Engine Size: 350 5.7
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 39
Pressure High: 175
Country of Origin: United States
By the I've chart this is what it is supposed to be. But as the ambient temp rises the pressures go up. And I know that this is supposed to happen. I've tried to lower pressure, when I lower it to say 22 on low side 70-80 ambient the evaporator starts to freeze up on the inlet just after the ot. I was wondering if moving the ot just after the condenser outlet would prevent the freeze-up and if i could run lower pressure say 22-25 on 90 ambient. That way I can get lower vent temps. Or am i not thinking right?
At 86 degrees look for a high side around 200+ psi, maybe a little higher depending on your fan clutch condition.. You cannot lower the pressures and expect good cooling, moving the O tube around won't do it either.. Charge the system, while watching high side pressure until the inlet temp of the evap is the same as the outlet temp, with the outlet just slightly cooler..
Freedoms just another word for nothing left to lose
so, what kind of vent temps should i expect on high blower. I've already been down that road i expect around 60-65 at idle at 80-90 ambient temp. I just would like to know what i need to do to get 40-45 temps at idle 80-90 ambient. I've just put in a parallel type condenser in and that has helped as far as the time it takes to cool. but on a 82 degree day sitting in traffic on high blower only get 55-60. Or could it be clutch fan ? how do I know if it is working? would it be better to remove it ? I know just need a new truck!
Is this a dual unit system and when you say you added a PF condenser which exactly does that mean. Did you just use a updated 6mm PF condenser?
yes it is and i'm not sure. It is a delphi aftermarket parallel condenser 17X24X1 1/4 direct fit replacement.
How much refrigerant do you have in it. If the condenser looks like this one, while better still not as good as a true PF condenser.
It has about 4- 4.5 lbs. What does a true pf condenser look like. Would I have to make new hoses?
5.25 pounds was the R12 refrigerant capacity. Spray some water on the condenser. If cooling improves you have an air flow issue or inadequate condenser for R134a.
This type of condenser is the best performing model I have seen to date. Yes custom hoses will be needed.
If you look on autozones site on 1988 5.7 chevy sub there will be a picture of the exact one that i have. I am assuming that with the better one i would have to have new hoses made.
If the fan clutch has more than 50k miles on it, you should consider a replacement.
With a 20 year old vehicle, it is unlikely the fan clutch is original. The bad news is it may have been replaced with the wrong unit. GM lists 5 fan clutches for that vehicle, but only one of them is the right one for the C60 option A/C. Since it is the most expensive clutch, the temptation to use the cheaper clutch is always there.
What you need is AC Delco Part Number: 15-4949 . About 200 bucks from the dealer.
Your fan shold ROAR on cold start - I mean wake the neighbor up ROAR. The same roar should happen after idling in traffic for more than 5 minutes with the A/C on high, when you accelerate.
There is a thread regarding testing of fan clutches in the FAQ section on this site.
"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.
I sprayed water on the condenser at 81 ambient and it made no difference on vent temp. It actually rose the low side pressure from 30 to 35. so now what?
How about getting vent temps both pressures at idle and 1500 RPM. Then do the same while misting the condenser with water. Let the vehicle build up pressures for a few minutes each time before writing down the results.
ok here is what i found out 78-80 ambient temp at idle the vent temp on high blower is 50. At 1500 rpm it dropped down to 45. misting water on condenser made no difference at ilde or 1500 rpm. At idle low side pressure was 32 high side 135 vent 50 degress. At idle with water low side was 29 high side was 115 vent 50 degrees. At 1500 rpm low side was 26 high side 145 vent 45. At 1500 with water low side was 24 high side 115 vent 45. so now what?
I think you're undercharging it trying to keep the pressures down, when the real problem is the fan and condenser. Conversion jobs especially these GM trucks often run at higher high side than factory R-134a systems.
Ice right after the OT is because of major undercharge, what little refrigerant is flowing evaporates right there. So you get one major cold spot, but you have no BTU capacity. The evaporator coil needs to contain liquid refrigerant (in a CCOT, it is nearly full of liquid refrigerant) in order to achieve cooling.
Edited: Tue May 26, 2009 at 11:51 AM by mk378
but ive already tried putting more 134a in it and when the ambient temp rises so does the vent temps i need to know what to do to lower vent temps not raise them. Are you saying that i need a different condenser or fan ? this is the second so called condenser that would work with 134a. and i'm running an aux electric fan. I'm getting really frustraded.
Condenser change is not going to help with the current high side readings. I agree that it looks low on refrigerant. A little surprised to not see your low side drop. How often is the clutch cycling and the time between cycle points?
it does not cycle off when the blower is on high if i turn it down to low of course the pressures drop and the compressor cycles off. takes about 15 sec and turns back on. If it is low on refridgerant how much should i add what should the high and low side pressures be?
As Chick stated it should be close to 200psi. With this being a dual unit system you very well could see pressures closer to 25/275. Couple things concern me here. You state it will not take any more refrigerant, correct? What has been your procedure on adding and removing oil? As for charging, if you can add more refrigerant, slowly add some refrigerant until the inlet and outlet on the evap feel the same. Careful to watch that your pressures do not get out of hand while doing this.
I just had a thought, would the expansion valve in the rear air have anything to do with my problem?
It will take more refridgerant. On a 80 degeree day the most i could get in it was about 45 on low side and 225 on high side.
when you pull a vacuumm does the oil come out with the refridgerant? if not them i think i may have too much oil in it. because when i changed out the condenser i pulled a vac for 2 hours then added about 4 oz of pag oil. because when i did the conversion the first time i added 8oz.
So you have never removed any oil but have added an additional 12 ounces?
no, the new compressor when i converted did not have any oil in it so i put 8 oz in. so when you pull a vac the oil stays in?
I put some more 134a in did't weigh it. at 80 ambient at idle 185 high side 47 low side vent 57. at 1500 high side 200 low side 43 vent 55
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