2013~2016 CX-5 AC Not Working After Long Sleep

[murdoc_47]

My 2014 CX 5 sat unused over the winter. I was waiting on the weather to improve to do some work on the engine. Engine work is complete, and car is running fine now, but I've lost AC for some reason. So here's what I've done to troubleshoot so far. Would appreciate any suggestions.

• Checked AC static line pressure. It is at about 30-35 PSI
• Tried to check AC pressure switch, but can't really get any probes in the tiny holes or back-stab it, so I just replaced it with a new switch-sensor
• Connector to compressor reading 0v when AC is supposed to be on
• I can jump the relay for the compressor and it will engage and run. I let it run for about a minute and the high pressure line did start to get cold.
• Replaced the relay, no change. Fuse is good.
• Cooling fans are also not turning on. Again, I jumped the relay and they will turn on. Swapped relays and still not working.
• Ran an extra ground from battery neg to engine block and chassis, no change

So it seems like the HVAC controls are working (light is on), but the PCM isn't calling for the AC and Fans to turn on. Are there other items other than the cooling fans and the pressure switch that are required to be on for the PCM to engage the AC Clutch?

Also, are there any phone apps that work with a bluetooth obd adapters that will scan for HVAC codes?

 

[murdoc_47]

Update! I found an iPhone app that would work with the Bluetooth ODB adapter I have. Looked everything over and one thing clearly stood out. The Evaporator Temperature sensor is showing -19 degrees F! So the system must think my evap core is frozen solid. Now I just have to find where this sensor is on the HVAC box, and cross my fingers that it is accessible without removing the dash.

 

[cz5gt]

not sure for gen1, I can take a look at docs and get back. But on gen2 if I recall its a nightmare to change.

 

[murdoc_47]

Thanks, I found it in the service manual and it looks like a complete quagmire, like dash-out, hvac box out cluster-eff. I did see a video online that might have shown the connector. I'm thinking I might just pull the connector and hang a replacement sensor in the cabin, or install a variable resistor in its place. Yes, it is cheating the system and might run the risk of freezing up my evap core. but there is NO way I'm pulling the dash on this for a sensor. I've done it on two other vehicles and it was NOT fun.

 

[hsdejong]

After a prolonged period of inactivity, the air conditioning seals can start to leak due to a lack of lubrication. Are you sure there is still enough refrigerant in the system?

 

[murdoc_47]

Yep. Hooked up my gauges. There is between 30-35 psi.

 

[Jmaz]

Thanks, I found it in the service manual and it looks like a complete quagmire, like dash-out, hvac box out cluster-eff. I did see a video online that might have shown the connector. I'm thinking I might just pull the connector and hang a replacement sensor in the cabin, or install a variable resistor in its place. Yes, it is cheating the system and might run the risk of freezing up my evap core. but there is NO way I'm pulling the dash on this for a sensor. I've done it on two other vehicles and it was NOT fun.

Good thinking. I like the idea of a variable resistor. Does Mazda service info have a graph of that sensor (possibly having temp vs resistance values) for enabling troubleshooting the sensor. That would allow obtaining a variable resistor of relevant resistance range and maybe give a good idea where to set it.

 

[murdoc_47]

Not sure, haven't had a chance to dig into it that far yet. The sensor readout from the OBD was a temperature. But I assume the PCM is just interpreting a resistance value to calculate that. My first try though is just hooking up a replacement sensor outside the hvac box and letting it just read the cabin air temp. If that makes the computer energize the compressor I will prove my suspicion. Right now the computer thinks the evap core is -19 degrees!

 

[cz5gt]

 

[murdoc_47]

Ok, so I did order another sensor and just plugged in in to see what would happen. Nothing. But I have learned a bunch and have at least partial AC now. Here's what I've learned:
Apparently the HVAC CM only polls that sensor when the entire AC is on and working. Even if the light on the dash for AC is lit, it doesn't mean that the compressor is engaged and all of the safety checks are passed. Things like: AC Pressure Switch!

With the HCM not polling the evap sensor, it HCM just stores a ridiculous number like -150 degrees. Once all of the checks pass, and the system is on, it starts reading somewhat real values. I say somewhat because they actually seem to high. I'm using an app on my iPhone and either the app doesn't know how to interpret the values, or the sensor is way to close to the heater core. Driving down the highway with the AC on, it is reading 70 - 80 degrees F.

Anyhoo, my compressor wasn't switching on because the pressure, even at 35 was too low. Once I added more refrigerant it started engaging, but cycling. Watching the pressures on the system I could see that it would engage, suck down the low side from like 45 PSI to 30, where it would then cut off. Once the low side equalized with the high side back up to at least 40 it engages again. So the cycle was 15 seconds on, 5 seconds off.

I've added more to the system, but am scared that I will overcharge the system. Right now when it is 75 degrees ambient air, car sitting in the driveway with no fan in front of the car, the high side gets up to around 165 PSI peak, and the low side will drop to around 40. But the air coming out of the vents is around 46 degrees. So that is good enough for me for now.

The only thing that slightly worries me is that the compressor still cycles at times instead of running continuously. But that must be by design right? I'm guessing the system's goal is just to keep the evap core cold enough to provide cold air, without it frosting over.