R134a conversion

[glen-sj]

My 92 525 A/C is no longer putting out cold air after 12 years, never been recharged. Decided to do the conversion to R134a yesterday.

Followed all the instructions given on E34.net to the letter. Removed the compressor and drier to drain the oil from it, about two oz. came out of the compressor and a few drop came out of the drier, altogether not much drained out. I pour about 3 oz. of the poly ester oil from the rerofit kit into the compressor and 3 oz. into the new drier. (Bentley show the system capicity is 6.8 oz.). Replaced with new o-rings at all the connections and installed new R134a drier from BMA. Proceeded to evacated the system to -29 psi using a vacuum pump for a hour, closed all the valves on the gauge manifold and disconnected the vacuum pump, held it for about half a hour with no changes to the -29 psi vacuum. So I proceeded with the freon charge, placed the 1st can in and started the engine and A/C on, fan at high and temperture at lowest setting for the second can, but only half of the third can emptied into the system. At this point still no cold air from the vents and the system will not take anymore freon. The instruction said the system requires 4.5 cans.

Have anyone encountered this? Did I overlooked some steps? Any recommendation is greatly appreicated.

glen-sj

[JR'Z 525]

Was it cooling before you made the changeover? Is the compressor cycling ie clutch engaging for a minute then dis-engaging? Any frosty or cold lines coming from the evaporator?
JR

[glen-sj]

Was it cooling before you made the changeover? Is the compressor cycling ie clutch engaging for a minute then dis-engaging? Any frosty or cold lines coming from the evaporator?
JR

Yes, it was cooling before but was low on R12, bubbles in the sight glass. The clutch engages when the AC switch is on. On frosty or cold lines coming from the evaporator. What you think is causing my problem?

glen-sj

[JR'Z 525]

Not sure what could be your problem. Wonder if something has plugged a line or if you would need to jump out a low pressure switch. I didn't have to jump one out when I converted mine over but your car might be slightly different. I once had a 87 325 that blew out the descent bag in the filter drier after many years. Luckily the suction side of the compressor had a screen and it prevented major havoc. Not sure if any of this might help but maybe someone with a bit more experience with A/C work could chime in. (Bill/Winfred/Anyone?)
JR

[JR'Z 525]

Your system capacity vs the can sizes. The 134 cans I get are not full 1 pound (16oz) cans. Seems like they are only 12 oz cans. So check your Bently for total capacity and do the math. You might need to add another can or so.
Also are you geting bubbles in the sight glass now?
JR

[JR'Z 525]

Your system capacity vs the can sizes. The 134 cans I get are not full 1 pound (16oz) cans. Seems like they are only 12 oz cans. So check your Bently for total capacity and do the math. You might need to add another can or so.
Also are you getting bubbles in the sight glass now?
JR

[winfred]

factory r134'd e34s run 3.5 pounds and factory r12 cars run 4.24 pounds, being a half pound or so off don't make much difference with ether. as for poor performance, is the aux fan working? should be on low with the ac and switch to high at around 275-300 psi, sometimes it takes a trip down the road to equilize the system and spread the oil around, did you replace the expansion valve? it may not be working properly

[glen-sj]

Thanks for the reply.

No, the expansion valve is original. The pressure switch is new. The system stopped taking the freon at around 2.5 cans and the sight glass showed a steady stream of bubbles. Would too much oil be affecting anymore froen from going in? After draining the old oil from the compressor, not much came out, about 2 oz. I put back 4 oz. of the new oil into the compressor and 2 oz. into the new drier. What should the pressure readings on the gauges be?

[glen-sj]

The R134a cans are 12 oz, so doing the math would need 4.5 cans of R134a. The problem is the system will not take anymore after 2.5 cans. There is still a steady stream of bubble in the sight glass and warm air from the vents.

[Bill R.]

3.42 pounds+- .05 4.5 cans is a safe maximum. The sight glass will still show bubbles with r134a when fully charged. You have to go by volume not the sightglass when charging with 134. If you actually pulled down to 29 inches vacum which is highly doubtful... most likely gauge error but even so if you pulled down close then the first can will be sucked in entirely by the vacum in the system. The next can will be close. Are you sure you're feeding it into the low pressure line and not the high pressure side? The larger diameter line is the one you want to tap into the schraeder valve on.
I think on the 525 its the lower line not the upper... The sightglass is on the high pressure line, you don't tap into that one. At any rate, you fed 2.5 cans in and now with the engine running and the ac turned on maximum cold you feed the rest in. IF you're on the right line and everything else is correct it will pull it in slowly, holding the engine at a higher idle helps too.
If you still can't get it all to go then you have to get a pan of very hot water and stick the can of 134 in it to heat it up and raise the pressure so it will be higher than the system pressure and go in. The water will chill down very quickly doing this so you may have to get more than one pot of hot water. Don't submerge the tap on the can just most of the can itself.
I strongly suspect you're using the high side line instead of the low side but if not then you can also check fittings where you're gauges screw onto the schrader and onto the can tap sometimes if those are overtightened the oring seal squiches and won't let gas flow .

The R134a cans are 12 oz, so doing the math would need 4.5 cans of R134a. The problem is the system will not take anymore after 2.5 cans. There is still a steady stream of bubble in the sight glass and warm air from the vents.