I think the compressor clutch is operated by a relay, which I think is in the engine bay fuse box.

 

Pressure isn't really a reliable indication of enough refrigerant especially if the compressor is not running.

E.g. this morning my ZS had 25psi on the low pressure side when running but wasn't cooling. After a recharge, still 25psi but the air is blowing 13ºC (next job being to clean the condenser..)

With the compressor off you could be looking at 45psi on the low side which might still not be enough.

I suggest trying a recharge at a no-cooler-no-fee place.

 

Well, checked the fuse and relay in the engine bay. Both are OK. The realy is the same as the one for the front fog lights, they work, so swapped the relays over. The lights still worked with the relay from the AC, but the AC not so the issue lies elsewhere.

Presumably the compressor (which as far as I can determine is on the front bottom of the engine, offside) is turned on/off with a clutch of some sort on the side of the housing, and run off one of the belts?

Would this indicate an electrical fault?

Or as Now2 has suggested, low gas level in the system? Anyone know if the pressure on the system is too low, whether the system defaults to a "safe" mode and does not run?

 

if the pressure on the system is too low, whether the system defaults to a "safe" mode and does not run?

Yes, it will not engage the compressor if there is not enough refrigerant.

Discount the most likely issue first before looking for electrical problems.

When filling it is important to remember that refrigerant is measured by weight, not pressure.

 

There is a pipe that runs through a hole in the bodywork, close to the mesh in the front bumper. This pipe rubbed through on mine and leaked it's gas out. The pipe leads to the receiver dryer, which is a cylinder close to the bumper, below the battery, with 2 small pipes connected to it, and an electrical plug on top.

Not sure if the ZS180 is prone to the same fault, but it is worth checking.

 

Thanks for the pointer. All my pipe work runs within the engine bay, the only place it goes through bodywork is where it goes through the bulkhead. I guess some pipe work may be re-routed because of the V6 configuration. Will check closely anyway. Cheers!

 

There are 2 fill points on the 180, one at the battery and one near the water expansion tank, which is high pressure and which is low?

 

One on the bulkhead is low, as far as I know.

 

I think the thicker pipes are the low pressure ones.

 

I have good pressure in the system, but no action when button is pressed with engine on and blower set to cold and on.

 

Same symptoms as me. Personally, I think next step for me is to have the system looked at by a prefessional. As was suggested in earlier posts, even with good pressure the system may not actually be properly charged with refrigerant. Rightly or wrongly, a friend lent me one of those recharge canisters, and I had a pressure of around 40-45psi after a few blasts, but still no clutch engaging on the compressor.

 

ok, quick update concerning the tri-switch which is refusing to budge, siezed solid so looks like the whole dryer unit is going to need removing. the AC system is completely dry and looks like been unused for quite some time.

i did notice that both fans briefly started up when i unplugged the connector, so the connection to ecu is ok.

 

If the system has been empty of gas for a long time, it is quite likely that the moisture absorbent in the dryer has become spent and will no longer remove moisture. Probably best to replace the whole reciever-dryer unit while you are at it (genuine MG Rover ones are eyewateringly expensive, but aftermarket reciever-dryer can be obtained new for a fraction of the amount).

 

do you know what the function of the tri-switch is in the AC system and would it stop the whole AC system from operating?

i've looked on ebay and seen quite a few with the switch quite cheap but still a risk them not being new.

thanks.

 

mine does exactly the same thing, light comes on, but air is not noticeably cooler and you cant hear anything engage
assuming it just needs refilled...how much does that cost?

 

assuming it just needs refilled...how much does that cost?

A refill at some well known big tyre fitting places could be between £50-60. Smaller garages might be cheaper. When there are deals normally in winter it could be as low as £25-30.