Fan stays on, overheat only when ac on
09-15-2010, 02:20 AM
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Fan stays on, overheat only when ac on
1992 TBI 305 RS
I bought a very nice thirdgen that was listed on here, but I have a couple weird issues.
1) The single electric fan stays on constantly. (Seems it could be the RELAY, FAN A/C PRESSURE SWITCH, A/C CONTROL HEAD, or COOLANT FAN SWITCH).
2) The a/c kinda works, the compressor says r12, and the fittings are still r12 fittings. But when I am at a standstill with the A/C on, the car overheats.
If I retrofit the system, what parts will I need to change?
Will r134a cool decently in an r12 system?
Will r134a ruin any components?
Will the r134a leak out of the r12 lines?
Can I drain the mineral oil and replace with pag-100 easily?
If I don't replace the mineral oil, I can potentially have an explosion, correct? What are the typical temps seen 134a in an r12 system?
I bought a very nice thirdgen that was listed on here, but I have a couple weird issues.
1) The single electric fan stays on constantly. (Seems it could be the RELAY, FAN A/C PRESSURE SWITCH, A/C CONTROL HEAD, or COOLANT FAN SWITCH).
2) The a/c kinda works, the compressor says r12, and the fittings are still r12 fittings. But when I am at a standstill with the A/C on, the car overheats.
If I retrofit the system, what parts will I need to change?
Will r134a cool decently in an r12 system?
Will r134a ruin any components?
Will the r134a leak out of the r12 lines?
Can I drain the mineral oil and replace with pag-100 easily?
If I don't replace the mineral oil, I can potentially have an explosion, correct? What are the typical temps seen 134a in an r12 system?
Last edited by RyanEricW; 09-15-2010 at 02:58 AM.
09-17-2010, 08:14 PM
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Car: 1989 GTA
Engine: SuperRam 350
Transmission: Pro Built S/S TH700R4
Axle/Gears: 3.27
Re: Fan stays on, overheat only when ac on
If I retrofit the system, what parts will I need to change?
New orifice tube is cheap. New accumulator. Unique R-134a service ports. Vacuuming the system is mandatory.
Will r134a cool decently in an r12 system?
It depends on your location. Up north, pretty good. Down south, pretty bad. The condenser on our cars is an old design (tube & fin) that worked well enough for R-12. But poorly for R-134a. Condensers on cars today tend to be larger and made of a better design (parallel flow).....R-134a as a refrigerant tends to run higher high-side psi. What this means is that the capacity of the condenser is maxed out at a lower level of performance. So in Seattle, R-134a will work good enough. In Phoenix, it won't be able to keep up. The humid south has just as much trouble as the ultra hot deserts in terms of comfort. Because getting rid of humidity requires colder temperatures to drip the water from your evaporator. R-134a runs warmer than R-12 (all other things being equal). And trying to evacuate heat from the system through the condenser to the ambient is harder when it's muggy out.
Will r134a ruin any components?
The hard thing is to get the chloride out of the lines (you can't). Taking the compressor off and draining the oil in it. And then manually turning the compressor by hand while dribbling new PAG oil into it will help flush the compressor out.
Will the r134a leak out of the r12 lines?
No. The hoses will be the same in either system.
Can I drain the mineral oil and replace with pag-100 easily?
Yes. In addition to spinning the compressor by hand and putting new oil into it, replacing the accumulator will get rid of the couple of ounces that it holds. It's a good idea to replace the accumulator any time the system is opened up. (The desiccant bags in there are pretty much useless if it's been opened up. Plus they're old and possibly brittle after 20 years anyways.)
If I don't replace the mineral oil, I can potentially have an explosion, correct?
No. Only time you would get an explosion is if you bust a line and it hit a flammable source. Even then, the flammable point on refrigerants tends to be in the 1500°F range. R-12 and mineral oil can catch fire just as easily as R-134a and PAG oil. This is all pretty much a moot point. A/C fires are extremely rare. Biggest danger of that tends to be a hot headlight filament breaking in a front end collision and a damaged condenser. But even then, the refrigerant and oil will be spraying forwards. And it dissipates quite rapidly into the air (which is good). It's not like gasoline that will sit on the ground and give off vapors for a long period of time.
What are the typical temps seen 134a in an r12 system?
Around 45-50° on MAX A/C.
You mention the car overheats with the A/C turned on. What temps does it run with the A/C off and with the A/C on? What year is your car? What is your location?
New orifice tube is cheap. New accumulator. Unique R-134a service ports. Vacuuming the system is mandatory.
Will r134a cool decently in an r12 system?
It depends on your location. Up north, pretty good. Down south, pretty bad. The condenser on our cars is an old design (tube & fin) that worked well enough for R-12. But poorly for R-134a. Condensers on cars today tend to be larger and made of a better design (parallel flow).....R-134a as a refrigerant tends to run higher high-side psi. What this means is that the capacity of the condenser is maxed out at a lower level of performance. So in Seattle, R-134a will work good enough. In Phoenix, it won't be able to keep up. The humid south has just as much trouble as the ultra hot deserts in terms of comfort. Because getting rid of humidity requires colder temperatures to drip the water from your evaporator. R-134a runs warmer than R-12 (all other things being equal). And trying to evacuate heat from the system through the condenser to the ambient is harder when it's muggy out.
Will r134a ruin any components?
The hard thing is to get the chloride out of the lines (you can't). Taking the compressor off and draining the oil in it. And then manually turning the compressor by hand while dribbling new PAG oil into it will help flush the compressor out.
Will the r134a leak out of the r12 lines?
No. The hoses will be the same in either system.
Can I drain the mineral oil and replace with pag-100 easily?
Yes. In addition to spinning the compressor by hand and putting new oil into it, replacing the accumulator will get rid of the couple of ounces that it holds. It's a good idea to replace the accumulator any time the system is opened up. (The desiccant bags in there are pretty much useless if it's been opened up. Plus they're old and possibly brittle after 20 years anyways.)
If I don't replace the mineral oil, I can potentially have an explosion, correct?
No. Only time you would get an explosion is if you bust a line and it hit a flammable source. Even then, the flammable point on refrigerants tends to be in the 1500°F range. R-12 and mineral oil can catch fire just as easily as R-134a and PAG oil. This is all pretty much a moot point. A/C fires are extremely rare. Biggest danger of that tends to be a hot headlight filament breaking in a front end collision and a damaged condenser. But even then, the refrigerant and oil will be spraying forwards. And it dissipates quite rapidly into the air (which is good). It's not like gasoline that will sit on the ground and give off vapors for a long period of time.
What are the typical temps seen 134a in an r12 system?
Around 45-50° on MAX A/C.
You mention the car overheats with the A/C turned on. What temps does it run with the A/C off and with the A/C on? What year is your car? What is your location?
09-18-2010, 12:47 AM
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Re: Fan stays on, overheat only when ac on
Thanks for the information! You mentioned the condenser is the main issue behind the poor cooling. Is there an afm condenser that is a newer design??
Also what orifice tube will I need and will it bolt up? Thanks
I have a 1992 Camaro RS. 305TBI 5sp manual.
The temperatures are perfectly fine around 170~ I think consistent until I turn on the A/C. It takes a few minutes to start seeing a slight raise in temperature until it full blown overheated once. (Ooops, poor car)
I am in Chicago, IL. We do get very hot days in the summer 90+ deg F
Also what orifice tube will I need and will it bolt up? Thanks
I have a 1992 Camaro RS. 305TBI 5sp manual.
The temperatures are perfectly fine around 170~ I think consistent until I turn on the A/C. It takes a few minutes to start seeing a slight raise in temperature until it full blown overheated once. (Ooops, poor car)
I am in Chicago, IL. We do get very hot days in the summer 90+ deg F
09-18-2010, 09:19 PM
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Re: Fan stays on, overheat only when ac on
I've heard of using 4th gen ac parts in a 3rd gen. I'd be willing to pull some of those parts from a junk yard. Things like the blower and maybe... the condenser if the price was right and I had the time and money for evac / recharges ( 80 bucks at Meineke ) . Never reuse an evap, always replace it as its only 30 bucks. Autozone will rent you a ac flush kit for free as well. I'm not sure if it is a suitable tool for a good evac though. Unless your upgrading parts or you want to do things on your own, just take it to Meineke. They have the right tools and price. Pep Boys was over 200 cause they said they check everything, bs whatever thats alot of money! lol
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