AC System Question

[TheImpalaMan]

Good Morning Everyone,
New to the forum, but joined to see if I can get the information I need to resolve the issue I'm having. Got a 2014 Sonic LT with the 1.8L (daughters car). Recently, had a leak in the AC system and found a crack in the condenser. So, I replaced the condenser and the compressor (just because the original wasn't doing so well anyway), I flushed out the evaporator core and the plumbing as well. After oiling the system properly and charging the system with the exact amount of refrigerant...the AC compressor doesn't engage. Thought it was the pressure switch, but after changing that, no change. I know what you are gonna ask first...how did I charge the system if the compressor isn't engaging? I jumped the relay circuit to engage the compressor to fill the system. After some web research, I found (please correct me if I'm wrong) that there are only 2 switches on the HVAC system for this car. One being the pressure switch (which I changed and it made no difference) and the other is the temperature switch inside the cab. I haven't changed that yet. I use a snap-on modis diagnostic scanner which enables me to test various circuits in the system. When I tested the AC circuit, the light would enable in the control board (in the cab), but there was no voltage to the relay telling the compressor to engage. I don't have a wiring schematic for this system.

Any help is appreciated.

-TheImpalaMan

 

[gnonne]

I've had three sonics and never had this problem. I've heard of others who did, though... The A/C is disabled when the car thinks the engine temp is too high, I believe.
The 1.8's are known for bad t-stat housings and bad temp sending units. That might be your problem. Depending on the miles, a cheap after-market t-stat and housing may have been previously installed. This could be a bad temp sender. If nothing else, check the connections there, trans end of the engine.

 

[TheImpalaMan]

Gnome - thanks for the reply, I thought about that because I have a 2014 Silverado that did the same thing, however...when that problem occurred the electric cooling fan would stay on if it was needed or not. Since the Sonic only has an electric fan, I would think it would stay on all the time as well (please correct me if I’m wrong). But that isn’t the case here which is why I’m thinking it has to be another circuit. I did ask the previous owner of the car had ever overheated, was informed that it had and the thermostat had been replaced about 3 years ago. I know, in my trucks case, that if you put anything other than a factory thermostat in, the computer will think the truck is overheating and put the electric fan on as well as disable the AC system.

Does anyone have access to the HVAC systems wiring diagram?

-TheImpalaMan

 

[gnonne]

OK - I should have thought of this first... If it worked when you jumped the relay, why not try a new relay?
Also, if it has a cheap t-stat in for 3 years, you will be doing it again...

 

[TheImpalaMan]

Tried changing the relay already, that didn’t work. After doing a voltage test, the relay wasn’t getting signal to activate anyway. So the fuse box is good, but I’ll swap the thermostat and temp switch to see if that makes any change. It’s a cheap enough swap anyway. I’ll keep you posted...and thanks again for the reply!

-TheImpalaMan

 

[gnonne]

Looking in some Buick forums (wanting to get a Verano for my wife) I stumbled upon some folks with an "AC off Engine Temp high" message when the engine is NOT hot.

Culprit was a corroded connector on the Engine Coolant Temp sensor, so it read hot. I think this is in the radiator in the 1.8L setup, but I'm not certain. I know there are two, one in the t-stat housing, which may be good, and the other, which causes things like this.

Some owners fixed the issue by unplugging the connector, cleaning it and reconnecting, after trying everything else...

No cost, so you might want to check it out. Not sure why it gets corroded, maybe the car is stored outside near an ocean? One owner reported that the connector had melted and was a closed circuit, even with the engine off.

 

[gnonne]

Part #21 in this diagram.

https://www.cheapestgmparts.com/oem...zb25pYyZ5PTIwMTQmdD1sdCZlPTEtOGwtbDQtZmxleA==

 

[Poobah47]

Good Morning Everyone,
New to the forum, but joined to see if I can get the information I need to resolve the issue I'm having. Got a 2014 Sonic LT with the 1.8L (daughters car). Recently, had a leak in the AC system and found a crack in the condenser. So, I replaced the condenser and the compressor (just because the original wasn't doing so well anyway), I flushed out the evaporator core and the plumbing as well. After oiling the system properly and charging the system with the exact amount of refrigerant...the AC compressor doesn't engage. Thought it was the pressure switch, but after changing that, no change. I know what you are gonna ask first...how did I charge the system if the compressor isn't engaging? I jumped the relay circuit to engage the compressor to fill the system. After some web research, I found (please correct me if I'm wrong) that there are only 2 switches on the HVAC system for this car. One being the pressure switch (which I changed and it made no difference) and the other is the temperature switch inside the cab. I haven't changed that yet. I use a snap-on modis diagnostic scanner which enables me to test various circuits in the system. When I tested the AC circuit, the light would enable in the control board (in the cab), but there was no voltage to the relay telling the compressor to engage. I don't have a wiring schematic for this system.

Any help is appreciated.

-TheImpalaMan

I am fighting a very similar issue. Any luck on the schematic? I found a sensor on the High side right at the compressor fitting. I would guess thats the temp semsor, 3 wires on it. I cant find the low pressure sensor.

 

[Poobah47]

Good Morning Everyone,
New to the forum, but joined to see if I can get the information I need to resolve the issue I'm having. Got a 2014 Sonic LT with the 1.8L (daughters car). Recently, had a leak in the AC system and found a crack in the condenser. So, I replaced the condenser and the compressor (just because the original wasn't doing so well anyway), I flushed out the evaporator core and the plumbing as well. After oiling the system properly and charging the system with the exact amount of refrigerant...the AC compressor doesn't engage. Thought it was the pressure switch, but after changing that, no change. I know what you are gonna ask first...how did I charge the system if the compressor isn't engaging? I jumped the relay circuit to engage the compressor to fill the system. After some web research, I found (please correct me if I'm wrong) that there are only 2 switches on the HVAC system for this car. One being the pressure switch (which I changed and it made no difference) and the other is the temperature switch inside the cab. I haven't changed that yet. I use a snap-on modis diagnostic scanner which enables me to test various circuits in the system. When I tested the AC circuit, the light would enable in the control board (in the cab), but there was no voltage to the relay telling the compressor to engage. I don't have a wiring schematic for this system.

Any help is appreciated.

-TheImpalaMan

The inside temperature sensor is a thermistor measuring the temperature of the air that has passed over the evaporator. As far as I know, yes, those are the two main measuring devices for A/C health.

The inside thermistor is easy to change and a cheap part. It's above the gas pedal to the right...contort a little and look up for 2 wires going into the center console. It untwists and pops out.

I fixed my neighbors replacing that part. Same issue, no clutch engage.

Good luck.