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88 Chevy Van A/C Confusion


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Mrmodify
Novice

Jun 16, 2014, 4:11 PM

Post #1 of 22 (3164 views)
88 Chevy Van A/C Confusion Sign In

I have a 1988 Chevy G20 Sports Van, 350, front and rear air. I converted the van from R12 to 134a years ago and over the last 4 years have had 2 compressor failures and 1 clutch failure. Each time I have flushed the whole system replaced the orfice tube and accumulater and filled with ester oil. I always used rebuilt compressors from a popular parts house. Back in March I recovered the freon and replaced another cratered compressor. This time around I bought a new compressor, removed every hose, both evaporator and the condenser and flushed till I was sick of flushing, a gallon worth of flush. I installed a new accumalator, office tube and installed a compressor suction screen kit. I filled with ester oil again, filled system with the recovered freon. The low side pressure was so low that pressure switch would not come in while running so I added 4 more cans. The pressure @ 80deg amb. Will run around 17 - 21#, compressor will cycle, accumulator and suction line to compressor are sweating like a pig waiting to be slaughtered, the front vents will freeze you out but the rear air will blow hot. I have all the tools needed and some knowledge I learned in H.S. Years ago (no such thing as R134a back then) I am lost and confused. I personally think the system is over charged because of the sweating but I don't know anymore. CrazyUnsure


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jun 16, 2014, 10:22 PM

Post #2 of 22 (3141 views)
Re: 88 Chevy Van A/C Confusion Sign In

Arrrr? That old and dual air. I actually don't know but rear should be high mounted in back - right? Rear should be an expansion valve and front an "O" tube and all things equal rear should be the pig on the system not the other way but now old so all bets off.






Can you do without it totally and put this back to single air for front only and plug off rear? It's final if you do or would be outrageous $$ to change your mind later no doubt. Plug kit or cut lines and have them welded (aluminum) into plugs as needed.


Not real surprised at eating up reman compressors and possible this may fair better with PAG 150 oil rather than Ester?


Notes: If this is using an R4 compressor the stink for this as it works too hard for a van like this. Lists 72oz charge and aim for a range on a converted system some low as 65% and max 80% of OE charge known not just the # I found.


Take pressures running just the front not both as it gets confusing.


You still have this so bet you want more so do it as right as possible,


T



Hammer Time
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Jun 16, 2014, 10:25 PM

Post #3 of 22 (3139 views)
Re: 88 Chevy Van A/C Confusion Sign In


Quote
I always used rebuilt compressors from a popular parts house.


There is your biggest problem. NEVER us reman compressors, new only, preferably Delco


Quote
I filled with ester oil again,

That is another problem. You should be using PAG oil. Ester oil has terrible lubrication properties. The only benefit is that it was compatible with mineral oil but the mineral oil is long gone.


Quote
The pressure @ 80deg amb. Will run around 17 - 21#, compressor will cycle, accumulator and suction line to compressor are sweating like a pig waiting to be slaughtered, the front vents will freeze you out but the rear air will blow hot


The rear has either a bad expansion valve or blend door problem. Pinching off the rear heater hose should answer that question of which one. You may also have a restriction in the front causing those low suction pressures.



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Discretesignals
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Jun 17, 2014, 12:15 AM

Post #4 of 22 (3132 views)
Re: 88 Chevy Van A/C Confusion Sign In


Quote
This time around I bought a new compressor, removed every hose, both evaporator and the condenser and flushed till I was sick of flushing, a gallon worth of flush.


There is another problem. You can't flush condensers out good enough due to their design. You should replace the condenser when compressor grenades. You should also replace the manifold hose if it has a muffler in it.





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Mrmodify
Novice

Jun 17, 2014, 1:57 AM

Post #5 of 22 (3121 views)
Re: 88 Chevy Van A/C Confusion Sign In

Thanks Tom, this vehicle does have a R4 compressor, rear evap is mounted above rear doors with a expansion valve. I am trying to keep the old girl original if I can but do agree a single would be easier.


Mrmodify
Novice

Jun 17, 2014, 2:08 AM

Post #6 of 22 (3120 views)
Re: 88 Chevy Van A/C Confusion Sign In

Thanks hammer time. I have learned my lesson on rebuilt compressors. The new one is a Delco. I always had good luck with rebuilt but that was years ago with r6's with r12. I going to assume the expansion valve is bad because there is no blend door or heater on the rear evap.


Tom Greenleaf
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Jun 17, 2014, 2:39 AM

Post #7 of 22 (3115 views)
Re: 88 Chevy Van A/C Confusion Sign In

Forget the blend door for heater as it's separate on the floor in a box like a toaster oven sort of thing, not in the rear overhead unit but shouldn't be fighting with it anyway just because.


You could pick no rear heat (I think) or any configuration on these but factory rear air was highest in back. X valve may be stuck open or clogged or you wouldn't be getting much out of front is wide open or charge too low.


R-4s: They should have put a timer on them for when they would explode for this size machine.


I trust you'll get it having been thru this a couple times........... T



Mrmodify
Novice

Jun 21, 2014, 12:35 PM

Post #8 of 22 (3054 views)
Re: 88 Chevy Van A/C Confusion Sign In

Evening All,
Just an update, I removed 80.6 oz. by weight of freon this morning, picked up a new orfice tube and expansion valve. Broke both lines at the rear evap., broke manifold away from compressor, ad broke line at orfice tube. Orfice had a small amount of metal on the screen of the orfice tube. I blew small quantities of dry air. (I have a heat type air dryer) through the hoses. Found rear evap. would not pass any air. Removed expansion valve and could not blow though it. Taking a break and will install rear evap unit and pull vacuum. I have a 1983 factory GM van manual that says unit with rear air holds 80 oz of R12, A local parts house shows a 88 chevy van with rear air holds 94 oz. of R12.


Hammer Time
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Jun 21, 2014, 1:23 PM

Post #9 of 22 (3051 views)
Re: 88 Chevy Van A/C Confusion Sign In

I don't know where you are getting these numbers from. The capacity of this system when it was R12 was 69 ounces. When you retrofit to R134 you only recharge at approx 80% of originally capacity so the charge here should be about 55 ounces and no more.



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Tom Greenleaf
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Jun 21, 2014, 9:12 PM

Post #10 of 22 (3044 views)
Re: 88 Chevy Van A/C Confusion Sign In

Note on % of charge R-12 > R134a: I show 72oz for OE R-12 (totally close enough) and charts can be wrong. Any underhood info to be used first.


80% of any (if any) known correct charge for R-12 of 134a is tops or you will lose cooling BTU up to harm - done - that's the way the molocules are and they way they take up space. More is NOT better with refrigerant anything.


Now - over years with a vehicle this old or older replacement parts are likely to reduce charge more. Hope any stickers that came with parts stated how much to reduce charge are still there.


OK: A system that hold this much was common. With R-12 off a pound wouldn't matter much but not so with inferior 134a* which is less capable of range where it will perform well.


* Inferior in that it's caloric ability is about 80% of R-12 so bolstering heat exchange ability of components is the answer w/o just making them bigger.


To get this right you need all info of what temps are where and pressures. If you know temps you know the pressure -- exactly.


When taking pressures better to use just front air on "O" tube as a working "X" valve will hog the bounty of compressed gas as it wants and needs.


Now it's full of yuk so all bets off. Rear lines almost never survive or come apart and new or made up ones should be barrier hose as 134a is a smaller molecule and will leak thru OR hose for this but not if used and excellent as OE mineral oil would have saturated the hoses and work OK with possible 2 year boosts if perfect.


Earlier mentioned just stick with the front and delete the rear A/C which is not practical for passenger vans in climates where A/C is a must. Just remember you are only splitting the BTUs of ONE compressor not getting more cooling but where it comes out so no real loss (some) of BTU output.


Back: It's a van so compressor is already stressed out, jammed in a tight doghouse for engine and known for high failures. OE fan clutches should pull out more than double what a car would of the time.


More: This van must be exceptional to be worth the wild expense it will take to make work as new. Converted you lose BTU about 20% without alterations of components. You can paint roof light reflective cover and treat windows up to insulate flooring to assist.


New this vehicle was a challenge to cool. Debris now is going to be the problem to fix and getting charge correct for the exact vehicle imperative. It just might be better @ 70% than 80% and can't know unless all observations noted for charging or compressor will just fail again and again,


T



(This post was edited by Tom Greenleaf on Jun 21, 2014, 9:23 PM)


Hammer Time
Ultimate Carjunky / Moderator
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Jun 22, 2014, 12:39 AM

Post #11 of 22 (3039 views)
Re: 88 Chevy Van A/C Confusion Sign In

I just looked closer at the chart for refrigerant capacity fo this vehicle and the 69 oz spec applies to a roof mounted unit only. The vans without a roof unit only hold 48 oz of R12 meaning a retrofit should only have a charge of 39 oz. You are way, way overcharging this thing. That will take that compressor out in a heartbeat.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Jun 22, 2014, 1:14 AM

Post #12 of 22 (3035 views)
Re: 88 Chevy Van A/C Confusion Sign In

Right - compressor would fail fast. Capacity can and probably unknown so careful monitoring pressures and temps everywhere may be the only way and know what should be where.


Should be top rear roof evap w TXV there no duct known (never took one apart) just control on/off or fan speed or vent louvers.


They all stunk IMO................. T



Mrmodify
Novice

Jun 22, 2014, 2:55 AM

Post #13 of 22 (3024 views)
Re: 88 Chevy Van A/C Confusion Sign In

As of this morning I have 11 oz of refrig. in van, I looked around vehicle for any info on a/c capacities. I see nothing. I checked the owners manual and still nothing. I have a chart that show ambient temp, low pressure gauge, high pressure gauge. @80 deg. I should have a low pressure gauge of 40 - 50# and a high pressure of 175 - 210# high pressure. & @ 90 deg. LP of 45 -55# LP, 250 - 270 HP. the temp here right now is 80 deg., How do you all suggest I get my pressures right since I have no way of really knowing proper amount. Hammer time you mentioned that 69oz is correct for a roof mounted unit only. The rear evaporator is mounted to the roof. Is this considered a roof mounted unit?


Hammer Time
Ultimate Carjunky / Moderator
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Jun 22, 2014, 3:17 AM

Post #14 of 22 (3020 views)
Re: 88 Chevy Van A/C Confusion Sign In

Yes, that would be a roof mounted unit. You cannot determine the charge through pressures. The proper capacity is 69oz of R12 or 55 oz of R134A.
Charge it with the proper amount and only then can the pressures be analyzed for performance.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Jun 22, 2014, 3:40 AM

Post #15 of 22 (3017 views)
Re: 88 Chevy Van A/C Confusion Sign In

Correct - you can't know capacity or what is in it by pressure only that it's functioning within perimeters. NAPA had a PDF that is missing upon a search on most vehicles.


If you have 11oz in there it's just static pressure. I SAID AND SOME MAY NOT DO THIS BUT WHEN SYSTEM IS TIGHT AND RIGHT JUST USE FRONT ONLY. REFRIGERANT IS THRU WHOLE SYSTEM ANYWAY BUT IT GIVES YOU PREDICTABLE PERFORMANCE PRESSURES FOR THE CONDITIONS AT HAND.


OE sticker on these was on OE accumulator must be long gone by now. IDK - If all fail put a sight glass in line at the right spot.


Info is never going to be sure on this because of too many variations when new never mind now old. Hey, A/C is put in yachts, limos, motor homes and aftermarket so you can get it right and take up hours getting it right but requires knowing system is ready and operational condition. Charge enough first as a liquid into vacuum. No oil moves till you feel cool air out vents so rush for that or even new compressor will fail.


Going round and round with this and mistakes are costly. Should you consider sending this out to total A/C specialty shop if you care enough to have it right?


Whatever you do keep track of what has been done - why how much of what kind of product......... T
PS: If and isn't this whole set up is mega thousands of bucks and mistakes take you right back to the beginning easily. Nothing cheap or simple about it.......



Hammer Time
Ultimate Carjunky / Moderator
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Jun 22, 2014, 3:51 AM

Post #16 of 22 (3013 views)
Re: 88 Chevy Van A/C Confusion Sign In

I have compared the capacity specs from both Alldata and Mitchell and what I found is that Alldata showed the different capacities for rof mount and inside mount, Mitchell did not differentiate so I would rely on Alldata to be more accurate.

Here is their listing
The first column is Kilos and the second is ounces
Remember, these are R12 capacities so take 80% of that.






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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Jun 22, 2014, 3:54 AM)


Mrmodify
Novice

Jun 22, 2014, 5:01 AM

Post #17 of 22 (3003 views)
Re: 88 Chevy Van A/C Confusion Sign In

Thanks Mr Greenleaf and Mr HammerTime. I looked though the reply's you all sent to me again to understand more. I read the post from Mr Greenleaf about charging a system. I decided to reclaimed the 11oz, pull a vacuum again and weigh my bottle again and start over. I normally pretty much do as your instructions say but the only thing I did different this time was flood the system with liquid though the high side to break the vacuum.
Total I loaded it with 29.4 oz of Freon give or take a little.
My High side was 320 - 350# and dropped to around 220 - 240# when condenser was cooled with water. My low side was at 45#. The air outside of vehicle was @95 deg. The air coming from the inside of the vehicle's center front duct was at 52 - 55 deg.
Now that I look at it I think my original 80.6 oz that I removed might not be correct but either way I think I am good now.
I think this will be good, let me know if you all think not. I thank you for all of you all's patents and guidance.


Hammer Time
Ultimate Carjunky / Moderator
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Jun 22, 2014, 5:14 AM

Post #18 of 22 (2998 views)
Re: 88 Chevy Van A/C Confusion Sign In

I think you are probably still too low on charge but you have to resolve those high pressures first. I would suspect a condenser or fan issue or maybe both. If you can drop 100PSI by cooling the condenser, then there is definitely an issue there. I would suspect fan clutch and/or shroud issues.It's entirely possible that your multi-fit aftermarket condenser may just be too small for this setup.

The liquid line should be warm to the touch if everything is working properly. If it feels hot to the touch, then the condenser didn't do it's job for whatever reason.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Jun 22, 2014, 5:15 AM

Post #19 of 22 (2997 views)
Re: 88 Chevy Van A/C Confusion Sign In

Again, again. The 11oz is going to give you static pressure consistent with temps of area of items - period. Fine for checking for leaks perhaps.


Sorry this is drawn out and complicated - many easier ones are too but this has a lot of variables and age plus converted and a dual system. That's a lot buddy.


Last is that we just want this to work out for you with the least possible pain. HT posted his findings capacities and close enough as this is a huge capacity system. 2oz off on a 14oz system would be hell. Just try hard not to make anything worse if not understood find out here or wherever - risks are high for messing up, Tom



Mrmodify
Novice

Jun 23, 2014, 2:58 PM

Post #20 of 22 (2969 views)
Re: 88 Chevy Van A/C Confusion Sign In

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
I want to thank everyone again for all of the help. I know I probably frustrated some of you and I am truly sorry. But I did listen to everyone of your posts.
With that said I thought about it last night and thought that the refrigerant had been reclaimed probably 3-4 times and maybe I got the Freon contaminated with to much air from reclaiming or from my gauge connectors , if my thoughts were correct this would make my pressures high because the air was being heated up and expanding.
This evening I reclaimed the Freon. Replaced the accumulator and filled with 3oz of oil and pulled a vacuum. I was having issues with my crappie 134A quick connectors for this whole ordeal so I pulled a vacuum for 1 hour using my r12 gauges on the pressure switch cutout port.
Sent the first 12oz can as a liquid into the high side, then filled though the LP port.
85 deg ambient, 70% humidity - 48 - 50 oz of Freon, Vehicle at idle, High Side @ 250# Low side @ 45#, Front air temp 50 deg, rear air @ 58 deg., Both evaps are sweating profusely, I know I am probably about 5 oz low but for now I think I am stopping at this point. I just have to figure out what I am going to do with the R134A in my reclaim bottle.
Thanks again guys, John




Hammer Time
Ultimate Carjunky / Moderator
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Jun 23, 2014, 3:06 PM

Post #21 of 22 (2966 views)
Re: 88 Chevy Van A/C Confusion Sign In

You can run it through a recycling machine and that will take the air out.

Glad to hear you finally got it resolved.

We will be locking this thread soon to keep the spammers out.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Jun 23, 2014, 6:25 PM

Post #22 of 22 (2962 views)
Re: 88 Chevy Van A/C Confusion Sign In

Glad to hear it John and congratulations for figuring that contamination with a wild assortment of bizarre complications alone never mind on an old and tougher system you seem to have it figured out and solved!


Great work,


Tom







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