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7/2/10 9:20pm - Original Message: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
I am getting ready to try to get the AC hooked back up and working on my 74. I had it disconnected since changing the engine this past winter. Last year i had recharged the system in the spring with 134. It never cooled very well. Some of the problem was that the vents inside the car didnt seem to have alot of air flowing out from them. the fan is moving air just seems to be leaks through vents.  are there any common issues there that I should look at in this area? next before i put things back together I was thinking about replacing the VIR valve. I see an original replacement costs are about $250, but i also see there is an updated VIR eliminator valve available that is about $50 less. What are your thoughts on this eliminator valve? Would you recharge the system with the r134 or go back to the R12? The compressor didnt make any noise so should I go back in with it or is it best to replace it at this time as well? I plan on using a flush kit on the lines before going back together then drawing down to a vacuum before doing a final charge.
As always, thanks in advance for you help.
Rodney


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7/2/10 10:58pm - Reply: 'AC Advice needed'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19449
Pluggin all of the leaks in the duct work under the dash will make a huge difference in cooling the interior. These things were never all that good in that respect from the factory. The ducts don't even fit together in most places. Getting the air to the vents' is a major ordeal. If you take the dash apart and look, you'd be amazed that you can get any air out the vents in the first place!
You should seal all of the duct junctions with thicker foam tape, and make sure the ducts are at lease close to mating together....most are not. Duct tape might come in handy, too.

I haven't has any luck at all removing the VIR assy and replacing it with the aftermarket tubes, but that's just me. The VIR is rebuildable, so that might be an option, too. I plan on rebuilding mine when I get around to fixing the air on the '74...the compressor took a doo-doo years ago.

I'd say fix all the dash vent/duct leaks, evacuate and charge with 134, and see how much better it is. Make sure your condenser is not full of leaves and bugs, too, as that will make it harder to cool the refrigerant once it leaves the evaporator.
Adams' Apple2010-07-02 20:01:07

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Joel Adams
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7/3/10 1:52am - Reply: 'AC Advice needed'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518

Hey Rodney, check to see if your heater core turns off..I think you should have a valve on the heater core coming off the intake???My dads 79 his valve stuck open and the ac could never overcome all the heat from that thing..I got one at Advance or Auto Zone..down by Hardees..if the heat is turned off the heater hose should go colder on the other side of the heater hose valve..not sure if you have one but thought I would throw that at you..maybe catch up with you at the show at the park in the morning.

Rich
ps, pass on the R12..not worth the money anymore..what is it 80% of 134 vs R12 charge...


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7/3/10 8:01am - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Thanks Adam, i saw when i reworked the radio that the vents needed attention. I did find a vender that sells reman VIR for 175, and he has kits to rebuild which looks as though it would just be the desicant bags and seals. Is their more to them than that? My dad said he used to rebuild them as well in his days as a mechanic.
Hey Rich, I'll miss you again this week as we are at the beach. Not home to often on the weekends as the wife likes the sun and sand. I dont, but there is golf and food here! You might find my dad there though. he has an 84 Monte ss or he could have his 99 30th anniversary firebird or his 80 daytona firebird. Hes going through his childhood again!! makes my wife nervous! have fun today.
Rodney


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7/3/10 12:14pm - Reply: 'AC Advice needed'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19449
The '74 doesn't have a water shut-off/control valve for the heater core....what were they thinkin? That is a great source of heat in the cabin, even with an A/C system that works.
The VIR rebuild kits will have a new desiccant bag and seals, fer sher, but I'm not sure what else they may have these days. $175 for a reman VIR may sound high(and it is), but the aggravation factor may come into play when re-building you own VIR....they ain't the easiest things to get on/off the car to start with, and if you're not comfortable rebuilding yours, a reman may save having to do it twice...or more.
You may not even have a problem with your VIR, but it might be a good idea to change/rebuild it, especially if the system has been open for very long. Corrosion can take hold pretty quick, plus the desiccant may be contaminated, or otherwise unable to do the job.


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Joel Adams
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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7/20/10 7:02pm - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
I ordered the VIR replacement kit and hope it gets here this week. I removed the old valve last night so I am ready to install the replacement update as soon as it arrives. I hope it goes on easy. The VIR valve had 5 lines going into it. I cant imagine that the replacement will just match up and I am having bad thoughts about getting the new part on and everything in place. I am going to be switching to r134 so I drained the old oil from the compressor and napa's tech line said add 11 oz. of ester oil for the change. I hope to put the oil in tonight and install the compressor onto the header brackets. I have to put the belt on the compressor before I bolt it in place because the tall valve covers dont allow me to move the compressor far enough for the belt to go on. Next will be to flush all the lines and replace all o-rings on the system and by the time that is completed hopefully the replacement valve will be here. I have read when changing to r134 that I should only use 80% of the original amount of freon. Is that correct? Thanks again for your help.

Rodney


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7/20/10 7:20pm - Reply: 'AC Advice needed'
yostusota
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York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518
Hey Rodney,
I have been meaning to ask you if your dad had got that big engine for his car yet? Say hi to Vernon for me! Tell him "one day" says hi. I will check on the charge amount again..it just sticks in my head that it is 80 % of R-12 to 134. I use that as a start then use gauges to see if I need more or less.
Rich

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7/20/10 10:28pm - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Tonight I started searching for air flow in the ducts. I removed the center wiper switch and the dash glove box area. Didnt really hear or feel any leaks. Pulled the fan out and didnt find any blockage there. While I am working on this if I have to remove the heater box I will replace the heater core just for good measure. Not sure what I am looking for so I brought the assembly and service manual in to do some research.  I also need to find out why the high speed blower doesnt work. I replaced the resistor when I did the motor thinking that would take care of it but it could be the switch as well.
Rich - as for dad, No the motor hasnt gotten here yet. Its coming from California. Must be on the long road here! Have you met dad? He has gone car nuts! I keep telling him there goes my inheritance. I have already put a claim in on his new Firebird. Told him to make it really nice for me!!

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7/20/10 11:41pm - Reply: 'AC Advice needed'
dskopp
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Oak Creek, WI - USA

Vette(s):
1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
Posts: 1956
I am under the impression that all C-3's, mostly sharks do not have factory A/C that keeps the cabin cool.  We have been having some 80 degree weather in Milwaukee as of late and I notice that me feet are very warm.  Maybe just more insulation on the floor will fix that.  What do you think Joel????

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7/21/10 12:37am - Reply: 'AC Advice needed'
suncountry Lifetime Member
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Moses Lake, WA - USA

Vette(s):
1976 L48 4-spd, Mahogany Metalic exterior, Buckskin interior 350ci/350hp, 3rd owner, fiberglass spring, 255/50-16's Torq-Thrust II

Joined: 4/16/2005
Posts: 2134
I replaced my VIR with an aftermarket valve that turns my system into a cycling comprossor. The system is charged with R12. It will keep me cool in 90 to 100 degree weather but I have to run the fan on high. I also insulated my floors when I rebuilt my interior along with shut off valves on the heater hoses. I also spent some time trying to seal my duct connections under the dash.

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C3VR Lifetime Member #110 We are all young at heart Glen
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7/21/10 9:22am - Reply: 'AC Advice needed'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19449
High speed blower works off of a relay...the resistor has no effect on the high speed. The blower relay is on the side , near the top of the evap. housing, under the hood. Check the connection there to make sure it is not corroded, or melted. Could be the switch, too, but the relay, or the wiring to/from the relay is a more likely suspect for no high blower. There is also a fuse for the high speed, too, if memory serves...

Heat shielding under the carpeting is a great way to minimize radiant heat on the tootsies!
Adams' Apple2010-07-21 06:23:48

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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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7/21/10 11:09pm - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Adam,  there is a relay on the side of the evap housing. it has a 3 plug connector and a single plug connector on it. the single is a black wire that is a ground. Checked it and it is a good ground. the 3 plug connector has an orange wire that is hot at all time with switch on, the blue wire is only hot when the hearter switch is in the high spot, thus the switch should be ok, the purple wire carries the current to the blower and that makes the high speed work. So I am assuming that i need that relay? How does the relay work? when the blue wire energizes it, does it pull the connection inside the relay to give a full 12 volts from the orange wire? I hate working with wiring but i guess i need to understand it. Thanks again as you were right on the money with your diagnostics.
Rodney


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7/23/10 1:46pm - Reply: 'AC Advice needed'
VetteSpecialties
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Mounds View, MN - USA

Vette(s):
70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe

Joined: 5/24/2007
Posts: 1031
The later C3s had a water shut off valve, as mentioned above.  It is easy to put one in the heater feed hose.  It is normally closed, so you can just leave the vacuum connection off.  When you want to use the heater, connect a vacuum line, and it will stay open.  A little crude, but effective, and decent looking.  Another thing to check under the dash is the little diaphragms that actuate the flappers.  If one of them has failed, it will leak enough vacuum to keep the rest from working well.  It is usually the that is hardest to replace.

Larry


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7/27/10 2:03pm - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Adam, thanks for the relay advice. After getting the correct relay i finally have a high speed blower motor! Now, i need to get the AC put back together. I received the VIR eliminator valve but its going to have to wait for about 2 weeks as we are heading for vacation. I dont think I can get it done before Thursday when we leave. I am super excited about having a cool AC car though! Now if the vents work I will be in business! I started a new post on vents but no suggestions yet. Might have to wing this and see what happens. Thanks again for the help from everyone on this forum.
Rodney


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8/15/10 11:16pm - Reply: 'AC Advice needed'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Thought I would update everyone on where I'm at with this AC changeover. Thursday night I installed the VIR replacement valve. That wasnt the easiest thing to match up piping and get everything to fit and not rub anywhere but finally its all connected. Then to fasten the VIR replacement valve tight (since the factory one doesnt fit the new valve) I went to Ace and bought a 4" rubber pipe cap with a clamp built into it. Drilled a hole in the clamp and cut the bottom out of the cap and it worked perfect. Pulled the system down to a deep 1/2 hour 28 lb vacuum and system held. wired in the new switch Started engine and charged the system with 134.  gauges read about 33 lbs on low side, 230 on high side. Have good cold air inside. Now, a question I have, the new valve is supposed to make it a cycling clutch. Mine doesnt cycle. it says it should kick in at 22 - 24 and off at 40 lbs. my system stays at 33 all the time. Clutch on compressor stays on. I turned the adjusting screw counter clockwise 1/2 turn like the instructions say to with the 134. Should I worry with this or just let it go. It feels good and cold but I cant drive it until I get my interior and vents back in. I'll start a new thread on that under interiors! By the way, I used about 36 oz of 134. Original R12 was 3 lbs.



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