don't want to hijack but am I right in thinking the N280 's pulsed power is 12v and fed permanent live and pulsed  " -- "  thro' the controller ? 

don't want to hijack but am I right in thinking the N280 's pulsed power is 12v and fed permanent live and pulsed  " -- "  thro' the controller ? 

No, it looks to be the other way round, unusually. Pin 2 of the N280 is permanently grounded, and Pin 1 is a PWM'd drive from the AC control module. That's how it is in the first wiring diagram I looked at anyway, surely must be consistent throughout?

Check the ECU coding. My other Fabia didn't want to run the AC because ECU simply thought the car wasn't equipped with such thing. The compressor is switched on by an electro magnetic switch operated by the ECU. It's powered by a 7.5V current IIRC, so simply getting a + from the battery might just fry it for good.

 

ECU coding as follows:

00061 petrol engine and air con
00071 petrol engine ABS and air con
00005 diesel engine and air con
00006 diesel engine air con and ABS

 

as per this.

 

It worths a shot. Coding this takes less than 1 minute.

Edited 13 June, 201610 yr by Alexandru

thanks chaps :sun:

Alexandru, remember the "electro-magnetic switch" (coupling) usualy is how the older "on demand fixed displacement" compressors were described, these "always on at reduced duty cycle variable displacement" compressors are controlled differently, it is a solenoid that moves the swash plate (or wobble plate) inside the compressor to change its displacement as demanded by the air con system, and maybe even inhibiting the air con during periods of big demands on the engine for acceleration.

Alexandru, remember the "electro-magnetic switch" (coupling) usualy is how the older "on demand fixed displacement" compressors were described, these "always on at reduced duty cycle variable displacement" compressors are controlled differently, it is a solenoid that moves the swash plate (or wobble plate) inside the compressor to change its displacement as demanded by the air con system, and maybe even inhibiting the air con during periods of big demands on the engine for acceleration.

Ah, interesting. I feel an experiment coming on.  In previous logs I'd wondered what the "Compressor shutoff" codes column meant, and going back over this thread I see that Dazza95 gave us this link back in post #11 that explains what they mean.  I've only seen codes 5 and 12, before/at start up, but yeah, might well see code 12s in high acceleration/power conditions. 

Edited 14 June, 201610 yr by Wino

From what I have read on a Ibiza forum, I'm not sure if all VAG cars with this compressor actually use that function/action, though it might have been that the guy that posted having trouble with power while air con was enabled had not reached FOT - as a side note, I think that lots of cars with smart charging also, if conditions allow, unload the alternator with FOT - and as some cars still have an electro-magnetic clutch on the compressor - I'd guess they also knock out the air con with FOT - me, well normally too cold up here to need air con and never use FOT unless car(s) deserve it after being allowed to "go flat" at an tricky moment!

Tried and failed to generate an engine-power code 12 shutoff this morning. An uphill section of dual carriageway from a roundabout, full throttle for about 30 seconds interrupted only briefly by a gearchange, no sign of compressor shutoff on the log.  So either you have to try harder, or it isn't implemented on 9N Polo, I suspect the latter

Maybe it's not working when under full throttle under normal driving scenes. Basically, the engine delivers all it's goods in that situation and the power 'lost' via compressor working isn't that significant. IMHO, it should cutoff when the engine is dying for any reasons, like driving uphill in the wrong gear and rpms are dropping too much. Another hypothesis would be that the engine is redlined or at least it's turning too fast than the compressor can keep up with.

Edited 20 June, 201610 yr by Alexandru

It is a bummer. I edited a little image into my previous post that explains the system.  Not really sure it's a wise design to destroy the compressor instead of the belt, but hey-ho, guess it drives the water pump on lots of the engines.

 

:'(

As its constantly driven the idea is if the compressor seizes the coupling breaks so the belt doesn't get thrown off causing loss of drive to components and damage.

I didn't realise Fabia had shut off codes, I thought that was something introduced on A5 chassis. A good indication why the system is inactive if it's a reason controlled by the ECU, ie low pressure, wiring issue etc.