When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Sure looks like a low charge. Outside possibility being a bad compressor. When they evacuate the system (usually down to <500 microns or 24-25 "Hg if they don't have a micron gauge) have them valve everything off and watch the gauge. If it loses vacuum, you got a leak. If it holds vacuum steady for a while, I would still have them use an electronic 134a leak detector after they charge it to confirm. If it is in fact low, there's no point filling it until you find out where it went. You might be ok for a while if it's a really small, slow leak but eventually you'll be right back at square one.
What's an electronic leak detector and how common is it at an indy shop?
Valid approach HZ60.I would be surprised if the factory fill PAG oil doesn't contain a tracer by now, but I've been surprised before !
Mark P if ever you decide to become a forensic accountant you'll do just fine.Great write up.Clearly shows the depth to which VCDS will let you go and that's just scratching the surface.
Haha, thanks Yeah, I like data acquisition and visualization of it. Check out my last 18 years of fuel and mileage Mark's S4 Quattrobonium
I noticed the PAG oil listed on that sticker. What is that?
What's an electronic leak detector and how common is it at an indy shop?
Electronic halogen leak detectors have been around for a long time, almost as long as I have. They have a small air pump inside to draw in air and various sensors to detect refrigerants. They either flash or beep or both with increasing frequency if a leak is detected. I used one for many years that was designed specifically for R-11, R-12 & R-22, guess that makes me a dinosaur. I'm sure there are electronic detectors for all the new fangled climate friendly stuff. I know for a fact that there's one for 410A, the R-22 replacement for residential units.
"PAG oil, or Polyalkylene Glycol, is a fully synthetic hygroscopic oil specifically designed for automotive air conditioner compressors. It is used in R-134a air conditioning systems to lubricate the compressor. When looking at PAG oil you will notice various numbers such as PAG46 or PAG100. These numbers refer to the viscosity of the oil, similar to 10W30 oil. In order to determine the correct PAG viscosity for your vehicle you will need to look up the specifications of your make and model of your vehicle either online or in the instruction manual" https://refrigeranthq.com/f-a-q/what-is-pag-oil/
Murray, I have the U.S. version of your Halocarbon certification. Here it's called an EPA CFC certification and there are several levels. I hold both Universal & Automotive certs.
Mark P the oil is introduced during the initial fill and roams around the system via the refrigerant gas.When you draw a vacuum on the system for a refill some, but not all of the oil is removed.When the refill is performed the Ac machine injects a quantity of oil based on the gas extracted.At least that's how my machine worked.
After seeing the A7 Advanced Measuring Blocks screen show "Compressor shut-off requirement", I inquired about where that is for the Q5 in standard Measuring Blocks. It's in 002.1 and the corresponding possible values are:
; 1 = Refrigerant Pressure too high. ; 2 = No Basic Setting ; 3 = Refrigerant Pressure too low. ; 4 = Engine running less than two seconds. ; 5 = Engine RPM too low ; 6 = ECON mode ; 7 = OFF mode ; 8 = Outside temperature too low ; 9 = Supply voltage too high ; 10 = Supply voltage too low ; 11 = Refrigerant temperature too high ; 12 = ECU load reduction request ; 13 = Refrigerant pressure sensor defective ; 15 = Refrigerant pressure 30x too high (?) ; 16 = Evaporator temperature below 0 °C ; 17 = Evaporator temperature below-5 °C ; 18 = Invalid outside temperature OR air temp at evaporator temperature defect. ; 21 = Outside temperature too low (with recirc) ; 22 = Outside temperature too low (without recirc) ; 24 = Compressor RPM too high ; 26 = Energy Management load reduction request ; 27 = No Basic Setting for Compressor Run-in.
I was excited to see that and wondered what my car would provide.
However, I also noticed that in 001.1 and 001.2 that electrical current values were provided and seemed to be non-zero in my tests when the compressor was on. I hypothesized that was directly related and got confirmation: That's the current to the compressor regulation valve. Should be less than 50 mA with the compressor off; between 300 and 800 mA with it running. 001.1 is the specified current 001.2 is the actual current.
So now what I realized was that in my prior tests, my compressor was indeed turning on. So it seems it wasn't any switch or sensor telling it not to. It was, and confirmed by it drawing current. Thus points again to likely just low refrigerant, either with or without a notable leak in system.
I still ran VCDS and found...
Car off: 3.2bar pressure and compressor off because of: ; 5 = Engine RPM too low
Car on, HVAC off: 3.2bar and compressor off due to: ; 7 = OFF mode
Car on, HVAC on, AC off: 3.2bar and compressor off due to: ; 6 = ECON mode
Car on, HVAC on, AC on: 5.4bar and compressor on as reflected by value of "0":
So now with this new info, I can see and update the pressure ranges as: (bar) S5: on: 13.4-14.4 Q5: off: 2.6-3.2, on: 4.2-5.4 A7: off: 7.8-8.4, on: 13.2-16.6
Time for recharge!
I'm happy with what I learned going through this process (so far).
After seeing the A7 Advanced Measuring Blocks screen show "Compressor shut-off requirement", I inquired about where that is for the Q5 in standard Measuring Blocks. It's in 002.1 and the corresponding possible values are:
; 1 = Refrigerant Pressure too high. ; 2 = No Basic Setting ; 3 = Refrigerant Pressure too low. ; 4 = Engine running less than two seconds. ; 5 = Engine RPM too low ; 6 = ECON mode ; 7 = OFF mode ; 8 = Outside temperature too low ; 9 = Supply voltage too high ; 10 = Supply voltage too low ; 11 = Refrigerant temperature too high ; 12 = ECU load reduction request ; 13 = Refrigerant pressure sensor defective ; 15 = Refrigerant pressure 30x too high (?) ; 16 = Evaporator temperature below 0 °C ; 17 = Evaporator temperature below-5 °C ; 18 = Invalid outside temperature OR air temp at evaporator temperature defect. ; 21 = Outside temperature too low (with recirc) ; 22 = Outside temperature too low (without recirc) ; 24 = Compressor RPM too high ; 26 = Energy Management load reduction request ; 27 = No Basic Setting for Compressor Run-in.
I was excited to see that and wondered what my car would provide.
However, I also noticed that in 001.1 and 001.2 that electrical current values were provided and seemed to be non-zero in my tests when the compressor was on. I hypothesized that was directly related and got confirmation: That's the current to the compressor regulation valve. Should be less than 50 mA with the compressor off; between 300 and 800 mA with it running. 001.1 is the specified current 001.2 is the actual current.
So now what I realized was that in my prior tests, my compressor was indeed turning on. So it seems it wasn't any switch or sensor telling it not to. It was, and confirmed by it drawing current. Thus points again to likely just low refrigerant, either with or without a notable leak in system.
I still ran VCDS and found...
Car off: 3.2bar pressure and compressor off because of: ; 5 = Engine RPM too low
Car on, HVAC off: 3.2bar and compressor off due to: ; 7 = OFF mode
Car on, HVAC on, AC off: 3.2bar and compressor off due to: ; 6 = ECON mode
Car on, HVAC on, AC on: 5.4bar and compressor on as reflected by value of "0":
So now with this new info, I can see and update the pressure ranges as: (bar) S5: on: 13.4-14.4 Q5: off: 2.6-3.2, on: 4.2-5.4 A7: off: 7.8-8.4, on: 13.2-16.6
Time for recharge!
I'm happy with what I learned going through this process (so far).
Nice work Mark! I took the liberty of saving your research data for future reference. Thanks! Just as an FYI, the normal operating pressures and temperatures measured at the service ports in an R-134a automotive system can vary due to several variables not found in say a residential system - engine rpm / compressor speed, airflow and air temperature over the condenser etc. The suction (low) side should read between 25-40 Psi which converts to a temperature range of 28.68 to 44.95 deg F. The discharge (high) side should run between 225-250 Psi or 138.7 to 146.3 deg F. These are just typical operating ranges, not set in stone. As always, evacuating and weighing in the proper charge is the best way to go.
Finally got an evac and recharge. It held vacuum for 15 mins with no loss so not evident of a leak. They added UV dye when they filled so we'll know incase it does leak in future where it is. Nice and cold again, and reported 6bar pressure engine off, hvac/ac "on", and 13.6bar pressure with car/hvac/ac on, now inline with other cars. Woohoo!
All done for $120, less than the dealer mere diagnosis fee if $155 nor the $285 they estimated when I asked fir a price for just evac/recharge. Also now had good experience with new to me indy shop I may benefit from in future.
09-28-2019, 02:56 PM
Yeah, I like data acquisition and visualization of it. Check out my last 18 years of fuel and mileage 
Mark's S4 Quattrobonium
