My apologies if this should be posted elsewhere on this forum, my first time posting a real thread here. I spent quite a bit of time reading other AC issue threads and they were quite helpful, but I still couldn't get to the bottom of my problem. I likely didn't diagnose something correctly so am seeking advice. Here is my main question:
My mechanic suggested that If all inputs to the AC are working correctly but the AC clutch still won't engage when the button is pressed, would that point to a wiring issue, or the ECM. He said it wasn't uncommon for there to be a short in the ECM. Was wondering how common that actually is in these cars, or did I totally miss something in trying to diagnos this? Here is the gory back story in case interested.
I am trying to fix the AC on my daughter's 2016 Sonic 1.8 LS (base model). I also happen to have a 2016 Sonic, it is a 1.4 LT. Many of the AC parts are interchangeable, so I was able to swap out a couple things to check them. I have tried the following:
Compressor and clutch work when jumping 30/87 at the relay, AC then also blows cold air.
(Since jumping the relay works, I assume this means the wiring between the relay and the clutch is also good???)
Checked refrigerant level just to be sure and it was good.
AC pressure sensor was reading correctly according to my scan tool, but out of frustration I changed it anyway
Evaporator temp sensor is good.
AC control switch in dash of car is good (swapped with mine to be sure).
The LS model doesn't appear to have an ambient temperature sensor, so couldn't check that.
I checked with my mechanic and he said if all those inputs are working correctly, it is most likely a short/issue in the ECM, or a wiring problem. I tried to start tracking that issue by checking voltages at the A/C clutch relay and they matched what my working Sonic AC was showing with the AC switch on and off. I had two +12V pins and one +3V pin with with AC button on. I also tried to test the ground with the volt meter, but probably did that wrong (I went from battery positive to that pin and it showed -12V, not really sure if that was a good ground test though or not). I now have a test light so can do it that way once my daughter brings her car back with her this weekend. Thanks for any advice!
My mechanic suggested that If all inputs to the AC are working correctly but the AC clutch still won't engage when the button is pressed, would that point to a wiring issue, or the ECM. He said it wasn't uncommon for there to be a short in the ECM. Was wondering how common that actually is in these cars, or did I totally miss something in trying to diagnos this? Here is the gory back story in case interested.
I am trying to fix the AC on my daughter's 2016 Sonic 1.8 LS (base model). I also happen to have a 2016 Sonic, it is a 1.4 LT. Many of the AC parts are interchangeable, so I was able to swap out a couple things to check them. I have tried the following:
Compressor and clutch work when jumping 30/87 at the relay, AC then also blows cold air.
(Since jumping the relay works, I assume this means the wiring between the relay and the clutch is also good???)
Checked refrigerant level just to be sure and it was good.
AC pressure sensor was reading correctly according to my scan tool, but out of frustration I changed it anyway
Evaporator temp sensor is good.
AC control switch in dash of car is good (swapped with mine to be sure).
The LS model doesn't appear to have an ambient temperature sensor, so couldn't check that.
I checked with my mechanic and he said if all those inputs are working correctly, it is most likely a short/issue in the ECM, or a wiring problem. I tried to start tracking that issue by checking voltages at the A/C clutch relay and they matched what my working Sonic AC was showing with the AC switch on and off. I had two +12V pins and one +3V pin with with AC button on. I also tried to test the ground with the volt meter, but probably did that wrong (I went from battery positive to that pin and it showed -12V, not really sure if that was a good ground test though or not). I now have a test light so can do it that way once my daughter brings her car back with her this weekend. Thanks for any advice!
