Hello everyone,

Since I bought my 2002 X-type I've had a problem with my AC, when it's turned on every few hundred meters on the highway I feel a little thump from the engine which I suggest is the magnetic coupling engaging and disengaging.
When inspecting the AC compressor I saw it was leaking oil and fluor quite badly around the axle seal so I decided to change it for a brand new one from Nissens. Hoping that this would fix the problem, but even after changing the AC compressor and filling it up to specs the problem consists.

I now feel it even more because the old compressor was totally worn out (could spin it with the ports closed with one finger), new one was quite hard to spin around by hand.

So now I'm thinking there is some kind of faulty sensor, or maybe a incorrect readout of the AC pressure which is causing it to disengage the coupling to protect the system. It engages after a few seconds and then you feel the bump. The AC keeps the car nice and cool, but this is causing unnecessary wear on my new compressor and clutch.

Anyone of you familiar with this problem? And any idea's where to start looking?
Faulty sensor? Faulty relay?

Greetings Marco

 

The AC clutch relay (R6 in the front power distribution fuse box) can eventually develop intermittent contact problems, so you might just try replacing that as a first quick and cheap elimination step.
You might try swapping R5 and R6 as a test. R5 is the power wash pump relay, so should be no issue trying it as long as it is the same type of relay.

 

I've swapped the relay from the horn with the one from the ac clutch. Problem persisted, any other ideas?

I find it strange that it only disengages the clutch for a few seconds, in my opinion if the system is damaging itself (too high pressure for instance) it would stay off or isn't this correct?

 

I have the fully manual climate system btw, don't know if that matters.

 

I've not had much to do with car AC systems, but reading other threads over the years it could be an over pressure issue that is causing the system to disengage.
If too much refrigerant is loaded into the system, it might cause the effect you have.
I'm not sure if a blocked orifice might also cause tripping out, but more likely just poor efficiency.

Another forum member is likely to have far better AC experience and insight than me on this subject, so I hope someone else will chime in to give some additional thoughts.

Looking a the schematics, you appear to have only two temperature sensors.

1. An Evaporator temperature sensor which connects back to the manual climate controller AC1 connector (pin 14 - Green wire).
2. And the Discharge temperature sensor which also connects back to the manual climate controller AC1 connector (pin 15 - Blue wire with Yellow stripe).

These sensors are NTC (Negative Temperature Coefficient) which will give a voltage reading between 0-5 volts to the controller (NTC sensors will make the voltage on the respective connector pins decrease when they detect an increase of temperature).
You might just want to check that you have some voltage on these two pins of the connector, that it is not at one extreme or other that might indicate a loom short (zero volts) or potential open circuit to a sensor (5 volts).

Apart from that, if it is not mechanical (incorrect refrigerant loading or circulation restriction) I can only think it might be the AC controller is having an issue.

Sorry I could not be of more help on this particular subject.....but another member is likely to offer some "pearls of wisdom".

 

Did you vacuum the moisture out of system before adding refrigerant

 

Thanks h2o2steam for you're reply, I'm gonna try that out.

And yes they pulled a vacuum for 20 minutes before filling up the refrigerant. If the system froze up I guess I would throw a fault code?