Re: 1988 Chevy Suburban r12-r134a retrofit problems
Posted: Thu Aug 19, 2021 4:19 pm
I have not had the time yet to empty and recharge the system with 36 oz of refrigerant but today I had the time to replace the LPCOS and it is now turning the compressor off at 26-27 psi and turns it back on at 40 psi.
Then I removed the duct that attaches to the rear of the heater-A/C housing under the dash so I could check the air mixing shutters to see if all the air was flowing correctly. It looked and felt like all the air is flowing through the evaporator. I stuck a long thermometer in there to get a reading right behind the evaporator. With the engine running @ 670 rpm and the blower on high,the pressure was 30 low and 180 high, the right side of the evap was 58* and on the far left side it was 80*. Looking at the back of the evap there is just enough condensation on the far right 1-1/2" to see it and none on the rest of it. It looks like only 1/4 of the evap passages are getting cold at all. I cut open the old evap and all its capillary passages are connected to a large plenum on the bottom where the refrigerant flows in from the orifice tube giving them all basically the same amount of flow . This one is getting cold on the end farthest from the orifice tube, it seems like the first 4"-5" of capillaries are completely plugged .This seems really bizarre to me but this looks like it could be the main reason the system is not working correctly. Are there any suggestions on how to diagnose this without taking the whole housing out again and replacing the evap again?
I want to thank all you guys again for your help.
Luther4130
Then I removed the duct that attaches to the rear of the heater-A/C housing under the dash so I could check the air mixing shutters to see if all the air was flowing correctly. It looked and felt like all the air is flowing through the evaporator. I stuck a long thermometer in there to get a reading right behind the evaporator. With the engine running @ 670 rpm and the blower on high,the pressure was 30 low and 180 high, the right side of the evap was 58* and on the far left side it was 80*. Looking at the back of the evap there is just enough condensation on the far right 1-1/2" to see it and none on the rest of it. It looks like only 1/4 of the evap passages are getting cold at all. I cut open the old evap and all its capillary passages are connected to a large plenum on the bottom where the refrigerant flows in from the orifice tube giving them all basically the same amount of flow . This one is getting cold on the end farthest from the orifice tube, it seems like the first 4"-5" of capillaries are completely plugged .This seems really bizarre to me but this looks like it could be the main reason the system is not working correctly. Are there any suggestions on how to diagnose this without taking the whole housing out again and replacing the evap again?
I want to thank all you guys again for your help.
Luther4130