Just had my A/C fixed and changed over to 134A.  Mechanic said he was worried about the air flow over the condenser.  When the car is still and the engine is idling the pressure builds and the air temp from the A/C climbs.  He sprayed cool water on the condenser and the pressure dropped and the air got colder...just as it should.  He mentioned adding an electric fan for the condenser, it seems the 81 vette had one.  I've looked through this forum and found a lot about electric fans but mostly for the radiator.   Need some advice.  Looked on some of our sponsors web sites and did not find anything specifically for the condenser.

The electric fan is on the rad. side, it draws air thru the condenser then thru the rad. I have the stock fan from my car (an '82) wich will fit your '81. Someone must have removed yours at some time. If you need it you can have mine, just pay the shipping. It's in good shape.

My car is an 80.  Looking at the AIM manuals there was no fan.  Did the 81 and 82 replace the engine driven fan with an electric fan or was the electric fan in addition to the engine fan?  You said it was on the radiator side...is that next to the engine or between the condenser and the radiator.

For 79 and 80 with the L82/AC combo an auxiliary electric fan was installed to supplement the mechanical fan. It's on the motor side of the radiator. Not on the L48s. For 81-82 pretty sure everyone got it.

OOPS, Mike you beat me to the reply but Im going to leave this one posted anyway. The 82 had an auxiliary electric cooling fan mounted just forward of the engine driven fan.  The electric fan is activated by a thermo switch mounted in the engine block.  It could be easily modified to be switched manually by the driver instead of operated by the thermo switch.  If you need one, Daves should fit and you can't beat free Crossfire19822008-06-12 17:39:28

Thanks for the offer Dave, I will PM you later to figure out the details.  You just gotta love this forum!

Just came back from my mechanics place.  Told him about the fan Dave offered.  We talked about some of the things I've read on the forum - sealing around the radiator, heater shutoff valves, etc.  He was in the process of putting new foam seal around the radiator so that was good.  The shutoff valves have already been installed on my car and he showed me where they were.  He said that if the condenser is being cooled the pressure is around 35 on the low side and 210 on the high with good cold air.

One of the inherent issues with changing to 134a is it's inability to cool as well(in most cases) as R12, in a system designed for R12. 134 runs at higher pressures, which means it also has higher temps on the condenser(pressure) side.
An electric fan will be a great help when idling, or driving slow. Once you get moving, if all of the rad/shroud seals are in place, you should have no problems with it at all.

If you're gonna go in a do the evap core, make sure to have the plenum re-sealed properly, so no hot air from the engine side will get forced into the A/C plenum...you'd be surprised at how many large gaps there are in the plenum halves from the factory, especially at the bottom.

As a follow up to Joel, the efficency loss between the two refrigerants is about 10% when you do the conversion.

 I've been following these posts, my '82 only has one fan between the engine and the radiator.....am I missing something?