2001 S-10 A/C electrical problem?

[RonnieT]

My wife drives around a 2001 S-10  4 cyl.  Manual shift that we bought new.

     Only ever did maintenance  and the usual brakes,  water pumps etc.

The A/C this summer decided not to come on, 

Meaning  the blower works and all the  door modes are correct only the  clutch on the compressor does not come kick in. First thought was  finally low on  refrigerant , No it was fine.

So I did the fuse and relay look and all  was good, so I figure it is a pressure switch or, ground or worse a Climate control  panel or the PCM?

 This model S-10  I think only has one  pressure switch that I can see it is near the accumulator but is  NOT on the accumulator,  it appears to be the High pressure line as it comes from the firewall mounted condenser from its bottom and is a small line.

    It has 3 wires not the normal 2.

The only wire that shows any positive voltage is  a wire that appears grey or tan? and the voltage showing on my test light is weak, not a full 12 volts.

 I also cannot  short around  any combination of these terminals and cause the clutch to kick in. This while the  Climate control is on Max A/C  and  the dial all they way over into the blue  color line.

  So I check on the relay again by changing it out with working Horn relay, still does not work. and I do not have at anytime a positive voltage on either clutch  wire at the compressor,

 Now while  the relay while  is installed in the relay box, only slightly raised I can short  to ground the  #30  terminal and the clutch will engage.

 #85 and #86 terminals I do have positive voltage  on one and also the other when the A/C is turned on. I have looked for  bad grounds, and loose connections all over the engine .

 I only see one pressure switch on the  A/C lines and I have looked  at  every inch of the lines in the grille and everywhere.

 I feel like it is a bad ground or a bad Climate control head.

  My CC head does not have a separate switch/button for the A/C only on the right had dial can you  turn on the A/C.

 Can some one help me with a wiring diagram of a clue where to look?

 No the motor does not speed up when  I  turn on the A/C.

 Thank you 

Ron

 

[Ferrnt]

Try this place... you have to sign up and from what I understand... don't abuse too much. I used them to "wring" out an issue last year. Used it for a wiring diagram.

BBBindustries.com

[Jsdirt]

You said the refrigerant was "fine" - what pressures are you seeing?

 

The cycling switch should be somewhere along the low side line, from the evaporator exit, through the accumulator, and back to the compressor, unless you have a thermal expansion valve system. If it's an orifice tube system, that's where the cycling switch will be.

 

Anything with 3-wires is a computer monitored sensor. 1 wire is a 5v reference - that's the low voltage you saw. The other wire is ground, and the last one is the signal back to the computer - pressure, or lack thereof, will change the 5v reference by pulling it down - the computer interprets the pulled-down voltage as data. If you unplug the sensor, the voltage will rise to 5v, or somewhere close to it.

 

I'd have to see a picture of the line it's on to determine if this was the cycling switch, or a high pressure cut-off switch.

[RonnieT]

Jsdirt, I will get a picture of the switch tomorrow, it  is NOT on the accumulator , the Accumulator  line comes out at the top of the condenser box and is a big line, this comes out at the bottom of the box and is a small line that  turns and comes up next to the accumulator, 

 As far as pressures, I do not have a nice set of  134 gauges, I have a single gauge mounted hose  that gives the indications of low,  good and too high.

 I installed a new can of 134 on the hose/gauge and tried to  inject it into the system thru the low pressure side  port, It would not take any of its contents.

[Jsdirt]

The low side line will NOT be going to the condenser. From the compressor, all through the condenser, and out to the orifice is all the high pressure side of the system.

 

I'm willing to bet it's probably just low on refrigerant. Those can gauges that come with auto parts store cans are garbage, as are some of the fittings.

 

It's amazing that nobody has sued the companies that sell these things - someone could easily hook one up to the high-side, and have the can detonate right in their face.

 

I'd find a buddy with gauges, or, just spend a few bucks on a diagnosis at a local shop. Tell them you just want to see if there's refrigerant in the system. Probably only cost you a half hours labor.

 

Or just buy a set yourself - Harbor Freight probably has a cheap set, along with the fittings, I'm sure. 

 

EDIT just to say, the proper name for the switch is the LPCO - Low Pressure Cut-Off.

[Doug_Scott]

I don't recall seeing a north American made GM vehicle that did not use a fixed orifice tube a/c system.  How sure are you that this is factory air? 

The fitting you attached the can to should be the low side. Follow that line all the way in both directions.  Moving to the front of the vehicle it will go to the compressor. Going to the rear of the vehicle it should go to the accumulator, and then into the heater box. The high side line will go from the condenser straight to either an expansion valve or you will see a connection in the line.  Right after the connection you should see a couple of dimples in the line.  Those dimples will be where the fixed orifice tube resides.  If you have those dimples you will also have a pressure switch on the low side.  Sometimes these switches can be in some pretty stupid locations that will require some acrobatic moves to see. Check the backside of the receiver/drier. 

[RonnieT]

Ok, I will find a set of 134 gauges tomorrow and get the right reading on the pressures.

   I was calling the  condenser the wrong name,  Not the one in front of the radiator but the one  coming from the "heater box".  The "LPCD" is on the line at the bottom of the "heater Box", the larger line is at the top of the Heater box and has the accumulator on it, I do not see any other switch on the lines or accumulator but will stand on my head again tomorrow to  see  if I missed it.

 the  port I was using trying to fill it with 134 was a port on the accumulator,, Low pressure side, and  it would not take any.

 In the past when I filled other A/Cs   the compressor would usually kick on  after about  most of a can would get into it.

 I don't think I one hose gauge  would fit on the other port, wrong size I think.

[Doug_Scott]

It's called "evaporator".  You are correct, the single gauge hose connector will not even come close to fitting high side port.  

 

I took a look at a few sites that sell a/c parts and they all list a fixed orifice tube.  The pressure switch usually attaches by way of a screw on fitting that has a Schrader valve in it.  This allows you the ability to change the switch without opening the system. Take a look around the low side lines and see if there is an electrical connector that is not connected to anything.  Also look for a threaded connection point on the low side.  I am wondering if maybe the switch has been removed for some reason.  The wiring connector will have two wires. 

[Jsdirt]

Yeah, it might be hiding behind the accumulator somewhere, especially if it's been changed once or twice before.

[RonnieT]

Ok, I have had some time to look at this closer,

    I only see the one Switch and it has 3 wires, I looked and felt around the Accumulator, its lines and looked at the lines coming and going to the compressor, evaporator and condenser, nothing more of another switch.

    I did borrow a nice set of gauges that attached to the  large High side  port and the small low side port on the Accumulator.

 The Low side gauge is also a valve   that allows the  134to go thru it and shut it  off too.

It also has a ball valve on each hose just above each port connection so 134 loss is very minimal if any.

 Now the problem is the  clutch will not engage  ( never do I get a 12 volt reading at its connection) only when I ground the #30 terminal on the relay.

   So without the clutch engaged  I am getting a reading of over 100psi on the LOW pressure side at the accumulator.

    The gauge is pegged at that reading when I open its valve.

Same reading I was getting with the cheap hose gauge.

    The High side port I am getting a reading of 50 psi.

   These readings are with no compressor  clutch running or engaged,

The refrigerant lines starting at the compressor is one large line that goes across the top of the radiator to the Accumulator,

the other line is a smaller line that goes across the top of the radiator also and then turns down and goes into the condenser  in front of the radiator. the other line coming from the condenser and goes up along the accumulator  where the  3 wire switch is and the large refrigerant port is, turns down again and goes into the heater box  ( evaporator) where at the top of the heater box a large line comes out at its top and goes to the other side of the accumulator.

         The A/C has never been serviced or any parts changed, never have I had to  add any refrigerant.

 I honestly think the trouble lies in something electrical? I am probably wrong but  think the climate control head is probably bad?

 I don't know 

 If I had a  wiring diagram I could possibly trouble shoot that 

    I have a picture of the 3 wire switch I will try to upload.

     thank you for any help you may have.

  Ron

[Jsdirt]

They must be using the computer to cycle the compressor these days. I can't keep up with all this modern crap! 

 

If it's got 3 wires, then it doesn't work like a normal 2-wire switch. The computer is interpreting data that it gets by the voltage it receives from the sensor, after sending it it's 5v reference (the sensor will take the 5v, and either pull it down, or up [only to 5v - not above] - from that, the ECU knows the pressure of the system - same way all sensors work on modern vehicles). The computer will then decide to kick the compressor on ... or not. The sensor itself could be bad - you'd have to know what "good" looks like, then test it in action ... but 2 different static pressures between the high and low sides suggests you've got a serious problem inside, such as a blockage. The desiccant bag can rupture, and flood the system with it's contents, plugging up everything along it's path - once modern condensers get plugged, the only solution is to toss them in the trash and buy a new one. They can never be reliably flushed - passages are far too small. Things used to be so easy, before the damn government decided R12 was going to destroy the world . Used to be able to easily flush tube and fin condensers, and use them forever. Also had much better refrigerant ... but I digress. Also could've suffered "black death" as a result of compressor failure - that usually requires replacing everything that cannot, or should not be flushed. Before jumping to those conclusions, you need to be sure these gauges are accurate, and that the refrigerant is actually making it to the gauge. Sometimes those adaptors won't depress the valve far enough to get an accurate reading. 100 psi would be normal if it were 100°F outside. 50 psi is too low, unless it's 50°F or so out. But, with the system at rest for any length of time, the high and low sides should be equal. I'd be looking at those gauges first - make sure you've got the valves open all the way, and if you do, make sure they're contacting the valve core inside the line when fully open.

[RonnieT]

Yes it was 100 degree plus out today in the sun when I put the gauges on it.  Will look again at the gauges and see what my  GMC 1500 says the pressures are, its a 2000 model so should be close to what I need to see since the GMC  A/C works fine.

 I guess I could get a new  3 wire switch and replace that ?

 Ron

[Doug_Scott]

With engine off both high and low side should be equal pressures.  With engine off and gauges connected with both valves closed, turn compressor clutch by hand and see if the pressures change in any way. Not suggesting you can turn it fast enough to generate pressure, just wondering if something is up due to compressor position internally. 

 

When you are getting 100 psi on the low side do you happen to have a can of 134a connected to the gauge set?  I ask because every gauge set I have used worked with valves closed.  The only time you would open a valve was to add or drain refrige

 

[RonnieT]

10 hours ago, Doug_Scott said:

With engine off both high and low side should be equal pressures.  With engine off and gauges connected with both valves closed, turn compressor clutch by hand and see if the pressures change in any way. Not suggesting you can turn it fast enough to generate pressure, just wondering if something is up due to compressor position internally. 

 

When you are getting 100 psi on the low side do you happen to have a can of 134a connected to the gauge set?  I ask because every gauge set I have used worked with valves closed.  The only time you would open a valve was to add or drain refrige

 

Will turn clutch by hand and feel for any resistance.

     Good Idea on the can of 134 on the gauge line, I don't  know if it was a full can or an empty one, it did have a ball valve just above the  can so I can isolate it, or I could shut off the can by using the valve attached to the can  to be sure it is isolated. 

 I lost the picture of the switch but will  snap another one.

[Doug_Scott]

It's a common misconception that a can of refrigerant will register a lower pressure as the contents go down.  A full can and a 1/4 can will both show the same pressure.  This is why you cannot just measure the pressure in the system without running the compressor to see if there is sufficient amount in system to test. 

If you are only showing 50psi with the system just sitting with engine off and an ambient air temp at near 100 degrees, you have virtually no refrigerant in the system. That means you have a leak in the system.  You can take a good look at all the components you can see and look for an oily patch.  Generally a leak will also leak some oil since the oil is carried by refrigerant.  When it leaks the oil will collect around it and will trap any dust that comes in contact.  Or, try to locate and borrow a leak detector.  Common points to look at are, compressor clutch seal, valve cores at gauge port connectors, "O" rings at pipe connectors, lines or hoses with any rub marks, condenser, or evaporator.