Aircon Compressor Not Engaging

[JayD]

My aircon compressor clutch isn't engaging. The blowers and climate control panel work fine, and if I give the compressor 12v direct from the battery the clutch engages. So I'm guessing either a compressor clutch wiring issue, or perhaps the relay our a fuse has failed.

I read it's a big yellow relay but can't see one under the bonnet - is it visible in the attached picture? Also is there a fuse dedicated to the compressor clutch?

 

[Ol’ Tarby]

Could need a regas. The compressor won't kick in if it's out of gas

 

[barnesautos]

The relay your after is the one at the back on the right . So it's closest to the wing .
Underneath is yellow wires , a thin grey wire and 2 larger pinkish wires that feed the clutch .
If the ECU doesn't see any gas pressure IE the system is empty it won't send an earth signal down the small grey wire to operate the relay

 

[JayD]

Thanks guys, I'll check it. I should have mentioned, my aircon guy confirmed it has enough gas (and he put it back in afterwards!). Is there any way to test the relay?

 

[Ol’ Tarby]

Thanks guys, I'll check it. I should have mentioned, my aircon guy confirmed it has enough gas (and he put it back in afterwards!). Is there any way to test the relay?

Stick 12v across the coil and see if it switches

 

[Mike@Rentech]

Pressure sensor probably faulty

 

[JayD]

Small update, the pink relay is for the interior blowers, not the aircon compressor. Removing it makes the blowers stop working.

The pressure sensor sounds like a possibility, since it didn't seem to suddenly die but seemed a poor before going completely, which could have been caused by the pressure switching toggling intermittently. Does anyone know which of the three pins in the conector I would need to short to test it?

 

[JayD]

Also, if needing to replace the switch, will I need to get it drained down to avoid it leaking or is it not in direct contact with the refrigerant?

 

[dane0]

mine had a cable running to the pump and upon wiggling that mine kicked in and out of engaging and i replaced that wire and its been fine ever since? runs dangerously close to the belts so it would have eaten though the cable?

 

[JayD]

Thanks will check that too.

 

[dane0]

Mine had a bullet connecter which seemed tight but with a pinch with the pliers never a problem again

 

[JayD]

Just an update, it turns out the issue was the connector for the pressure switch that is located near the top of the radiator (on the nearside) had come off. The connector and wiring were nowhere to be seen! It had somehow become unclipped and disappeared down into the depths of the engine bay. I managed to drop a spare bit of wire down from above which I then tied around the pressure switch wiring to allow me to retrieve it. All working now, though it reminded me it's probably due a regas come the summer.

Thanks for everyone's help.

 

[dane0]

Just an update, it turns out the issue was the connector for the pressure switch that is located near the top of the radiator (on the nearside) had come off. The connector and wiring were nowhere to be seen! It had somehow become unclipped and disappeared down into the depths of the engine bay. I managed to drop a spare bit of wire down from above which I then tied around the pressure switch wiring to allow me to retrieve it. All working now, though it reminded me it's probably due a regas come the summer.

Thanks for everyone's help.

The simple things are the worst in cases like this because it's so annoying it was so simple! But also a bonus it's a free repair