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AC "sufficient" on the highway, but not in town

torque395 on Wed May 26, 2010 3:21 AM User is offline

Year: 1996
Make: Chevrolet
Model: Suburban 2500
Engine Size: 6.5L TD
Refrigerant Type: R-134a
Ambient Temp: 80
Pressure Low: 30
Pressure High: 250
Country of Origin: United States

I know I have a slow leak, I have to add a can of refrigerant once in a while. On an 80 degree day I'm doing good to get 60 degree air in town, but its easy on the highway. On a cooler day I can get 50 or 55 degrees pretty easily. I really think the system has too much oil in it, I know the previous owner and he works on his own AC stuff. He likes to use interdynamics Arctic Freeze refrigerant which contains oil and sealer and performance booster all in the can with the refrigerant. Since hes refilled it a time or two or three, and ive filled it (i think ive used some cans with oil in it, but usually i get the kind with no oil) I think there is too much oil in it. I have removed the radiator, cleaned it and the condenser squeeky clean. The fan does not freewheel when you spin in, it has resistance and when you take your hand off of it, it does not continue to spin. The engine does not have any problems getting hot, even on the hottest days.I dont think there is any problems with it getting enough air. The other day I hooked up the gauges and after adding one can of refrigerant I was right at 30psi low and 250 on the high side at about 1600 or so RPM. This is a diesel truck with high gears (3.42) so it runs low RPMs and i imagine the crank pulley is larger to compensate for the low engine speeds.

Does it sound like my problem could be caused by too much oil in the system? My guess is that the oil is mostly in the condenser, displacing the refrigerant and thus causing it to not get very cold. Does this sound right?

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

bohica2xo on Wed May 26, 2010 2:34 PM User is offline

What you have is a swampy mess. Your pressures indicate the compressor is still capable of pumping, so...

1) Find the leak.

2) Fix the leak.

3) Flush to bare metal.

4) Replace the Orifice tube, rear TXV if so equipped, and dryer.

5) Add proper oil charge.

6) Evacuate & charge by weight.

Only real way to get the system back to a known condition after a dozen or more magick in a can top-ups.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

torque395 on Thu May 27, 2010 1:13 AM User is offline

I added some yellow dye to the refrigerant and the only place I can see any of the dye at is around the oring where the low side hose connects to the compressor. I forgot I had taken that loose a long time ago and didnt replace the orings because the AC didnt work. So that is probably the leak. The rear system does have a TXV.

Where do I put the oil at when I fill up the system? In the compressor?

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

arnea on Thu May 27, 2010 8:42 AM User is offline

I have the same issue with my 97 chev suburban dual system. Compressor failed, replaced compressor,accumulator, orifice tube, tvx, condenser, flushed system, and added the required oil into the components as per the shop manual and charged from a 30lb cannister with a scale to 64 oz. If I drive it in the highway it works OK. If I am in town and the temperature is 90 or above it blows somewhat cold out of the vents but never cools off the interior. What am i missing??/ could the system have too much oil in it??? Thanks Arne

bohica2xo on Thu May 27, 2010 12:21 PM User is offline

Torque:

I usually put as much of the oil as I can into the compressor, and the balance in the accumulator. Be sure to turn the compressor by hand to clear the oil out of it after you close the system up.

Once the system is in vacuum & ready to be charged, I charge liquid into the HIGH side with the engine OFF. Try to get as much of the charge in as you can, before starting the engine. Once you have 75% (or as much as it will take if less than that) of the charge in, close the high side valve. Charging into the high side like this keeps the liquid refrigerant from washing the oil out of the compressor.

With a bulk charge in the system, start the engine. The compressor will probably be cycling - let it cycle. Charge the remaining charge through the low side as a gas, the cycling will eventually stop if you have the doors open & both evaporator fans on high.


Arne:

Sounds like an airflow issue. It cools well on the highway. Tired fan clutch / dirty heat exchangers / missing fan shroud - are the top 3 reasons for this. Some pressures would help with the diagnosis in your case. If your high side is hitting 300 psi on a warm day, then it is airflow. Run a full load test & idle test, then post the pressures here.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

HVargas on Thu May 27, 2010 12:25 PM User is offlineView users profile

Quote
Originally posted by: torque395
I added some yellow dye to the refrigerant and the only place I can see any of the dye at is around the oring where the low side hose connects to the compressor. I forgot I had taken that loose a long time ago and didnt replace the orings because the AC didnt work. So that is probably the leak. The rear system does have a TXV.



Where do I put the oil at when I fill up the system? In the compressor?

Very good information from bohica2xo. Your system should have a rear expansion valve. We list one for the vehicle. You will need to remove it to flush the system anyways so it is always a good idea to replace it. I would recommend adding about 3/4 of the oil to the compressor and the rest in the accumulator.



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arnea on Thu May 27, 2010 12:48 PM User is offline

I have replaced the fan clutch and the original evaporator was also replaced. I was wondering if adding and electric fan would help???? Arne

torque395 on Thu May 27, 2010 2:07 PM User is offline

Arnea I have a question for you. Its unrelated to your problem, but still AC related. Do you get good air flow from the front passenger side vents? Mine do not blow much air and while the driver side vents move quite a bit, I dont know if they are moving enough air or not. Makes me wonder if my evap is partly clogged.

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

arnea on Thu May 27, 2010 2:11 PM User is offline

I'll check..Arne

arnea on Fri May 28, 2010 7:58 AM User is offline

I checked the air flow last night and found the air flow to be the same in the center and side vents...Arne

torque395 on Sat May 29, 2010 11:50 AM User is offline

Thanks aren.

Guys I discovered my leak for sure. I was changing injectors on my truck last night and I kept smelling the refrigerant. It has sort of a sweet smell to it, if youve ever dont AC Work before then Im sure you know what it smells like. It is coming from either than one O ring like i think i mentioned) or from the compressor housing (which is possible being an HT6). I think its that oring where the hoses mount tho. Also in dead silence you can hear the leak. I had never noticed that before.

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

bohica2xo on Sat May 29, 2010 2:46 PM User is offline

If you can hear it, you can find it with soap bubbles. It will not stay charged for more than a few days if it is that big of a leak.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

torque395 on Sun May 30, 2010 9:39 PM User is offline

It stays charged for a couple weeks. Even after winter time it still has some charge in it, but not enough to operate. I put a can or two in it every few weeks. Id never heard it leak before, but i could smell it while working on it, and when i turned everything off to go inside for the night i could hear a gurgling sound coming from the compressor area.

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

torque395 on Thu June 03, 2010 12:47 AM User is offline

I thought today that I should mention that when I shut my truck off you hear the AC system hissing for several minutes (pressure equalizing between the high and low side). Does this indicate anything? Perhaps a clogged orifice tube?

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1996 Chevy Suburban 2500 4x2 6.5L Turbo

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