Resolved 2015 Golf AC not working, condenser fan works when radiator commands it but not when AC commands it.

[MrNomad105]

Followup.... after significant persuasion, my kid allowed me to swap the G805 from her working Golf to the defective Golf. VCDS read 1.8 bar KOEF. It's unlikely the G805 is the issue. I look forward to your assistance in this most perplexing problem.

 

[Uwe]

Do u think it wise to try these tests before I visit VW and buy a $125 G805 from VW?

No. In many modules, IDE01475 and IDE02325 will make things worse; as in delete the parameterization. VCDS should warn about that. Take heed of that warning and do not ignore it unless a specifically documented procedure calls for one of these.

-Uwe-

 

[NZDubNurd]

Second post in this thread:

Please check the charge in the ac system. 2.0 bar is way to low even for ambient pressure especially in AZ where I'm sure the temps are well into the 90's. You should be a ambient pressure of at least 7bar is not more. At 2.0 bar I would say the system is low on charge. The fault in the ECM for the fan could also be a factor in terms of function.

I am missing something simple but I cannot charge the system to a low side pressure of 100psi. What am I missing?

You don't charge an AC system to any pressure reading - you charge it with the right amount of refrigerant.

Evac down to nothing, charge with correct weight of refrigerant. If the weight is right, the pressures should sort themselves out, assuming no other issues.
2.0 bar is not even close to what it should run at - it suggests it's VERY low on refrigerant.

 

[EuroX]

Second post in this thread:




You don't charge an AC system to any pressure reading - you charge it with the right amount of refrigerant.

Evac down to nothing, charge with correct weight of refrigerant. If the weight is right, the pressures should sort themselves out, assuming no other issues.
2.0 bar is not even close to what it should run at - it suggests it's VERY low on refrigerant.

I never said to charge a AC system to a pressure reading. Please don't assume if you don't know diagnostic procedures and values, thank you.

 

[MrNomad105]

Thanks for the input. I truly appreciate the help but what's missing is the reason the bar does not change when the compressor is running. On my daughter's working 2017 Golf TSI, KO EOff = MVB says the bar = 8.6. KO ERunning = MVB bar = 14.2. That makes perfect sense. High side pressure is higher when the compressor is running. Ergo, bar is higher. If the G805 is the only device rendering a pressure measurement, the G805 is working.

On my 2015 Golf, bar doesn't change when the compressor is running so while I acknowledge it should be charged to 500 grams, bar will continue to be inaccurate. The 2015 Golf has manual HVAC & I believe it works as follows. The G805 sends a PWM signal to the J301. The J301 accepts that data and sends instructions on the CAN to the ECM to turn on the condensor fan. It also sends instructions on the LIN to regulate the compressor control valve. Until the J301 responds correctly to compressor off/compressor on, evac and refilling isn't going to correct the incorrect data. On my gauges, low/high side pressures change appropriately when the compressor engages, but bar remains stuck at 1.8 to 2.2 depending upon which G805 in installed. Amongst the G805s I tested is the working G805 I removed from the working 2017 Golf. Bar remains stuck on my 2015.

To break the deadlock, I could purchase an inexpensive scope and read the signal from the G805. If it varies when compressor on/off, then my problem is downstream, most likely a J301.

Comments & suggestions r welcome. It's no fun driving w/o ac in Tucson.

 

[NZDubNurd]

I never said to charge a AC system to a pressure reading. Please don't assume if you don't know diagnostic procedures and values, thank you.

I realize that - You said it was low and that he should check the charge. The OP quoted he couldn't charge up to that pressure - making it sound like HE was filling to a pressure, hence why I quoted him saying it.

 

[MrNomad105]

Thanks for your assistance but I cannot get past the observation that the bar doesn't change, compressor on or off. If my understanding of how the G805 and the J301 work is correct, the J301 is defective. Is there a procedure I must follow when replacing the J301? Are there codes that need to be xferred? If so, please point me to them.

BTW, using a breakout box I determined that the CAN network is properly terminated. High side was 2.68 to 2.74 and low side was 2.3, 2.4 so there are no shorts. The data emitting from the J301 may be incorrect.

Thanks again for your help.

 

[EuroX]

I would check is the head is sending out a signal to ac compressor. I also don't think the head would cause faulty reading to be honest. Did we verify that it has the correct amount of freon in it? Probably anywhere from 330-625grams.

 

[MrNomad105]

I am certain the compressor is engaging because the high/low pressure changes KOER. No, I have not emptied the system and verified the correct amount of R134 which is 500 grams for the 2015 Golf. I used gauges, pressure and ambient temp to charge the system but that mistake notwithstanding, I cannot explain why BAR remains the same when the compressor is off or on. That makes no sense. To check the wiring, I temporarily replaced/spliced the wire between G805 violet/blue and pin 16 of T20D, the manual HVAC control module. No difference, so the harness appears intact.

Is there a specific procedure to be followed after swapping the J301, the manual HVAC control module? Mitchell Wiring says to follow the: "Guided Fault Finding or in Guided Functions when installing a new Climatronic Control Module – J255- or A/C Control Module-J301- using the Vehicle Diagnostic Tester". If u know of such a procedure, please fwd.

 

[EuroX]

We cannot proceed until we know we have the correct charge in the ac system. System needs to be evac'd and recharged with correct amount. Then we can proceed to troubleshoot. I would rather check and confirm correct charge vs throwing parts at it. I agree the pressure should change. However based on data provided earlier it looks like the ac compressor is not coming on.

With compressor running this value should be between 0.5-0.8Amps:

IDE00966 Compressor current: actual value 0.000 A

 

[MrNomad105]

Wilco. Will handle this weekend. I might as well remove the compressor and check oil levels too.

Once the system is evacuated, what method do u recommend to force the compressor on to receive the balance of the 500 gram charge?

 

[EuroX]

Compressor does not need to be on in order to take a charge. You need to EVAC the system and put it in a vacuum, then the system will draw it in. I have a ac machine for this. But if you got a scale and gauges you can probably get by.

 

[MrNomad105]

Given I have found so many lousy repairs performed by the body shop I decided to remove the compressor, check the oil quantity, and inspect the control valve. Admittedly, I could have inspected the valve w/o removing the compressor. I drained the oil from the compressor and found no debris. I also found no debris on the small filter on the valve. The valve operates when 12v is applied.

What was disturbing was the oil qty. There was much less than 1/2 oz. The spec calls for 2.5 oz +/- .3 oz of PAG 46. I realize that some oil may be floating around the system, but how much would u add before reinstalling the compressor?

I'm waiting for new orings to arrive.

 

[EuroX]

0.43oz is normal for that amount to be in the compressor alone the rest will be in the system. Please make sure the system is charged with the correct amount of freon.

 

[MrNomad105]

On 9/13, I charged the 2015 Golf TSI S with 500 grams of R134 after evacuating to -30lbs and confirming there were no leaks. Prior to this test, I removed the compressor, drained the oil which contained much less than .5 oz, no debris, and added .5 oz of PAG 46. I removed the AC valve, tested with 12v & watched it/heard it operate, noted that the screen was clear, no debris, reinstalled.

Here are the test results:

With the system = -30lbs, before charging with R134, HVAC Refrig Pressure = 2.2 Bar.
Using an external fan blowing air thru the condenser, with 502 grams added, HVAC read 2.6 Bar. Head pressure was 51/215. Compressor load =2.0 Nm, Coolant Fan Activation = 10%, Specified Value = 0%, fan never came on. Cabin AC air was cool. A/C compressor torque was -8.69 Nm. Ambient appx 80F.

Using 01-Engine Output Test Fan 1 control circuit, VCDS replied REFUSED BY CONTROL MODULE.

I conclude that the BAR remains incorrect and I need to address it. In earlier tests, I tested the G805 power, ground, and signal leads using an ohm meter. I also replaced the G805 with an off-brand part and a second OEM G805 part and got similar results. However, I tested ground using an ohm meter which does not place a significant load on the ground. The next test should test ground using a test light which places a load on the ground. Also, if I had a scope, I could measure the PWM signal at the G805 violet/blue with engine off (100lbs) and engine on (215lbs). The scope will report and confirm changes based on pressure whereas a defective J301 will not. However, I thought I’d provide the test results before proceeding.

In an earlier test, I bypassed the PWM signal wire to the J301 with an external graft. I concluded that the harness was not at fault. I also used a breakout box to test the CAN termination resistors and achieved 67 ohms.

I performed a full scan and it reported: 15048 - Coolant Fan Control Circuit 1 P0480 00 [032] - Electrical Malfunction.

Comments and suggestions r welcome.

 

[EuroX]

To me none of that adds up. I will assume it was 30 inches of mercury and not pounds. Think it would be best to post those IDE channels with those values. Are you sure wires are not shorted together for the switch ort shorted to ground. Also have you taken a resistance reading of the wires for the switch?

 

[MrNomad105]

Ok, I understand your frustration and appreciate the help you tried to provide. Sorry to be such a burden but I will continue the learning process and when I figure it out, I will let u know what fixed it.

My next step is to redo the G805 wiring tests using an actual load on the ground and a scope to measure the PWM signal under changing conditions (KOE Off and KOER). Once I establish the G805 is doing its job, I need to trace the operation of the next device in the series which I expect is the J301. Ebay had a used unit for sale recently.

In the interim, I'd like to drive the car so I may add a signal generator to the condensor fan so I can establish medium fan speed. Fortunately, I have access to a working Golf for comparison. I reported earlier tests confirmed that BAR is lower when KOE Off and higher when KOER. I also swapped the working VW's G805 into the dysfunctional VW and it made no difference.

The car was hit twice in the front before I got it and the repair work was shoddy so anything is possible.

Thx again for your effort.

 

[EuroX]

If the car was railed twice I would be looking at resistance values for the 3 wires for the sensor or run a dirty overlay to see if anything changes. To make a long stort short pressure readings do no add up. But if you have high resistance that will definitely be a factor.

 

[MrNomad105]

Yes, the front was wrecked twice & I have absolutely no confidence in the body shop who fixed this car so looking for dumb mistakes makes perfect sense.

I apologize but I do not know what a "dirty overlay" is.

Today’s assignment was to repeat the electrical tests on the G805 presently installed using an ohm meter. I do not have access to a scope (yet). These G805 tests included the ground, input bat voltage, and output PWM which sends signal to HVAC module T20d, pin 16.

I tested the ground wire using a test light connected to bat + to place a load on the ground. OK.
I tested the bat voltage wire using a test light connected to ground. OK.
I tested violet/blue PWM output four ways:
KOE Off – voltage was 8.69. I disconnected PWM from harness and voltage rose to 10.84 so the harness is depressing the signal which is prob normal.
KOER – voltage was 9.70. I disconnected PWM from harness and voltage rose to 12.20. In my novice opinion, this makes sense because high side pressure is higher when the engine is running. Remember, during an earlier test, I took a G805 from another 2017 VW Golf and installed it in my 2015 and got the same bogus readings.

Conclusion: G805 wiring is correct.

Several weeks ago I bypassed the harness, connected G805 PWM to pin 16, T20d with an external wire and observed no difference so the harness is not a factor.

Mitchell Wiring says the G805 circuit shares the same wires with Air Quality Sensor but this car has the cheaper AC system which means it has no Air Quality Sensor. Mitchell wiring also indicates that violet/blue is connected to the FRESH AIR BLOWER CONTROL MODULE but the fan speeds work OK so I assume neither of these are factors.

Question: Is the following correct? The G805 passes information to the J301. The J301 combines the G805 information with data from other sources and sends an instruction via the CAN network telling the ECM to turn on the coolant fan. Is that how this works?

After these tests I examined the long code in HVAC and found an error. In Long Coding 6, Bit 4-7 was NOT set to R134. Rather, it was set to 10 Coolant Type R1234yf. I changed it to R134, saved the setting. Next, I looked at 01 Engine A/C compressor torque and it read -16.97Nm. I’m pretty sure it was -9 yesterday before the freon coolant change.

After these tests I ran another scan of vehicle type AU which is 2015 Golf. Next, I examined the 19 - Can Installation list. 40 – AC Compressor, was not checked. It was not installed so I checked it and saved it.

I asked CAN to look for connected modules and it could not find the compressor. That seems incorrect but u r the expert and I look forward to your comment.

BTW, all of these tests were conducted using an external house fan that blows thru the condenser to control head pressure. The front bumper is off which permits massive air flow. FYI, I installed a SPST toggle switch into the signal wire on the condenser coolant fan. When I drive the car, the toggle switch disconnects the signal wire from the coolant fan module. The absence of that PWM signal causes the coolant fan to operate at full speed (emergency mode). When I arrive at my destination, I simply toggle the switch (close the circuit) which reconnects the PWM lead and the fan shuts off. I suspect this procedure causes the 15048 - Coolant Fan Control Circuit 1 P0480 00 [036] - Electrical Malfunction but I clear the code before tests. This temp fix allows me to use the car w AC and not blow up the compressor.

I opened the 01 Engine controller and used OUTPUT TEST FAN 1 CONTROL CIRCUIT to try to turn on the fan. It replied REFUSED BY CONTROL MODULE. Perhaps that was caused by the coolant fan disconnect but I'm certain I cleared the DTC.

How often should the ignition be turned off/on after changes?

I sincerely hope I am giving you the information you need to help me remedy this. At some time in the future, I hope to buy you a giant Starbucks for all of your patience and help.

 

[NZDubNurd]

Conclusion: G805 wiring is correct.

Several weeks ago I bypassed the harness, connected G805 PWM to pin 16, T20d with an external wire and observed no difference so the harness is not a factor.

Mitchell Wiring says the G805 circuit shares the same wires with Air Quality Sensor but this car has the cheaper AC system which means it has no Air Quality Sensor. Mitchell wiring also indicates that violet/blue is connected to the FRESH AIR BLOWER CONTROL MODULE but the fan speeds work OK so I assume neither of these are factors.

Pin 6 or 16? Depending on versions etc, BOTH of these could be the signal wires from the High Pressure Sensor. I won't have the correct diagram here, but pin 16 on Climatronic and pin 6 on standard AC go to the pressure sensor, for early MK6 Golfs. The Climatronic IS likely to have the air quality sensor, so perhaps you need a different wiring diagram??? I'd be more inclined to purchase a short Erwin subscription and use that wiring diagram, based on VIN - even though Erwin has been known to have mistakes, "Mitchell" could be too generic, perhaps??? I have no experience with them, but other may have?

I assume that by doing continuity tests AND matching colours, you've found the correct pin? VW has a habit of using the same colour wires more than once too Sometimes on the same module!

Also, that it is the correct connector connected to the sensor? VW has a habit of allowing connectors to be interchanged sometimes, and sometimes they are close enough on the loom to do so!

The Compressor won't be found on the CAN gateway - it's only modules that can be registered that show; for example - your scan shows 5F is not registered on the CAN gateway, but if you tick it in the installation list, it will be, and you won't have the fault for it. Likewise, if you unplug the module, it would also clear the error, because the CAN gateway won't see it any more. I don't think it affects your issue at all, and I assume It's "unregistered" for a reason, anyway?

From what I know of the MK5's the AC wuold send a CAN request, as you say, to the engine ECU. The engine ECU then decides what to do with the fan,, based on whatever algorithm it uses. the request from the AC might be overidden because of a fault code or other signal input, but generally, the ECU is likely to do what's expected.