HVAC only blows air out defrost vents

RPEACY19

MEMBER
1998 DODGE DURANGO
5.2L
V8
4WD
AUTOMATIC
286,473 MILES

Okay, so my vehicle listed above SLT, with 318 magnum engine is having issues with the HVAC only blowing air out of the dash defrost vents and the vent on the back of the center console. The rear roof A/C blows fine as well, but my front and floor vents do not blow air out at all and the defrost vents blow air. I'm thinking constantly even when the HVAC system is totally turned off. And the A/C is not blowing cold anymore, thinking that may be because the front vents are not working, that's what I figure that problem is. I'm pretty sure this vehicle uses the vacuum system and not the electronic one as this is the first generation. I'm pretty knowledgeable on the older vehicles but not sure where to start on this one. How can I fix this and is this why my A/C is not blowing cold? And yes, it's full of Freon and the compressor does engage and run while the A/C is in the on position. Your help would be greatly appreciated. Thank you

Tuesday, May 24th, 2022 AT 5:47 PM

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

You have two issues going on. The vents are staying in defrost because of the actuator that you are referring to. Yes, you are correct that this vacuum controlled so this could be a connection issue or a cracked line. So, we should hook a vacuum gauge to the line and move the control module to the defrost position and away from it and see if the vacuum is being applied or not.

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

I am attaching the process from the manual that will show how to access this.

Once we know if there is vacuum or not, then we will know what direction to go but if you are then we need to replace the actuator.

If not, then we most likely have a crack in the vacuum line.

As for the no cold air, that is going to be a different issue that we should be a new post started for.

We are going to have to check the pressures when the AC is turned on so that we can see what they are doing. Even if the compressor is coming on it may not be building pressure.

Let me know what happens with this actuator and we can go from there.

Thanks

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Wednesday, May 25th, 2022 AT 11:18 AM

RPEACY19

MEMBER
2 POSTS

Okay, I will check the actuator door; it has been raining here since I first wrote that question. As soon as it quits raining, I will check that and the A/C pressures and let you know something on the actuator door, vacuum pressures and A/C pressures. Thank you

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Thursday, May 26th, 2022 AT 3:20 AM

KASEKENNY

MECHANIC
18,907 POSTS

Thank you for the update. Clearly both of these are important but I would start with the actuator door because if the door moves and it blows cold then that is the issue and not the pressure.

Let us know what you find.

Thanks

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Thursday, May 26th, 2022 AT 9:43 AM