terryKS

Hey Dodge gurus,

Ive got a blend door issue I think and not sure where to start to get it taken care of.

Just got back from 350 mile trip (one way). In the way down the story goes like this:
A/C on "MAX", Fan on "low", temp control "full cold"
A/C blowing ice cold, then suddenly decides to blow completely hot air out of the vents.
I turn control to "off", wait about 5 seconds, turn back to "A/C max" and boom, Ive got cold air again! Until the next time, sometimes 2 minutes, sometimes 5 minutes, sometimes 30 seconds!
Everytime it turns to hot, I hear this "thump" coming from under the dash, so I feel its gotta be a blend door problem, Am I right?

FYI... I just had a new compressor installed and the freon level is correct, this problem I had even before the new compressor install.

Now for the trip home:
A/C on MAX, Fan on High, TEmp control on full cold
A/C worked well, ran about 3 hours straight before deciding to go "thump" and turn hot on me. I turn it off and back on again and Im a happy camper for another 45 minutes or so until it does it again.

All in all, I probably switched it off and back on again, 200 times on the way down and maybe 6 on the way back. Dont know if having the fan on high made the difference on the way home or what? Cant quite figure out why it would?

Like to get this matter resolved so any and all help would be greatly appreciated!!

rockwithjason

Sounds like a control problem to me. I would check out all of the vacuum switches in the dash module and see if anything is wacky there. The hot water and the doors are all controlled by vacuum so if you have a bad control switch strange things can happen.

J BODY

If you remove the mode door actuator which is located down by the passengers feet you will find that the adapter that goes from the gear on the motor to the blend door cracked.....check it out and see if I'm right.

....the part is available separately. Cheap fix.

terryKS

J Body, Ive looked under the passanger side dash, Can you be a little more descriptive on what I am looking for? Do I need to remove the glovebox to view this item?

AS for the control switch, I have removed this from the dash, took it apart to see if maybe the metal terminals on the temp control switch might be worn out and shorting across. To my surprise, they looked to be in good shape! All the vacuum lines were connected also.

J body, you seem as though maybe youve seen this problem before, just give me a little insight as to what to look for.

Thanks Guys!

J BODY

Blend door actuator, it's a little motor attached to the bottom of the HVAC box. Go down from the right edge of your cupholder (ok, I see you have a 6spd...no cup holder, but you get the general idea) and underneath the dash. You'll see a motor attached to the box. It's held in place with two philips head screws and has a three wire connector (blue, yel/orn, blk/grn). The outer screw is easy to get to, the other one requires you to roll your carpet back and get a knife and cut, hack, mutilate the pad under the carpet so you can access the screw. I use a very short 1/4" wrench with a philips bit (from a nut driver kit, you know the hex shaped ones) taped in it. If you're carefull you don't have to remove the hard to get to screw, but can back it out enough to pry the motor down far enough to get the black plastic adapter out and inspect it. On a side note, and this has only happened one other time, I had a truck that would blow cold OK on low and medium, but on high it would start blowing warm. After near suicide I found that the actuator motor was weak, and the forced air from the blower on high would actually push the mode door allowing hot air to blend with the cold......fun .

terryKS

Thanks!
I will check it out in the morning and let you know what i find out!

heykw

what was the fix I am dealing with the same issue on a 96 please help!

TucsonDiesel

I had the exact same problem. Broken blend door where it attaches to the motor. You can get to it without removing the dash, but it takes some effort.

If you elect to remove the dash to get to it, I recommend replacing three things

1) Blend door motor

2) heater core

3) blower motor

Trust me, once you have the dash removed (which can only be removed by taking out the steering column), you will want to replace those items

heykw

tuscon diesel what year truck did u have the issue with? I am working on a 96 and I can not locate the blend door.

TucsonDiesel

I have a 99. I used to have a 96, and I think the door is near the same place as the 99, but you might not be able to get to it without taking out the dash.

I think the problem manifests itself after the door breaks near the motor shaft, the door is plastic, and then the incoming wind pushes the door over to bring in the hot air.

If you turn the AC totally off, then on, there is reset cycle on the blend door, then it goes to where you have set the thermostat. This allows it to work for awhile

heykw

does anyone have any pics of the blend door on a older truck such as a 96 I have looked under the dash and I do not see any motor thanks

oobudoo

The blend door is easy to check and does not cost anything. Turn the key on (no start), turn the hvac **** to off, and turn the temp. control **** all the way to cold. Now look under the dash (a flashlight will help), passenger side, way back to where the hump in the floor meets the underside of the dash. You can actually see the shaft turn between the motor and the ducting. It is about 1/2 in. in diameter with a flat spot. You can also hear the motor if it is quiet. This shaft is connected to the blend door by a plastic part (Interposer). If the interposer is cracked or broken the shaft continues to turn because the blend door does not stop the motor when the blend door is closed. If you turn the temp. **** to hot the shaft will turn the other direction.

Note that if the interposer is broken, the shaft motor turns non stop all the time as long as the key is on. If the temp. **** if half way between hot and cold the motor should stop turning.

For mine, I purchased a "Heater Treater" on Ebay which is a metal replacement instead of the oem plastic part. Do a search on Ebay "Heatertreater" (One word)

Getting to the rear screw is the most difficult part of the repair.

I found this info after spending over $700 on a/c work from a local repair shop. I hope this helps

heykw

Thank you, I will check it out as soon as I gat a chance what year is your truck.

heykw

I checked the door and all is well and is working as it should. I was driving down the road and the a/c stopped working I quickly stopped and checked the compressor and it was not engaged. The pressures are good so what gives is it a pressure switch? Which one? Thanks for all the help so far.

Busboy

Do you get condensation draining from the drain hole? If not the drain could be plugged causing the evaporator to freeze up. How do you know the pressures are good? To see if the LP sw is bad with the compressor NOT running (in failure mode) remove the plug from the LP sw on the accumulator (cylindrical black thing near the fire wall) and short across the two terminals. If the compressor cuts in then likely the lp sw is bad. This can be changed without discharging the system as there is a schrader valve to prevent freon depletion.

Before changing the sw I would ensure that the system is fully charged and operate the system with a gauge set on so you can see both hi and low pressures.