C3 A51 Air Con Compressor not turning

[abyj]

Got it - So the likely scenario of what happened is that the coil in the compressor clutch failed taking out the BSM, which as a result is now not sending the correct signals on to the compressor. So in theory if I replace the BSM and the compressor clutch the AC should be back in business. Any complications replacing the BSM? - just simple plug the new one in and it should work? i.e. no programming or gotchas?

[ozvtr]

There is no "coding" required for the BSM.
I am not too sure about the current crop of BSM's. There were multiple versions of the original BSM's BUT later ones appear to all be the same. The diesel versions may have extra circuits for heaters and what-not.

[abyj]

An update on this in case anyone has a similar issue one day. I purchased a new coil off alibaba and found a second hand BSM on ebay. It was hard to find the correct size coil to get as I hadn't yet taken the old coil out the car - alibaba had multiple coils for the same air compressor part number for my car. Anyway, to prevent the old BSM potentially damaging the new coil (in case that's what caused the coil to fail) I replaced the BSM first. On testing, I found that the voltage across the coil plug still did not show 12V. Also the fault codes could not be cleared, i.e. they persisted even with the replacement BSM. I was worried I might have a dud BSM. But I read somewhere that someone plugged a bulb across the solenoid plug and that cleared the faults. So I plugged in the new coil and voila!, the faults cleared. I should have tried testing with the bulb before getting the BSM, because now I'm not sure I needed the replacement BSM. Anyway, bottom line is that the clutch now engages! The compressor turns. Hooray! Replacing the coil was pretty straight forward, no special tools needed. With the wheel arch/guard removed there was ample space to work with - remove the nut (use the locator plugs to get leverage to undo the nut), slide off the clutch and spacer, remove the circlip, remove the pulley (actually I needed a gear/jaw puller to get this off), remove the circlip, remove the coil. Reverse order to get back together.

However the aircon is still not blowing cold - I hear a hissing sound from the vents/dashboard on the inside of the car, and research so far suggests that a regas will sort out the issue (although the pressure shown in Lexia 3 with the compressor running varies around 10bar, so shouldn't be a low gas/pressure issue) - I'll raise this under another topic to close this topic out... Thanks all for your help.

[ozvtr]

I purchased a new solenoid off alibaba and found a second hand BSI on ebay.

You mean coil and BSM?

On testing, I found that the voltage across the solenoid plug still did not show 12V. Also the fault codes could not be cleared, i.e. they persisted even with the replacement BSI. I was worried I might have a dud BSI. But I read somewhere that someone plugged a bulb across the solenoid plug and that cleared the faults. So I plugged in the new solenoid and voila!,

This shows the BSM monitors the impedance of the coil circuit and shuts down power if there is no continuity. Interesting. A digital miltimeter would have too high an impedance to cause current flow. BUT an incandescent lamp would have a low impedance and so the BSM would then power the coil circuit.
Don't you love programmers? Instead of telling you what's wrong, they just say "Hey dude, like there's something wrong man. I'd tell you what's wrong but it's cutting in to my gaming time bro".

However the aircon is still not blowing cold - I hear a hissing sound from the vents/dashboard on the inside of the car, and research so far suggests that a regas will sort out the issue (although the pressure shown in Lexia 3 with the compressor running varies around 10bar, so shouldn't be a low gas/pressure issue) - I'll raise this under another topic to close this topic out... Thanks all for your help.

Yes, hissing, is a classic sign of under charge. Should be around 7 bar WITHOUT the air con running and around 17 to 20 WITH the air con running.
You are lucky. If the pressure was any lower, the AC system would not run (under pressure cut off)...and you would be even more confused, because you wouldn't consider 2 independent faults (coil AND refrigerant loss at the same time).

[abyj]

I purchased a new solenoid off alibaba and found a second hand BSI on ebay.

You mean coil and BSM?

Yes, I did. Updated my post above to prevent any confusion.

However the aircon is still not blowing cold - I hear a hissing sound from the vents/dashboard on the inside of the car, and research so far suggests that a regas will sort out the issue (although the pressure shown in Lexia 3 with the compressor running varies around 10bar, so shouldn't be a low gas/pressure issue) - I'll raise this under another topic to close this topic out... Thanks all for your help.

Yes, hissing, is a classic sign of under charge. Should be around 7 bar WITHOUT the air con running and around 17 to 20 WITH the air con running.
You are lucky. If the pressure was any lower, the AC system would not run (under pressure cut off)...and you would be even more confused, because you wouldn't consider 2 independent faults (coil AND refrigerant loss at the same time).

Good to know on the pressures - I was searching online to find out what the good range should be, but not able to find anything.
To save a few $$, I was looking at this product, any experience with it?
https://hychill.com.au/products/minus-30
https://www.amazon.com.au/HyChill-Minus ... d_source=1

[ozvtr]

Ha, ha, ha. The biggest problem with that stuff is that you will get brow beaten by every Helen Lovejoy on the planet! Because it's flammable. ("Won't somebody think of the children!")
It's a mixture of propane and butane. Not legal for that use in some Australian states. In many parts of the world it is legal.
HOWEVER flammability is it's ONLY disadvantage.
1) Global warming (green house gas) index of 0! NOT a green house gas. Occurs naturally.
2) Compatible with all oils, including PAG and POE. So it's compatible with what oil is in the system now.
3) Lower pressures required to change state. Less work for the engine to compress the gas. Slightly better fuel consumption (when using the AC compared to other refrigerants). Slightly more power at the wheels (when using the AC compared to other refrigerants). Not much. But every bit counts.
4) Requires about 1/3 of the volume of synthetic refrigerants. If an average charge of refrigerant R134a was 600 grams (it varies from car to car), then you would need less than 200g of Hychill.
5) Cheap. Propane and butane are cheap to produce. ALL synthetic refrigerants are produced by Dupont! And they charge a pretty penny for it!! They know that auto manufactures are trying to make a "greener" AC system AND trying to bring down the cost of production. So Dupont is charging a S#!t load for R1234yf, before time runs out!!!!
6) Does not form acids in the presence of moisture.
There are 2 reasons why the system needs to be vacuumed down to get rid of the moisture.
1) Moisture will form ice on the TX valve and inhibit its efficiency.
2) When combined with synthetic refrigerants (R12, R134a and R 1234yf) moisture (water) forms very nasty acids that loves to eat metal parts of the AC system! Particularly Aluminium! Not a problem with propane.
Have I gone on enough yet?
The major problem the authorities have is that the gas goes through the fire wall and into the evaporator in the cabin.
They have no problems with it in the engine bay as fire fighters can use the same solutions as a petrol fire. And 200g of propane wont burn for long.
The funny thing is that they have no problems putting 20-30 KILOs (!) of LPG in the boot to power the car. There is NO firewall in the boot of modern cars so it is considered part of the cabin!
Have I used it? You guess.