Re: High Side Temp Sensor

What year STS ? It makes a difference.

For the refrigerant discharge temp (high side), look in the refrigerant line between the compressor and expansion orifice. The sensor will be a fitting with electrical connector. The next fitting is the high side test port - Schrader valve with black cap.

 

Hi,
I pulled some codes recently and one of them is AC 1312, High Side temp sensor.

Does this mean the sensor is bad?

Probably, but not necessarily. It COULD mean a fault in the circuit (shorted wire, loose connection), but most likely it is a failed sensor.

Finally, what exactly does it do?

As it's name implies, it monitors the high side refrigerant temperature. If the system is low on refrigerant and not functioning efficiently, it will trip the MIL and set a DTC or if severe enough, it will disable the compressor.

 

If you do have a defective sensor, you can NOT just replace it. If you remove it you will be venting the R134a into the air - not what you should be doing. You will need to have the system purged of the R134a, replace the sensor, then have the system refilled with more R134a. And that is presuming that your system uses R134a.

 

==============================
I pulled some codes recently and one of them is AC 1312, High Side temp sensor.
when discussing codes - ALWAYS post the complete code - AC 1312 is NOT a complete code -
along with its complete definition as listed here -
http://www.cadillacfaq.com/faq/answers/dtccode.html

example:B1312 - High Side Temp Sensor Open Circuit

Does this mean the sensor is bad?
not necessarily -
open circuit means either the sensor isn't plugged in -
there is a broken wire - or the sensor itself has been physically damaged -

where is it located?
that depends on the year/make/model of the car -

Finally, what exactly does it do?
it senses the temperature of the hot - liquid freon - usually after it leaves the condenser -
if the freon is still too hot - it disables the compressor - which pumps the freon around -
so the hot liquid freon stays in the condenser a little longer to get cooled off more -

 

Hey thanks, I was called out of town on emergency and just got back.

My car is a 1996 Seville STS


I'm only getting 50 degrees out of the vents. Would the bad sesnor cause that?

I was researching and thought I had a blocked orifice, but if my issue is the sensor, I would go ahead and replace the orifice and dryer if I have to drain the system to replace the sensor. Is that correct?

Thank you very much!

 

Ranger, would a bad sensor cause the air to be sub par, or does it just monitor the refrigerant? I'm getting 50 degrees at the vents, 40 is frigid in my car. I put some gauges on the system and my high side gauge is spot on, but the low side is reading almost zero. My research says that's usually a blockage going from the high to low side of the system at the orifice. Compressor and air seems to be fine just not ice cold.

Thank you!

 

Re: High Side Temp Sensor

Submariner409,

Thanks! I have a diagram of the unit and the high side sensor seems to be behind the grill (# 8 on the diagram) as the next thing in line is the high side port. I've attached a picture of the diagram, would you confirm this for me?

Thanks again!

 

Re: High Side Temp Sensor

Submariner409,

Thanks! I have a diagram of the unit and the high side sensor seems to be behind the grill (# 8 on the diagram) as the next thing in line is the high side port. I've attached a picture of the diagram, would you confirm this for me?

Thanks again!

================================
#8 is the HIGH PRESSURE SWITCH -
I suppose you could change it if you want -
but it will NOT solve your problem -

your code points to a problem with the HIGH SIDE TEMPERATURE SENSOR CIRCUIT -
if you are just going to try replacing parts without actually diagnosing the problem -
you should at east try replacing the right part -

#3 on your chart is the HIGH SIDE THERMISTER - (a thermister is a temperature sensor) -

you're welcome

 

(EDIT: See the later, correct post by basscatt) I didn't follow the high side far enough.

Do some in-depth searching to find out if the temp sensor is isolated from refrigerant pressure by a metal bulb. If it is, you can change the sensor without evacuating the system. If not, you have quite a bit of work ahead.

Think of the light bulb inside being the sensor, the glass enclosure as being the isolation bulb that the sensor screws into.

 

Will do, thanks for the help!

 

Yep - I followed the high pipe but not far enough ..............

 

Re: High Side Temp Sensor

Basscat, thanks for the clarification. Would a high side thermister keep my AC from cooling efficiently? I'm reading 50 degrees at the vent, 40 is ice cold. I was thinking that issue might be a clogged orifice, but maybe not. Also, does the unit have to be drained of refrigerant to replace the high side thermister? Thanks!

 

Re: High Side Temp Sensor

Basscat, thanks for the clarification. Would a high side thermister keep my AC from cooling efficiently? I'm reading 50 degrees at the vent, 40 is ice cold. I was thinking that issue might be a clogged orifice, but maybe not. Also, does the unit have to be drained of refrigerant to replace the high side thermister? Thanks!

======================
Would a high side thermister keep my AC from cooling efficiently?
possibly - but not very likely -
you must understand how the refrigeration system works to properly diagnose a SYMPTOM -

basically - cold low pressure liquid freon passes through the evaporator and picks up heat from the cabin -
this causes the freon to boil - and turn to a warm - low pressure vapor -
the warm vapor goes through the compressor and becomes high pressure - hot - liquid freon -
the high pressure hot liquid freon goes through the condenser -
dumps off heat and becomes a warm - high pressure liquid -
the warm high pressure liquid hits the orifice tube and becomes a cold - low pressure liquid -

------------------

there are several sensors throughout the system - all/most are monitored by the computer -
some are there to protect the system - some are there to optimize the effectiveness of the system -
these sensors usually simply disable the compressor -

LOW PRESSURE SENSOR protects the compressor -
freon carries the oil that lubricates the moving parts of the compressor -
if the low side pressure is too low - it can't carry enough oil - the sensor shuts off the compressor -

HIGH PRESSURE SENSOR also protects the compressor and other components on the high side of the system -
over pressure can blow out seals or even cause the condenser to rupture -

LOW SIDE THERMISTOR is there to optimize the efficiency -
too cold and the outside evaporator can can ice up and cause lack of air flow -
thus reducing cold air blowing into the cabin -
this will disable the compressor to stop the flow of freon -
to give the evaporator a chance to de-ice -

HIGH SIDE THERMISTOR is also there to optimize the efficiency -
its purpose to make sure the high pressure liquid freon has dumped enough heat going through the condenser -
if the high pressure freon is still too hot - the sensor disables the compressor - which stops the flow of freon -
so the hot - high pressure liquid freon spends more time in the condenser to dump off more heat -

-------------------------

now to move on to DIAGNOSIS -

FIRST - we need BOTH - HIGH side and LOW side pressure readings -
along with ambient temperature - and relative humidity if available -
and discharge air temperature from the center vent -
with the fan set to medium/low speed - temp set to 60* - engine at 2000rpm -

without this information there is no way to ACCURATELY offer any diagnosis -

---------------------

 

Basscat,
Okay, High Side Thermister sensor wire was loose. Pushed it on tight, AC 1312 code gone. I bought some AC gauges and here's what she read at 85 degrees and 81% humidity, fan on low, @2000 RPM... 27 PSI low side...300 PSI high side Read 50° at the vent Clogged orifice? Thanks!

 

Basscat, Okay, High Side Thermister sensor wire was loose. Pushed it on tight, AC 1312 code gone. I bought some AC gauges and here's what she read at 85 degrees and 81% humidity, fan on low, @2000 RPM... 27 PSI low side...300 PSI high side Read 50° at the vent Clogged orifice? Thanks!

========================
27psi is definitely too low - should be around 40 and 300 seems pretty high -
clogged orifice tube is a distinct possibility -

 

Re: High Side Temp Sensor

Basscat, thanks for the info.