C3 A51 Air Con Compressor not turning

[abyj]

I have a C3 1.6L A51 and the air con is not working. It's a Sanden 1363F (9670318880). I see the air con compressor is not turning, seems the clutch is not engaging. I checked fuses F4 and F14, they are fine. Any tips to troubleshoot? Can just the clutch be replaced on these models? I saw this post, which has some good ideas, that I can try if the clutch can be repaired/replaced. viewtopic.php?p=801580#p801580.
Any other tips or posts to have a look at?

I don't have a Lexia, but that's another post I've enquired on.

[Steve Walsh]

The clutch wont engage if the pressure is low in the system, Clutch can be tested, test for 12v at supply wires, if you have 12v there try 12v into compressor

[PaulC5]

If the air con has not been regassed in recent years it probably needs doing. Taking it to a garage that does air con will check everything and this check and regas will be a lot cheaper than replacing the compressor hoping that it is at fault.

[ozvtr]

Ah! A future Queenslander!

Get a cheap multimeter from Supercheap or REPCO or JAYCAR or EBAY Or whatever! Don't pay more than 10 bucks! A cheap meter is all you need.
Check for power at the two contacts of the yellow clutch connector.
Remember one side of the electrical connector is connected to the car (look for volts) and one side is connected to the coil (look for Ohms)!

If you have power there then it's either the clutch coil or adjustment of the clutch. Use the meter on Ohms and check the resistance of the coil, it should be low Ohms. If you get high Ohms the coil is stuffed. If you get low Ohms swap the probes around. low ohms good, high ohms bad.
If you get low Ohms both ways and you have power there, with the engine running and the AC on, try tapping the face of the clutch with a rubber mallet or the like.

If you have no power there AND you are sure the fuses are OK the most likely culprit is the lack of gas. You would need a set of service gauges to check the system pressure. At rest it should be around 100 psi. Anything below (I think) 50psi will shut the system down. There are a million things that can cause the gas to leak out. Damage to lines (fracturing, rubbing), badly crimped fittings (seen that), leaking schrader valves in the service ports, damage to the condenser from stones! And so on.
Leakage is not the only thing that will shut the system down. Problems with the radiator fan(s) and over pressure are only a couple of other things that could shut the AC down. But a lack of gas is the usual suspect.

Also for help closer to home you can try the "Aussiefrogs" website.

[abyj]

Thanks all.
@steve I can see no voltage coming into the compressor at the plug which is at the end of the clutch/pulley when the car is on and aircon turned on in the cabin (measuring the plug coming from the car, thanks @ozvtr). So it could be a pressure issue, the previous owner refilled the aircon not long before I purchased it, but as you said could have lost pressure due to a variety of reasons. However, if I apply 12V to the other side of the plug, i.e the part that looks connected to the clutch/pulley end of the compressor, which I would expect would activate the clutch, I still see no response, i.e. compressor does not turn!

What ac diagnosis info does the Lexia3/Diagbox give me, when that arrives?

[Steve Walsh]

You should be able to activate the clutch without the engine running when you give it 12v, you can see and hear it pulling in. I think diagbox might give you some clues but I cant remember . If it was regassed recently I would have it checked at a garage, chances are you have a leak

[ozvtr]

If the compressor clutch won't engage when 12v is applied to the clutch coil, then I doubt the compressor actuator test would work.
Unfortunately LEXIA will only tell you that the AC system is enabled or disabled not why. If you are lucky it might tell you what the "high side" AC pressure is (depends on the car).
Is the clutch coil drawing excessive current? Or no current?
Be careful, some coils have a built in diode to quench the back EMF from the coil. If you have the polarity incorrect from your test supply you may just get a short across the diode.

I would ignore the fact that there is no voltage from the BSM at this time (one problem at a time).

Yes, the usual suspects like EBay and Aliexpress have clutch coils for sale. But ascertain one fault at a time.

[abyj]

If the compressor clutch won't engage when 12v is applied to the clutch coil, then I doubt the compressor actuator test would work.
Unfortunately LEXIA will only tell you that the AC system is enabled or disabled not why. If you are lucky it might tell you what the "high side" AC pressure is (depends on the car).
Is the clutch coil drawing excessive current? Or no current?
Be careful, some coils have a built in diode to quench the back EMF from the coil. If you have the polarity incorrect from your test supply you may just get a short across the diode.

I would ignore the fact that there is no voltage from the BSM at this time (one problem at a time).

Yes, the usual suspects like EBay and Aliexpress have clutch coils for sale. But ascertain one fault at a time.

I would say the clutch was drawing excessive current - When I applied the 12V, the cables from the 12V supply got super hot very quickly! I connected the green/yellow cable to gnd and the other colour (red I think) to +ve. It is tricky to get to the spade connectors in the plug, and maybe the crocodile clips I used touched inside the plug, and that caused a short circuit - However, I did check this before with the continuity functionality in the multimeter and it suggested they weren't touching - but they're so close, it could have move between testing and applying the 12V... If I find a way to be sure they're not touching using some other terminals, I'll try that.
Makes sense that if the clutch isn't engaging then there could be a fault with the clutch. Is there a certain resistance the clutch internals/coil should be? I tried searching technical data sheets for this compressor, but not found anything useful.

As you say, once I've worked the clutch out, I can move on to why there's no signal coming from the car to engage the clutch.

[xantia_v6]

It is not a good idea to apply an un-fused 12V supply to the compressor clutch, as they typically have a suppressor dioode built in, and if 12V is applied with the wrong polarity, it will cause the diode to go short-circuit, effectively destroying the clutch coil. The coil resistance should be between 1 and 5 Ohms.

Diagbox will tell you if the compressor clutch is energised, and if it is not, then it will tell you if the compressor has been inhibited due to a pressure fault or by the engine ECU, which should then lead you to an engine fault code.

[Steve Walsh]

It is not a good idea to apply an un-fused 12V supply to the compressor clutch, as they typically have a suppressor dioode built in, and if 12V is applied with the wrong polarity, it will cause the diode to go short-circuit, effectively destroying the clutch coil. The coil resistance should be between 1 and 5 Ohms.

Diagbox will tell you if the compressor clutch is energised, and if it is not, then it will tell you if the compressor has been inhibited due to a pressure fault or by the engine ECU, which should then lead you to an engine fault code.

Thats interesting, I have had a few apart over the years and not found a diode, Ohms test on a good coil will usually give a resistance reading which ever way you connect the test leads, I would have thought a diode would stop a reading one way but I could be wrong..

[ozvtr]

Diagbox will tell you if the compressor clutch is energised, and if it is not, then it will tell you if the compressor has been inhibited due to a pressure fault or by the engine ECU, which should then lead you to an engine fault code.

ABYJ says he applied -ve to green/yellow and +ve to the other wire, which is correct polarity.

You might not get a fault code for AC low pressure. Not all engine ECU's report AC pressure. The A51 C3's don't run what you might call, sophisticated engine ECU's. I have a SAGEM 1.4 petrol ECU in my C3's and a BOSCH 1.6 petrol ECU in my C2. They do not report AC pressures. Just clutch inhibited or not, but no reason! And no engine fault codes associated with AC at all. Having said all that I don't know what engine/ECU is in this car.
DIAGBOX will tell you that it THINKS that it has applied power to the clutch coil but I don't believe that there is any feedback from the power circuit to indeed confirm that power has actually been applied to the coil. The actuator test asks the operator to listen for and confirm that the clutch is actuating (as ACTUAL confirmation that it's working). But in this case we know the coil is not working. However it would be helpful to know that nothing (else) is inhibiting the AC.

Unfortunately I suspect that the clutch coil has gone short circuit and taken out the driver transistor in the BSM. Yes, it should have taken out the fuse first. But i have seen crazier stuff. You could make sure that there is power on both sides of the clutch fuse in the BSM (I'm not sure if you have done that).

Logically, the next step would be to remove and replace the clutch coil, then activate it by applying independent power.
The question is; are you up to the task?

[abyj]

Diagbox will tell you if the compressor clutch is energised, and if it is not, then it will tell you if the compressor has been inhibited due to a pressure fault or by the engine ECU, which should then lead you to an engine fault code.

ABYJ says he applied -ve to green/yellow and +ve to the other wire, which is correct polarity.

You might not get a fault code for AC low pressure. Not all engine ECU's report AC pressure. The A51 C3's don't run what you might call, sophisticated engine ECU's. I have a SAGEM 1.4 petrol ECU in my C3's and a BOSCH 1.6 petrol ECU in my C2. They do not report AC pressures. Just clutch inhibited or not, but no reason! And no engine fault codes associated with AC at all. Having said all that I don't know what engine/ECU is in this car.
DIAGBOX will tell you that it THINKS that it has applied power to the clutch coil but I don't believe that there is any feedback from the power circuit to indeed confirm that power has actually been applied to the coil. The actuator test asks the operator to listen for and confirm that the clutch is actuating (as ACTUAL confirmation that it's working). But in this case we know the coil is not working. However it would be helpful to know that nothing (else) is inhibiting the AC.

Unfortunately I suspect that the clutch coil has gone short circuit and taken out the driver transistor in the BSM. Yes, it should have taken out the fuse first. But i have seen crazier stuff. You could make sure that there is power on both sides of the clutch fuse in the BSM (I'm not sure if you have done that).

Logically, the next step would be to remove and replace the clutch coil, then activate it by applying independent power.
The question is; are you up to the task?

The same fuse is used on the instrument panel and I have no issues there, i.e. there must be power on both sides of the fuse.

I retested the clutch using some insulated spade connectors and can confirm that the compressor clutch measures almost 0 ohms. So the clutch seems to have failed (does it really matter which way you measure? not sure I measured both ways). However, there must be some other issue because there is no voltage coming in to the clutch when the A/C is turned on in the cabin. I need to resolve that before replacing the clutch.

The Lexia3/Diagbox arrived during the week and I had a look at the live values and fault codes on the BSI ECU today:
The live values indicate no issue with pressure - it reports:
'refrigerant pressure' of 5.3bar
'low pressure safety' and 'high pressure safety' as inactive
(so refrigerant pressure is not causing no voltage to come through to the clutch) Other interesting values:
'engine coolant safety device' as active - what is this? I'm assuming nothing to worry about as the BSI reports these other values:
'status of the air conditioning compressor clutch' as clutched.
'air conditioning compressor request' as active
'refrigeration compressor control' as active
'compressor authorisation output control' as active
'compressor authorisation information' as active

2 fault codes showing in the BSI and BSM:
F994 - Engine Fusebox: Fault in the air con compressor clutch control circuit
F995 - Engine Fusebox: Fault in the air con compressor variable capacity piloting control circuit

Does anyone know how I can get a wiring diagram? Where are the relays that control the aircon? The diagram might help me to diagnose these faults. Should I be able to see wiring diagrams in DiagBox? I have internet turned off on my DiagBox laptop so it may be trying to download them...
Anyway, thanks to you all for your help so far!

[ozvtr]

The later model BSM's don't have relays, they have power transistors (to drive the clutch). They are also potted making them virtually impossible to repair.
And from your LEXIA reports it looks like the BSM does monitor the clutch control circuit.
A quick look at the circuit diagram shows no fuses associated with the clutch circuit! The closest thing is a fuse for the interior fan motor.
Clutch power comes out of pin 1 and pin 5 of the 5 pin yellow connector on the BSM. A green wire with a yellow stripe is always chassis ground.
As I said before looks like the clutch coil has gone short circuit and taken out the BSM.

[abyj]

The later model BSM's don't have relays, they have power transistors (to drive the clutch). They are also potted making them virtually impossible to repair.
And from your LEXIA reports it looks like the BSM does monitor the clutch control circuit.
A quick look at the circuit diagram shows no fuses associated with the clutch circuit! The closest thing is a fuse for the interior fan motor.
Clutch power comes out of pin 1 and pin 5 of the 5 pin yellow connector on the BSM. A green wire with a yellow stripe is always chassis ground.
As I said before looks like the clutch coil has gone short circuit and taken out the BSM.

Thanks ozvtr - were you impacted by Cyclone Alfred?

I found this post, viewtopic.php?t=72256, which is a similar model car, guessing the aircon wiring won't be majorly different, however it shows different pin numbers for power to what you mentioned. Aside from that, what I'm worried about is, if I just go replace the BSM and clutch, that whatever caused the issue in the first place re-occurs. So keen to understand the cause, if I can.

[ozvtr]

Thanks ozvtr - were you impacted by Cyclone Alfred?

Thanks for asking. Not really, I'm in Ipswich. Copped flooding around the area but the wind didn't reach this far inland.

I found this post, viewtopic.php?t=72256, which is a similar model car, guessing the aircon wiring won't be majorly different, however it shows different pin numbers for power to what you mentioned.

Your link shows basically the correct circuit. But it has some errors. The compressor is labeled 8020 but the symbol is incorrect (that's just me being picky). The compressor has 2 electrical connectors, 1 black, 1 yellow. The black one (NR=Noire, French) is on the "back" of the compressor and regulates the refrigerant pressure. The yellow one is the compressor clutch. It's the same as I said.
As you can see power comes from pin 1 of the 5pin (5V) yellow (JN=Jaune, french) connector of BSM (labled PSF1, again french). Did you get all that? HOWEVER THERE IS NO RETURN WIRE!!! There should be a wire connected to the black dot!!! It should go either to chassis ground or back to the BSM (pin 5)!
As you can see, the BSM does have 2 relays BUT, none of them are connected to the compressor. The compressor is connected to a "chip" symbol, meaning it's a solid state control device (no fuse, well not one for the clutch alone).

Aside from that, what I'm worried about is, if I just go replace the BSM and clutch, that whatever caused the issue in the first place re-occurs. So keen to understand the cause, if I can.

The clutch coil is just that, a coil of very fine "enameled copper wire". The enamel is an insulator and is very thin. The enamel can break down for a number of reasons (usually heat) and expose the copper to another layer and short out the coil. It's not uncommon. Any electrical device manufactured like this can have this happen. Devices like motors, solenoids and relays can all suffer this. It's a lucky dip you might say. It's possibly a manufacturing defect. If you buy an aftermarket coil, at least it won't be the same manufacturer. But that's your call.