78 Vette - A/C issue
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
78 Vette - A/C issue
I just got my wife the 25th Anniversary Vette for our 25th Anniversary. Low miles, island car, 23k miles - been in a garage most of its life.
I've been working on the A/C trying to get it cool because it's hot here. I have replaced the compressor, evaporator, accumulator and all of the o-rings and seals. I did a vacuum leak-down and it's all sealed. I've loaded it with R134 and it gets cool. The accumulator sweats nicely and the low-side pressure is low (60) and the high is high (275 - if I'm looking at the right scale). The problem is that it gets cool, but not cold.
Any ideas?
I've been working on the A/C trying to get it cool because it's hot here. I have replaced the compressor, evaporator, accumulator and all of the o-rings and seals. I did a vacuum leak-down and it's all sealed. I've loaded it with R134 and it gets cool. The accumulator sweats nicely and the low-side pressure is low (60) and the high is high (275 - if I'm looking at the right scale). The problem is that it gets cool, but not cold.
Any ideas?
Le Mans Master
Joined: Feb 2011
Posts: 5,943
Likes: 61
From: Southern NH
2 things come to mind here. first, what is the condition of your fan clutch? you need a good amount of air going across the condenser to get the a/c really cold.
second, how much R134 did you put in? you only need about 80% of R134 compared to R12
second, how much R134 did you put in? you only need about 80% of R134 compared to R12
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
Thanks for the reply. I've got about 32 - 36 oz of R134 in there. I'll check the fan clutch tomorrow. I found buried in another site a page that suggested these vettes need a pusher fan on the condenser for the R134. I know the temp gauge was showing hotter now that the A/C is running.
If anyone has any other thoughts on the matter, I'm always ready to learn! Thanks!!
If anyone has any other thoughts on the matter, I'm always ready to learn! Thanks!!
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
According to this: http://tech.corvettecentral.com/2008...4-ac-retrofit/
60 on the low side is a hair high, but it will probably come down with a pusher fan, right?
Thanks for the help - if something else comes to mind, don't hesitate to mention it.
60 on the low side is a hair high, but it will probably come down with a pusher fan, right?
Thanks for the help - if something else comes to mind, don't hesitate to mention it.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
When I was researching this I read that the Condensor should be a cross flow unit so thats what I used. Depending on how stuck you are on originality, consider going to an electric fan setup like a Spall or the like, cleans up a lot of junk under the hood and you can use a controller for the fans to make them come on when needed
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Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
Hot water shut-off valve doesn't have a vac hose attached and it's passing hot water through it. Also, the fan clutch is questionable. When the engine is cool, the A/C is cold.
So, next question: Where does the water valve get its vacuum from?
So, next question: Where does the water valve get its vacuum from?
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
Great, thanks for the quick reply. Currently there is no hose there so I guess I'll take the dash apart and see if I can find something missing where the other end would attach.
Le Mans Master
Joined: Feb 2011
Posts: 5,943
Likes: 61
From: Southern NH
i would look around the engine compartment first before i go tearing the dash apart. you might need to look up from under the car. chances are the hose just popped off and is hanging down somewhere
Drifting
Joined: Apr 2014
Posts: 1,396
Likes: 129
From: Plainfield IN
Vacuum line goes from the valve to the top of the firewall where there is 2other lines also. From there it goes to the dash controller. Mines missing too, but I found part of it sticking thru the firewall. It's 1/8" white or yellow and it is more like plastic than rubber. I've not seen it sold fom any parts supplier - one member suggested using air shock lines - and I have some - looks like it could work. Is your hot water shut off valve metal or plastic - mine is black plastic.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Google 134a temperature pressure chart. What pressures you are seeing greatly depend upon the temperature and humidity at the time reading are being taken and air flow across the condenser. It seems to me you are overcharged unless you were doing this in a Central American rain forest at the height of summer or you had minimal flow across the condenser. When you have an air flow issue, you can run water over the condenser when charging to bring pressures in line. And it is always better to be a bit under-charged than over.
As far as reading the gauges, do not pay attention to the inner temperature rings. While useful in determining system efficiency, they are nothing but a distraction in most instances. Use only the outer PSI scale.
As far as reading the gauges, do not pay attention to the inner temperature rings. While useful in determining system efficiency, they are nothing but a distraction in most instances. Use only the outer PSI scale.
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
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From: Marco Island Florida
I'm pretty close to the central American location - I live on an island on the southwest corner of Florida - the only place south of here is Cuba - I'm about 90 minutes from Havana. It was well over 90 degrees with more than 90% humidity when I took those readings. Gotta love Florida.
The water shut-off on my car is metal. I'll check for a vacuum port on the firewall in the morning. Also, I'll run water through the condenser once I get the shut-off valve straightened out and if readings are still high, I'll bleed off some of the pressure.
Thanks for the help - y'all are the BEST!
The water shut-off on my car is metal. I'll check for a vacuum port on the firewall in the morning. Also, I'll run water through the condenser once I get the shut-off valve straightened out and if readings are still high, I'll bleed off some of the pressure.
Thanks for the help - y'all are the BEST!
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
For even better hot water control go to a big box hardware store and get a ball valve to put in the heater hose to REALLY turn off the flow through the heater core. Someone on the forum (search for heater hose valve) can give you specific parts to get but it's an easy fix. When heat is not needed, like never in your part of the world, just cut the water off to stop all hot water flow through your heater into the cabin.
This does not replace the factory valve. Just supplements it.
This does not replace the factory valve. Just supplements it.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
This is what I use in place of the vacuum valve. Just close it all summer and open it in the fall.
http://www.napaonline.com/Catalog/Ca...271_0361163975
http://www.napaonline.com/Catalog/Ca...271_0361163975
Drifting
Joined: Apr 2014
Posts: 1,396
Likes: 129
From: Plainfield IN
I'm pretty close to the central American location - I live on an island on the southwest corner of Florida - the only place south of here is Cuba - I'm about 90 minutes from Havana. It was well over 90 degrees with more than 90% humidity when I took those readings. Gotta love Florida.
The water shut-off on my car is metal. I'll check for a vacuum port on the firewall in the morning. Also, I'll run water through the condenser once I get the shut-off valve straightened out and if readings are still high, I'll bleed off some of the pressure.
Thanks for the help - y'all are the BEST!
The water shut-off on my car is metal. I'll check for a vacuum port on the firewall in the morning. Also, I'll run water through the condenser once I get the shut-off valve straightened out and if readings are still high, I'll bleed off some of the pressure.
Thanks for the help - y'all are the BEST!
Thread Starter
Instructor
Joined: Jan 2008
Posts: 144
Likes: 0
From: Marco Island Florida
Finally fixed it. I hooked the shut-off valve to a full-time vacuum source and capped the lead through the firewall. The car gets cold now and the "Max" setting on the A/C works.
Thanks for the help. Y'all are the best!
Thanks for the help. Y'all are the best!