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High low side, drops when rpm's increase

Jag987 on Thu August 27, 2015 12:08 AM User is offline

Year: 2003
Make: Honda
Model: Odyssey
Refrigerant Type: R134a
Ambient Temp: 70
Pressure Low: 70-90
Pressure High: 200

I think I am dealing with a bad control valve of some sort, but help me talk this out.

New compressor install, old one grenaded and filled system with metal debris. Condenser (that I hope had the desiccant inside), discharge line, and both expansion valves were replaced. The rest of the lines and evaporators were flush clean, thanks to Hecat, and blown dry with dry air. Added correct oil charged, vacuumed for hours, held pressure, recharged to spec. Low side was 70-90 and high started at about 200 and climbed some. As engine speed was increased, low side fell. At about 2,800 rpm's, low side was below 40 and there was cold air at the vents. Any time rpm's went down, low side pressure went up. Rpm's go up, low side went down. High side changed some, but was never too high or low. Driving around town there is little to no cooling, but does just fine on the highway. At idle, water on the condenser does not change low side more than about 10 pounds and does not create cold air from the vents. Then the low side is 35-40ish, the front and rear systems produce cold air, when it is higher neither does.

I really think there is a bad valve in the compressor, when rpm's go up, there is enough volume flowing to compensate. My other ideas are maybe a expansion valve stuck part way open or the desiccant was not in the condenser (I did not want to pull the plug off to check before I installed it and the condenser was pressurized when I gout it).

Thanks for the help again everyone!
Jag


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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

HECAT on Thu August 27, 2015 8:22 AM User is offline

Nothing is wrong with the high side, so the condenser spray did almost nothing. The theoretical lack of a desiccant sock would effect moisture removal, and not operation. So maybe I can help with the elimination of one theory. When the pressure in the Evaps becomes low enough, efficient refrigerant boiling and heat removal occurs (blows cold). So I believe you are on the right track that the TXV orifice(s) may be open too much, or the compressor just cannot suck enough at low RPM (defective compressor, RCV, etc.). Make sure it is not re-heating, and you are not fighting the effects of the heater core.


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Jag987 on Fri September 04, 2015 12:32 PM User is offline

Ok, I got to look at this again today for a few minutes. At idle:
ambient temp: 87 outside, full sun
Low side: 64
High side : 235
Vent temp: 63
so it is working, just not very well
at 2500 RPM's
low side: 42
High side: 300 and rising
Vent temp: 58 and falling slowly.

There is no reheat from the heater core. This is a dual system. I did not measure the rear vents with a thermometer, but the temp was about the same as the front and did also drop with engine speed increase. I only held it at higher speeds for about 2 minutes. Both cooling fans are working, but as Hecat pointed out, that would only affect the high side and my problem seems to be the low side. Both low side lines were very close to the same temp before they rejoined so I don't think there is a txv issue. If that was the case, I would expect the front and rear systems to be producing much different temperatures and I have a very hard time believing I got two new ones that were both bad.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

Jag987 on Thu October 01, 2015 4:17 AM User is offline

New compressor installed, everything is good now. Well, except getting paid to do it again.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

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