CDTI aircon

pletevl · 10th April 2021, 13:04

Hi all,

The air con on my 75 CDTI packed up last summer. I never got round to looking at it until today.

I have a DELPHI DS150 car diagnostics reader. I plugged it into the 75 and checked a few things out.

I can test the radiator fan and both speeds are working correctly.

When I click on test the compressor, nothing is happening, not even a click of any sort.

Any ideas ?

Thanks.

Pete.

mh007 · 10th April 2021, 13:44

The test you are doing is for the AC compressor clutch yes?

Even if the AC system is out of gas, you should still hear the clutch 'kick in' at least (during the component test).

So, I would be checking power to the compressor & working your way back.

If you have power at the compressor, I would say the actual compressor has failed or the compressor clutch has seized.

SD1too · 10th April 2021, 15:05

Hi Pete,

I'd suggest that you put your diagnostics reader away and do the standard checks.

With engine running press the windscreen demist button. Does the compressor clutch engage?
If it doesn't engage, locate the single red wire supplying the compressor clutch and place your voltmeter on it. Do you see +12v?
If no, you may have low refrigerant gas. Book a mobile specialist to extract and check that you have 450g.

Simon

pletevl · 10th April 2021, 16:38

Simon, When doing that test the clutch does not engage. I have not measured the voltage on that red wire, I will and let you know.

Pete.

Mike Noc · 11th April 2021, 10:14

Quote:

Originally Posted by SD1too

Hi Pete,

I'd suggest that you put your diagnostics reader away and do the standard checks.

With engine running press the windscreen demist button. Does the compressor clutch engage?
If it doesn't engage, locate the single red wire supplying the compressor clutch and place your voltmeter on it. Do you see +12v?
If no, you may have low refrigerant gas. Book a mobile specialist to extract and check that you have 450g.

Simon

Far better to do the test the OP has carried out Simon.

That way you are directly testing the component you want to check out, and if it doesn't engage it can only be the clutch itself or the supply to it.

pletevl · 11th April 2021, 10:51

Mike, even if the system is low on gas, the clutch would engage with this test?

Pete.

SD1too · 11th April 2021, 11:12

Quote:

Originally Posted by pletevl

... even if the system is low on gas, the clutch would engage with this test?

No Pete, that doesn't follow when you're following my recommended procedure. If the refrigerant pressure is too low the trinary switch will instruct the ECM to inhibit operation of the compressor by not engaging the clutch.

Please continue with the three points I gave you. If you see +12v at the compressor clutch then that will confirm a fault, but I think the most likely scenario is that your system is low on refrigerant gas.

Simon

mh007 · 11th April 2021, 17:55

Quote:

Originally Posted by SD1too

No Pete, that doesn't follow. If the refrigerant pressure is too low the trinary switch will instruct the ECM to inhibit operation of the compressor by not engaging the clutch.

Please continue with the three points I gave you. If you see +12v at the compressor clutch then that will confirm a fault, but I think the most likely scenario is that your system is low on refrigerant gas.

Simon

I use a Snap On Modis Ultra & this test does work with ignition on/engine off when doing a component test even with a system that is low on gas (too low to allow the A/C system to operate normally).

Also works on a Triton that I'm 'test driving'.

Mike Noc · 11th April 2021, 18:59

Quote:

Originally Posted by pletevl

Mike, even if the system is low on gas, the clutch would engage with this test?

Pete.

Yes Pete this is a manual diagnostic A/C clutch check.

SD1too · 12th April 2021, 07:25

Quote:

Originally Posted by Mike Noc

Far better to do the test the OP has carried out Simon.

That way you are directly testing the component you want to check out, and if it doesn't engage it can only be the clutch itself or the supply to it.

Quote:

Originally Posted by Mike Noc

Yes Pete this is a manual diagnostic A/C clutch check.

Hi Mike,

Pete has already performed the manual diagnostic clutch check hasn't he, and the result was no response. You've said that this indicates either a clutch fault or no supply to it. I'm sure we both agree that it would be sensible that the next step is to check for the presence of a voltage and that is exactly what I have recommended to Pete. His Delphi DS150 cannot do that for him.

So Pete we're waiting for you to get out your multimeter!

Simon

10th April 2021, 13:04	#1
pletevl Posted a thing or two rover 75 cdti(rhd), MG ZR(lhd), MG TF(lhd), MG TF(rhd), mini mpi (lhd), Renault megane III (awful) Join Date: Mar 2014 Location: East of France Posts: 1,278 Thanks: 124 Thanked 114 Times in 93 Posts	CDTI aircon Hi all, The air con on my 75 CDTI packed up last summer. I never got round to looking at it until today. I have a DELPHI DS150 car diagnostics reader. I plugged it into the 75 and checked a few things out. I can test the radiator fan and both speeds are working correctly. When I click on test the compressor, nothing is happening, not even a click of any sort. Any ideas ? Thanks. Pete.

10th April 2021, 15:05	#3
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,337 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Hi Pete, I'd suggest that you put your diagnostics reader away and do the standard checks. With engine running press the windscreen demist button. Does the compressor clutch engage? If it doesn't engage, locate the single red wire supplying the compressor clutch and place your voltmeter on it. Do you see +12v? If no, you may have low refrigerant gas. Book a mobile specialist to extract and check that you have 450g. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce. Last edited by SD1too; 10th April 2021 at 15:09..

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10th April 2021, 13:44	#2
mh007 This is my second home MG ZT260 SE, MG ZT190+, MG ZTT 160, R75 Conn SE 2.0, R75 Conn SE 2.5 X 3, R75 Club SE 1.8, P5B Coupe Join Date: Jul 2009 Location: Keynsham, Bristol Posts: 4,211 Thanks: 65 Thanked 635 Times in 499 Posts	The test you are doing is for the AC compressor clutch yes? Even if the AC system is out of gas, you should still hear the clutch 'kick in' at least (during the component test). So, I would be checking power to the compressor & working your way back. If you have power at the compressor, I would say the actual compressor has failed or the compressor clutch has seized.

10th April 2021, 16:38	#4
pletevl Posted a thing or two rover 75 cdti(rhd), MG ZR(lhd), MG TF(lhd), MG TF(rhd), mini mpi (lhd), Renault megane III (awful) Join Date: Mar 2014 Location: East of France Posts: 1,278 Thanks: 124 Thanked 114 Times in 93 Posts	Simon, When doing that test the clutch does not engage. I have not measured the voltage on that red wire, I will and let you know. Pete.

11th April 2021, 10:51	#6
pletevl Posted a thing or two rover 75 cdti(rhd), MG ZR(lhd), MG TF(lhd), MG TF(rhd), mini mpi (lhd), Renault megane III (awful) Join Date: Mar 2014 Location: East of France Posts: 1,278 Thanks: 124 Thanked 114 Times in 93 Posts	Mike, even if the system is low on gas, the clutch would engage with this test? Pete.