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PSI readings are not correct! Please Help!

joshgray01 on Wed June 17, 2009 10:41 AM User is offlineView users profile

Year: 1997
Make: Dodge
Model: Dakota
Engine Size: 4 Cly
Refrigerant Type: R143a
Ambient Temp: 90
Pressure Low: 55
Pressure High: 275
Country of Origin: United States

I replaced my factory air compressor (The compressor clutch was not working properly) with new compressor from Advance Auto Store. I also replaced the condenser (I broke off the orifice tube by accident, rookie mistake), the accumulator, and the orifice tube (The orifice tube came new with the condenser.) I flushed the evaporator and the lines. Also, replaced all of the o-rings, and put 7.75 PAG 100 oil back into the system. I also turned the compressor by hand around 15 times (before turning on the A/C). I pulled 29 mercury for an hour, and performed a leak test for 30 minutes with the manifold gauges. The pressure held and I then added 2 and half cans of R134a (32 ounces- per spec). The gauges read on the low side 55, and on the high side read 275 (At idle speed, and around 55 on the low and 350 on the high at 2,000 RPM's on the highest setting!) However, my truck according to the manual calls between 30-45 PSI on the low side, and 190-210 PSI on the high side. So, I knew right then there was a problem, and also the temperature coming out of the middle vents on the highest setting was 66 degrees, and on the lowest setting read 51 degrees. Here is were everything started to go down hill. I adjusted the pressure a little bit to try to pull the PSI down some. Nothing really changed, and I was, "content" with above average cooling with all of the work I put into it. A week later the compressor clutch burnt up, it was literally glowing red, and my infrared thermometer said the temp was 315 degrees. So, under the warranty they replaced my compressor, and accumulator. I repeated all of the steps (Above) that I did in the first replacement yesterday. The PSI is still reading the same as the first time around 55 on the low and 275 (At idle speed, and around 55 on the low and 350 on the high at 2,000 RPM's.) So, I evacuated some freon out back out of the system, and it did not perform any better. In fact on it the air at the vents got a little warmer, and on the lowest setting the clutch cycled on and off around every 5 seconds it would cycle off for about 3 seconds, and the PSI would jump on the low side from 33 to 65 PSI, and the high side would go from 225 to 350 PSI on the lowest setting! On the highest setting the clutch did not really ever cycle off, and it is always blows warmer air on the highest setting versus the lowest setting (About 18 degree difference!) Please help I do not want to burn up this compressor too and I would like to be able to correct the problem, and finally have properly functioning system. Any ideas or suggestions?

FYI: On the truck under the hood a sticker states freon level should be around 1.75 Lbs and the oil is SP-20, but I went to the Dodge dealership to purchase the SP-20 oil, and they never heard of it. However, everything else states that my truck calls for PAG 100 oil. So, that is what I put into the system. Any suggestions for the conflicting information?

Thanks in advance,


mk378 on Wed June 17, 2009 11:16 AM User is offline

I'm thinking a couple of things. First it could have too much oil. Compressors usually come filled with oil, often enough oil for the whole system. Did the compressor have any instructions about oil?

A major reason for excessive high side pressure is inadequate condenser cooling. Is it an engine-driven fan? Can you spray water on the condenser and get the pressure to drop?

Voyager97 on Wed June 17, 2009 12:07 PM User is offlineView users profile

SP20 is the same as PAG 100. SP20 is simply the brand name for the oil used by Sanden Compressors.

Vic @ Pennine AutoChill

joshgray01 on Wed June 17, 2009 12:15 PM User is offlineView users profile

I believe the instructions said to add oil, and when I did add the oil I could not see any oil in the compressor from the suction side opening, or discharge side opening. I will double-check the instructions tonight to make sure on adding oil, and let you know what it says. Also, when I added the oil to the compressor (Added oil on the suction side). The oil actually reached the very top opening of the suction side, but I did not see any oil on the discharge side. I was wondering at the time if oil should come all the way to the top with adding only 3.5 ounces of oil to the compressor (FYI: I added 4.3 ounces to the accumulator). The fan is actually a electric motor fan style that operates on my truck both the radiator and the condenser (I watch the fan yesterday, and it was kicking on when the clutch was cycling on and off.) When I get home after work today I will spray water on the condenser to see if helps to drop the pressure, and let you know the outcome of it. FYI: When I am driving down the road at highway speeds. The temperature was blowing about the same verses when the truck is parked and at idling speed (About 1-2 degree variance.) Note: when I purchased the new condenser it was only capped on the inlet pipe, and not the outlet pipe. However, the orifice tube was in there on the outlet pipe. This was my first time purchasing/changing a condenser, and I was wondering if both sides should have been capped, but I am just not sure if that could make a big difference, as say buying a new accumulator and only one side was capped. Thanks and I appreciate your help.

joshgray01 on Wed June 17, 2009 12:21 PM User is offlineView users profile

Thanks for the website (Voyager97)! It is a very helpfull site.

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