Summer's here and true to form, it's stifling hot. My A/C has been operating fine for 20+ years but I think it could be better and was wondering how much efficiency is lost with an old condensor? New ones are $260 and up nd don't really want to spend that kind of money plus the expense of recharging the system afterwards without some sense that it will make a significant improvement.

I know many have rebuilt/replaced or upgraded their A/C systems over the years so trying to distinquish how much a new condenser contributes to improved cooling while disregarding other changes is a challenge. So I guess I'm looking for opinions for any that have replaced only their original condensor, perhaps because of damage or a leak.

Did the new one make a big difference? That's all I want to know.

Thanks

 

It is my understanding that a new parallel type condenser will work better if you are using R-134A refrigerant. Hopefully Larry AKA Powershift will see this and chime in. He has a wealth of knowledge with respects to our AC systems. Jerry

 

If using R12 I doubt changing the condenser would make an improvement. When properly charged and all components working correctly the evaporator temp must be above freezing or ice up will happen. The evaporator temp and correlating pressure is controlled by the expansion valve in conjunction with the STV/APV. If your system was converted to R134 was the STV adjustment made. If using R134 changing the condenser (might) make an improvement (IF) you change it to a parallel flow. The original design uses serpentine flow. But again the evaporator temp is controlled by other components and also influenced by the outside temps. If a gauge set indicates the system is working properly and outlet temps are normal I would look into resealing the inner and outer box seals, repair any rust out, and install cabin insulation. These are not easy jobs and opening the system to do this will be required. I am not aware of anything that can be done on air flow circulation other than checking to make sure the inlet and outlets are not obstructed with debris.

 

Yeah, that's my question - is the condenser still working correctly, i.e. transfering a sufficient amount of heat? Aluminum oxides, even anodized surfaces will break down over time and aluminum oxide makes a better insulator than a conductor of heat or electricity.
The STV was bypassed during the conversion and now uses a temp control module to cycle the Sanden compressor. I think it would be quite a job to configure a parallel flow radiator to fit in our cars. And not likely worth the expense and effort.

 

The purpose of the condenser is to condense the refrigerant vapor coming from the compressor and then to subcool it about another 5-10 F below this condensing (or saturation) temperature. If it can do this on a hot summer day, it is doing all it can.........or is supposed to do.

Let's say outside temperature is about 90F. So for an R12 system you would ideally want a HI side (or condensing) pressure of about 200-220 psi. This corresponds to a condensing temperature of approx 142 F (210 psi). Then you want that condensed refrigerant to be further cooled (or subcooled) another 5-10 F below that. Let's use 5 F. This would be 137 F. For R134a the HI pressure would be about 250 psi with a temperature of 145 F. The sub cooled temperature would then be another 5 F below that, or 140 F. You can see the refrigerant makes only little difference in these temperatures.

So what you need to do is to check and verify your HI side pressure (and temperature from published VP vs T charts) and the temperature of the liquid refrigerant going into the accumulator/drier and see how they compare. The main thing here is to keep the HI pressure below the numbers I provided above, and to accurately measure the amount of sub cooling temperature drop. If your condenser is meeting these two criteria it is doing its job. A bigger, cleaner, or more efficient condenser will only serve to drop the final liquid temperature going into the receiver/drier (and hence TXV valve) a few more degrees...........which is a small part of the total refrigerant system load (and ultimately your cabin cooled temperature.......which is what you really want).

So setup to get accurate HI pressure, and accurate temperature of refrigerant going into the receiver/drier. That will determine if your condenser is doing its job or if you should consider replacing it with an upgrade. However, I don't have personal experience with condenser upgrades and who sells the best for our C2 cars. Steve Vaughn who is posting right now about his 67 car AC system has a OAP Condenser versus original. It appears right now that we cannot get a full refrigerant charge into his system due to some condenser issue. We hopefully will see where this leads.

If folks have used upgraded condensers vs OEM, please provide your experiences.

Larry

 

Thanks Larry, very useful information.

 

The EVAPORATOR and its operation are probably the bigger threat to inadequate cabin cooling. The evaporator is much more difficult to upgrade due to design and space limitations. But you can be sure that heater hot water valve is operating correctly (no hot water into heater box during AC operation) and that ALL of you heater and AC box seals are fresh and not old and deteriorated. Also that blower motor is not restricted with any debris buildup and that the fresh air vent(s) into cabin is CLOSED TIGHT when AC is operating.

In addition, your STV valve needs to be opening correctly and not creating any issues with evaporator refrigerant pressure. A slight problem with STV will create a lot of dissatisfaction with cabin cooling.

Larry

 

Thanks again Larry. I've left the hot water connection off completely for 20+ years as I've never needed heat in the vette here in Florida. I should have any debris as it's never been parked outside for any length of time since I took the entire dash and ductwork out many years ago.

Now the STV valve is another question. When I converted to the Sanden compressor, I also had the refrigerant temp control module added but I can't say for certain if the STV was opened up and blocked off internally at that time. After I put the gauges on it and see that the condenser is doing okay, I'll probably drain the system, remove and disassemble that valve to make sure it's blocked off. If it wasn't, would I be able to tell from the pressures I'm reading?

 

You can never BLOCK IT OFF. Repair it, yes.......gut the internals, yes............or replace it with a STV shell/bypass kit.

Ideal LO pressure for R12 is 30 psi and 26 psi for R134a. Any pressure above this will negatively affect cabin cooling. Pressures below this can cause evaporator icing over time. If evaporator becomes iced over, cooling is lost because cabin heat cannot be effectively removed and cabin cooled.........ice acts as an insulator on the evaporator surface.

Larry

 

Thanks Larry, while I said 'blocked off', I meant disabled but again, it's been so long I have no memory of what exactly was done, if anything.