Automotive Air Conditioning Information Forum (Archives)

98chrysler on Sun April 15, 2012 10:43 AM

Year: 1999
Make: Chevrolet
Model: S10
Engine Size: 2.2
Refrigerant Type: 134
Ambient Temp: 75
Pressure Low: 25
Pressure High: 150
Country of Origin: United States

I recently purchased a 99 s10 with the 2.2L inline 4. I did notice it was not cold when I bought it, but I figured it was simply low on refrigerant. I got it back to my shop and drained the system vacced it down for 30 min. and refilled it to the proper level of 28 oz.. The compressor runs fine and engages when the a/c is turned on but it fails to get cold inside. Tonight it was 75 degrees or so outside and the coldest it would get was right at 65 at the vent. I have approx. 25-30 psi on the low side and 150 or so on the high side. The accumulator freezes up almost immediately when the a/c is turned on and gets a fair layer of ice on the outside but the evaporator does not ice over. It remains free and air flows through it. I pulled the blower motor resistor and actuated the blend door and it is moving fully closed. I could also see the evaporator through the resistor hole and I checked the core temp with a inferred temp gun and it was 34 deg. The air flowing out of the evaporator is right at 60 deg . so I know it isn't a blend door issue. I thought I may have a restriction in the system so I evacuated the lines and pulled the orifice tube and it was nasty. The DPO had replaced the compressor before I bought it but must have not cleaned out the system well. I replaced the orifice tube and accumulator with new units and flushed out the evaporator, condenser, and lines with flush solvent and blew them out with air. I vacced the system down again and charged it back up with the same issue. What gives? I have checked everything I can think of and it is still mediocre. It's almost like the evaporator is not exchanging heat if that makes any sense. The accumulator reads at 22 degrees with the inferred gun. I should be freezing. After talking with other S10 owners it seems that it is not performing the way it should.

mk378 on Sun April 15, 2012 11:51 AM

Ice on the accumulator usually means the evaporator is also very cold. Is the compressor cycling (it should). It could be freezing up almost immediately. Clamp off or bypass heater hoses to make sure there is no reheating. Kind of remotely possible the evaporator is partly blocked but I would think with that much debris or sealer in the system the condenser would be clogged too.

Edited: Sun April 15, 2012 at 11:54 AM by mk378

98chrysler on Sun April 15, 2012 12:04 PM

The accumulator is about 22 deg F on the outside given my inferred temp gun is accurate. The evaporator core is 30-35 deg F with the gun on it. The air right out of the evap core is only 60 or so and I can see full actuation of the blend door, so I think reheat is unlikely. I also checked the operation of the recirculation door and it is working properly as well. The compressor does not cycle at all. There is only one pressure switch on the high side line just before the FOV and the high side pressure never exceeds 170 psi even at 2500 rpm for 3 min high and low pressures stay fixed. I did flush the evap out and I got no debris from it. I was also able to blow air through it freely with a air gun.

GM Tech on Sun April 15, 2012 2:12 PM

V-7 compressor systems are not supposed to cycle by design-- the compressors destroke to reduce capacity

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Sun April 15, 2012 2:50 PM

Right, I missed that. Low side should stay at the setpoint of about 25 like it is doing. He measured 34 at the core it must be an airflow issue.

98chrysler on Sun April 15, 2012 3:03 PM

Quote
Originally posted by: GM Tech
V-7 compressor systems are not supposed to cycle by design-- the compressors destroke to reduce capacity

Wow that sounds complicated and over-designed. The airflow through the evap is good. With the blower motor resistor removed I can access the back side of the evap core and take temperature measurements. I can also put my hand in there and feel the air coming through the evap. I also thought there my be a buildup of crud on the front side of the evap. I was able to remove the blower motor and inspected it using my video borescope. It looked clean and free of any debris.
So far today I have recovered the system again and pulled the FOV and inspected it for debris. There was nothing on it and it was open. I then removed both lines from the evap and blew through ti in both directions with an air gun. It seems to be open and free flowing. I then charged the system up a few oz at a time vs the full up front charge. I found that the system works better with about 18 oz in it vs the total 28 oz. Better but it is still only outputting 55 deg or so.

98chrysler on Tue April 17, 2012 12:33 PM

Here are a few pics I snapped after cutting open the old accumulator. I looks like there is some sort or stain on some of the surface. Does this look like black death? The previous owner had a compressor replaced due to as failure. Could some of this "corrosion" be inside of the evap causing it to be inefficient? Or is this normal in a 13yo. accumulator?

70monte on Sat April 21, 2012 10:49 PM

Almost sounds like the issue I had with a 2000 S-10 with the 2.2L. My friend and I never did fix it and he is not interested in trying to mess with it anymore. I think our issue is an evaporator core that is not sealed into the evap box correctly because I checked all blend door operations as well as clamping off the heater hoses with no results. Lines coming out of the evap to the accumulator were very cold just no cold air coming out the vents. I will be interested to see if you get yours fixed so maybe I will have some more ideas on the vehicle I worked on. Do a search for "2000 S-10" to read the issues I was having.


Wayne

Edited: Sat April 21, 2012 at 10:51 PM by 70monte

98chrysler on Fri June 08, 2012 7:25 AM

Yeah I got frustrated with the entire deal, and am now partially satisfied with mediocrity I guess. I have been through the entire system. I even went as far as to replace the evaporator and seal it up. I also put in another larger orifice tube. I did find that part of my problem was the radiator cooling fan. I had installed a high flow electric fan on the car and it was over-cooling the condenser to the point where the pressure was so low on the high side it was almost ineffective at least that is my theory. I rewired the fan to run on the low speed setting with the a/c on and I now have 275 high side vs the 150 from before. It seems to cool better like this. It's still not right. It gets warmer the further I drive the vehicle and even on it's best day is only 50 deg or so at the vents.

iceman2555 on Fri June 08, 2012 12:08 PM

Hi efficiency fan and over cooling the condenser??????

Not sure about this theory, but have a very high suspect that the condenser is restricted. The debris on the orifice tube indicates that a serious amount of debris was produced by the previous compressor failure. There is a good possibility that much of this debris is located in the inlet side of the condenser. This restriction of flow could result in the lower pressures indicated and the lack of cooling. Check the temperature drop across the inlet and outlet of the condenser...post results. Suggest to completely charge this system prior to this test..in fact this must be done and undercharged system will not produce the proper test parameters. ,

A disruption of refrigerant flow will result in a repeat compressor failure. Migration of lubricant is essential for compressor longevity, a undercharge or restriction will decrease the flow and the compressor will fail. Also operation of this compressor in a undercharged mode will result in serious damage. The control valve senses this undercharge as a low pressure concern and de-strokes the compressor. In the de stroked position, lubricant flow is disrupted to the compressor and this will also result in failure. Get it charged and post some surface metal temperatures. Evap In and Out---Condenser In and Out.

Let us know.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

70monte on Sun June 17, 2012 5:44 PM

Our symptoms sounded almost like 98chrysler's and we replaced everything including the condensor with no luck. I was thinking that our truck had a mechanical fan clutch but it's been so long since I've worked on it that I don't remember.

I do remember that the accumulator temp was very cold taken with my infrared thermometer and that I could not understand why the vent temps were not a lot better given that all of the blend doors were working correctly.

I still wish I could fix this truck since I don't like not being able to figure out a problem like this.

Wayne