A/C conversion from r12 to r134a complications

[Sam Thompson]

Hi,
I am in the process of converting my 1986 BMW 325es’s A/C system over to r134a. I got into the project which involved removing all of the tubes to and from the condenser, evaporator, and compressor, then I realized that it looks as if someone has used some sort of leak stop in the system which has left a coating on the tubes. The expansion valve was clogged on the high side to show the extent of the situation. I cannot take the evaporator out of the housing without removing the entire dash which is quite more of a project than I had anticipated. So, my question: Is flushing the tubes, condenser, and evaporator enough, or am I going to have to buy new tubes too. Originally, I was planning on putting new o-rings on all the fittings, replacing the expansion valve, and drier.

Topic

[college man]

Flushing the tubes is enough. You don’t need to
remove the evap. just flush through it.

[Sam Thompson]

Should I replace the rubber lines if they still look good?

[college man]

If the lines are in good shape. no need to replace.
just use all new O rings. 😉

[John B Kobberstad]

What are you going to do about the compressor? Oil for R 12 is not compatible with oil for R 134A. O rings and seals for R 12 are not compatible for R 134a. You can’t flush a compressor. You need to replace all O rings and seals as well as Schrader valves with those that work with R 134A.
Look in the “How To” forum for the O ring color changes info. Do your research well before hand.
If that compressor has had a stop leak or similar junk added to it get a new one. You should be able to flush the lines but the Accumulator, Oriface tube, Receiver/Drier and compressor should be replaced. If you replace the compressor DO NOT get an R 12 compressor, make sure you get the R 134A compressor. There is a difference R 12 seals in it will not work with R 134A. You will have to put the proper amount of oil for an R 134A system in and the R 134A weight of charge may not be the same as the R 12 weight of charge. This is very important to convert with the right amounts.

[John B Kobberstad]

[quote=”samtheman” post=61888]Should I replace the rubber lines if they still look good?[/quote]

They need to have the R 12 oil removed so they should be flushed good with A/C flushing fluid and nothing else NOT WATER!!!!

[Sam Thompson]

I finished the conversion. Except for the pressures are WAY too high. I put the right amount of oil and Freon the system per BMW specs, but the pressures are 300 high and 80 low. The air is not even cool out of the vent, except when driving for a bit with the fan on low, then if it is tuned on a higher speed it momentarily blows cold. What could be wrong?

[Bill]

The properties of R134 are different than R12. You need 10 to 15% less of R134 to charge.

The system is probably overcharged.

The high side pressure will be higher than it would be on R12.

[college man]

[quote=”wysetech” post=63987]The properties of R134 are different than R12. You need 10 to 15% less of R134 to charge.

The system is probably overcharged.

The high side pressure will be higher than it would be on R12.[/quote]

+++1 on the above. You should have subtracted 15% of the of the R134a
charge. Example original charge 2 LBS(32oz) R12 New charge R134a
32oz-15%= 27.2 oz or 27oz

[Sam Thompson]

When I charged the system I charged it with 32oz of r134a. The factory charge of r12 is 2.42 LBS. The official BMW conversion guide said to put in 2 LBS or 32oz. I removed the glove box and got to the lines coming out and to the evaporator. the smaller one was very warm when the system was running.

[Author]

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