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Old 07-15-2018, 08:35 PM   #1
9 LIVES
 
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Weird A/C problem

My 2012 3500 - 2 years ago my A/C evaporator was clogged up with road dirt (sucks not having filter)

Fast forward to 2 weeks ago while coming home from Blountville TN to Charlotte NC towing my travel trailer my A/C was acting like the evaporator clogged again. You could hear the A/C blowing hard inside the dash but VERY little was making it out of the vents. The little bit that was coming through the vents was cold but not enough flow to justify keeping it on. The day after we got home I went to unhook the camper and go to work and the A/C was working like normal.

Now this past Wednesday we leave for a trip from Charlotte to Orlando FL and the A/C does the same thing 3 hours into an 8 hour trip! Here is the thing though....if you let the truck sit for a couple hours the A/C will act normal and work as it should for maybe 1-3 hour then start acting up. I'm at a loss

I plan to bring it in to the shop that cleaned the evaporator last time but don't want to bring it in blindly and pay a couple hundred bucks if that's not the issue. I realize they would likely trouble shoot it first....but that cost money as well. Any ideas of what could cause it to do this on and off ?

My wife believes that maybe some of the debris that is blocking the evaporator is "settling" or falling off the evaporator while it's sitting. And that while at highway speeds it's blowing the debris back onto the evaporator "re-clogging it" I don't completely agree with her theory as this last trip to Florida on the way home when it stopped working we had the A/C off for about 3 hours and the windows down. After a quick bathroom break I decided to turn the A/C back on to see if it works and it did start to blow normal for about another hour or so. In my mind the quick roadside bathroom break wasn't enough time for any debris to fall off the evaporator.

During the 2 "off" non traveling weeks. I mostly did city driving for work with dozens of start and stops during the day. So not the same driving conditions as when i'm hauling the camper when it seems to consistently stop blowing.

Was wondering also if it could be the A/C and heater door actuator failing? Working more or less when it wants to? While it's not blowing strong I did try to go back and forth between heat,A/C,floor,defrost etc... all seemed to work and blow the same quantity (poorly)
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Last edited by 9 LIVES; 07-15-2018 at 08:43 PM.
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Old 07-15-2018, 09:45 PM   #2
blackmega3500
 
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Quote:
Originally Posted by 9 LIVES View Post
My 2012 3500 - 2 years ago my A/C evaporator was clogged up with road dirt (sucks not having filter)

Fast forward to 2 weeks ago while coming home from Blountville TN to Charlotte NC towing my travel trailer my A/C was acting like the evaporator clogged again. You could hear the A/C blowing hard inside the dash but VERY little was making it out of the vents. The little bit that was coming through the vents was cold but not enough flow to justify keeping it on. The day after we got home I went to unhook the camper and go to work and the A/C was working like normal.

Now this past Wednesday we leave for a trip from Charlotte to Orlando FL and the A/C does the same thing 3 hours into an 8 hour trip! Here is the thing though....if you let the truck sit for a couple hours the A/C will act normal and work as it should for maybe 1-3 hour then start acting up. I'm at a loss

I plan to bring it in to the shop that cleaned the evaporator last time but don't want to bring it in blindly and pay a couple hundred bucks if that's not the issue. I realize they would likely trouble shoot it first....but that cost money as well. Any ideas of what could cause it to do this on and off ?

My wife believes that maybe some of the debris that is blocking the evaporator is "settling" or falling off the evaporator while it's sitting. And that while at highway speeds it's blowing the debris back onto the evaporator "re-clogging it" I don't completely agree with her theory as this last trip to Florida on the way home when it stopped working we had the A/C off for about 3 hours and the windows down. After a quick bathroom break I decided to turn the A/C back on to see if it works and it did start to blow normal for about another hour or so. In my mind the quick roadside bathroom break wasn't enough time for any debris to fall off the evaporator.

During the 2 "off" non traveling weeks. I mostly did city driving for work with dozens of start and stops during the day. So not the same driving conditions as when i'm hauling the camper when it seems to consistently stop blowing.

Was wondering also if it could be the A/C and heater door actuator failing? Working more or less when it wants to? While it's not blowing strong I did try to go back and forth between heat,A/C,floor,defrost etc... all seemed to work and blow the same quantity (poorly)
It's the resistor going out! When it starts to go it draws way too much electricity and makes the control panel freak out.

Replace the blower fan and resistor at the same time, not a can be found for cheap.
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Old 07-15-2018, 10:07 PM   #3
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The evaporator could be freezing up then un-thawing while it sits.

Sent from my SAMSUNG-SM-G890A using Tapatalk
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Old 07-15-2018, 10:50 PM   #4
blackmega3500
 
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Quote:
Originally Posted by okie18 View Post
The evaporator could be freezing up then un-thawing while it sits.

Sent from my SAMSUNG-SM-G890A using Tapatalk
Highly unlikely.

The reason I told him resistor is what he is describing is exactly to a T the issue I had which I originally though was the control board going out since the a.c. on lights would randomly flicker, not switch fan speeds, and would remain lit even after it was turned off.

The electrical draw in those resistors is pretty sensitive, and even the slightest push up on the drivers side window switch would make lights flicker.

The way I tracked to the resistor was a shade tree mechanic trick of giving the blower box a swift smack when it was barely blowing any air.....

Literally few good smacks and it was back to blowing normally for a bit then back to a slight flow out of the vent.

Hooked up to a snap on scanner and could actually see the a.c. control status was spasing out repeatedly switching between lo, med, hi with the switch in multiple positions. The only one it didn't do it on was low, which obvious requires the least amount of controllable electric output.

Replaced the resistor and the a.c. blower since they're both right there and cheap at $70ish for both parts, and the problem all went away with only a 10min install time.

His model year resistor looks to be around $30 which is a lot cheaper than trying to pay a diagnostic fee.
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EFI by ATP in Idaho, s364.5sxe/FI ETR s488 with V2 cover, s&s 135% overs, Hamilton springs/ pushrods and 188/220, suncoast Comp68 getting it all to the ground.

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Old 07-16-2018, 05:55 AM   #5
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Quote:
Originally Posted by okie18 View Post
The evaporator could be freezing up then un-thawing while it sits.

Sent from my SAMSUNG-SM-G890A using Tapatalk


I think a freezing evaporator would be causing the high pressure switch to kick out the compressor for protection. Hooking up gauges or an indicator light to the compressor would tell if this is the case.

Blackmega is on to something.
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Old 07-16-2018, 08:19 AM   #6
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I just went through this. Turned out to be a blend door, which was extremely easy to fix.

They're about $28 shipped ($42 from dealer), pull the center console on the dash, drop the cup holder, and the two you're looking for are there. I just swapped them both since they were cheap.
2010 DODGE RAM 2500 PICKUP 6.7L L6 DIESEL Turbocharged Heater Blend Door Actuator | RockAuto

If it was the resistor, you would have no change in one of the settings for fan speed. Also, those normally fail to full bore, not the other way around.

As for the evaporator clogging, since you dealt with it, you know it sucks. A quick alternative I've done is to remove the resistor and use that slot to get a dish plate scrubber up there (soft plastic bristles), then I hooked it up to my drill, and just brushed all that junk off. After I went at it with my generic weed killer sprayer with water in it. Worked great.
And here's a great filter retofit kit for $30 so it doesn't happen again:
'09-'18 Dodge Ram 1500/2500/3500 Cabin Air Filter Kit
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Old 07-16-2018, 08:33 AM   #7
blackmega3500
 
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Quote:
Originally Posted by CorneliusRox View Post
I just went through this. Turned out to be a blend door, which was extremely easy to fix.

They're about $28 shipped ($42 from dealer), pull the center console on the dash, drop the cup holder, and the two you're looking for are there. I just swapped them both since they were cheap.
2010 DODGE RAM 2500 PICKUP 6.7L L6 DIESEL Turbocharged Heater Blend Door Actuator | RockAuto

If it was the resistor, you would have no change in one of the settings for fan speed. Also, those normally fail to full bore, not the other way around.

As for the evaporator clogging, since you dealt with it, you know it sucks. A quick alternative I've done is to remove the resistor and use that slot to get a dish plate scrubber up there (soft plastic bristles), then I hooked it up to my drill, and just brushed all that junk off. After I went at it with my generic weed killer sprayer with water in it. Worked great.
And here's a great filter retofit kit for $30 so it doesn't happen again:
'09-'18 Dodge Ram 1500/2500/3500 Cabin Air Filter Kit
It's more common than you think, what he described is exactly what I dealt with that the resistor and blower fixed.

The blend doors usually cause inconsistent delivery from the vents from I've seen. And they don't often just refresh after sitting.
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07.5 6.7l Mega-longbed conversion dually with 22.5s
EFI by ATP in Idaho, s364.5sxe/FI ETR s488 with V2 cover, s&s 135% overs, Hamilton springs/ pushrods and 188/220, suncoast Comp68 getting it all to the ground.

2014 BMW X6 ///M factory 560hp twin turbo AWD
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Old 07-16-2018, 09:40 AM   #8
CorneliusRox
 
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Quote:
Originally Posted by blackmega3500 View Post
It's more common than you think, what he described is exactly what I dealt with that the resistor and blower fixed.

The blend doors usually cause inconsistent delivery from the vents from I've seen. And they don't often just refresh after sitting.
I'm pretty sure the blend doors on your truck are still vacuum controlled though. The 4th gen's switched to stepper motors for control (about time) and I had one failing that would allow for terrible AC (like described), then when winter came, it would not let much heat at all out. That's when I finally dug in and found the issue. Wish I would have done it way sooner.

Either way though, I replaced my blower and resistor recently too, just because I was going through the whole system and they were cheap. My blower started making a whining noise and I didn't want it drawing too much current and hurting other components.

Blower ($42):
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Resistor ($28):
2010 DODGE RAM 2500 PICKUP 6.7L L6 DIESEL Turbocharged Blower Motor Control Module / Resistor | RockAuto
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Old 07-16-2018, 11:12 AM   #9
9 LIVES
 
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Thanks I'll look into replacing those
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