My retrofit job (on '85 240 DL on which the compressor died) is almost done. I bought the Volvo R134 conversion kit from FCP Groton, and a DKS 15BH compressor from Air Parts in Ocala. All the new stuff is in place except the compressor (it is a near match of the old one, except the Zexel nameplate instead of Borg Warner -- is the Zexel a rebuilt?).

Jon at Air Parts said that it's set to go with oil & all for 134a, even though it still has the R-12 labeling. Guess I'm OK without changing the oil?
I was planning to have my local shop evacuate the system prior to a DYI recharging. Jon said to not have the compressor running when recharging -- sound right?
Also, I've got the apparently high side port next to the dryer (on the tee fitting that comes with the kit) -- can it be filled from there, or where? The compressor has the old style ports on the back, apparently functional.

Any guidance on how-to for an A/C rookie on the final steps would be appreciated.

Ken,

A few things you need to know. I did my 89 which should not be that different except for maybe the compressor, anyway...

Firstly your car came stock with an evap designed for R12. It would still work for R134, but not that efficiently. I believe though that the volvo kit for your car came with the new evaporator anyway and likely you changed it. Big job I know. If you did not, you CAN do without.

Nextly, any connections that were open need to have new o-rings installed. You should have lubricated the orings with ester (POE) oil prior to closing the fitting. Fitting do not need to be tigtht, it's not the tightness that makes the seal, it's the system pressure against the oring.

Nextly, realize that R12 ran with mineral oil, R134 runs on ester (POE) oil. Reason is different refrigerants carry different oil. If you do not replace the original oil with the replacement POE oil your compressor will sieze up quickly. Think of it like this, with apporx 10oz oil in the system (approx) and the system having a static pressure with r134, the oil is dissipated everywhere. When the system runs (i.e. compresosr kicks in) the oil needs to be 'carried' by the refriegerant to keep the compressor lubricated. R134 DOES NOT carry mineneral oil, hence we need to have POE oil in there. Likely the kit came with a bottle. Whatever components you removed can be flushed but not necessary. At least add some oil to the compressor and if you cannot get it all in there add it in other places around the system. Realize though that you have not dumped out ALL the old mineral oil, so given that oil takes up space, you are changing the volume and hence affecting the ability of completely filling up the refriegerant. Likely not a large issue though, but it too can affect performance. The old mineral oil will just stay dormant in the lower points of the system (i.e. bottom of condenser).

Nextly regarding charging, there are two methods, by pressure, or by weight. I suggest you use the pressure method given the change in internal volume and the fact that you can better diagnose by monitoring high side pressure. This can be done by the shop assuming you do not have all proper tools and guages. You charge ONLY from low (suction side) NEVER from high (discharge) side. The port beside your dryer is high. You should have a suction port at the back of the compressor. Hopefully your replacement compressor has r134 fittings.

A vacuum needs to be pulled on the system prior to charging. This is to remove all air from the system, and all moisture. If this is not done moisture can freeze up, block the system, you will not be able to fully charge, and internal corrosion will occure. No choice around this. This is done by the shop just prior to charging. It is also an indicator of whether or not the system has a big leak. If there is a small leak they will have to detect it afterwads using a refrigerant detector or UV method.

If the vacuum holds, the system will be charged up with r134 until the high side pressure reaches a maximum or 2.2 to 2.5 times the ambient temperature in degrees F. This should correspond to approx 80% of the original r12 charge.

Note one last thing, an r134 system needs to have a pretty exact charge to cool well, unlike r12. Also, r134 molecules are smaller and hence it can leak out faster.

Another thing... The condenser is likely old and dirty, inside and out. You need good cooling there where the refrigerant is compressed. If you can flush it, great, if not at least hose down the outside very well through the grill. You will probably eventually realize that you will need to add a condenser cooling fan to it to help cooling, if your A/C is poor in traffic.
On the highway, the wind cools it down.

Enjoy!
Greg Mustang
Montreal - Ottawa
Canada

Greg (et al),
Thanks for the tips. That should give me the info I need. It gets confusing with the expansion valve vs orifice tube design, but your post and others in the archives have got me straightened out.
I did put in the new evaporator and receiver/drier and compressor-to-condenser hose, and O-rings that came with the Volvo kit. I'm going to undo the fittings again to clean them up (I'm concerned about how well they'll seal if I don't get rid of residue from the old O-rings and sealant). Don't know yet if I'll flush the condenser. Then I'll attach the new compressor -- hope it is an R-134a type port on the suction side -- I'll compare to the old compressor with R-12 ports. Oil should be OK as received from Air Parts.

After having the system evacuated, is it a reasonably straight forward recharging? I assume it's charge from the suction port on the compressor, and read pressure on the high side. What about the low pressure cutoff switch on the drier? Do I need to jump that? And, what should high side pressure be? 150-200?

go to http://www.aircondition.com/ and download the ac advisor program on the left side of the page. It will help you figure the pruper amount and correct pressures.
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '82 Mercedes 300SD

You should consider upgrading to the newer evaporator and condensor that was introduced in 1991. These units are more efficient and work better with R134a.

Hi Ken

If you decide to do this yourself here is how:

http://www.brickboard.com/FAQ/700-900/VolvoR134Conversion/R134ConversionPage1.htm

Your Zexel compressor should already be filled with ester oil from your parts guy. Zexel is a good brand & should be new not rebuilt.

Have you flushed the system?
Do you have and electric fan in front of the condenser & is it working?
Have you changed ALL o-rings to R134a style?

I would replace the cycling switch on the accumulator. I would rewire the AC electric fan to come on when the compressor clutch is engaged.

I would consider letting your mechanic who does the evac. go ahead & recharge & leak test. You only use about 70% r134 versus R12 and getting the right amount is critical. Too much or too little can wreck your compressor. Hope this helps!

DannyMac
92 240GL, 132K, 86 740 GLE, 162K

I think the R134a charge is generally 85% of the R12 charge.