Neither the front vent or defrost work?

JEREMY400

MEMBER
2004 CHRYSLER PACIFICA
3.5L
V6
4WD
AUTOMATIC
160,000 MILES

So, I had my vehicle listed above at the shop not long ago because the AC/heat was not working properly. At times it would switch on its own from cold to hot and it only blows in the rear. Neither the front vent or defrost work. I was told it was the HVAC control head. Well parts for this vehicle are discontinued and I could only find one at a salvage yard. I tried installing 3 different ones and the same problem still exists. Nothing changed. Do you think there could be an issue in the harness that connects to the control head? The mechanic looked at it. Said no. He doesn't know what else to say. Any ideas would be appreciated. Thanks.

Saturday, September 7th, 2024 AT 4:47 AM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
54,137 POSTS

When you say the vents are not working can you hear the blower motor still working for the front? I have seen the mode actuator go out and cause this issue, this is why I ask if you can hear the blower still working. Here is the location of the actuator so you can swap it out if you can hear the blower motor running. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.

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Saturday, September 7th, 2024 AT 8:02 AM

JEREMY400

MEMBER
27 POSTS

I already changed the mode door actuator and yes, I can hear the fan. I can get a video of it when I get home. I don't understand how it changes from cold to hot on its own. The mechanic said the same thing which is why he was thinking HVAC control head. I appreciate the response!

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Saturday, September 7th, 2024 AT 8:51 AM

KEN L

MASTER CERTIFIED MECHANIC
54,137 POSTS

Yes, a video would be great! I am wondering if the engine is overheating and turning the A/C off? It could be a evaporator temperature sensor as well. Here is the HVAC system wiring diagrams so you can see how the system works. You might be able to get a CAN scanner to tell you what the reading is. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Let me know what you find, and I look forward to the video. Check out the images (below). Let us know what you find.

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