2009 Edge compressor not turning on at idle

[retro31337]

My 2009 edge has been having problems with the AC recently. I'm in Vegas so it's super hot right now.

The AC was only blowing cold sometimes, I couldn't really find a pattern to it until now.

I filled up the freon, it was really low, 15psi at the port.

Everything seemed to be fine for a few days. Now when the engine coolant is hot and the car is at idle, the compressor won't turn on. I can see it trying to turn on every 40-45 seconds because the rpm gauge will jump a bit.

I've read other posts about the cooling fans not running at the proper speeds to cool the car and the PCM won't let the compressor turn on at a high temp. How do I diagnose the fans are bad? The ac seems to run just fine when I'm driving at 45 mph or so.

Has anybody done a fan replacement before and how hard is it? I'm pretty handy, I just don't want to break something then end up having to take it to the shop anyways.

Thanks

[Cerberus]

Unfortunately,  using pressure as a reference for AC fill level is really not the right way to do it at all. If you jad a proper guage set so you could watch high side and low side pressures, you could have a solid idea of actual charge level by factoring against ambient air temperature.

But, you are supposed to evac and fill the system by charge weight. There should be a sticker under the hood which tells you what the correct charge weight is.

 

If the compressor is short cycling it could be low on refrigerant, or paradoxically overfilled. Too much refrigerant can male it so the compressor won't start because it's unable to start up when pushing against such a head of pressure.

 

You said you had 15psi on the low port, was this with the compressor clutch engaged or no?

 

Lastly to your question, I believe forscan may have the ability to command the fans on which will give you the ability to see if they are responding as commanded

[Cerberus]

There is a relay associated with AC clutch. It's worth checking / swapping that to see if that changes anything. 

 

[Cerberus]

The easiest test of fan function is just crank the AC up to max in the heat of the day with all the widows open and see if the fans come on.

If not, there is something wrong. Could be a fan control module if your model has one, fan itself or even a loose wire to a pressure sensor on the system. 

[WWWPerfA_ZN0W]

two things usually will prevent a/c and rad fans working properly, besides bad fans: bad a/c transducer or high pressure switch, and incorrect refrigerant pressure / usually low.

 

so check refrigerant pressures with a pro set of gauges, don't try to correct the situation with ac-in-a-can. we have had many members stuck in the too low too high situation using those quick fixes. edge ac pressures work within a fairly narrow range.

 

the transducer can be replaced without evacuating the system, if the schrader valve is not leaking.