Dodge Sprinter Air Conditioner (A/C) Issue and Fixes
Updated: Aug 24, 2020
First Issue: A/C does not operate well at idle
This story starts off with some preventative maintenance. I sent my ATC (climate control computer) away to get rebuilt for about $100 (ebay). After doing some research and having intermittent A/C clutch engagement for the A/C, this seemed like the first step in getting a good running A/C system (A/C had poor performance at idle). I received the incorrect ATC back, but the company quickly fixed that issue and sent me the correct rebuilt one.
Once I got the correct one I installed it back into the dash and tried it out. Keep in mind it had been out for months as I was working on the van. However now the A/C compressor will not engage at all. As I had to leave in 5 days the van went into a A/C shop and they got the compressor going but realize it was fried. They replace compressor, drier, A/C pressure sensor and recharge the A/C. A/C compressor runs great only when they short the ATC out of the system (send 12v+ to A/C compressor clutch separate from the ATC). Which brings us to the second issue.
Second Issue: A/C compressor will not engage and auxiliary fans run constantly
For the time being I had the A/C shop install a 12 volt toggle switch to engage the A/C clutch, as after all every other A/C part was functioning correctly, the clutch was just not receiving a signal to engage. Well it worked. 6000 miles through Canada and the USA with that system. However I would not recommend that method, you have to keep in mind it cut out the safety features of the ATC (high pressure, icing up, etc...), which in my case was negligible as the auxiliary fans were on constantly and every other component was new, but that is not the case for every system. I needed A/C for my trip and this worked.
After the trip I borrow a scanner to try and solve the A/C issue and the auxiliary fan issue (it is surprisingly loud). I borrowed a SnapOn Souls Ultra scanner, but there are much much cheaper ones on the market that will do the trick. A lot of people recommend the Autel MD802 Pro scanner (all function model).
I then scanned every module in the memory and the van had a ton of stored codes (full list at bottom of page), but without knowing when then were stored I cleared all of them and after running the van, A/C, heat and transmission I re-scanned the modules and only got two codes back, both in the "aircon" (ATC) module:
The A/C compressor control is to be expected as my compressor is controlled outside the ATC by a toggle switch currently, but the Refrigerant Pressure Sensor may be the fault I am looking for. This would cause the fans to run non-stop and the A/C clutch would not engage from the ATC. Makes me thing the A/C shop didn't have a scanner or I would not have had to go through the toggle switch route.
Scan of ATC data showed the sensor getting its 5 volts and showed the refrigerant pressure at 841.39 inHg (approx 400 PSI) which is the maximum. Given the compressor was not engaged this indicated a fault in the sensor or wiring. This info was thanks to Midwestdrifter in this thread on sprintersource Forum.
So I began wiring testing of the sensor. This is the wiring diagram for the pressure sensor:
There are three wires that need to be tested that go to the sensor:
Brown/Red - Sensor feedback line
Red/Blue - 5 volt power source
Brown/Blue - Ground
When disconnected from the pressure sensor the harness showed:
Brown/Red - 5v
Red/Blue - 5v
Brown/Blue - continuity to ground
All of those were correct and as they should be. Using alligator clips I connected the sensor and noticed that I was getting a reading of .033v (33mV), which is way to low. The sensor feedback should be between .1 - 4.8 volts.
I continued testing and found that the 5v power supply had now dropped to 4.5v when connected to the pressure sensor (even when checked at the ATC).
I ran 3 new wires separately from the harness (to rule out wiring/shorting issues) and attached them to the sensor with a new harness I got at a junkyard and still no difference. Supply voltage dropped to 4.5v and the sensor return never got close to .1v
To rule out the pressure sensor I purchased a 12v to 5v transformer and connected it directly to the sensor and measured the sensor output. Now I was getting .8v which was withing the desired range and the sensor supply was staying at 5v (from my transformer). I hooked up the sensor and tried it powering the system through the 5v transformer, but allowing the sensor return line to connect to the ATC and the A/C worked! (aux fans off, compressor on) (I did need to ground the Brown/Blue as it is a shared ground with another sensor).
A/C compressor clutch was receiving its needed 12v+ of power from the ATC and A/C was functioning as it should. Sensor feedback was showing 1.046v after a few minutes running.
This eliminated the sensor as an issue and indicates that the ATC was not providing the required 5v to the sensor.
Remember step 1 of fixing my poor A/C performance was to have the ATC rebuilt by a ebay repairer... It appears that they sent me a faulty unit which resulted in months of diagnosis into the A/C not functioning. The repairer did advertise a 1 year warranty, which is not up yet so I will be sending in the unit for repairs and pending their response I will be either recommending them as an ATC re-builder or deterring others in the future from using them....
I am assuming they bench tested the voltage output, but not under load. I am hoping they fix the issue with a fixed ATC.
UPDATE (JUL 2019): I received the warrantied ATC computer from the ebay re-builder and the A/C system is working great again. Just a bummer that they sent me two faulty ATC computers, but in the end they fixed it (except for the lost time/money on fixing working A/C parts, which may or may not have been going out anyways).
FINAL CONCLUSION (second fault): Fault in ATC caused a low 5v power supply to refrigerant pressure sensor, in turn causing the sensor return feed to ATC to indicate high pressure (in error). Once 5v supply to pressure sensor was provided the A/C performed correctly.
This was a really long process for me and would not have been possibly without the help of others. If you are struggling with an A/C issue please don't hesitate to contact me and I will do my best to help out. I have learned a lot about the A/C system in the process.
UPDATE (AUG 2020): On a recent road trip I noticed first intermittent A/C and then no A/C. A quick inspection of the A/C while on and off revealed that the outer A/C clutch failed at the rubber damper, as the compressor was replaced by a shop in 2019 this was upsetting. However as I did authorize them to install a direct 12 volt toggle switch to the clutch this may have contributed to the short life span and additional strain on the rubber damper. As of now I am just replacing the outer clutch piece (had to purchase the entire A/C compressor clutch for $60 as I could not find the outer clutch piece by itself or in salvage yards), but suspect that the compressor may need to be replaced also if there was some sort of additional strain coming from it. A/C is one of the system components of my van that I do not want to fail on the road, due to the need for advanced tools to fix it.
Here is a full list of the codes pulled from my Dodge Sprinter: