AC update ES12 and help needed.

[rswamy]

Ok, finally got back in the country after a long vacation. I installed the new rennaire Evap, pulled vacuum for 24 hours, let it sit for an hour no apparent leaks. Static charged with couple of 6oz ES12 cans. Idled the engine and got only about 70deg on the vent. Charged the system while running with another 3 6oz cans drove around, I get about 65deg at the center vent driving around stop and go, on the highway the best I got was 57. Any input will be greatly appreciated. With the pro-cooler help? What else can I do. Oh, when I get back to my driveway vent temps are back up to 72-74. Ambient was around 93-97 during this time.


August 17th, 2010

First of all, did a lot of reading, now I'm really using what I learned in Thermodynamics in Engineering school. Thanks for your suggestions and help of several posts here. I mounted a couple of 9" fans (600 CFM, 6amps each, fits pretty good, only drilled 4 holes each) on the outside of the deck lid, off center to the left and right about 3 inches (wish I had taken some pictures, I can if anybody needs some), used the rear defogger/wiper fuse in the engine compartment, put a $10 25amp relay from O'Reillys'. Spliced into the compressor clutch to drive the relay. Pretty simple project, here is link to the fans from JEGS

JEGS 52112 JEGS Straight Blade Universal Electric Cooling Fans

Fits pretty good inside the whale tails. I’m getting 65deg at the vent when stopped , 45 driving around city, 35-40 on highway in the last couple of days. That’s pretty good considering Memphis temperatures (95-100) lately. Next I may try to put a bigger condenser on the deck lid like "Tsuter" did in one of the posts. I had to let out a bunch of ES12 since I was obviously overcharged. ES12 does really work. I believe my low side is still high (28-30psi) at 1800 rpm, high side seems ok around 200-215. May need to fine tune the ES12. based on what I let out I'm guessing I have about 2, 6oz cans of ES12 in there.

[88911coupe]

Were you using pressure guages to monitor things while you were adding the ES12? Also, do you know what the conversion is from R12 to ES12? I'm assuming ES12 is some sort of R12 replacement...correct? I have used Duracool and used their conversion data to determine exactly how much I needed to add to make it comparable to R12 but I also used guages to monitor the high and low pressures. I was getting around 30 on the low side and about 250 on the high. I'm only getting down to about 30-35 degrees below ambient on fan setting 2 so I'll need to add a procooler and/or an additional condenser, which is discussed extensively on a couple of threads. I'd like to know which is more effective...adding the procooler or an additional condenser, say behind the rear wheel.
Good luck

[rswamy]

I'm getting about 40 on the low side and 240-250 on high side. From what I read on the EPA site Es12 and duracool are essentially a blend of hydrocarbons butane and propane. I did read somewhere that 5oz of Es12 = 15 oz of R12. So I may be a overcharged. Seems like I'm on the same boat as you 88911, I'm looking for the most effective upgrade to do next. I'm thinking the procooler will be good, the other option is either addition or replacement of condenser. When I drive around the vent temp drop to around 60s, I can only assume that a more efficient condenser would help. My impression is the procooler essentially reduces refrigirant temp prior to getting to the condensor. BTW, between fan speed at 2 and 3 I get about 2-4 deg delta in vent temp.

[wwest]

Originally Posted by rswamy

I'm getting about 40 on the low side and 240-250 on high side. From what I read on the EPA site Es12 and duracool are essentially a blend of hydrocarbons butane and propane. I did read somewhere that 5oz of Es12 = 15 oz of R12. So I may be a overcharged. Seems like I'm on the same boat as you 88911, I'm looking for the most effective upgrade to do next. I'm thinking the procooler will be good, the other option is either addition or replacement of condenser. When I drive around the vent temp drop to around 60s, I can only assume that a more efficient condenser would help. My impression is the procooler essentially reduces refrigirant temp prior to getting to the condensor. BTW, between fan speed at 2 and 3 I get about 2-4 deg delta in vent temp.

First you need to analize just whats going on at the compressor.

Is it running, clutch engaged full time or is it cycling...?

In the older systems the compressor only cycles off when the evaporator surfaces and the airflow, are cooled to the thermostatic control switch setpoint. If it runs then cycles off and on then your thermostatic switch may be the cause for low cooling.

If there is no cooling and the compressor runs continuously and you're sure the system is charged then you undoubtedly need a new compressor.

[rswamy]

Wwest, when on the driveway the compressor does not cycle, I imagine that is cause the vent temp does not fall within the delta measured by the switch. I don't know if it cycles off while driving around, I'll look into that. However, I don't know if the compressor is bad since I'm reading good pressures low and high.

[rswamy]

Next steps, probably desert duty front condenser and procooler. I am not getting much air flow out of the front condenser fan, any ideas?

[T77911S]

there are other substitutes out there that are not flamable. freeze12 is one. just something to consider, plus, if you ever take your car to a shop, they cant touch the ac system with propane or butane in it. i am not sure if they can recover freeze12.

[rswamy]

Has anybody attempted, to put condenser fans on the decklid. Would like some ideas.

[mppickett]

I suspect you overcharged. You can try to bleed a little off (run it for at least 15 minutes to make sure the gasses are well mixed).

[rsscotty]

As I recall, your system capacity is around 40 oz. of R12.

A 6oz. can of ES12 is equivalent to 18oz. of R12.
So your system should take about 2 1/4 six oz. cans.
From your description of 2 cans put in static, then 3 more six oz. cans...it sounds like massive overcharge.

[Vmarch]

How many of you out there are engineers? Why would you alter something that Porsche engineers worked long and hard on perfecting at the time? put it back to R-12 or change the drier, hoses and expansion valve and charge it with an 80% charge of 134.

[scottb]

Originally Posted by Vmarch

How many of you out there are engineers? Why would you alter something that Porsche engineers worked long and hard on perfecting at the time?

Um, I hate to break it to you, but even if Porsche engineers worked long and hard on the a/c (and I think it was an afterthought for the US, frankly), they far from "perfected" it. LONG non-barrier hoses, not enough condenser surface, lousy vent placement. insufficient air flow...the list is endless. There are many people who have made the 911's a/c much better than what came with the cars came from the factory...and to my knowledge none of them are Porsche engineers.

[rswamy]

I hear you scott, we wouldn't have so many threads on AC if the engineers had done a good job. I also think the blower in the front condenser is lame at best. I ordered a couple of 9" fans for the rear condenser. I realized after I charged (overcharged) the system that I had too much ES12, thanks to posts here. I will update the post when I make progress on the project.

[chamilun]

I installed a fan over the rear condenser and it does make a difference, but only in consistency. It seems the air cools quicker, and stays cool, but it doesn't lower vent temps. Great for sitting in traffic

[rswamy]

Originally Posted by chamilun

I installed a fan over the rear condenser and it does make a difference, but only in consistency. It seems the air cools quicker, and stays cool, but it doesn't lower vent temps. Great for sitting in traffic

IMHO it should lower vent temps, cause when I'm sitting in traffic the vent temps go up. Two reasons for this is engine is in idle speed and secondly the condenser is running hot compared to while driving. I believe the fans should make a difference on the rear condenser in vent temp, agreed that engine speed will also make a difference. I ordered 2 9 inch, 600 CFM fans and will get that in the mail tomorrow.

[Vmarch]

Gee I guess I am wrong then after replacing all hoses with barrier hoses on my 79sc, new drier, new front condenser fan, new expansion valve and 39oz of R-12 I get 28 degree vent temperatures on a 90 degree day.

[scottb]

Originally Posted by Vmarch

Gee I guess I am wrong then after replacing all hoses with barrier hoses on my 79sc, new drier, new front condenser fan, new expansion valve and 39oz of R-12 I get 28 degree vent temperatures on a 90 degree day.

Imagine how cold it would be if Porsche's engineers had actually designed a good system!