Air conditioning not working

Midwestdrifter

Engineer In Residence
Two things will cause the fan to run, the pressure sensor being disconnected or out of range (its on the high side line, near the firewall?) I would check to make sure the shop didn't unplug it, or damage the wires.

Or the ATC not getting CAN communication from the ECM. With the AC off, and the ignition on, the fan should not run. if it does, it means a CAN communication problem.


You can bypass the ATCs control of the clutch. DO NOT run the clutch with the cabin fan off. Do not run in ambient temps under 60F. DO not run the clutch if the condenser fan is not running. Normally the ATC will turn the condenser fan on if the pressure gets high enough (215psi?). its okay to have the aux fan not running on the highway, in stop and go traffic the pressure may get too high without extra cooling, and damage the compressor.
 
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alexk243

KulAdventure
Two things will cause the fan to run, the pressure sensor being disconnected or out of range (its on the high side line, near the firewall?) I would check to make sure the shop didn't unplug it, or damage the wires.

Or the ATC not getting CAN communication from the ECM. With the AC off, and the ignition on, the fan should not run. if it does, it means a CAN communication problem.
Any easy way to diagnose the CAN communication problem? Can I test output from the ATC?

Also if they install the switch to remove the ATC will the fans running constantly have a negative effect?

KulAdventures.net
 

alexk243

KulAdventure
. You can bypass the ATCs control of the clutch. DO NOT run the clutch with the cabin fan off. Do not run in ambient temps under 60F. DO not run the clutch if the condenser fan is not running. Normally the ATC will turn the condenser fan on if the pressure gets high enough (215psi?). its okay to have the aux fan not running on the highway, in stop and go traffic the pressure may get too high without extra cooling, and damage the compressor.
Will the AUX fan run off I am taking the ATC out of the system?


If I mess up one of the first steps (under 60 or cabin fan not on) what happens?

KulAdventures.net
 

Midwestdrifter

Engineer In Residence
Any easy way to diagnose the CAN communication problem? Can I test output from the ATC?

Also if they install the switch to remove the ATC will the fans running constantly have a negative effect?

KulAdventures.net
With the AC off, and the ignition on, the fan should not run. if it does, it means a CAN communication problem.

The aux fan running non stop will cause no problems. If it is not running, just don't spend a lot of time idling with the AC on.

Will the AUX fan run off I am taking the ATC out of the system?


If I mess up one of the first steps (under 60 or cabin fan not on) what happens?

KulAdventures.net
The Aux fan may still run even with the compressor clutch disconnected.


Without the ATC controlled the clutch, there is a small chance the evaporator could ice up. This system has a expansion valve, so that does most of the control work, so you don't have much to worry about. The only real concern in hot weather is to avoid stopped operation without the aux fan running, as the higher pressures will wear, or possibly damage your shiny new compressor.
 

Midwestdrifter

Engineer In Residence
Connect a compatible scanner such as the Autel MD 802. Scan the ATC module will report a relevant code for wiring faults. You can also view the AC pressure, evaporator temperature, and ambient temperature from the ATC. All of these should have sensible values in them.
 

alexk243

KulAdventure
So I did my 20 day trip out to the west coast and back with a toggle switch running my A/C compressor and it worked great, but I am still dealing with underlying issue and have not located a scanner to look into the communication issue yet.

Side note the electric fans are still always on when the van is on, even with A/C off... Not sure what is causing that...
 

Dougflas

DAD OWNER
If it is any help, if the switch on top of the drier is unplugged, the electric fans will activate
 

Midwestdrifter

Engineer In Residence
If the ATC cannot get communication from the ecu the fan will stay on. If For some reason the engine coolant temperature sensor is unplugged it will also run continuously. The best approach would be to scan relevant codes from ATC, ECU and cluster. It would also be good to double check the reading from the AC pressure sensor.
 

alexk243

KulAdventure
So I finally tracked down a scanner and scanned everything I could.


There were a ton of codes stored, but as my vehicle is an 04 with 270000 miles I had no idea how long those codes were stored. So I cleared everything (after taking pictures of all the codes) and ran it, cycled through gears, drove, turned AC on/off, heat on/off etc... and scanned it again and only two codes came back up:


Test of the Aircon system shows the AC is off per the ATC and the Fan is on, which if the aircon computer (ATC) is saying this then I would assume it is not a communication issue...

The AC compressor code is to be expected since I am operating my AC compressor clutch outside the ATC (toggle switch), but the other one is not... that part was replaced when I had all the AC work done and I am assuming that may be the cause of my constant fans on, would that be accurate? What does it take to fix that part?



In case anyone wants to read through it, here are all the codes stored in my van prior to clearing them (unknown age):










Clearing all the codes had no effect on the Aux Fans.
 

Midwestdrifter

Engineer In Residence
Here is the details on 1003-7

Refrigerant pressure sensor (B56)

Refrigerant sensor (B56) or external 5V supply short
circuit to voltage(+) or open circuit

a. Cable A81.1/11 to X82/12 has a short circuit to voltage(+) or open circuit.
b. Cable X82/12 to B56/3 has a short circuit to voltage(+) or open circuit.
c. Cable A81.1/19 to X82/11 has a short circuit to voltage ( +) or open circuit.
d. Cable X82/11 to B56/2 has a short circuit to voltage(+) or open circuit.
e. Refrigerant pressure sensor (856) is faulty
This code will result in the fan running 24/7. It will also result in the ATC refusing to engage the AC compressor. Check the wiring to the AC pressure sensor. The diagrams are in the service manual. One pair of wires supplies ground and 5V, the other reads the pressure as a voltage (0-5v). The 5v supply is shared with several other sensors attached to the ATC, so since those are not showing errors, it is probably the harness section to the AC sensor, and not the ATC itself.

With the scanner, see what the AC pressure sensor is reading (ATC live data). It is probably reading zero or max (400psi or something). This would confirm a faulty sensor or harness.
 

alexk243

KulAdventure
Here is the details on 1003-7



This code will result in the fan running 24/7. It will also result in the ATC refusing to engage the AC compressor. Check the wiring to the AC pressure sensor. The diagrams are in the service manual. One pair of wires supplies ground and 5V, the other reads the pressure as a voltage (0-5v). The 5v supply is shared with several other sensors attached to the ATC, so since those are not showing errors, it is probably the harness section to the AC sensor, and not the ATC itself.

With the scanner, see what the AC pressure sensor is reading (ATC live data). It is probably reading zero or max (400psi or something). This would confirm a faulty sensor or harness.
This is all starting to make sense now... Makes me feel like the A/C shop didn't have a scanner or this would have been solved a while ago.

My A/C Clutch wont engage and is controlled by a toggle temporarily (most like due to this issue).

In the scanner it showed a 5V signal during a data test from the scanner. The pressure, if I am not mistaken, was near 800.... and didn't change while operating A/C or not (neither did the 5v). I dont have the scanner now and will have to go borrow it again to recheck these numbers.

I had previously visually inspected the wires and harness, but can do it again. I believe they replaced the switch when the replaced the compressor and drier. Does replacing the sensor require the system to be drained? Also is there any other weak points in the wiring besides where the harness attached to the sensor in the engine bay?
 

Midwestdrifter

Engineer In Residence
On some vehicles the sensor has a shrader valve below it, so it can be replaced without recharging. I don't know about the sprinter.

You don't really need to get the scanner again. The service manual has the details on the sensors expected outputs and wires. You can just use a multi-meter with continuity and volts to check the harness. With the sensor unplugged and the ignition on, you should get 5v between two of the wires at the plug. You should get continuity between the other wire (signal wire) from the sensors plug and the other end at the ATCs connector.

800in/hg is about 400psi, so the wiring or sensor is bad.
 

Midwestdrifter

Engineer In Residence
The wiring diagram you want is 8W-42-4.

At the sensor here is the pin out.


REFRIGERANT PRESSURE SENSOR
CAV CIRCUIT FUNCTION
1 18BR/BL SENSOR GROUND
2 20BR/RD REFRIGERANT PRESSURE SENSOR FEEDBACK
3 20RD/BL 5 VOLT SUPPLY
 

Midwestdrifter

Engineer In Residence
Testing the sensor

DIAGNOSIS AND TESTING - A/C PRESSURE
TRANSDUCER
The A/C pressure transducer is tested using a
DRBIIIt scan tool. Refer to Body Diagnostic Procedures.
Before testing the A/C pressure transducer, be
certain that the transducer wire harness connections
are clean of corrosion and properly connected. For
the air conditioning system to operate, an A/C pressure
transducer voltage reading between 0.7 and 4.56
volts is required. Voltage outside this range indicate
a low or high refrigerant system pressure condition
to the ATC control module. The control module is
programmed to respond to a low or high refrigerant
system pressure by suppressing operation of the compressor.
Refer to the A/C Pressure Transducer Voltage
chart for the possible condition indicated by the
transducer voltage readings.

Voltage Possible Cause
0.0
1. No transducer supply voltage from ATC control module.
2. Shorted transducer circuit.
3. Faulty transducer.

0.150 to 0.450
1. Ambient temperature below 10° C (50° F).
2. Low refrigerant system pressure.

0.451 to 4.519
1. Normal refrigerant system pressure.

4.520 to 4.850
1. High refrigerant system pressure.

5.0
1. Open transducer circuit.
2. Faulty transducer.
 

alexk243

KulAdventure
Connect a compatible scanner such as the Autel MD 802. Scan the ATC module will report a relevant code for wiring faults. You can also view the AC pressure, evaporator temperature, and ambient temperature from the ATC. All of these should have sensible values in them.
Would this one work to scan the ATC and climate control for issues?

https://amzn.to/2tzDyD2
 

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