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Help! Lots of A/C Problems, 2007 SXT 3.8

884 views 8 replies 6 participants last post by  guyonearth 
#1 ·
It started a couple months ago while on an out of town trip. First we started having problems with the A/C temp. It has front/rear, left/right climate controls, if that helps. It started blowing warm air through every vent in the van & making a strange screeching sound in the front of the van every few seconds. The whole vehicle slowed down & drop a couple hundred RPMs each time it made the screech sound. Now, it only did this when the rear system was turned on. If I turned the rear A/C off the noise & RPM drop stopped & it would start blowing cold air again. If I turn the rear A/C back on, it blows hot air through ALL the vents, both front & rear & the sound & RPM drop comes right back.

Ok... a couple weeks later, the blower fan started intermittently working. Even when it blows air it will randomly start switching back & forth between cold & very hot air. Now, sometimes the fan doesn't always come on at all or takes a couple minutes to start blowing. A few days ago, while parked in my driveway, there was a loud thump under the floor of the van when the air kicked on & it felt like a hammer hit the floor board. I'm at a loss as to where to start. I've had it to two garages & all they want to do is add freon & send me on my way.
 
#2 ·
do you have automatic or manual AC controls? (slider for hot and cold, knob for fan vs. changing the temperature)

the first set of symptoms, squealing and slowing down, sounds like the compressor is having trouble, but the second set of symptoms sounds like the AC controller is malfunctioning

does it work at all or still occasionally blow cold air now after the hammer sound you heard?
 
#3 ·
Hmm, this is a strange case.

You mention heat through the vents, a screeching sound, and a decrease of RPM's, I would inspect the AC compressor, maybe it's faulty and or possibly about to seize?

When the compressor kicks on you will notice that when you're at idle, the RPM's will decrease a bit on normal vehicles.

Also, you mention the sound going away and cooler air from the vents when you turn the AC off, so I would inspect the compressor 100% at this point.

That's the screeching part anyways, as for the blower issue/hot air then cold air, those are 2 different systems.

Now, I am not 100% certain for 4'th gen vans but i assume it's quite similar to that of a 5'th gen. The HVAC controls have a common door driver which tells the vehicle computer how much to send to the ac coil and the heater core to get the blend of hot/cold. So, if you select the coldest setting, the computer sends no coolant to the core, and you get maximum (or close to) of cold coming from the ac coil. When you select the highest heat setting, the vehicle sends hot coolant to the core and that then warms the air. It also has to do with the wiring of the actuators as well in some way too.

In terms of the blower, there will be something aging and having some sort of an issue somewhere within the system. It could be the HVAC controls having a problem, or it could be the resistor/power module(auto only) I wouldn't say the blower is bad, it either works or it doesn't. So that would bring this issue down to a faulty HVAC control unit, or the resistor/power module.

It is also important to note, if you have the auto climate, it will try it's best to keep the temperature at the desired setting you select. So, it will blow cool air or warm air until the temp is close, then it will mix the air and slow the fan speeds down, if you have auto, that could be normal. The unit also uses a series of sensors around which help it work as it should, one is a infrared sensor on the middle air vent for the front and one next to the display for the rear, and there is a solar sensor as well(at least on a 5'th gen). If these have a fault, your ac unit could become either very non responsive, or it could become very sensitive. Also, auto climate (when it;s cold and the engine is cold) will have a delay until the engine warms up enough, then it will gradually step up the fan speed, but it will be on minimum (or some vehicles off) until the engine can provide some warmth. If your manual climate is doing this then something is seriously wrong 😂

What i suggest is, have the AC compressor inspected, have them make sure it functions as it should, but the sounds you hear would definitely raise questions about the compressor itself. For me, if it squeals and can be heard, if I can't get then squealing to go away then I will replace it.

What you can try yourself, set the climate to a comfortable setting, set the fan speed to auto, and leave it cool down and the fans will slow down once it gets close to the desired temperature.Leave the fan in the auto setting. Take a hot cup of coffee or tea or something and put it up close to the infrared sensor in the center, move it pretty close so it can sense the heat. See if 1) the fan speed increases 2) it should blow really cold air compared to without the cup in front. If it doesn't respond (in the auto mode) then it's faulty. Try this for the rear as well, the sensor is right next to the rear temp display on the roof. (I conclude you have the auto because only the auto climate has driver temp, passenger temp, and then rear temp. The manual climate will only have front temp and rear temp)
 
#4 · (Edited)
O7Grand, did you forget to mention that you "topped up' the refrigerant prior to your planned trip? This reads like your compressor is slugging liquid.

I would start by allowing a shop remove all the refrigerant and then reinstall it with the measured amount. This takes a calibrated A/C charging machine and a trained technician.
 
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#8 ·
O7Grand, did you forget to mention that you "topped up' the refrigerant prior to your planned trip? This reads like your compressor is slugging liquid.

I would start by allowing a shop remove all the refrigerant and then reinstall it with the measured amount. This takes a calibrated A/C charging machine and a trained technician.
The A/C had never been touched or topped up until a week after I started having problems on the trip. Nobody local has the proper equipment so I'm considering taking it to a Dodge dealer to be diagnosed for $150. The problem is, I'm out of work & am afraid that I won't be able to afford the full repair cost at the dealer, plus the nearest one is a four hour round trip. I wonder if it's worth a half day out of town & if the dealer can narrow it down enough for me to fix it myself. I'm still trying to trace down some of the problems & appreciate the forums info.
 
#6 ·
i've heard of problems like this and other generalized electrical havoc from the connector on the AC controls behind the bezel it sits in on 3rd gen vans, but not so much on 4th gen vans

it's a few minutes and a few screws if you want to look back there to check for burning or corrosion

if it's going from cold to hot then it's moving blend doors, and if it's moving blend doors i can't imagine anything causing that besides the control module itself

none of this explains the squealing and thumping from what's presumably the compressor malfunctioning, i'm not sure how the control module would cause that besides just turning it on and off
 
#9 ·
1. Whatever garages you went to aren't worth a damn.
2. Assuming you didn't overfill the system, you've got a bearing failing in the clutch, most likely, or an internal compressor fault. You also risk throwing your serpentine belt and leaving yourself stranded.
3. The issue with the internal controls is separate. Sounds like a failed thermostat control, but you should just replace the whole dash module.
 
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