I have posted on this issue before. My AC works sometimes. It would get very cold for a couple mins or longer and then stop. Sometimes it would not get cool at all and other times it works great. Any ideas???

 

If you search, there are quite a few threads on this issue.

The system is cycling because it's low on R134a;refrigerant. There are some parts that are known to go south:

- The evaporator is guaranteed to fail. It may be leaking slowly but surely.
- The compressor may need to be re-shimmed.
- System needs to be charged with a kit.
- Etc...

The A/C on 850s are not very well designed. Other members could also give you more insight.


JPN

 

What about the A/C pressure switch? When an A/C pressure switch is failing, it will have some of the same "failure" issues as many note with these A/C systems (such as the compressor with constantly cycle on/off, but you will not get any cold air from the vents, etc). A pressure switch most of the time is a very simple, easy & inexpensive fix.

I've come across such A/C failures on many Fords, BMW's, Toyotas, etc... and nearly 90% of the time, the culprit was a bad A/C pressure switch. Once the A/C pressure switch has been replaced with a new switch, the A/C system works properly again (also providing there were NO leaks in the system after a thorough check of all components). Depending on various system designs and the manufacturer, there are methods of jumping the A/C pressure switch for determining if it is the point of failure, before replacing expensive and labor intensive parts.

Is thisa possibilty with the Volvo A/C system?

 

It is possible the Low pressure switch is bad as well. It is easy to jump to test or just use a test light and make sure both wires show power to them.

But the Compressors fail alot more than the low pressure switch does.
That is also easy to test if it is the compressor as well.