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Residual pressure??

Cutlass84 on Sat July 26, 2008 7:11 PM User is offline

Year: 1995
Make: Dodge
Model: Dakota
Engine Size: 318
Refrigerant Type: r134a
Ambient Temp: 100
Pressure Low: 35
Pressure High: 250
Country of Origin: United States

Hey everyone, I've been trolling the forums for a while, figured I'd go ahead and see what you guys think of my predicament.

I don't know if this is a combination of problems, but it has me baffled.

My '95 dakota has always had at best marginal a/c. In an attempt to remedy this I have replaced:

-the condenser (with a 6mm picallo tube and fin because the truck came with an serpentine r12 looking one from the factory for some reason?)
-New chinese compressor from napa
-Orifice tube
-removed evaporator from heater box for cleaning with can of coil cleaner

After all of this I evacuated the system and attempted to recharge. The truck should take 2 lbs according to the sticker, but was showing normal readings on the guages with just over 12 oz of r134a. The low side line got cold, high side was scalding hot. It wouldn't even blow less than 60 at the vent.

I was thinking there may be too much oil in the system, so today I removed the drier to see if it would give me any indication. I'd say well over 5 oz came out of it. I left the lines open for probably 5 minutes while I messed with it. I then reconnected them and took the line at the condenser loose to look at the orfice tube.

When I pulled it loose, I was met with an additional blast of refrigerant??? along with a fairly sizable quantity of oil. How was there this much pressure stopped up at this point after having the system open like this? There are no mufflers in this system.. Pretty straight forward system really..

I am stumped.. What do you guys recommend? Flush, replace drier, add correct oil and try again?? This is getting expensive!!

'95 Dakota sport - 318/5 speed/2wd
'84 Cutlass - Olds 455/700r4

GM Tech on Sat July 26, 2008 8:32 PM User is offline

Re-read your title-- it is called residual pressure- when you first recovered the refrigerant it immediately boiled and there were cold spots anywhere in the systemthat liquid was trapped, or laying-- then a few moments later, those cold spots warmed slightly and was able to boil off some more liquid- most like liquid trapped in and under an oil pocket, now that creates gas when something boils and the associated pressure increase in what you saw and felt-- no big deal- you must wait untl the entire system reaches ambient if you wish to not experience this-- or put heaters (hairdryer etc) on the cold spots-- most likely the accumulator and evap-- If I want to avois this- I run the blower motor on low to warm the evap while pulling a charge out...

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......

Chick on Sat July 26, 2008 8:52 PM User is offlineView users profile

I find it pretty cool when pulling a vacuum and the accumulator "pops" from the refrigerant being pulled out of the oil...not all the time, but it does make people look...

Email: Chick


Freedoms just another word for nothing left to lose

Cutlass84 on Sun July 27, 2008 1:16 PM User is offline

That makes sense..

Any idea why the system is not taking the full charge like it should? Does this sound like there is too much oil in the system??

'95 Dakota sport - 318/5 speed/2wd
'84 Cutlass - Olds 455/700r4

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