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AC only cool...driving me nuts!


cheese's Avatar
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08-26-03, 06:53 PM   #1  
AC only cool...driving me nuts!

Hello guys!

I am pulling my hair out over this one. It should be so simple, but I can't get it right. I have a 1985 chevy scottsdale PU, 5.0, A/T. It has been converted to 134A long ago, shortly after the stuff began to get popular. My condenser line rubbed the side of the radiator and got a hole in it and the refrigerant leaked out. No problem, I replaced the condenser, changed the orfice tube while it was empty, vacuumed it down, added 2 oz of oil and filled it up again w/134A. Now it only blows cool. The temp at the vents is 60 degrees AT NIGHT! It used to freeze me out to the point that even low was too cold after awhile. What am I overlooking? Anyone seen this before? My pressures are 35/225. Thanks for any suggestions.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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msargent's Avatar
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08-26-03, 07:21 PM   #2  
When you replaced the condensor, was it the same size and design as the old one? Many times "they" update a design, and therefore the capacity is less than what you took out..Could be too much oil added..(did you add directly into the new condensor, or shoot it in after vacuuming?)
I SHOULD know the names of the different designs..but it's late, and a tough hot day has sapped the ole pea brain.. Tube and fin versus serpintine?????

 
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08-26-03, 08:52 PM   #3  
besides seeing if the condenser was of different design, did you notice if the orfice tube was the appropiate one for the vehicle or was it a different design from the one you removed the reason i say this is someone may have installed a variable orfice tube in it previosly which usually works more efficient much like an expansion valve.
do you have good airflow, fan working good?
what was the ambient temperature when you had the guages installed and noted those pressures? was this at idle.
did you see if the system held a vacum perhaps it has a leak at one of the orings fittings that you had undone to replace condensor or orfice tube.

 
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08-26-03, 11:28 PM   #4  
Thanks for the replies!

The new condenser is identical to the old...it has one continuous tube weaving back and forth through the fins, not the manifold on both ends. I have good airflow, condenser outlet line is not hot, but warm, and I installed a heavy duty fan clutch to be sure. The temp outside I would guess to be around 80 when the guages were installed, and at idle. The orfice tube looked to be the same, but who knows...it was a different color though. System is not leaking...still read those pressures. I did try adding a bit more, and now the pressures are around 45/260. (too much, but I gave it a try to see what the effects were). No better.

I am wondering about the "too much oil" theory. This is some history to go by to give an idea of how much oil might happen to be in the system. My compressor grenaded a few years ago. I flushed the entire system, replaced the compressor, dryer, and orfice tube, and added 2 oz of oil for each component...8 oz total..might have given an ounce extra for good measure. Then, a while later, the condenser rubbed through and I had to replace it. I added 2 ounces of oil then to replace what was lost. Then, it wouldn't do well, and during testing, I managed to damage a schraeder valve and lost my refrigerant again, so while it was empty I took it back apart and changed the orfice tube. I added 2 oz again, to replace what was lost. That is where I am now.

Also, I want to mention that I felt over the case and changed the selector switch on the instrument panel while keeping my hand on the linkage over the box. It moved well when I selected different positions, and I can hear the blend door flop back and forth when I change from hot to cold. I think I will bypass the heater core for testing purposes just to positively eliminate the possibility of getting heat mixed in.

What gets me is that the system is so simple...what can be so wrong?


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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08-26-03, 11:29 PM   #5  
Oh yeah...I also pulled the blower motor and resistor out to gain access to the evaporator to make sure nothing is blocking it. It is clean and clear.


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08-27-03, 02:02 AM   #6  
Your original pressures sound good. That indicates everything should be functioning properly. It sounds to me like the blend door isn't closing properly or all the way and you aren't getting proper heat exchange. I would check the mode controls and see if you can manually move the blend door and see what happens.

 
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08-27-03, 03:28 AM   #7  
Joe_F
I'd agree .

Make sure you buy the correct OEM orifice tube as well. If memory serves right, color MIGHT make a difference .

 
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08-27-03, 07:55 AM   #8  
My .02, I'm going to side with Yamaha W on this one. My 90 Suburban the diverter door was not moving correctly, the inexpensive (read cheap) plastic connector was broken, not allowing the air to come out of the proper outlets. The air when on normal would also come out of the heater vent, cool not cold.
I replaced this piece and now you will get frozen out even on a
90+ day.
I had this same problem on a 70's vintage Blazer.
Remove the glove box, slightly to the left of center and low is an access cover three screws I think, this door is under this cover, you should see a white plastic connector in the middle of the door.
The linkage goes through the door straight back, or toward the front of the vehicle. The plastic part is attached to the door with one screw and to the linkage with a pin, (looks like a small nail).
If this is broken the part is $3.00 at the dealer, if you need the part # I can give it to you may save some time at the parts counter.

 
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08-27-03, 08:41 AM   #9  
FIRST KNOW THE R-134A DOES NOT CHILL LIKE THE R-12.YOU LOSE ABOUT 4-5 DEGREES. ALSO THE TEMP DOOR, RAPIDLY MOVE THE LEVER FROM COLD TO HOT, YOU SHOULD BE ABLE TO HEAR THE DOORS HIT THE STOPS INSIDE THE HEATER BOX, IF YOU CANNOT HEAR IT WHEN GOING TO COLD, THE TEMP DOOR NEEDS ADJUSTMENT.

 
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08-27-03, 05:10 PM   #10  
as joe stated alot of orfice tubes can be different in how they meter the freon and color is one way of indicating this if it was a different color you probably got the wrong one or atleast changed it from one that was working better in your vehicle with r134a.

 
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08-27-03, 05:40 PM   #11  
If you had the wrong orifice tube, it would affect the high and low side pressures. It really sounds like it's the mode control.

 
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08-27-03, 05:50 PM   #12  
My last cent on this..If the system cooled very good before the hole in the condensor line, and now it doesn't, then it seems normal to assume the problem lies with the repair procedure and/or parts used. Alldata usually offers temperature charts for the condenser, vents, inlet and outlet temps of the evaporator. It should give you a list of ambient temps and humidities to match up to the actual temps of the trucks components. The temps on various components will help determine what corrective action(s) are needed.
I'd still lean to the orifice tube, or too much oil..

 
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08-28-03, 12:52 AM   #13  
Thank you all for your thoughts! I drove the truck on service calls today, and it actually did pretty well. It stayed cool. Long idle times let it warm up a bit, but I can live with it until I get some more time to look at it. I still plan to bypass the heater core to eliminate the possibility of heat mixing, but I don't think there is a mode controller or blend door problem after checking the actuators. (and I hear the blend door flop from one side to the other when switching it). I need to replace the heater hoses anyway, so I'll bypass the core with an old hose before I put new ones on, just to make sure.

The condenser is an exact GM replacement part. I don't have line temps for you yet, but have access to a temp gun, so I might try to get some readings for you.

Thanks!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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08-29-03, 01:19 PM   #14  
Here's something that might be interesting:

It rained today while I was driving this truck. I have a thermometer in the vent to keep an eye on temps. The vent temps were around 60 while driving, but when I hit the rain, they went down to 40 and got so cold that even the low setting was too cold for me. The outside temp didn't drop much. I know humidity does contribute to ac operation, but 20 degrees worth?


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08-29-03, 01:38 PM   #15  
Joe_F
Is the rain somehow cooling the condenser and lowering the head pressures perhaps ?

I have seen some guys test for that by "cooling" the condenser with a garden hose.

 
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08-30-03, 01:14 PM   #16  
Not exactly sure if that's what is going on or not, but it would seem so. The funny thing is that the head pressure is not high.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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