134A isn't as cold as r12, that is a fact, the second fact is that the volume is less than R12 in a charged system.
To compare it to an r12 unit, is ok, but was your condensor and evap changed over for a parallel flow which will generate a colder air did you replace the Dryer as well.
The Low pressure switch is usually on near the dryer. Over pressure isn't on some of the systems
So actually the Temp Switch that rests on your Evap, is what controls the on/off cycling of the AC. The Thermo switch should be physically attached to the Evap, on my 81 diesel it was into a brass tube that was attached with wires to the core, and the temp probe was placed inside of it. This held true to my 90's Cabriolets.
The really only time the unit cycles on/off is when the temp probe is frozen enough to say that the evap is freezing and needs to shut off to defrost. If you have the unit on full fresh air over the core, then it may never turn off as it isn't detecting the build up of frost/ice on the core.
On my cabbies in 90 degree air I don't think it would ever cycle, but on certain 50 degree days it would cycle on/off.
Also I have found that since I perveted the system to run R134a when entering a Hot car, as the cabin was up in the mid 90's, I would roll down the windws to vacate the hot air. The I would usually have the AC selector on to Max this allows the system to use Cabin air over the evap. Since this is re-cycling the Cabin air it gets cooler faster. After running for a couple of minutes I would then roll the windows up. If I had it on Max eventually on long runs the unit would turn off and on as sufficient cold cabin air would cause the system to freeze up. But in the Deep South, that is a very rare condition for short hops.
Verify that your max ac closes the external flap on your air plenum, and if there isn't foam on the edges to seal it is not on it then you are sucking hot engine/hood air over the core. Some where I have a how to on it, and I can't remember when VW placed a screen over it, that was missing on my 81 and after a couple of years with no Debris Guard over the hood vents, and no screen on my fresh air deflector, I sucked enough debris in to plug my drain, causing so much water in the heater box, that ie would freeze solid and cause a fog of ICY air out the vents.
To compare it to an r12 unit, is ok, but was your condensor and evap changed over for a parallel flow which will generate a colder air did you replace the Dryer as well.
The Low pressure switch is usually on near the dryer. Over pressure isn't on some of the systems
So actually the Temp Switch that rests on your Evap, is what controls the on/off cycling of the AC. The Thermo switch should be physically attached to the Evap, on my 81 diesel it was into a brass tube that was attached with wires to the core, and the temp probe was placed inside of it. This held true to my 90's Cabriolets.
The really only time the unit cycles on/off is when the temp probe is frozen enough to say that the evap is freezing and needs to shut off to defrost. If you have the unit on full fresh air over the core, then it may never turn off as it isn't detecting the build up of frost/ice on the core.
On my cabbies in 90 degree air I don't think it would ever cycle, but on certain 50 degree days it would cycle on/off.
Also I have found that since I perveted the system to run R134a when entering a Hot car, as the cabin was up in the mid 90's, I would roll down the windws to vacate the hot air. The I would usually have the AC selector on to Max this allows the system to use Cabin air over the evap. Since this is re-cycling the Cabin air it gets cooler faster. After running for a couple of minutes I would then roll the windows up. If I had it on Max eventually on long runs the unit would turn off and on as sufficient cold cabin air would cause the system to freeze up. But in the Deep South, that is a very rare condition for short hops.
Verify that your max ac closes the external flap on your air plenum, and if there isn't foam on the edges to seal it is not on it then you are sucking hot engine/hood air over the core. Some where I have a how to on it, and I can't remember when VW placed a screen over it, that was missing on my 81 and after a couple of years with no Debris Guard over the hood vents, and no screen on my fresh air deflector, I sucked enough debris in to plug my drain, causing so much water in the heater box, that ie would freeze solid and cause a fog of ICY air out the vents.
