AC not delivering chilled air

[k100dennis]

I used the AC the other day and found it was no longer delivering chilled air. I've checked visually and can confirm the following - orange light comes on (on the fan switch), condenser cooling fan runs (car stationary), engine loads/speeds up slightly when the switch is activated, drive belt is in place. What I can't confirm is whether or not the compressor is actually turning (electric clutch activating).
Can anyone give me a clue what to look for please, I'm not sure it can be easily seen that the clutch has engaged. Also, is there a separate fuse for the compressor, or is it a single fuse for the AC system complete ? The AC has always worked really well, so I may need to be looking for a gas leak once I get these answers.

[spot01]

With bonnet up & engine running, on most cars you should be hear the clutch clunk on & off when you switch the A/C on & off (be careful not to get too close to fan with hair, clothing, etc.) They are usually quite loud & easy to hear.


I think there may be a separate fuse on the Gen 4, but unsure on Gen 3. It is usually a large rating, eg, 20 amps. There might also be a fusible link for A/C & possibly a relay.

[Kingbrown]

There's a plate on the outside of the compressor pulley that only turns when the clutch is engaged.

When the compressor clutch is energised you should hear a loud click or clunk when it engages.

Check for a significant difference in temperature between the two refrigerant pipes at the compressor.

[k100dennis]

Yes, I thought the outer part was supposed to turn. I watched yesterday and it is not moving. I need to find the fuse and / or relay. The fan is running, I suspect the compressor not running is the problem.

[spot01]

Note they usually have a safety cutout so the compressor won't run if it is very low on gas.


I guess you haven't used it since last summer, being Tassie? Gas may well have leaked out since then if not run regularly to keep the seals good. If it has never been re-gassed, probably needs doing anyway.



You might be able to get a meter onto the connector to see if it gets power to the compressor when turned on?

[aussieintas]

I always run mine every week for 20 to 30 mins just to keep it lubricated etc.

[k100dennis]

I usually run it weekly at least. Has only been a problem in the last week or so. Just about to look at a work colleague's Paj to check the compressor when it's operating.

[k100dennis]

Just checked / confirmed my compressor clutch is not engaging, so I suspect it is as described - low on gas, safety cut-out switch prevents the compressor running. Hmmm, now to find the leak.

[Kingbrown]

The dual pressure 'safety' switch shouldl only operate when the system is running abnormally (low suction pressure or high discharge pressure). If your compressor isn't running then those abnormal conditions wouldn't be met in the first place.

So, first things to check are that there's continuity in the clutch coil and that it will pull in when 12V is applied to the clutch coil.

If that checks out ok and your fuse and compressor relay are also checked as functional , then you can start looking at the various control elements (including the hp/lp switch) and the gas.

[erad]

Try to find the 12 V connection to the compressor. Hook a separate 12 V supply directly to it and see if the compressor clutch clunks in. If it does, then you know the clutch is OK. Next step if this is the case is to find out why it is being naughty. Find the pressure switches in the refrigerant lines and check them for continuity. Almost certainly you are low on gas, and if that is the case, it is off to the A/C man for a re-gas. Get them to put some UV dye into the gas as well so that they can trace any leaks.

[k100dennis]

So I presume they do a leak detection process before just re-gassing the system ? Otherwise it would be pointless I guess.

[spot01]

So I presume they do a leak detection process before just re-gassing the system ? Otherwise it would be pointless I guess.

I would assume so, perhaps just putting a bit of gas in to then test for leaks?
Note there is also a measured amount of compressor oil in the system, so an oily residue somewhere might give away the location of the leak.

[erad]

Before any re-gas of a system, they should pull a full vacuum and check that it holds for a certain time. This also gets rid of any moisture in the system. Once they are satisfied, they should then recharge with new gas.

[Swede50]

Also,
Get them to replace the receiver drier or desicant bag if so fitted.
The molecular sieve in the drier/desicant bag removes moisture in the system.
A good insurance for long life of the system.
Servicing of the A/C system should be done on a regular basis.
They will add some oil with the fluro leak detection dye,,,
The dye if not previously put into the system will stay there for life and makes accurate diagnosis down the track much easier.
You could go to the VASA web site and find a local accredited expert.
Make sure you find someone that knows what they are doing.
ONLY get it re-gassed with R134a ,,,, there are Hydrocarbon gasses around,, flammable and not good,,, Denso compressors have a history of failure with Hydrocarbon gas.

[k100dennis]

Thanks for that, very good information. Now I just need to find a credible AC service place. Cheers.