A/C 240 72 rebuilt and cooling performance...

[richard1]

As most followers on the subject know, my A/C original system has been fully restored and runs with freeze R-12. It work fine in the morning at around 75F.

In the afternoon when over 85F the performance is close to none.....mostly hot air...or mild.

My A/C tech told me to install a pusher electric fan in front of the condensor. I installed properly a Hayden 3680 as a pusher toward the engine. Today, the car has been in the sun all day. I barely see any improvement on the A/C performance at close to 100 degrees here in Vegas.

Here are some questions in my mind:

1-I have a original radiator shroud......does it needs to be removed for better airflow from the electric fan?

2-The engine thermostatic fan is still in place and i don't want to remove because the car is an original unrestored.

3-The Hayden fan is a 12", 800 CFM connected to the switch and goes direct to the battery. I use the fan when needed...only in the afternoon.

To conclude, my feeling is the fan shroud is restrictive (as a closing funnel) for proper cooling of the A/C condensor and overall engine bay to dissipate heat at 100 degee temperature. The engine temperature is always below the middle mark at any time as before in the most severe summer conditions but I still have the A/C performance issue.

Would it be better to remove the fan shroud? I would prefer not.

Otherwise, if it is the solution to the problem, I can remove for the summer time.

opinions are welcome.

[Arne]

I'm not an A/C expert, but I'm having a hard time seeing how the shroud could be the problem. The opening in the shroud is larger than the pusher fan's diameter, so the pushed air shouldn't be restricted. Besides, the heat of the day is when you WANT the shroud to help keep the engine temp down. The fact that your engine doesn't run hot in the heat of the day tells me the shroud is doing what it is supposed to do.

I'm thinking something else must still be wrong. Are you certain they got the correct amount of R12 in there?

[ChrisB77]

I think Arne hit the nail on the head! Over or undercharged A/C systems can perform OK when outside temp is lower but will struggle as the temp rises. Your A/C tech could have easily verified the effect an added condensor fan would had with a box fan and a spritz of water on the condensor. Someone needs to check the high and low side pressures when the temperature is high and A/C is not working. Keep us posted. WE can figure this out!

[sblake01]

Did your AC tech use the Freeze12 pressure/temperature chart when he charged your system? The readings would be little different than the chart for regular R12 since the Freeze12 charge requires roughly 10% less by volume. I'm guessing also that Arne has nailed it. Performance drops as ambient temp rises = undercharged. It's kind of a 'feel' thing so I can't say exactly what the readings should be. A rough estimate would be 34-37 psi on the low side and 140-150 on the high side @ 1500rpm. The ambient air temp must be taken into condsideration. The effects of a condenser fan are marginal and would really only be noticed at idle.

[hls30.com]

I agree with those above, and will offer one additional suggestion.

seal the Condenser core and the radiator to the core support-that is to say, close off any path the air could take around the condenser core, be sure all of the air the fan pulls/pushes flows through the cores(condenser and radiator).

I had a similar situation here in Savannah, I installed a SPA pusher fan-relayed off the compressor clutch, and it had a bearly noticeable effect on cooling. In a frustrated state I popped the hood and put my hand in the voids between the core support and the condensor core-WOW was there air coming out!

I drove to Home Depot, bought some grass edging extrusion and stainless steel duct tape, and proceded to trim up a box to seal up the voids. The sound of the fans changed with every fitting, and more importantly, I could see fog in the car!

I made it work first, then went back and made it pretty. I still used the black edging material, but trimmed it close, and replaced the stainless tape with a heavy rubberized tape. It was not nearly as noticeable to look at, but the air coming out of the vents was cold!

Will

PS I used the blact tape to seal the radiator to the core support as well. lLater, I replaced the radiator, I replaced the tape with strips of weatherstripping applied to the frame of the core.

Edited May 8, 2009 by hls30.com

[richard1]

We are a great community to help each other and it has been proved one more time since I am a member here.

I have to say that all your comments have been a direct hit in many ways.

I am just disappointed with the A/C master technician that rebuilt my entire original dealer installed A/C unit two years ago and how he has been lazy to figure out the problem, perform minimal checks and procedures and very simple ones after being paid thousands of bucks two years ago..

You guys figured the fix it has been a direct hit.

This afternoon, I called several A/C shops and explained my problem, ask if they have Freeze 12 and what they thing about with an average price to fix the issue, the entire system being brand new from two years ago.

The best shop with freeze 12 gave me a quote to flush the system and refill. It cost me $120.00. My master tech told me to install a pusher fan, I spent over a hundred bucks to do it myself and it was not the fix. Furthermore, he was asking me $500,00 to do it.

To cut short.......there is no leak in my A/C unit but the only part that has never been replaced is the condensor. Connections are tight without clues of any leak.

The pusher fan seems to help a bit at stop and go traffic but I still have vapor lock problem over 100 degrees as today but I switch the electric fuel pump on and it cures the problem.

The engine temperature stays below the middle line and runs fine aside of the vapor lock problem.

So.....too much bla bla bla?

Yes.....the freeze 12 has been drained and refilled ......the problem is fixed... and A/C is blowing very cold. Maybe the fan will help in the worst of the summer days when we will reach 115.

Thanks to everybody

PS. My tech has done a very good job but he may have personal issues. I will not trust him anymore. The A/C maintenance is the only thing I don't do on my car.

[Z train]

I just picked up a 810 Wagon.Once it was running to my liking,i turned the A/C on.ANd to my surprise,it was blowing at 52 degrees,which is only about 5 degrees+/- 2 from on the money.ANd this is just a 3 core radiator,factory fan & 180 stat.And this is on a 102 degree day in Tucson.I'm not where i want to be,but i'm damn close for not touching the system.

[sblake01]

52 degrees where? This is what my 810 reads at the center vent so I think yours could be cooler. The only mods to my system are a condenser fan and Freeze12 refrigerant. Notice that the fan speed is only on the second setting. This car will freeze you out!

Edited May 9, 2009 by sblake01

[Z train]

Steve-my measurement was at the center vent.I was shocked when i hit the switch and it got that cool.It tells me the system is tight.I'm gonna have it topped off with R-12 in the near future.

[The570z]

@sblake01

Ironically enough, vent temps below freezing indicate a problem, your thermostatically controlled expansion valve(its the deal on the end of the evaporator core where the high side line comes in to it) is not functioning properly. Its whole job is to keep the core at or above 32 degrees. Evaporator core temps are not supposed to drop below freezing because ice will form and either block the airflow or insulate the core and prevent cooling.

/end bubble burst.

Oh and on a side note, R-12 if you can afford it, is a much better option then freeze-12 as it does not leak out of a sealed system. Freeze-12 and R-134a will leak out over a couple years even in a perfect, brand spanking new a/c system.

[sblake01]

Thank you for that (on both notes) but I do know what I'm doing. No unsolicited advice/education necessary, thank you. I've been an HVAC and MVAC tech since the mid 80s. Or, to put it another way, if you're profile is accurate, I've been doing it longer than you've been alive. Those readings are kind of 'slight of hand'. The temp doesn't actually stay at that point. Those readings are taken at the point where the temp switch kicks out the compressor. It does take a few seconds for the temp to stop dropping, stabilize and return to above freezing so that the comp. will resume. The system does not stay below freezing and no ice forms. I can actually make any vehicle, regardless of what type of ac system it has, show a below freezing reading as long as everything is working properly if you get the reading at the right point. It doesn't mean that there's anything wrong with the system.

Your argument for not using R134a in an R-12 system is a valid one due to the higher pressures it requires to perform and the smaller size of the R134a molecule but Freeze-12 actually runs at lower pressures than R-12 and I've had no problems with it leaking out. The systems in my 810 and Z aren't 'brand spanking new' but they have been working properly for well over a 'couple of years' without any leaking or loss of peroformance.

Edited May 9, 2009 by sblake01

[doradox]

Those readings are kind of 'slight of hand'. The temp doesn't actually stay at that point. Those readings are taken at the point where the temp switch kicks out the compressor.

Sleight of hand like being on recirculate and a low fan speed. On a cool California evening as well maybe.

Z train is knocking 50 degrees off the outside temp and that ain't too bad.

Not disagreeing with your points at all though.

Steve