Intermittent A/C?

[jrobie79]

They said the evap temp sensor was stuck t 24deg and was telling the A/C system it was to cold.
The sensor was $15.87 GM GENUINE 1551267 @Rock auto

Where is that sensor installed? I know theres a pressure sensor on the high pressure like in the engine bay

 

[Trippers99hoe]

Mounted to evaporator core ,the wire for it comes out of heater a/c box behind the glovebox directly below the passenger air bag


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[jrobie79]

Great thanks, I wish I knew how to use my tech2 to it's full capabilities to help with this. There's no codes, but I couldn't seem to find out what that sensor or the pressure sensor were giving for readings

 

[Trippers99hoe]

I don't have a tech 2,but somewhere in there you can see all the temps.
I bet somebody here will help you through it.

 

[Foggy]

If your temps etc are reading "normal" ... then it could just be an old fashioned
mechanical issue.
Make sure your electric fans are kicking ON
Check to make sure you don't have any debris like a plastic bag covering the condensor/radiator areas
Make sure your AC belt isn't vibrating/flopping/worn: it is a "stretch to fit" belt and
can be worn out without any normal signs

 

[rockola1971]

May also be the coil (or something) freezing up.

My 2001 with manual hvac controls will start blowing ambient air after about two hours when on road trips. After stopping to get gas or eat there would be a big puddle of water under it and the AC blows cold again.

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Evaporator Coil freezing up is a symptom of a problem, not the problem. The cause is low refrigerant or severely restricted airflow across evaporator coil. Low refrigerant and low airflow causes coil to get below 32 deg and humidity in vehicle freezes on contact which is your ice buildup. Shutoff a/c and it starts melting. This applies to all A/C and Refrigeration systems, especially your central air at home. Keep those filters changed out as needed at home!

 

[gooffeyguy]

Evaporator Coil freezing up is a symptom of a problem, not the problem. The cause is low refrigerant or severely restricted airflow across evaporator coil. Low refrigerant and low airflow causes coil to get below 32 deg and humidity in vehicle freezes on contact which is your ice buildup. Shutoff a/c and it starts melting. This applies to all A/C and Refrigeration systems, especially your central air at home. Keep those filters changed out as needed at home!

It's fully charged, so not sure what exactly the problem is with it. But like I said, it takes a while for it to do it, like when on a road trip and you've been driving for a couple hours with the AC on.

A few years ago my home AC coil would freeze up due to a bad txv valve.

 

[rockola1971]

It's fully charged, so not sure what exactly the problem is with it. But like I said, it takes a while for it to do it, like when on a road trip and you've been driving for a couple hours with the AC on.

A few years ago my home AC coil would freeze up due to a bad txv valve.

A bad Epansion (TXV) valve could cause your problems also. Yours should be located behind the evaporator coil near the firewall. A total blast to get to.

 

[LRD_V8R]

Check refrigerant pressures first. This is a common symptom of low refrigerant. As the system runs, the low side pressure will drop during certain events (like hitting the gas). If it gets too low (typically around 20-25 PSI), it will cut off the compressor until the pressure climbs back up to the minimum threshold to turn on (either in the 40 or 50 PSI range). I prefer to check this using actual gauges and then working from there. If you have a tech 2, you can compare what the PCM is seeing to what the gauges actually read. this can tell you quickly if one of the sensors is failing.

Then there are more insane scenarios where the contacts in the connector from the wiring harness to the compressor connector are corroded, causing intermittent cycling of the compressor. That one took a minute to solve.

 

[Foggy]

My 94 step side has this issue too for the last several years.. I've replaced every component except
the evap core - the entire dash has to be removed and still bust up the air box too ...
So when the airflow thru the vents starts to decline and not be so cold, I just turn off the compressor but keep the system on for a couple of miles. Then air starts to flow better
and I turn back on the compressor and get cold again for period of time.
Remember in these years of GM, if you have it on Max/Recirculate (which you should once cooled down)
the compressor will still run even though the AC light is turned off

I just live with it since my 94 is my toy now. I'm sure the evap core is full of 28 years of
shit so it freezes up easily