if it's there or not.
Best i can say is to follow the hoses, you'll see one open.
- Dan M
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cuzindoug
GenIII
8/19/2005
01:23:03
| RE: AC/heater only blows out defrost vents
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Quick questions: 1.Did you do any cleaning inside the truck before this happened or did you "screw" with the knobs(A/C etc) before this happened? 2.When you turn the knob(selector) do you get a slight sound like the rush of air or do you hear it constantly? The reason why I ask this is because the vaccuum line "might" have come loose from the back of the control panel. If answer to you question as to where the lines come in from the engine compartmant, on the passenger side firewall, right by where the a/c and heater lines go in. (The vaccuum lines run along the entire length of the firewall inside the engine compartment from driverside to passengerside, check the tee connections)
If it ain't broke, fix it til it is.
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Dan M
Dodge Dakota
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8/19/2005
11:58:20
| RE: AC/heater only blows out defrost vents
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There should be 4 hoses if I recall correctly coming from the back of the hvac control unit that go to actuators in the cab. 2 on driver side and 2 on passenger side. These should be colored. Theres a black line that runs from the hvac unit out the firewall (either where heater core or evaporator core is) and connects to the engine vac system.
the hoses on the back of the hvac unit are held in place with a clip or some kind as i recall. You can take your hvac control out of the dash to verify this.
if you look on drivers side to right and above gas pedal you can see the actuator - silver/grey color. And there's another one on passengers side up in behind glove box (on passenger wall). You should be able to see both, though the one one drivers side more easily.
http://www.bigworm.com/~danm/dakota/pic/HPIM0431.JPG - you can see "softball" on left behind air hat. This is the pressure regulator. Follow lines from here to trace vac lines in engine compartment. You should find a couple of T connections.
Again, I have a 95 but I can take some closer pictures where the vac hose for the hvac unit is on my truck if that would help you
- Dan M
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wildbill
Dodge Dakota
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8/19/2005
12:07:40
| RE: AC/heater only blows out defrost vents
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Dan M...thanks for your much needed response.
I looked at the link with picture and the 97 is different...I have NO "softball" visible in the engine compartment...probably hidden in the bumper area like on a Jeep...which I will search for now..... May I take you up on the closer pics where the vac hose for the hvac unit is on your truck?
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Dan M
Dodge Dakota
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8/19/2005
13:38:20
| RE: AC/heater only blows out defrost vents
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I'll get the pictures tonight.
Do you have cruise control? If so, start there at the TB and follow the vac hose from the throttle assembly.
- Dan M
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wildbill
Dodge Dakota
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8/19/2005
14:44:25
| RE: AC/heater only blows out defrost vents
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it has cruise and I have vacuum to it.
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Riq
Dodge Dakota
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8/19/2005
16:11:58
| RE: AC/heater only blows out defrost vents
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If this helps, I also have a 97 cc v6 with similar problem. If cruise is on and ac is on any setting, and the engine is working hard, the ac blows only out the defrost. Was much worse before I checked and plugged in fittings tighter at the unit close to firewall, so I still have a little vacuum leak or my engines just getting loose.
so many projects..so little time
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draggindakota
Dodge Dakota
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8/22/2005
13:39:02
| RE: AC/heater only blows out defrost vents
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I had the same problem. 1st time was a resistor behind the dash that they fixed. Second time was after i put my engine back in I forgot to hook up the vacuum line that goes to the softball sized black sphere on the firewall. This was for a 93 3.9
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zzark
Dodge Dakota
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8/22/2005
22:56:41
| RE: AC/heater only blows out defrost vents
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Thanks Dan M. I always wondered what that black ball was.
I was looking at some of your pix.
I also have a black lab (and a green truck)
zzark
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Dan M
Dodge Dakota
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8/23/2005
05:20:14
| RE: AC/heater only blows out defrost vents
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Sorry I have not gotten to the pictures yet. Do you still need them? Been so busy the last few days. How the h3ll does a data center loser power multiple times? Oh yeah, someone got fired for manually shutting down power to the entire facility. I wonder if they got fired because of or they went out in true cowboy style!
- Dan M
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wildbill
Dodge Dakota
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8/23/2005
10:06:18
| RE: AC/heater only blows out defrost vents
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Dan M.....I found the "softball" but it isn't round it is more rectangular and under the windshield wiper tray cover! In finding that, I thought I had found my problem...the plastic hose going to the vacuum booster was cracked. I fixed that and it did not fix the problem. So, I started pulling things apart inside, blew air thru the black line in the hose grouping that attaches to the heater control switch, and I can hear air escaping somewhere under the dash! I guess the black plastic line decided to break somehow. Man is it crowded under there...I can not even see where it is leaking from! I'm thinking about just running another line and splicing into the switch. One of these days I would like to meet the "person" that designs where everything goes because it could have been done much differently to facilitate working on.
I do not need the pictures and appreciate the offer.
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Dan M
Dodge Dakota
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8/23/2005
11:27:37
| RE: AC/heater only blows out defrost vents
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glad you are making progress, isn't this fun? It maybe that the hose is cracked/broke under the dash near the HVAC controls. You may be able to fix it by just removing the instrument panel bevel and the hvac unit and the radio and not have to remove the entire heater and A/C case (which involves evacing a/c system, draining coolant, and a host of other things).
You can get a new set of hoses for HVAC from dealer (will be color coded).
- Dan M
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Bornloser
Dodge Dakota
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11/28/2008
19:51:44
| RE: AC/heater only blows out defrost vents
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Thanks for all the info, I have a 98 with same problem, I have vacuum, now i'm sure it's the switch
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Brian Celia
Dodge Dakota
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5/11/2009
11:56:35
| RE: AC/heater only blows out defrost vents
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I have a 2002 Dodge Dakota - 3.9 L and in June of 2007 I had only air coming out of my defrost vents, so I had the vent control motor replaced and it was working great, until about a week ago now the air is only coming out of my defrost vents again. I can't imagine the vent control is crap after 2 years of replaced?? maybe it could be an old vacuum line? Please advise as to the best way to start as I don't want to bring to the mechanic again and blow hundreds of bucks
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RON
Dodge Dakota
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8/02/2009
13:09:42
| RE: AC/heater only blows out defrost vents
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RECENTLY HAD THE SAME PROBLEM ON MY 93, YOU ARE GETTING NO VAC. TO THE CONTOLER. PULL THE AC.CONTROLER OUT OF THE DASH ON THE BACK YOU'LL FIND A BUNCH OF COLORED VAC. LINES. LOCATE THE 3 THAT ARE ON THE FAR END THEY ARE LIGHT GREEN DARK GREEN AND BLACK "THEY ARE ALL ON ONE HARNESS" THE BLACK LINE SPLITS INTO TWO LINES CUT IT BEFORE THE SPLITTER HOOK A VACUME LINE OFF YOUR ENGINE THROUGH THE FIREWALL TO THE BLACK LINE GOING INTO THE AC CONTROLLER BEFORE THE SPLITTER, JUST TUCK AWAY THE OTHER END YOU CUT, AS IT HAS NO VAC. ANYWAY. IT MIGHT NOT BE THE WAY THE FACTORY WOULD ADVISE YOU TO FIX IT, BUT TI'S VERY INEXPENSIVE AND IT DOES WORK
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