| Author | Message | ||
     Edward Mckinley Experienced User Username: ed_mckinley Post Number: 17 Registered: 2-2013 |
Last year after finishing up a complete restoration on my 89 corniche I had the air conditioning checked out at the local dealership (Steve Foley Bentley). The system was converted to R134 in the past and I was told that after testing it showed no leaks and they simply recharged the refrigerant. Afterwards I could hear a slight whining when the compressor ran, like belt noise but It worked great blowing cold all summer. Last week I turned on the AC which is now blowing cool air not cold and the whining noise is gone. I'm wondering if perhaps the drier should have been changed, and also is it normal to have a little compressor noise? Any help is much appreciated | ||
| michael vass Prolific User Username: mikebentleyturbo2 Post Number: 193 Registered: 7-2015 |
Hi Edward Sounds like your car has lost a little gas, you should be able to get it checked for free at most garages. Mike | ||
| Omar M. Shams Grand Master Username: omar Post Number: 688 Registered: 4-2009 |
Dear Edward, Can you confirm that the clutch on your compressor is actually engaging and the refrigeration system is operational? If the answer is yes then you have three things wrong. First you have a leak. Secondly you have insufficient gas in your refrigeration system (as a consequence of the leak) and thirdly you have an issue with your compressor (based on the fact that you have stated that it makes a whining noise). The noise is not a show stopper if you can live with it. If the compressor clutch is not engaging then come back to us for more support. Thanks Omar | ||
| Edward Mckinley Experienced User Username: ed_mckinley Post Number: 18 Registered: 2-2013 |
The clutch is engaging. Interestingly it was very difficult to hear the whining noise under the hood, it was much more apparent inside the vehicle | ||
| Omar M. Shams Grand Master Username: omar Post Number: 689 Registered: 4-2009 |
Dear Edward, To confirm if you have insufficient gas - check the sight glass on the receiver drier using a flash light when the compressor is engaged. You should see a stream of flowing fluid that is full of bubbles. That will confirm that you are low on gas. Now your challenge is to find that tiny leak that takes a whole year to spill out. Are there any obvious signs of wetness/oil-damp marks along the system that you can see? It is pointless to just fill the system with gas as it will then spill out again from the leak. Thanks Omar | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1556 Registered: 6-2006 |
Hi, Omar is right but I'd add that yes the dryer should have been changed. Not only because of it's age but also because older dryers were not designed to work with 134a gas and oils. A leak detector dye is favourite for slow leaks. Leaving traces of dye on the smallest weeps. 134a will find its way out of the system much more easily than r12. As for the noise, it's hard to tell without hearing it, but possibly too much or too little gas may have been added. Also check that the in line valves have been removed. | ||
| Edward Mckinley Experienced User Username: ed_mckinley Post Number: 19 Registered: 2-2013 |
OK thank you, I will take a look when I return home this evening and report back | ||
| Omar M. Shams Grand Master Username: omar Post Number: 690 Registered: 4-2009 |
Thanks Paul - Yes spot on. Then there is also the leaky hose phenomenon that has been previously reported on this forum. When you convert from R12 to R134a, sometimes the hoses allow infitesimal quantities of the newer gas to seep out over time. | ||
| David Gore Moderator Username: david_gore Post Number: 2078 Registered: 4-2003 |
Edward, Re the R12/R134 refrigerant conversion, this should have involved 4 steps if done properly: 1. Evacuate the system and replace the flexible hoses with R134A-compatible hoses. Replace the receiver/dryer. 2. Replace the compressor oil with R134-compatible oil. 3. Put the system under vacuum for a minimum of 24 hours to check for leaks from the compressor/evaporator. 4. Charge the system with R134A and check pull-down. R134A in R12 systems has reduced cooling capacity and diffusion of the refrigerant through the hoses does not always show with a dye check - been there, experienced that. There is a new refrigerant [R406? - Duracool 12A in USA/Canada] available for R12 systems which is compatible with the R12 hoses thus reducing the possibility of long-term leaks and would only require replacement of the receiver/dryer and possibly the R134A compressor oil, vacuum leak test and filling with the new refrigerant. http://www.duracool.com/Duracool/refrigerants.html | ||
| Edward Mckinley Experienced User Username: ed_mckinley Post Number: 20 Registered: 2-2013 |
Ok so it appears that the clutch is not engaging, which explains the quiet running! | ||
| Omar M. Shams Grand Master Username: omar Post Number: 691 Registered: 4-2009 |
I am confused. You told us the clutch was engaging and now it is not. What happened from the time it engaged some 12 hours ago to now where it is no longer engaging? | ||
| Edward Mckinley Experienced User Username: ed_mckinley Post Number: 21 Registered: 2-2013 |
I was mistaken, as I can hear a click at the compressor when it is calling for cooling but the clutch is not turning (engaging) | ||
| Omar M. Shams Grand Master Username: omar Post Number: 693 Registered: 4-2009 |
Dear Edward, Get an assistant to help you for this next test. Take a meter or a test light and attach it to the wire that goes to the compressor after disconnecting that wire from the compressor. When you have done that, ask your assistant to switch the aircon on to the point where you hear that click that you reported in your last post. At that time your tester will either read that you have a power supply at your compressor or not. If there is a power supply then your compressor has failed. If there is no power at that wire then come back to us. Thanks Omar | ||
| Edward Mckinley Experienced User Username: ed_mckinley Post Number: 22 Registered: 2-2013 |
Finally resolved the problem, it turns out that I had a leaking shrader valve which depleted the system of freon and shut down the compressor. Replaced valve, put under vacuum and recharged system. Thanks for all your help |
