Front HVAC not working in minivan
Ok so this is our wheelchair van, and I'm pretty sure I'm going to have to take it to the shop but I am hoping for an idea of what is going on.
We have a 2014 Dodge Grand Caravan with less than 45k miles that's been fully modified for wheelchair use. (This shouldn't impact much but it does mean the electric is a bit more complex). It has separate front and rear controls and separate driver passenger front controls for the HVAC. The rear works fine, but the front passenger stopped switching off of the heat maybe a year ago. I forgot about it because we don't drive the car often and since we don't have a front passenger seat in the vehicle, no one is right in front of those vents. The driver side and rear kept working fine.
In the past month, the front vents no longer have any air movement with the very small exception that occasionally when I switch the AC on there's a bit of a very short, light cold breeze. Even more rarely sometimes at highway speeds this breeze will continue longer.
No setting change this afaict, there's no defrost, no switching to a different temp or set of vents that makes the blower work.
I did check the fuses under the hood and they look fine, I haven't gone behind the glove box, in part because I suspect this is going to be out of my skill set.
Suggestions for what could be the cause? Again I know I'll need to get it to a mechanic just hoping to have knowledge going in.
That sounds like a blend door not actuating. You can search on YouTube for 'Blend Door Grand Caravan' and you're likely to get videos showing you what you'd be doing in terms of effort - you can figure out from there if you want to attempt that part.
This part sounds like your blower motor is not running and the breeze is a result of ram-scoop air pressure just from air getting pushed into the interior intake from driving speed mostly.
Blower motor could be a bad fuse, bad motor, bad motor resistor, or bad wire connection.
Blend door makes sense for the heat issue. Just wasn't sure if it could also have caused or be related to the later blower issue.
And ok the options for the blower make sense with what I've been trying to figure out and are why I'm not super inclined to manage any of it, diagnostics are already going to probably cost me some labor and at that point, fixing all of it will probably be about the same.
This is almost assuredly the correct answer.
Pretty much all vehicles use blend doors to switch the airflow from the heater core or the AC evaporator to control warm/cool demands. The heat-only part a year ago is almost certainly a blend door issue.
In multi-zone systems like this each area will have its own door and blower motor. Being no air coming through now, it is likely the blower motor or something related (fuse, resistor, etc mentioned above).
The caveat here is that systems like these are complex and have complex electronics to control them, so could just as easily be a failure in the electronics/board that controls the system.
I checked the fuses so probably something at a different part of the circuit but yeah seems likely.
This is true, though typically these systems are (supposed to be / matter of good engineering principles) designed so that the cheapest / easiest to replace items are spec'd to be the most likely to fail (in comparison to the rest of the system collectively) and keep that theme in order of cheapest/easiest to most-expensive/most-complex.
There is always random chance that a high MTBF (mean time before failure) part will die first for whatever reason, and there is also stuff like parts design succumbing to 'value engineering' (make that part shittier to save us money!) - but in general since vehicles come with warranties car companies want the costly stuff to at least be engineered to survive past the warranty period, so the 'make the cheapest part after the fuse into another fuse' principle generally holds.
I had air die on my Promaster van a while back and did some diagnostics - fuse and relay were good if I remember correctly - I pulled and tested the resistor (these aren't resistor blocks anymore but the name has carried over from ye-olden-days) and the blower motor. I couldn't find specs on the solid state device incorrectly called a resistor which I'm pretty sure was a signal-controlled PWM voltage controller, and as such I didn't know what signal to feed it in order to drive the output (and by doing that confirm if it was working or not), but the blower motor spun right up when I hooked it up to a 30 amp capable power supply in my lab.
I tried replacing the PWM driver (the resistor) and that didn't do anything. In the end I replaced the blower motor and that fixed it - even though it did work in my lab, it had aged/degraded enough that it was basically drawing too much power and was out of spec to the point the PWM module didn't output enough power to run it.
That tangent probably wasn't useful, but I just felt like sharing a related story of fixing vehicle air since it was at least on-topic.
I'm not a mechanic but it sort of sounds like one of the
air mixing flapsblend doors could be acting up? These flaps are what move when you select the air to go to your head, body or legs. I suspect this only really because you mention you have a small breeze when you first turn the AC on. I can imagine that at highway speeds, the air flowing into the cabin has enough pressure to push the flap open a bit to give you a little breeze. I could be completely off though.It could also be a blower motor, I have a 2011 Caravan and had one die on me a few year ago. If you're going at highway speeds the air pressure from the outside intake can be enough to push some cool air through even with the motor dead iirc.
That is kind of what I'm thinking is happening with the blower yeah, just not sure what part has died in the whole system...
The blend door is almost certainly the cause of problem 1 just not sure if problem two is related.