Year: 1982
Make: Chevrolet
Model: Corvette
Engine Size: LS1
Refrigerant Type: R134a
Country of Origin: United States
Hello,
I'm completely incurable... I have a systemic need to get in over my head...
I found this 1982 Vette, crossfire injection, primer black, peach of deal, low low price.... did I mention it didn't run? Well, that still didn't stop me from making an unsound decision.
A trailer ride, six months, and 200 bucks later; believe it or not that crossfire was running like she just got off the lot... 23 years ago. But in all honesty she did run well. Never overheated, sort of rode well, and would even bark the tires (on a good day with the stars aligned).
As you might can imagine, the crossfire was just not enough and the automatic was just not cutting it any more. Soo.... I decided to swap in an LS1. Mind you at this point the most I've done is rebuild a few brake calipers and regularly change my oil. Yet, some how the used LS1 is cleaned, refreshed, and ready to go in to the vette. The old mill is sitting idle out of the car and now I'm scratching my head at how to mate the old with the new.
Sorry for probably going too far into it, I guess I just want to convey that I'm serious and committed to seeing this through.
Right now I've decided that the old vacuum A/C and Heat controller has to go and a newer electronic one should be installed. And here in lies the dilemma.
I'm fine with putting in a modern OEM controller or installing simply an on/off switch for heat or A/C and a knob for the blower, but I have NO clue what I'm doing. I don't know where to begin, or even if the system is/should be TXV or OT. All I do know is that I have a V7 compressor included with the purchase of the used LS1 motor and I'm handy with tools.
Where do I start with the referb? Should I just buy a gutted system used in conjunction with an LS1? Would it be easier to just buy the parts piece meal and fab up a simple toggle/knob for controls?
Oh the A/C Heater controls currently in the vette have not ever worked since I've owned her.
Thank you for any and all advise,
~ Kip
Initial Purchase:
Cleaned Up:
I was reading one of the Hot Rod magazines that devoted the whole recent edition to LS1 conversions.
In 1990s, GM always matched a variable displacement compressor (VCD)with a orifice tube A/C system. Some rodders report success matching the V7 compressor to a conventional expansion valve (TXV) evaporator although the VDC control fights the TXV for refrigerant flow control and wide swings in louver temps are the result. In later years GM used a dual/cross charged TXV with VDCs.
At your experience level, going electronic control with stepper motors for A/C mode control etc., you would be prudent to investigate Vintage Air's GEN 4 control system for sure success.
Check out "How To Air Condition Your Hot Rod" from AMAZON for installation step by step with GEN 4.
Idea: (AMA might consider to become a distributor/installer of these GEN 4 A/C for Hot Rods with electronic controls)
Cordially,
hotrodac
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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Edited: Mon January 24, 2011 at 7:24 PM by ice-n-tropics
Would take quite a large potentiometer, actually a rheostat to control a blower motor, least a 250 watt size, I do have a couple I use for load control, about six inches in diameter.
Stock is always the easiest way to go, including R-12, can't say I am an expert on Corvettes, but understand the condenser is the key problem, just too small, a parallel flow would help some, even with R-12/
Kip,
We all make our own choices and live with it.
My $0.02:
I was recently facing the same choices for a Chevelle and went the GEN 4 route due to a higher confidence level and to eliminate unexpected surprises. In my case the time investment and the car appearance and value were key factors.
Cordially,
hotrodac
-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Tex:
I have never had a V7 "hunt" when connected to a TXV system. Since the V7 is native to that engine & PCM, it would probably be easier to swap the TXV for a FOT if it did in fact hunt when completed.
Just my .0002 cents. YMMV.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
All depends upon if you want to do some R&D or just not reinvent the wheel, but just copy a late model system as much as you can, save the evaporator and duct system. That can test you.
KIp,
For blower speed control, you could use the AC switch that has 3 spped resistors built into it.
Would not be a bit surprised if your climate control was similar to that of my 82 Chevy motor home. Has a sliding mode bar, off, AC Max, AC, Vent, Heat, and Defrost. I think, haven't looked at it lately, but close. Either ACmax or AC supply 12V to the compressor circuit, but ACmax closes the recir door for internal rather than external air source. Its a combination electrical and a vacuum switch. Vacuum switch activates actuators to direct air flow either to the floor, dash, or defrost vents.
Directly below the mode bar is a temperature bar that operates a cable that opens or closes and anywhere in between a heater core feed valve independent of the position of the mode switch. The more this valve is opened, the more heat you get.
A vertical blower motor switch on the left is a multiple switch that fires one of these.
The blower resistors add resistance in series with the blower motor to control the blower speed. Very simple, full speed applies 12V directly to the blower motor.
The compressor 12V may be a bit different than mine, applies the 12V to an evaporator thermal switch that fires the compressor clutch directly. If the evaporator is below 33*F, compressor shuts off, that can happen either with the compressor cooling the evaporator or its just cold outside. AC compressor will never switch on below 33*F, but after the evaporator gets below 33*F, it has to warm up to 39*F before this thermal switch closes again to operate the compressor.
Other GM vehicles in this era used a cycling switch for this same function, but has to have a pressure of greater than 44 psi to switch on the compressor and when it drops below 25 psi, switches the compressor off again. A direct relationship between pressure and temperature exits so either pressure or temperature can be measured. Temperature measurement is more precise, but if its cold outside or if you are low on refrigerant, either will keep the compressor from running.
My system refrigerant flow from the high side of the compressor goes to the condenser, a receiver with a sight glass to a TSV valve, to the evaporator, than back to the low side of the compressor. TXV valve closes with an evaporator temperature capillary tube to slow down the refrigerant flow to reduce compressor cycling, but still cycles. GM also goes from the high side of the compressor to the condenser, a fixed orifice, evaporator, then an accumulator to prevent liquid refrigerant from entering the compressor. But these systems will cycle very frequently, especially in cooler weather.
These systems never used a high pressure cutoff switch, but rather a pressure release valve, kind of dumb, as if your condenser would get loaded with debris or cooling fan didn't work, would blow out R-12 into the atmosphere if the pressure exceeded about 430 psi. But was in the early 90's that GM added a high pressure cutoff switch to switch off the compressor in the event of a high side pressure increase. The pressure would have to drop to around 220 psi before the compressor could switch on again.
A V-5 or a V-7 compressor is quite the innovation, a variable displacement type of a compressor that doesn't cycle and uses the fixed orifice accumulator type configuration. At say 70*F ambient, its flow output is very low and vents will only blow out cool air, but at 95*F, the air becomes ice cold. These compressors run all the time provided the pressures are within what is considered normal operating range. Typically just a high side thermistor is used, while I haven't exactly measured it, if the corresponding temperature relates to pressures of between 40 and 430 psi, the high side pressures have to be within that range. The thermistor requires electronics to make this conversion to operate the clutch relay, so below 40 psi, the compressor won't even turn on. So if the ambient temperature is below about 33*F, the compressor will not run. Or will shut down if the pressure increase to around 430 psi. Honda and Toyota used a pressure switch in the 80's and early 90's for this same function called a dual function switch that offers either closed or open contacts to break the 12V line feeding the compressor clutch coil circuit.
So there you have it, a climate control switch that always supplies 12V if in any of the AC positions, feeding either an evaporator thermal switch, cycling switch or a dual function switch, that is by the way, much cheaper to do with a thermistor feeding the already existing A-D converter in the PCM to control the clutch relay.
In theory at least, could also go from your climate control through an accumulator mounted cycling switch to a high side mounted high pressure cutoff switch to the coil of a relay to switch on the compressor coil of a V-7 for safety control. The cycling switch shouldn't cycle unless the pressure drops below 25 psi, but also adjustable to make an easy to wire system. You don't want that compressor to run if the low side pressure is below 25psi either due to loss of refrigerant or its cold outside, nor about around 400 psi. These are the basics of AC control. In PCM vehicles, more games can be played by switching off the compressor if the ETC shows an engine overheating condition, or if you floor the gas pedal.
Hope this helps.
Kip and Nick,
More than a few cars have turned to crispy Critters because of inadequate blower resistor design/installation.
If the airflow from the blower wheel slows or stops while current flows through the resistors the nearby plastic housing can soften and ignite if there is improper thermal increase protection.
Brad,
Yea, hunting happens only at certain medium/low refrigerant stabilized rpm mass flow rates not associated with Sin City ambients.
2nd, the dual charged txv has zero or "negative" superheat at very low mass flow w/ VDC in min. stroke. This keeps adequate oil return to the VDC. Another solution is a nicked seat txv that never completely closes. A fixed orifice tube is a good countermeasure for both potential negatives.
hotrodac
-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Well the thing is with nichrome resistors, the thicker the wire you use in a design, the longer the length of the wire that has to be used, and that cost more money for the stock holders. In designing a nichrome resistor, the key factor is the color of the wire when operating under full load, a bright white color normally doesn't last very long, even like to avoid a dull red color as oxidation will occur. Prefer maintaining the same color as the wire, that way, they will last. For some applications in my own vehicles, I wound my own. Termination is also important, somehow a cheap brass eyelet doesn't hack it.
Should we talk about PWM power MOSFET transistor that blow well ahead of its protective fuse that costs two arms and two legs?
Well after some research it seems that the vintage air is very well more cost effective. I still haven't ruled out the cobbled together approach. Either way I'll report back with what I decide (probably with questions not too far after the parts arrive).
Edited: Due to a blank post, initially.
Edited: Mon February 07, 2011 at 9:59 PM by kipring
Kip,
Either way you go, it will be best if the acceleration performance is not degraded too much w/ AC.
The OEM A/C draws in 20 to 30% hot humid outside air (OSA) which adds to the parasitic horsepower draw and adds to the heat dissipated by the condenser. The OEM air inlet mode necessitates a larger condenser and more condenser air flow. OSA also adds 10 degrees to the louver temperature in the 100% OSA mode.
The Vintage Air Gen IV has no OSA.
hotrodac
-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Edited: Tue February 08, 2011 at 6:25 PM by ice-n-tropics
Car should have MaxAC that closes the recirculation door cutting off fresh air intake. Use to be 100%, but was reduced to 80% so the occupants wouldn't die of CO poisoning. Not sure what year this was implemented.
And if you are driving on the Dan Ryan in Chicago completely stalled in traffic with cars all around you on a extremely hot windless day, is that fresh air intake really taking in fresh air?
Kip,
The LS1 has a serpentine belt dedicated to A/C only with both a slack side idler pulley and a tight side idler. You might do well to check or replace the top tight side idler pulley because this is normally Verboten due to high belt load.
hotrodac
-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
Those tensioner and idler pulley bearing see the same radial load as the compressor idler pulley so should be the first to go since they are so much smaller. But due to the smaller radius of their pulleys, do see less of an angular load. But really shouldn't see much for an angular load if the alignment is correct, but comparing a single roll bearing with a dual roll bearing at the compressor. The compressor bearing experiences a lot more heat, so its grease tends to dry up at a much faster rate that results in failure.
All are very limited lubricated bearings, not exactly like changing your engine oil, what little grease in there is expected to last for life, augmented by grease loss through the seal.
Typically the bearing cage is the first to go, thick riveted steel cages last the longest, worse is using plastic where friction of the balls causes heat and can be welded to the cage locking the balls. Garbage.
One heck of a problem area where maintenance is required. And not very easy maintenance at that especially in a FWD vehicle where they jam the front of the engine at the inner fender well.
Should advertise, if you need even more problems, buy one of our vehicles.
A lot of LS1's moving into older vettes forgo the dedicated A/C belt and opt for one belt to run it all. I guess it best to try and stick with the dedicated belt?
Thanks again,
~ Kip
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