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Poor Cooling

JLHAWKINS on Mon June 08, 2009 11:54 PM User is offline

Year: 1988
Make: Oldsmobile
Model: Cutlass Ciera
Engine Size: 3.8
Refrigerant Type: R-12
Ambient Temp: 88
Pressure Low: 28
Pressure High: 240
Country of Origin: United States

The above vehicle belongs to my 87 year old Mother who still lives by herself. She no longer drives but the vehicle is occasionally used to carry her places by myself when I visit and my sister who lives in the same city.

The vehicle has been in the family since it was new and currently has less than 70K miles. It has never had a compressor failure but I had to replace the compressor pulley a couple of years ago which required removal of the compressor. I recovered the R-12 (I have a make-shift rig that works pretty well for a DIYer although too time consuming for a professional), replaced the pulley, pulled a vacuum and recharged using the recovered R-12 supplemented with a little new. It didn't cool very well and I thought maybe I had missed it on the vacuum. I recovered again, pulled a vacuum and charged with virgin R-12 from the 12 or 13? oz cans. While the system was empty, I checked the orifice tube and found no debris of any type. It still didn't cool very well, vent temperatures around 60 but even when the vehicle was new, the cooling was never impressive. Since the vehicle was not driven much, I just kind of left it like that. Now for a confession. That was before I discovered this forum; I did not have a high side adapter for the vehicle nor a digital scale at that time so I charged it using the low pressure only (not good!). I now have both.

This past weekend, I was visiting and carried along my gauges. Driving the vehicle at moderate speeds still produces the 60 vent temperatures which makes riding in it tolerable. When I first put the gauges on and started the vehicle before the engine compartment got warm, at 1500-2000, the low side would pull down to 20 and drop out the compressor indicating a possible low charge. High side was around 190 at this time. As the engine compartment temperature increased, so did the pressures until they reached the above pressures. These were with the controls on "Max", condenser fan running, door open, blower on "high". Under these conditions, vent temperatures were around 70. Also the vehicle was sitting partially in the sun. From the forum, I understand that the high pressure should be about 2.5 times ambient which this is close. Of course the underhood temperature was much greater than the 88 ambient. The discharge tube from the evaporator and the filter/drier were not the least bit cool to the touch. The orifice tube for this vehicle is located adjacent to the condenser discharge up front and a long way from the evaporator. The line was cold just downstream of the tube.

Based upon my limited experience, it would appear that the system is undercharged but what about these pressures? The condenser is clear and the condensing fan running at what I would consider "high". I wish that I had "misted" the condenser but I didn't. I had a similar experience with a 134 conversion on a Buick utilizing the same compressor and the pressures had to be higher in order to get the inlet and outlet tubes of the evaporator the same temperature. It acted similarly as the underhood temperatures increased.

Any assistance on this would be appreciated.

Thanks

Chick on Tue June 09, 2009 7:19 AM User is offlineView users profile

Check for a leak, especially the front seal of the compressor.. Make sure the condenser fan is working properly, and you need the exact amount of refrigerant in the system..


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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

GM Tech on Tue June 09, 2009 8:14 AM User is offline

How is the airflow out the vents? Does it blow the hair back on your forehead? it should.. The evaporaotrs in 88-93 on GM "A" cars were known for porous leaks- allowing refrigerant and oil to leach out- which collects dirt and dust and plugs the airflow path-- you can pull your blower motor resistor and look at the air inlet face of your evap and determine if yours is leaking. It was always worse in Midwest due to acid rain aggravating the problem. I have had cars that I could not tell the difference between high and low speed blower- could hear it, but could not feel it.

I also agree the shaft seal is a good place to look for the leak-- is there oil slinging?

Sounds like you have the 3.8L - since that uses a cycling compressor the DA-6 (later the HD-6) all other "A-car" engines used the V-5 compressor- doesn't cycle.

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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......

JLHAWKINS on Tue June 09, 2009 10:06 PM User is offline

Thanks for the input. The next time I visit Mother who lives about 150 miles away, I will check more closely the things mentioned. By the way this is a Tennessee car near Nashville.

Concerning the airflow from the vents, I consider it poor even on "High" so a dirty, somewhat clogged evaporator is a very good possibility. I will pull the blower fan motor and take a look next time and report my findings.

Thanks again for your assistance.

JLHAWKINS on Sun July 12, 2009 10:54 PM User is offline

Just an update on this vehicle. I went to visit over the July 4th weekend and checked the vehicle again. As suggested, I tried to check the evaporator face for debris by removing the blower motor. I could not remove the blower motor from the case all the way due to the location of the power steering pump on this 3.8 engine. I noticed how large the opening for the blower motor resistor bank and how it was located very close to the evaporator core face. I removed the resistor bank and could see the face of the coil fairly well. It was pretty much clogged with leaves and other types of "tree" debris. It did have one small spot where it looked like dust had maybe gotten on an oil leak but it must not be much of a refrigerant leak as none has been added in the last 2 years. I vacuumed it out as best I could, blew it out with air and cleaned the face with "Greased Lightning" as best I could.

I reinstalled the resistor bank, hooked up my gauges and started the vehicle. The first thing I noticed was a large increase in air flow from the vents. Second, the accumulator started sweating, something it hadn't done before. Pressures were about the same as before with an ambient of mid-90's but the vent temperatures were in the upper 40's. Alas, cool air and lots of it. I had noticed on this vehicle that the air flow from the vents had not been what it should for many years. I don't know if it is what should be now but I know it is greatly improved and cooling is now acceptable.

Thanks for the suggestion about the clogged coil. You were right on target. I had a similar experience with my S-10 Blazer where I vacuumed a large quantity of water oak leaves from the case on it. There too, air flow and consequently both heating and cooling were improved. I just never really thought about it on Mother's car.

An observation from an amateur in automotive A/C, air flow over both coils, condenser and evaporator, play a major role in determining a system's performance. Poor air flow on either equals poor system performance.

Thanks again for you assistance. We are now riding in comfort!

GM Tech on Mon July 13, 2009 11:10 AM User is offline

Certainly appreciate the feedback- good to know we could help......got to keep Mom cool!!!!

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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......

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