yes.its just below the alternater driven by the belt.AC selected to on and the fan speed was just no:1.outside temp was ard 19 degrees.Normally the RPM goes erratic worst when the outside temp is hot.during cold weather is not that bad,but still affects the RPM.
i look at the compressor for the clicking sound tomorow again.

thanks Tech!!!

Vollic

 

When you have the A/C on fan speed 1 and it is chilly the compressor will cycle alot to prevent the lines from freezing.

 

For the thermostat there is 2 types.one is 87 degree and the other is 90 degree.is there a difference.which is the correct one to buy?

Vollic

 

I think the 87 is the one for the S40. I think the 90 is for the S70.

 

ok!thanks!Still trying to hunt for the coolant sensor from web.

Vollic

 

Hi Tech,

i've just replaced the thermostat and the coolant sensor,and the surge still persist.

vollic

 

That should have taken care of it. Are you 100% sure you don't have any vaccum leaks?

 

Sorry tech Don"t really understand what is vacumm leak.can u explain?
initially i tot may be it was low on gas or leak.i went to the mechanic to service and they said was fine.
we can narrow down the fault to just the AC sys now which is causing the erratic RPM.The loud 'bong' sound and the hissing/crackling gas sound i can hear when in the car when the AC is turned on really sounds unusual. or there must be a sensor some where is faulty.Lets hope its not the compressor.......

Vollic

 

Vaccum leak would be a Broke rubber hose coming off the intake manifold.
You will have a slight change in idle when the A/C kicks on but it should return.

Is the Freon level ok in the A/C system?

 

If it's a broken rubber hose then the AC should not be cold.The freon level was good.

Vollic

 

I mean a broken Vaccum hose.

 

I don't think there is a broken vacuum hose.does the AC compressor has a thermostat in it?

Vollic

 

The system has a low pressure switch that cycles the A/C when the pressure gets low (Temp low).
I think there is one on the compressor as well that can be bypassed.

 

But whenever i switched on AC the compressors starts with a loud 'bong' sound,like as if the compressor sounds like it's over loaded followed by the hissing gas sound being pumped by the compressor(is quite loud when you're in the car).whenever the bong sound comes on from the compressor that is the time the rpm surge and the car feels like losing power and slight vibration from the car.
Basic car AC sys comprises of a compressor,evaporator,condenser ,expansion valve and.......did i miss out anything.If a clogged or faulty condenser will it cause clogging of the freon sys (pipelines)causing the hissing sound?I don't think is a faulty climate control module because the AC works quite fine.

Vollic

 

Check the Gap on the compressor clutch.
If the orface tube gets a small tear in it it will hiss/squeel.

The clutch might be going bad making the Bong noise.

 

Hi tech!To check the gap is it easy?Is it on the compressor area.I've got no idea.But i know there is something call compressor clutch.How it functions?And where is the tube that u mentioned?Guidance needed.
Thanks!

Vollic

 

The orface tube is in the High pressure pipe by the firewall.
The Gap I speak of is the gap between the outer clutch and the pulley area.
The clutch works by a magnetic feild.

 

The tube are of rubber type?and wats the limit for the gap check?

Vollic

 

The orface tube is plastic with screen in it.
I will have to check tomorrow on the Gap spec.

 

Is the orifice tube which is in the high pressure pipe located in the engine bay?Becos i can only see some rubber and copper tubes near the fire wall.

Vollic