Automotive Air Conditioning Information Forum (Archives)

70monte on Wed June 08, 2011 4:55 PM

Year: 2000
Make: Chevrolet
Model: S-10
Engine Size: 2200
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 34
Pressure High: 255
Country of Origin: United States

I finished helping a friend repair the AC system on his S-10 but the problem is that its not cooling well at all, especially on max blower speed. I think I know what the problem is but wanted some input to see If I'm correct. Now for some background on what was done for this repair.

The compressor, accumulator, evaporater, condensor, OT, and all O-rings replaced. All O-rings and line connections coated with Nylog except the connections at back of compressor. 9 oz of Pag 150 installed in various components of system. Turned compressor by hand about 15 times to distribute oil.

I vacuumed the system down for 30 minutes and then let it sit for 30 with no sign of vacuum drop on the gauge. Vacuumed down the system for another 20 minutes with about 15 minutes of sitting time with no drop.

I than charged the system with 28 oz of refrigerant which is what the label called for. I was only able to get 75 degree vent temps at about 1500 rpms with the blower on high and the AC set at Max. Now here is where I hope the problem is.

The evaporater was changed, not because it was bad, but because the outlet line would not come loose from the accumulator. We ended up cutting the accumulator off which ruined the Evap outlet line. Of course when we took the old evap out, the evap box gasket got messed up and when we put everything back together, the box was no longer airtight, with air coming out aroung both inlet and outlet lines and along the top of the box. With this being the case, would this have a large inpact on the vent temps? The owner had somewhere to go so he was going to get some type of AC tape to seal the leaks on the evap box and let me know if the vent temps decrease. I was able to get vent temps of about 64 degrees by turning the blower speed from 4 down to 2.

The OT is in the inlet of the evap line right where it goes into the evap box so I was not able to see if the line was cold beyond the OT location since it was inside the box, but the outlet line was very cold and sweating.

So, how much does a leaking evap box affect vent temps and is this probably what the problem is.? If not, what else should I look at if vent temps do not get better once the owner seals the box up? The only other thing that I think may be a possibility but I doubt, is the fan clutch is probably original but the owner didn't want to replace it at this time. Increasing idle speed and taking a test drive did not decrease the vent temps at all so I don't know if the clutch is bad or not. It does not freewheel when you turn it by hand and has resistance. Thanks for any input you can give me.

Wayne

JJM on Thu June 09, 2011 12:21 AM

Sounds like everything was done right, and pressures look spot on.

At this point, it does appear air intrusion could be the issue - good call. Try clamping off the heater hoses for about 15 minutes or more and re-check the vent temps. If the vent temps improve, blend door issue - entirely possible doing an evap on an 11 year old vehicle.

Joe

70monte on Thu June 09, 2011 12:34 AM

Joe,
Thanks for the reply. If sealing the case doesn't work, I will try clamping off the heater hose and see what happens. Thanks.

Wayne

GM Tech on Thu June 09, 2011 8:10 AM

That's why I don't change accumulators unless system is contaminated.......

-------------------------
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......

70monte on Thu June 09, 2011 1:04 PM

The system was clean as the original OT did not have any debris on it. I should have left the accumulator on but I've always been told and have read to change the accumulator out whenever you open the system. Next time in this situation, I'll leave it alone.

The other issue though was that the owner had tried loosening this fitting before I got to his house and had twisted the evap outlet line pretty good but it wasn't that noticible until we opened up the evap case. Thanks.

Wayne

70monte on Mon June 13, 2011 11:43 AM

Just an update. the owner got the evap box sealed up but that did not change anything. Vent temps are still not very cold.

I have a question about the Condensor for this truck. The owner ordered the parts and the condensor he got was a Tube in fin design that was thinner than the original. He said they gave him the option of that one and a Parallel flow. Could the size and type of condensor be the problem.?

I don't think I installed the OT in backwards but if so, would this cause the poor cooling.? I don't think I did because the evap outlet pipe is very cold and sweating.

I don't think its the fan clutch because vent temps don't come down when you drive the truck.

I have not had a chance to talk to the owner until today so he hasn't gotten to clamp the heater hose off yet to see if its a blend door issue.

Where would the blend door be located on this truck? The fan pushes a lot of air through the inside vents so there doesn't seem to be any restrictions.

Can anyone give me any more suggestions because he is pretty bummed out that its not working considering all of the money he has spent on parts. I can't think of anything I've done wrong. Thanks.

Wayne

JJM on Mon June 13, 2011 10:35 PM

Another reason I recommend OEM parts - they only bite once.

You've got the wrong condenser in there. Tube and fin is not adequate for R-134a - especially if it's smaller than the original parallel flow. You get away with tube and fin on retrofits of older vehicles with huge condensers to begin with, but not R-134a vehicles, no way.

Also make sure the condenser is plumbed properly.

Joe

70monte on Tue June 14, 2011 12:38 AM

Joe,
Thanks for the info. I guess that might explain the problem. I guess we are going to have to swap it out for the correct one and see what happens. Just for clarification on the condenser plumbing, top line of condenser is from compressor and lower line of condenser is out to the evaporater.

Wayne

Edited: Tue June 14, 2011 at 1:02 AM by 70monte

70monte on Thu June 16, 2011 5:51 PM

Just an update. Today I used my infrared temp gun on the accumulator which is attached to the evap outlet line and the lowest temp reading I got was 46 degrees. Most of the readings were around 53-54 degrees. It was in the upper 80's and humid outside.

With the readings off of the accumulator, I'm thinking the problem is also pointing to a blend door issue. I know he had some kind of door issues because he cannot get any air through the floor vents. I don't know if this truck has a door to control heat/AC and one to control air flow location or what.

The wrong condensor is letting the system get pretty cold so I think he is going to focus more on a door issue right now than the condensor.

Wayne

JJM on Thu June 16, 2011 9:17 PM

Again, clamp the hoses as I originally suggested.

I'm still leaning towards the condenser. It's clearly the wrong one, inadequate for R-134a, and your pressure vs temperature readings confirm not enough heat has been removed from the refrigerant. If you were reading 34PSI on the low side, that should translate into 38.91F. You're looking at temps at best 46F, mostly 53-54F.

Also, measure the difference between the accumulator temperature and evaporator inlet temperature. On a properly charged CCOT system the inlet and outlet temperatures should be the same, or the outlet slightly colder than the inlet.

Joe

70monte on Fri June 17, 2011 12:33 AM

I did try measuring the temp difference between the inlet and outlet lines of the evaporator but the OT is in the inlet to the evap and the line behind the OT is inside the evap box so that you cannot tell what the temp is.

I also believe that part of the problem lies with the condesor but I also think that there is a blend door issue as well as the vent temps should be colder than they are even with the wrong condensor.

When he comes back from vacation, we will clamp off the heater hoses and see what we get. I will also try to convince him to change out the condensor but he is not too keen on doing that since he will be out more money for another condensor and refrigerant. I told him that is probably what its going to take to get this thing right. Thanks again for your input.

Wayne

70monte on Sat July 30, 2011 10:16 PM

Ok, I was finally able to get back to working on this vehicle with no success. The ambient temps today were around 97 degrees and very humid. My low side pressures varied between 30-35 and the high side from 260-275. Today vent temps were around 82-84 F* with AC on Max and blower on high with doors open at around 1500 rpms.

I also clamped off both heater hoses with no affect on the vent temps.

The accumulator and outlet line from evap were between 41-60F* depending on if I had it on Max AC or regular. Temps were taken with an infrared temp gun. The line and accumulator felt very cold and were sweating profusly.

We replaced some questionable vacuum lines in the engine compartment and took off the underdash trim and the glove box so that we could see the vaccum actuators. There were four that we could see.

When we moved the selector switch for AC, Vent, Defrost, and feet, all of the actuators moved at different times. Since I don't know which actuator actually controlled which door, I'm not sure if the correct ones were being moved. The flap for the foot vent actuator had some problems because it didn't look like it was fully moving in its arc. I disconnected it from the actuator and moved it by hand with no change in vent temp but you could feel more air through the foot vents.

When I rotated the cold to hot selector rotating switch, the hot side would get very hot but there was no movement of any of the actuators and I could not hear anything moving or changing. This is electrically operated so I'm not sure what it actually moves and if its a door, where is this door located?

All of the vacuum operated actuators had strong vacuum to them so I don't think there is a vacuum issue. The reg AC to max AC door worked correctly. The fan cage is behind this door. We had strong flow through the vents. I pulled off the rubber hose that goes from the bottom of the fan case to the evap box case and fairly hot air came out.

I compared the design of the new condensor we installed vs the original one and they appeared to be identical in design so I don't think its a condensor issue.

Does anyone know if there is a way to test the cold to hot selector switch on the control panel and does anyone know exactly what this operates? I still feel like we are getting hot air from the heater core interfering with the cold side of the evap but I could not see any other actuators other than the four vacuum ones mentioned earlier.

Where do I go from here? This has got me at a loss. Any help would be greatly appreciated.

Wayne

Dougflas on Sun July 31, 2011 9:03 AM

to positively eliminate the heater problem, disconnect the core and jump it out with a piece of hose. To check the condenser, mist it with a water hose. If the high side drops radically, the condenser air flow needs to be looked at. For about 25 bucks or so, you can purchase the all data cd on this vehicle.

70monte on Sun July 31, 2011 10:16 AM

I did some more research and I think I may have found the problem. My first mistake was assuming that the blend door actuator was vacuum controlled. After taking the heat/AC control panel loose, I saw that it had an electrical plug to the back of the rotary hot/cold knob. It didn't hit me until later that I should have been looking for an electrical actuator instead of a vacuum one.

I found a diagram online of where this electrical actuator is and I know why I missed it when we were poking around in the dash. It's located behind one of the vacuum actuators inside the passenger side of the dash behind the glovebox kind of high up near the top of the dash.

According to what I've read online, this electrical actuator is famous for either stripping the inside gear or causing the gear to crack.

Hopefully I can look at the vehicle again today after work depending if the owner is available or wants to mess with it.

Dougflas,
I will do what you suggested if I find out that the blend door actuator isn't broken. I'm betting it is though. I actually was going to mist the condensor but it started pouring rain and we stopped for the day. Thanks for the additional suggestions.

Wayne

70monte on Sun July 31, 2011 7:42 PM

Well, failure once again. I went over to the guy's house on my way home from work to remove the electrical actuator. I removed it and tested it by turning on the blower and rotating the heat/cold dial and you could see the gear move back and forth. I opened it up and all of the gears inside looked new.

I then turned on the AC and manually moved the blend door to the cold position and that did not change the vent temps.

We went to mist the condensor and it got soaked instead but it did not change the vent temps. I didn't have gauges on the system as we both didn't have much time to work on this today.

Soon after soaking the condensor, Ice formed all over the evap outlet line, the accumulator, and the line going to the compressor. This is the first time this has happened while working on the system. I'm assuming that soaking the condensor somehow contributed to the icing since this is the only thing different we have done.

What does the icing up of the above mentioned parts mean?

Since the blend door doesn't seem to be an issue, could it be possible that the wrong OT is installed? It came with all of the other AC parts that the owner ordered and I believe it was the same color as the original one.

We didn't have time to isolate the heater core so we will have to try that the next time.

Does anyone else have any suggestions on what to do next? We might have to have the current charge reclaimed and start over and so I can check the OT position in the line.

Wayne