Frost
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Frost
Why would my 90 F250 get alot of frost on the, I think it is called, Evaporator? I am looking at a cylinder shaped object on the passenger side of the engine near the back that is connected to the AC lines and after running AC or Heater it gets all frosty white. How can I fix this, I have AC, not the best but it works.
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From: Northwest Germany
1SG,
the cylinder you mention is the A/C accumulator on the outlet side of the evaporator. The suction line goes from the accumulator to the compressor.
I would say the compressor cycling switch is broken and does not open (if so, the compressor runs continuously), causing the frost. You find that pressure switch fitted to the accumulator, has a 2 wire connector with rubber cap. You can remove the switch without discharging the system, there is an automatic-valve inside the fitting.
LoL Dieter
the cylinder you mention is the A/C accumulator on the outlet side of the evaporator. The suction line goes from the accumulator to the compressor.
I would say the compressor cycling switch is broken and does not open (if so, the compressor runs continuously), causing the frost. You find that pressure switch fitted to the accumulator, has a 2 wire connector with rubber cap. You can remove the switch without discharging the system, there is an automatic-valve inside the fitting.
LoL Dieter
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Thank you, I was told by another person to check this switch. I will do my best, I hate electrical problems. I was wanting to change out the R12 but am being told two different stories, one says just buy a kit fropm autozone and do it, the other tells me I have to change out parts, one being the compressor???
I was surprised that it frosted up even while running the heater, is that because it(AC Parts) dries out the air.
I was surprised that it frosted up even while running the heater, is that because it(AC Parts) dries out the air.
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Joined: Jul 2004
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From: Northwest Germany
1SG,
1. I have no experience with converting R12 to R134a, but you can find many threads in the forum about this point.
2. The airflow goes first through the evaporator (which dries the air e.g. in DEFROST) and then passes the heater. So the heater does not affect the frost.
3. The OEM pressure switch may cost about $ 40. Simple to remove without any tool, should be just hand-tight.
Dieter
1. I have no experience with converting R12 to R134a, but you can find many threads in the forum about this point.
2. The airflow goes first through the evaporator (which dries the air e.g. in DEFROST) and then passes the heater. So the heater does not affect the frost.
3. The OEM pressure switch may cost about $ 40. Simple to remove without any tool, should be just hand-tight.
Dieter
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Other than a Tag, is there any other way to know if the system has already been switched over to 134
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Joined: Jan 2003
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From: St. Louis
yes the 134 system will run different pressures than an r-12 though only slightly you can tell by the correlation of the temp to the refrigerant pressure. this is best done when the system has not been running. Refrigerant,in any amount, in an enclosed container(such as your vehicles ac system) that is not under any other forces(such as the system compressor running) will always be a certain pressure at any given temp. For instance at 70 degress farenheight 134 will be 78.6 pounds per square inch guage pressure while r-12 will be 77. But ay 95 degrees the 134 will be 113.9 and the 12 will be108. So the best way to tell is without the sytem having run for a long period and with the tenp inside the vehicle and out being about the same check the pressure of the system. It will be easier to tell the diff at very warm temps as that is when the pressure diff between the two refrigerants is greatest. Also you need a refrigerant pressure chart and a good accurate set of guages.
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The low and high side service ports should also have the adapters on them if they have already been converted.
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From: St. Louis
this is true a proper 134 change should have the quick connect type access fittings for 134 where the 12 system should have regular screw on type access fittings. Key word here PROPER.
Last edited by tinman67; Sep 5, 2004 at 03:29 PM.
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alot of help, mreally appreciate it men. I bought a pressure switch that the parts store reffered to has a clutch or something switch. I'm gonna try that and see how it runs. called around and most shops I called wannted 250-300 dollars to convert, I thought that was rather much considering some of the other work I need to get done to the truck.
What is my worst case, if I continue to FROST up like I have, knowing that I will be using the heater and defrost alot this winter???
What is my worst case, if I continue to FROST up like I have, knowing that I will be using the heater and defrost alot this winter???