A/C question

[slo325i]

Ok... it's getting hot as crazy now and it's not even the summer yet. The a/c has never worked in my car and I'm almost positive that it's still the old R12 system. For those of that never converted to the new system, how are you guys keeping your cool??

If you guys are paying to get the R12 system refreshed, how much are you guys paying?? I'm sure many of you are wondering the same thing. pLease let me know.

Justin

[Adrian_Visser]

I'm no a/c expert but I've heard you can get recharge kits for r12 systems that use a mixture of propane and some other gases, but if the system has no refrigerant in it it's probably because the seals are shot, I don't know what the cost difference is between r134 seal kits and r12 ones or even if you can get r12 seal kits anymore

[Liam]

All that really needs to be done to convert to 134a is to flush the system change the compressor oil to PAG or POE, install valve adaptors, evacuate and charge it.

For it to really work correctly the expansion valve should be changed but they will work with R12 valve.

Now the why it leaked out and quit in the first place could be a problem.

[slo325i]

Well i know that the old compressor was swapped out with the new one and the PO never felt the need to recharge. Since there's like no pressure in the lines now I'll go ahead and put all new o-rings on there. Is there some kind of a detailed (with pics) write up on diy converting to R134??

[netcsk]

I did all of the above paired with a new drier and a new/rebuilt compressor. Later on I added a 16" pusher fan to keep it real cold.
It does well enough, even on the hot days.

This weather is crazy huh? 91F right here right now. It was freezing last week.

[slo325i]

I did all of the above paired with a new drier and a new/rebuilt compressor. Later on I added a 16" pusher fan to keep it real cold.
It does well enough, even on the hot days.

This weather is crazy huh? 91F right here right now. It was freezing last week.

Yea man, tell me about it...

Anyways, the expansion valves are the high/low valves where you hook up the lines to recharge right?? Where could I get those?? Local autozone??

Justin

[nataku83]

I think those are called the service valves. The expansion valve is near the evaporator - it's where the pressure drops, and the refrigerant goes from liquid -> gas and the temp drops. I'm not sure exactly where it's located on the car, but it's a single unit, ~25 on pelicanparts: http://www.pelicanparts.com/bmw/cata...pg3.htm#item17

[Knockenwelle]

R12 is the way to go. Germans designed older cars for warm weather, not hot. 115 deg here in AZ will tax even the best A/C system, so making them perform at max efficiency is critical. R134a has only about 80% of the latent heat of vaporization as R12: this is a measure of how much heat it takes to change the state of the substance from a liquid to a gas or vice-versa. This is why people say R134a "doesn't work as well." Although a system designed and optimized for R134a can work just as well as an R12 system, an R12 system converted to work on R134a will not ever achieve the performance it was designed for.

A/C systems are closed systems. If everything is in proper working condition, they should never need to be serviced or topped off. If the system is low, there is a leak. Refrigerant does not disappear. The best solution to a leaky system is to find and fix the leak. This is most usually o-rings, hoses (especially at fittings) or compressors, but other possibilities do exist.

Forget using stop-leak. It doesn't work, and can cause compressor damage. Using anything other than the refrigerant and associated oil the system was designed for can also cause compressor damage. Converting a system from R12 to R134a without flushing the system with A/C solvent and replacing the filter/dryer can lead to chemical reactions that can destroy metal parts, and often causes compressor damage. Using propane is an especially bad idea, as it not only has different thermodynamic behavior than both R12 and R134a, but is also flammable.

The short version: for A/C to work properly and reliably, it must be 100% to start with. R12 is more expensive, but worth it and the correct choice for the E30.