GeTCrAzYKiD

Ok, Ive done some recearch before postingbut nothign really helps my situation..

My pressures are about 30-40 low side and around 200-250 high side, the a/c compressor does not shut off and i see a switch on the high side and i am wondering if there is a low side switch. so that i can check them both. i have not gottan around but im asking to i can check it tonight, also i looked and i do not have a fan infront of the condensor so i am picking up a genaric fan at my local auto store. but it is blowing cold and it is half full of freon and it was completely converted. i filled it half way and it started to develop high pressures slowly from teh beginning. i already purchased a dryer and am replacing it today i will check back in a few thanks alot guys!

GeTCrAzYKiD

bump, anybody..or did i post in the wrong section?

classicauto

iTrader: (3)

well.....the dryer should have been replaced when you switched refridgerants......

But 134a will run at higher pressures than r-12...and 250 on the high side is *fairly* normal for full blast on a smoldering hot day....

As far s the compressor not shutting off, if its turning on, off, on, off then you have low refridgerant or a problem....its hould pretty well run steady on a hot day....

GeTCrAzYKiD

everything was changed when it was converted with new the new lines, the whole nine yards. I sucked it down yesterday and I only charged the system half way and i started to see it go high. so i guess i will continue to fill to the proper level and see if it cuts off and if not jump the switch and see if its bad. and I searched mazda and napa pepboys etc. and the high pressure switch is not available anywhere anymore. but i think when i get the fan on it should drop atlease 15-20 psi.

as for as temps they say around mid to low 90's and heat index is around 105. but im going to suck it all out today and prabably put in a new expansion valve also to eliminate any possible leaks. thanks

2713ddddavid

iTrader: (1)

Only use 75% as much R134a as you would R12. I.E. 1LB R12 = 3/4 LB R134a.

So at "half way" you really are just about full.

(I`m a Heating/Cooling tech for the last 25 years)

Turbonut

iTrader: (1)

R134-21oz should fill the system
My Jeep at 90 degrees calls for 38/47 - 250/300

2713ddddavid

iTrader: (1)

Yes 21 oz is correct. Just short of two 12oz cans.
In automotive the running pressures are not very reliable due to the large amount of variables. How fast the engine is running is a big factor in the equation.
The only way to charge one(car) correctly is to pull down into a vacuum for 1/2 hour or so then weigh the correct amount of refrigerant into the system. Not even the sight glass method is correct except under the narrowest of conditions.

Innovation

iTrader: (1)

Freeze 12 works better and is also a direct drop in for R-12. www.freeze12.com

Sideways7

iTrader: (7)

He already converted to R-134, so its too late for that. There are replacement cans out there that come with a gauge that tells you the pressure as you're filling. I always thought the best way was to fill to a certain pressure.

Innovation

iTrader: (1)

There is alot of controversy with 134a in our old cars. I wouldn't use it because of high pressures. After alot of research and some advice from some of the 7 guru's I went with freeze12. I get 38 degree temps from the vents and after 3 months in the Florida heat I have had zero problems. He can still switch with just a simple flush, evac and recharge. Maybe a drier change because it's full of 134a oil.

Sideways7

iTrader: (7)

Actually, Freeze 12 can use any of the oils used by r12 or r134.

GeTCrAzYKiD

ok, after work today (before i read this post again) I decided to suck it all down and replace only the drier and see what would happen.

I sucked it to a vaccum till 25-27 its hard read the gauges and i changed the drier real quick. I sucked it down to a vaccum again same reading and left it suck it down like that for around an hour. closed off the gauge and let if sit for about 30 minutes to see if it leaked. no leak. so i moved on. started the car jammed a wrench in the pedals and kept it around 2k rpms. (SINCE I DID NOT PURCHASE THE SMALL FAN I WANTED I PLACED A SHOP FAN ON THE FRONT OF THE CAR TO KEEP IT COOL ) connected the first can (12oz) - opened line slow and pressure jumped to about 65 on low side. Compressor kicked on and high began to rise. keep in mind the temps out side were around high 80's now. i rinished the first can and the high side was around 150 and still rising slow. as i started the second can (4 oz) the high side was up to 275. and then SLOWLY got its way to 300. I continued to see if the high pressure switch would kick it off and as i got half way throught the 4 oz the pressures started to drop (why?) to around 250 and still SLOWLY dropping. I started the last can anoth 12 oz (after reading i see i put a little too much i will suck some out tomorrow thanks btw) the low pressures seem really well still hanging around 22-25. as i finished the last can the pressures bumped back up to 350 on high side. I left it run again to see if compressor would cut off, nothing. but the pressures began to drop again (why?) after i was finished i left the car idle and i watched pressures. the look like the stop at 42-45 low side and 325 high and stayed that way for a good period of time. so then i removed the fan that has been sitting on the front of my car this whole time to simulate stopping at a stop light. the low side stayed the same but the high side rose to just about 340 and stayed that way for another good period of time. and i did check the cooling from inside (I wish i had a temp gauge) but it was blowning nice a cold but not as cold as i wanted it to be (I assume that i drain some freon out and it with blow colder). but i turned off the car pressures regulated to 300 high and 75 low and i turned the fan on and the high dropped quick to stop in about 30 seconds to 155 and the low to raise to 75 and that was it my day was over. I drove the car around and a/c was nice and cool id guess around high 50's low 60's. but like i said i think it will cool better once i get the over charge off right? Thanks guys for all your help, if you have any input, i kept notes while i was conducting my a/c refill and repair.

Yes I intend on getting the correct fan for the condensor.

catchafox

its not blowing cold because of your high head pressure, and this is caused by two factors over charge and air flow. chech your sight glass it should go clear (no bubbles) afer 3-5 seconds of compressor kickin in if you over charge the head pressure will go throught the roof and dstroy your compressor in time. The second problem is not having the fan so it carnt remove the heat out of the refrigerant in the condenser so the heat stayes inside the pipe work so get a 10-12" fan and mount to condenser.there is a low side switch inside the evap box this cycles the system off when down to temp they do fail over time and some can be adjustable(mine is).Also the reason the head pressure goes up after adding gas is because you are dumping liquid refrigerant into it which the compressor tries to compress even more so the pressure spikes, you need to let the system settle for 5min or so before adding/removing gas just to let things settle down.Hopes this helps.

GeTCrAzYKiD

thanks. I suck a little out. some good amount of bubbles fly by. even after u changed the drier. does it also take time to dry it out? the low pressure switch, are you talkign about the expansion valve because thats all I can find.

GeTCrAzYKiD

but my pressures will drop when i take out that about 7 oz (<.5 lb) of overchargeright?

jackhild59

iTrader: (7)

The low pressure switch only comes into play in low load situations. As in when you are staying cool and the interior fan is at lower speeds. The switch cuts off the compressor at about 26 psi on the low side and switches back on at around 35-40 psi. This switch has two functions.

Function 1: It keeps the evaporator from freezing.

Function 2: In a low gas situation, it keeps the system from going into vacuum on the low side and sucking in air/moisture etc and destroying the system.


Yes you are overcharged. You will never find the correct charge level for 134A in your system because the system is not sized with adequate condensing capacity to deal with the 134a. You will always experience either high head pressures or low cooling or both. The problem is magnified by your high cooling load environment, Florida. Your compressor life will be shortened. If you understand pumping losses you will realize that the extra 50-75 psi your compressor has to pump is sucking the horsepower right out of your car and the higher the rpms, the worse it gets. A condenser fan will help, but not solve the problem. An aftermarket parallel flow condensor will probably solve the problem along with the condensing fan. but you will spend in the neighbor hood of $200 to retrofit the condensor and fan.

You seem detail oriented. Don't reinvent the wheel. You have gotten several suggestions to use Freeze12. Lots of guys in arizona, california and texas use freeze12 and are very happy with the results. It solves all of the problems that you will continue to have with the 134a. It is not expensive, can be purchased without a liscense on ebay.

Good luck.

GeTCrAzYKiD

ok, now when i bought the car it was already retrofitted and i compared the a/c lines switches and with another rx-7 side by side. and i know that the compressors are different but the lines should be that same? but all of my lines were different in size from the other rx-7 so i assume that the guy changed everything properly he says he took it to a shop. but if i can put the freeze 12 in i still will and the fan is a must. thanks.

GeTCrAzYKiD

i just noticed that when i disconnected the pressure switch up by the drier the compressor cuts off, is that telling me its bad, or is the pressure limit on it higher than 350?

Sideways7

iTrader: (7)

If you want to run freeze12, its not a big deal. You can technically buy it without a license in e-bay, but its still illegal. You can take the EPA certification test for 20 dollars at www.epatest.com. It takes about an hour or 2 to read through the material, and about 10 or 15 to take the test. It is 20 questions and open book. I highly recommend it as you can legally buy any refrigerant used in cars, plus it helps you get a better understanding of the basic workings of car A/C systems.
I switched my MX-3 over to freeze12 and it cools great, even in 100 degree weather. It runs at similar pressures to r12 and has similar cooling properties, so it won't overtax your system. If you decide to go that route, get your stuff here: http://store.lenzdist.com/index.php They are much cheaper than anywhere else and very helpful if you can't find what you want. I'm not sure if they have a complete retrofit kit, but you can call them and ask. You can find those other places, such as here: http://autorefrigerants.com/co00031.htm. They generally run between 30 and 45 dollars depending on what is included. Some places have complete kits that have several cans of freeze12 and some oil as well. Just look around and see what you can find.

GeTCrAzYKiD

well i will take all into consideration. I will purchase it leagally, I was certified through my company that i work for so its no big deal for me thats why i took advantage to do my own. I'm just going to order it when i finally go through with it. but i know the car was completely retrofited. the lines were replaced because i see that the fitting ar not screwed on the whole line was replaced so this guy did it the right way and i found out before i prchased it he had a front mount and when he had it installed the fan was removed to fit it after a/c was repaired i assume. But i will figure out what i can do but in the mean time with fan set up i sucked out 6 oz's of freon and left it run and the temps got better (45-50 at 95 outside) so now i just need to set up a permanent fan and i think all's well pressure are also within specs 40 - 250. at same temp outside so i think im good now. thanks im going to see what i can do about getting back to 12 for that freeze 12. or should i stay where i am now that its ok?

2713ddddavid

iTrader: (1)

Based on retros I`ve done it sounds like you have it right square in the ballpark. Your pressures are fine based on the outdoor temps. Since your lines were changed
I would stick with the 134a setup you now have seems to be working well.

My 2006 chevy has vent temps of 47 - 48 degrees when outdoor temps are 90.

Enjoy your A/C

jackhild59

iTrader: (7)

Retrofitting has nothing to do with the lines. There are two distinct systems used on the FC. compressors are different and the lines are a little different configuration and attatchement to the compressor is very different.

If the lines were replaced, they probably had leaks, but this wouldn't affect the balance of the system.

When you control the high pressures as you have done by reducing the charge, you absolutly reduce system capacity. This will result in slower cool down at high load and outside temps. It could also cause compressor quick-cycling at lower loads and lower outside temps. You could fry your compressor clutch if it is excessive.

R134a is ok for moderate climates in our FC systems. Not a good compromise for high heat and humidity areas.

Good luck

jackhild59

iTrader: (7)

That has nothing to do with the balance of the system. If you find out that he replaced the condenser with a parallel flow unit, then you are good to go with the 134a. I seriously doubt this was done.

http://www.ackits.com/index.cfm?fuseaction=Parallel

Your temps are ok for a retro fit. How would you like to have 34*-36* air on a 104* day? Dallas, TX humidity? On high fan after interior is cooled down. Thats what I get on my 1990 vert with R12 100% stock system with NO fan in front of the condensor.

Really.

Freeze12 should do the same. Some people claim quicker cool down for Freeze12, but my experience with it is slightly slower.

Good luck.

Sideways7

iTrader: (7)

My mx-3 was low of freon when I bought it, so I can't compare, but when it was recharged and retrofitted with freeze 12, it saw 35 degree temps and cooled down pretty damn quick.

jackhild59

iTrader: (7)

I think that anyone would be happy with a system that worked so well. Good work.

My wife drives a 92 Celica GT convertible and it is R12. Works great. I am restoring a 1992 Celica GT coupe for my middle son to drive. I am going to use Freeze12 in it to compare. It won't be done this year, but I will have two identical systems side by side to compare.