Low pressure ac switch location

[UmmScott]

I’m happy for any advice: this is what has been done so far.

Evap and Dryer freezing up, but only on lowest 3 fan settings. I checked refrig level and it’s perfect. I had the system evac’ed, power flushed, and the oriface tube replaced. I also had the computer re-flashed to an upgraded AC program.
Did not fix the problem.

I would physically turn the compressor off by turning the AC off in the cabin. Let it thaw out, then turn it back on. After a few reps of this, the compressor refused to turn back on.

After parking with the motor off for about 20 min’s the compressor will start but back to square one with the freezing on lowest fan speeds.

From my research (not claiming to be an expert by any stretch), I think it either has to be the AC pressure switch or the evaporator temp sensor.

im hoping it’s the pressure switch under the hood instead of the evap temp switch behind the dash.

Any advice will be appreciated. I’m certain I’m the least knowledgeable of anyone on this thread.

thanks in advance.

someone did all that and didnt check the pressure switch...
Wow [emoji16][emoji16]

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[TheBigDirty]

When I was first looking at this, I was pretty sure that I followed that line, with the pressure sensor in it, from the compressor to the condenser, which lead me to believe that it is a high pressure cutout. This is where Im so confused on this one.... the picture posted of the service manual labels the "low pressure" switch to be right by the filter/drier which on the truck is in the discharge line.

Every where I look try to look at different schematics, they all show that pressure switch in the line with filter drier and this line is labeled as the "discharge line".

The following is from AC Delco parts website.

A/C Refrigerant Discharge Hose
Part Number: 15-34531
Product Notes:
A/C Refrigerant Discharge Hose
All; Compressor To Condenser; AC FRT AUTO/AUX CONT(CJ2), AC FRT MAN/AUX CONTROL(CJ3), REAR AUXILLIARY AC(C69); VIN: 0, Eng Code: LMG*; All; Compressor To Condenser; AC FRT AUTO/AUX CONT(CJ2), AC FRT MAN/AUX CONTROL(CJ3); Exc REAR AUXILLIARY AC(C69); VIN: 0, Eng Code: LMG*

Per Vehicle: 1; Years: 2007-2014

This kinda confirms my prior belief that there is no low pressure cutout, only a high pressure cutout.

Keep in mind my truck does have rear aux heat/ac. Maybe this differs for trucks w/o rear aux heat/ac?

What service manual was the picture taken from?

 

[PG01]

When I was first looking at this, I was pretty sure that I followed that line, with the pressure sensor in it, from the compressor to the condenser, which lead me to believe that it is a high pressure cutout. This is where Im so confused on this one.... the picture posted of the service manual labels the "low pressure" switch to be right by the filter/drier which on the truck is in the discharge line.

Every where I look try to look at different schematics, they all show that pressure switch in the line with filter drier and this line is labeled as the "discharge line".

The following is from AC Delco parts website.

A/C Refrigerant Discharge Hose
Part Number: 15-34531
Product Notes:
A/C Refrigerant Discharge Hose
All; Compressor To Condenser; AC FRT AUTO/AUX CONT(CJ2), AC FRT MAN/AUX CONTROL(CJ3), REAR AUXILLIARY AC(C69); VIN: 0, Eng Code: LMG*; All; Compressor To Condenser; AC FRT AUTO/AUX CONT(CJ2), AC FRT MAN/AUX CONTROL(CJ3); Exc REAR AUXILLIARY AC(C69); VIN: 0, Eng Code: LMG*

Per Vehicle: 1; Years: 2007-2014

This kinda confirms my prior belief that there is no low pressure cutout, only a high pressure cutout.

Keep in mind my truck does have rear aux heat/ac. Maybe this differs for trucks w/o rear aux heat/ac?

What service manual was the picture taken from?

My 13 lt with rear Heat/air has it right there, like the pic and fwiw it is called a low pressure switch/pressure sensor

 

[TheBigDirty]

My 13 lt with rear Heat/air has it right there, like the pic and fwiw it is called a low pressure switch/pressure sensor

Where have you seen it called a low pressure switch? Other than that service manual picture. That line runs from the compressor to the condenser. When the compressor is running, that line is hot. That tells me it is in fact a high pressure switch. If it were a low pressure switch, it would either be on the suction accumulator or in line between the suction accumulator and compressor and would feel cold and sweaty while the compressor is running.

 

[PPV12HOE]

On mine the low pressure switch is in the line... the high pressure switch is located in the rear of the compressor...

 

[UmmScott]

2013 body styles ONLY have a high pressure cutout.

There is NO low pressure safety. Its controlled thru an evap temp sensor

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[kbuskill]

2013 body styles ONLY have a high pressure cutout.

There is NO low pressure safety. Its controlled thru an evap temp sensor

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I thought I remembered @Rocket Man confirming that the SUVs didn't have the evaporator temperature sensor and that only applied to the Silverados.... maybe I'm confused.

On my '08 Burb the low pressure switch is on the accumulator as I recall.

 

[PG01]

Where have you seen it called a low pressure switch? Other than that service manual picture. That line runs from the compressor to the condenser. When the compressor is running, that line is hot. That tells me it is in fact a high pressure switch. If it were a low pressure switch, it would either be on the suction accumulator or in line between the suction accumulator and compressor and would feel cold and sweaty while the compressor is running.

I dunno, I lookeded at the pretty pic then poppeded my hood and didn’t see another switch In mine....my baddddd

 

[wjburken]

I dunno, I lookeded at the pretty pic then poppeded my hood and didn’t see another switch In mine....my baddddd

The picture does says low pressure sensor and not low pressure switch.

My manual shows the low pressure switch on the accumulator but my 2013 doesn’t match the picture so I give up.

 

[brichter]

If I recall correctly, the low pressure switch is located on the high pressure hose, and it detects low refrigerant pressure and interrupts the compressor cycle when the refrigerant is lost. That's why they call it a low pressure switch, because it's function is to detect low pressure.

 

[1BADI5]

I replaced my low psi switch on Friday......not the compressor is working correctly. I think its time to get the R34 evac'd and replaced.

 

[TheBigDirty]

Ok so to summarize....

A freezing evaporator can be caused by several different conditions.
A) Inoperable blower motor
B) Clogged filter or clogged coil
C) restriction in the metering device
E) low freon charge
F) improper compressor cycling

There is no low suction pressure cutout on the tahoe, only a low system pressure cutout.

If system charge has been verified to be correct, hi & low pressure's are within range (before the evap coil is frozen) there is plenty of air moving across the evaporator....

The culprit appears to be a faulty evaporator temperature sensor. Apparently this sensor is prone to failure and determines the cycling rate of the compressor to keep the discharge air a constant temperature dependent upon blower speed and temp of air entering the coil.

In the OP's case, it sounds as though, given all system components check out, that the evap temp sensor is keeping the compressor running too long and causing the evap coil to freeze up, because its simply running the compressor too long.

In my case, I feel as though its satisfying pre maturely therefore the discharge air is coldish but not ice cold. I still need to do verify my system charge with real pressure gauges, but Im fairly certain it's fine. I dont think my orifice is clogged, because the line becomes cold and sweaty directly after it but this will be confirmed when I get some real hi/low gauges on it.

Feel free to tell me if im way off on this one.

 

[TheBigDirty]

Trying to find information on the location of the low pressure ac switch for the 2011 Chevy Tahoe. Suspect it needs to be replaced but can’t locate it.

I looked up the evap temp sensor,
found it on Amazon for $24 & the best part is.... almost all reviews said it fixed their evap freezing prob

Part number 15-51267

 

[Cjherndon]

Thanks BigDirty for posting that. I assumed my evap temp sensor was the culprit. My next question is...anyway to replace this part without pulling the dash and steering col out?

 

[kbuskill]

Found a pic in my phone of my low pressure switch on my '08 Burb. Mine is on the accumulator...

 

[TheBigDirty]

Thanks BigDirty for posting that. I assumed my evap temp sensor was the culprit. My next question is...anyway to replace this part without pulling the dash and steering col out?

There is one video on youtube. But other reviewers have described a similiar method...

Removing the air bag to get to the connector, and cutting a hole somewhere in the evap box, top or bottom, dealers choice, to fish the new one in place, then plugging or patching the hole

 

[TheBigDirty]

Here's the youtube link

 

[Indy1K]

So, I am dealing with Evaporator Freeze up on my 2007 Tahoe. There has been discussion that the Evaporator Temp Sensor is the culprit. I cannot find any reference to this sensor for the 2007 Tahoe. It appears to be available for 2008 and up.
Can someone tell me if there is an Evap Temp sensor on the 2007 Tahoe that controls the compressor cycling?
People are saying it is the LP sensor that controls the compressor clutch. I dont think that would be the case on a fully charged system.

Thanks ahead of time.

Kevin
2007 Tahoe LTZ
2002 and 2008 Avalanche

 

[cbb468]

I have 2016 gmc yukon denali 6.2 liter. I dont see the location of the low pressure switch. Any help i dont see the dryer on the firewall either.