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64 impala a/c question

ro.co3 on Mon June 16, 2008 2:25 PM User is offline

Year: 1964
Make: chevy
Model: impala
Engine Size: 350
Refrigerant Type: 134a
Ambient Temp: 80
Pressure Low: 40
Pressure High: 200
Country of Origin: United States

I've been following this forum and it looks like a lot of knowledge here. I just changed over my 64 impala to 134a and at first all went well. But the other day I noticed that the evaporator was freezing up and I thought it might be low on gas. So I shot some more in and then no cooling. Maybe to much. Anyway I started over and filled it again from scratch and the cooling finally came back but not great. I'm getting down to 57* at the vent at best. I think I might be having problems with the throttling valve not working right so maybe I need to retrofit with out the TV and go with a in line orifice tube and a thermo clutch cycling switch. Any feedback would be appreciated.

ro.co3 on Mon June 16, 2008 3:19 PM User is offline

I forgot to ask another question. If its getting down to 57* at the vent while I'm driving 55mph and then goes up to 65* at a traffic light does that mean I need more freon or less. Thanks again.

ro.co3 on Sun June 22, 2008 11:21 AM User is offline

I sure would like to get some feed back about my systems problems. I added more gas and it is working better ,down to 47* to 51* outside temp around 80* . I would like to get to around 40 degrees below ambient temps ,is that to much to shoot for?

tony1963 on Sun June 22, 2008 12:09 PM User is offline

One consideration is to convert the whole system to the CCOT type where you have an accumulator and a pressure switch at the accumulator. When the pressure drops, the compressor kicks out. I've done some of these on early to mid-70's GM designs with good results. You can buy the accumulator and lines for retrofit over the counter.

The last one that I did was on a 73 Caprice wagon. It worked well and the owner was happy. On your vehicle, my suggestion is to continue to ping the talent on this board. I don't have the experience to help you specifically if you want to keep the system OE.

Grove Automotive Group, Inc.

An Alabama Corporation

JJM on Thu June 26, 2008 3:09 AM User is offline

Did you test the STV by seeing if it holds vacuum and system pressures respond to adjustments? What about the TXV has it been tested? Perform this quick TXV test:

With the engine running at 2,000 RPM record your pressures. Now partially cover the condenser with a piece of cardboard to obtain a high side pressure of 325 to 350 PSI (be careful here). If the low side pressure rises, suspect the expansion valve.

Are your suction lines sweating excessively with the 40% or below relative humidity? If so, this is usually an indication of a flooded evaporator.

If you want a more extensive TXV test, carefully remove the sensing bulb from the evaporator outlet pipe, making sure not to kink or otherwise damage the capillary tube. Prepare a container of crushed ice and water (32ºF), and another container of hot water (approximately 125º or more). Start the engine and run it at 2,000 RPM, and record your pressures with the air-conditioning on. At this point your low side will be high. Immerse the sensing bulb in the container of ice water, and the low side pressure should drop. Immerse the sensing bulb in the container of hot water, and the low side pressure should rise. If the pressures do not change, or change very little, the expansion valve is defective and must be replaced.

I would strongly advise against downgrading to CCOT. These systems work, and your system was among the best engineered and cannot compare with CCOT.


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