so if a person orders a new condensor from say, rusty, will it be a parallel flow one or not? Are those only available aftermarket generic? Do the replacements have any larger capacity to handle 134 better?

You would need to specify if you wanted the PF condensor....
As far as I know they are only aftermarket generic....for 80-85 123's .... later cars may have had them stock...
They are more efficient... in an effort to make up for the R134a being a less efficient molecule than the R12.
But rememeber, airflow across the condensor is the most important limiting factor... so be sure your fan is good and working properly first.

Striplin,

I'm sure that Dave has researched this to death, so he can tell you exactly which PF condensor will fit best.

I do know that a standard replacement condensor will be a serpentine, not a PF.

Good luck,
PS, in Daves case, he needed to replace some components anyway, so it made all the sense in the world to use a PF and other components necessary for a GOOD 134 conversion. That said, if you don't need a condensor, you will be money ahead simply fixing your leak or whatever is wrong and staying with R12. LB

vent temps
 

SoCal; 96 degrees OAT. Freshly repaired AC with new compressor, all lines and receiver drier. Aux fan relayed in to run when compressor clutch gets juice. This has become standard practice at the shop where I work.

Vent temp @134 degrees starting out (parked in the sun). It took less than two minutes to reach 60.
High side = 265
Low side = 62 ( a bit higher than I like to see but I expect it to fall when I charge with R-12).

Vent temps are 55 to 60 degrees during freway traffic jam (35 minutes)
43 to 47 degrees @ 70mph.

Control wheel set to minimum and fan on high. A lower fan speed setting will usually decrease your vent temp readings.

NOTE !!! These readings were taken using, uh, test gas.
100% propane. When I am dead ass sure I have no leaks I will drain and refill with R-12 and then post my findings here.

One last note: The water temp stayed at 85 degrees even while climbing a 7% grade @ 75 MPH and 12 pounds of boost.

On my 300D which is converted to 134 I was unable to get a satisfactory vent temp until I adjusted the cutout switch and the evaporator temp switch. Once the gauge pressures and cutout points were satisfactory I noticed the compressor was still cycling and unable to drop the vent temp below 42-44. By adjusting the evap. temp switch I was able to get the vent temp at idle down to 32F. I have it set to a low of 36F. With high fan speed the car will quickly cool to 42 and when the fan switches to low the temps are between 36-40. This is with a stock condensor and very dry 90+ degree ambient temps. Also, my 300D is black in color.

I just converted a friends 300TD to 134 and had to perform the same adjustments to get satisfactory vent temps. Although on his vehicle we installed the updated pressure switch when we replaced the dryer. The new pressure switch had no visible adjustment screw but I noticed it would not cutout the compressor with low side pressures as low as 17 psi. By adjusting the temp switch at the evaporator I was able to get vent temps of 36F again.

My thinking on this is that with a correct charge if the vent temp isn't low enough and the compressor is cycling then the only solution is to make the compressor run longer, assuming no other problems with components. If the pressure switch is cycling the compressor at 25psi it seems logical that by getting it to cycle at a lower pressure the refrigerant will be evaporating at a lower temperature. If the temp switch at the evaporator is cycling the compressor then adjusting that will make the compressor run longer producing a lower vent temp. In my case is was easy to see the pressure switch causing the cycling by watching the gauges. To see the temp switch causing the cycling I watched the vent thermometer and with the passenger kick panel removed could hear the switch clicking. To adjust the temp switch there is small flat head screw on the face. Clockwise makes it colder. It only takes very small adjustments and by watching the vent thermometer and listening to the compressor you can fine tune it.

Very timely info
 

I need to see if I can adjust the TD evap switch. Just today I discovered it was limiting the evaporator temp to well above freezing (compressor cutting out) and had no idea it was adjustable. Excellent info!
Although, it was 100+ here today and I had 39-42f vent temps. It just needs to move more air.

Now, I need to find the other end of that vac hose coming off the center vent pod...:eek: I can reach in there and feel it but have no clue where it goes heading off toward the drivers side.


edit: No adjustment on this switch. :confused: It was covered with felt insulation. Unplugged the two wires and removed the felt... nothing.

If it's a stock switch it's a very small flat head screw on the face of the switch, recessed a bit. On those I have seen it's got some reddish type color over it. If it's the available aftermarket switches it's under the white plastic cover and will be a philips screw. If you can't find it post a pic.

Define the "face". There are the two contacts facing me, the cap tube coming out of the right side and I feel nothing on the left side. Let me go take a closer look... Found it. Covered in the glue that held the felt on. It is tiny 1-2mm screw located just under the left terminal. I made one turn CW.

How did you know to turn CW? Is it somewhere back in the thread that I haven't re-read....

Here ya' go Jimmy.

One turn seems like allot. If it gets too cold it will freeze the evaporator and reduce efficiency. Did it improve your vent temps?

I think if there's enough air passing over the evap it might not freeze. I'll find out today and report.

edit: One turn CW had little affect. I pulled over and shorted the sw to make sure that it was the switch cutting off. Sure enough, my vent temps dropped to around 36f. I'll try another turn or so CW.

Some direction needed.
 

I have an '82 300Dt which was converted to r134a by PO. I feel it is in need of the stated adjustments at the evap temp switch and cutout switch. Where do I look for these jewels? I've seen some references but for us non-AC types it would be helpful with more direct language.

I notice on the expansion valve, there appears to be an adjustment screw with a "D" shaped ring for easier turning. Any gains to be had here?

I'm a total beginner with auto AC systems so pease excuse my ignorance.

Thanks
Sam

The switch is located about a foot to the left of the expansion valve. It is a small box about 1x1.5" with two wires and a thin metal capillary tube coming off the right side going into the evap box.
I suspect, unless you added a PF condensor with the R134 conversion, adjusting this switch will offer you no gain.

I've been following this thread since it started, interested because my (new to me) 82 300D TD came with records that suggest the A/C (which wasn't working) hadn't actually been working for 12 years. The dealer referenced the need to recharge the A/C to the previous owner, and they said not to do it (go figure!).

Anyway, I took it to my trusted mechanic and he said, "let me pressure test it, and see what it looks like." I picked up the car later that day and was shocked to find the A/C runing perfectly (3-days later still is), and while I have not recorded the vent temps, I can tell you it borders on too cold (been 94-98 degrees the past week here in VA). It cost me $101. I was again shocked when he told me he recharged it with R134; I asked how that could be done as I imagined it was R12 in 1995 when last charged.

He told me, "that's just a myth, no problem at all!"

All of this seems to go against the recommendations of this thread where everyone seems to religiously change out the components, flush the system, etc.

All I can tell you is that it continues to blow cold air, and isn't leaking (did a blacklight test back at the shop this afternoon given he'd added dye for that purpose.

I'm no auto A/C expert; am I being lead astray here and looking at catastrophic consequences in the near future? I am enjoying the cool interior!

Simon

I'd be interested in what your mechanic did for $101. Purge, dryer, what type of oil??? You might want to start saving up for a new compressor.

I can assure you that a W123 AC with R134 will not cut it here in Texas this time of year.

Four years later...
 

Did Dave ever replace the evaporator on the 240D?