89 240, Is there a good, cheap way of diagnosing my non working AC? Not interested in any ideas with the words, "take it to..." Thanks in advance Dave

 

Well you could always take it to .. oh wait, nevermind
You should have two green wires on the dryer for the low pressure switch. With the A/C turned on, if you short those two wires together and the compressor comes on, then most likely it is low on refrigerant.

Is it the original R12? After replacing two broken lines and most of the o-rings, and the dryer, I refilled my original R12 system with "freeze-12" since it is compatible.

You can still buy R12 off e-bay but you need a EPA section 609 certification.

 

bubba- As far as I can tell, it has never been changed. There are no stickers under the hood indicating otherwise. What is current and legal? I'm in upstate NY, dont really need AC, thought if I could fix it without dropping much $ on it, I might do it. I'll try your compressor trick see if it is working. That test is engine on, yes? Thanks Dave

 

Yes, with the engine and AC on. Current and legal is R134a which Volvo started using in 1993 (last year of the 240). When you short the two green wires together you are *temporarly* bypassing the low pressure switch.

 

bubba- you know I tried turning on the AC this afternoon and I felt it get a little (I mean a little) bit cool. I'll try that jumper trick tonight and see what it does. What is involved in an R134A conversion- just refrigerant, or hoses and other stuff? Thanks, dave

 

I would say at a minimum: the dryer, expansion valve, oil in the compressor, refrigerant and o-rings.

 

NO! Not correctly anyway.

 

Gdog-just not worth dropping significant dollars into fixing. Dave

 

It's possoble to diagnose A/C systems, you will need pressure gauges and a thermometer, plus the factory manual.
If you are willing to find or borrow these items, it is definitely a driveway job, however, repairs should be left to professionals if you want a long lasting, trouble free repair.
Sometimes it is worth going to teh pros, they have the tools and experience, often they know what fails on a particular system and can diagnose it very quickly.

Regards, Andrew.

 

More AC A/C Compressor, Low Sensor, High Sensor Pics at: https://volvoforums.com/forum/album.php?albumid=156

 

if your fill ports are threaded you have an r12 set up. if the fill ports are quick release style, then it is 134a.

I see from rockauto that your system uses the receiver/dryer txv setup.

The first thing you need to do is see if there is still gas in the system. Get a gauge that will let you hook up and verify the pressure. A full system should be equal to the ambient temperature more or less. ie 70psi at 70F. This is with the engine off and cold.

If you have less then ambient air temp, then you need to fill.

If you have way less, then have what's left recovered by a professional, and check for leaks with a vacuum test.

If its at zero, tear into it. Check out the condenser and evaporator for oil stains, if stained, replace. Clean out the coils on both if they are ok.

Buy a new receiver/dryer and txv. If the compresser wont kick on from the low pressure switch, try it again right at the compresser. if it still wont kick on, replace it.

Since we are tearing into the system, break all lines at their connections and blow them out and replace the orings.

Also add about 6-8 oz of oil just before you recharge the system. Add it to the lines on the low pressure side just before the compresser.

 

What about evacuating the system before charging it with freon?

 

if the gauge reads zero, there is nothing to evacuate. if its low, I did say to take it to a shop and have them recover the left over gas and do a leak check.



"Current and legal is R134a which Volvo started using in 1993 (last year of the 240). "

r12 is still legal. it is just expensive. it's illegal to manufacture it.





Also you should be able to check the clutch with the engine off and with the key in the on position. Doing the above bypass/jump on the low pressure switch will still engage (you'll hear a click and see it move) the clutch.

 

From the first link I found via google on the topic...

"The whole idea behind refrigerant circuit evacuation is twofold. First, a proper evacuation will identify the presence of leaks, both big and small, in the refrigerant circuit. If a leak is present, a properly administered evacuation process will usually detect it.

Second, a proper evacuation removes gases and moisture from the circuit so that, when charged with refrigerant, only refrigerant and oil are present within the system. Any water or air remaining within the circuit compromises cooling efficiency and reduces system reliability."


Zero psi on the gauge means there's ambient air in the system which contains water vapor and other contaminants. Leaving that in there will promote internal corrosion in the AC components not to mention reducing cooling efficiency; i.e. some component will fail before it should and it won't cool as well as it could either.