A/C Sytem question

[Keith Seymore]

Locked up the air conditioning compressor in lil Red yesterday (during a period of "brisk" acceleration).

Doing some reading on the Rock Auto site and they mention replacing several components in addition to the failed compressor. They reference this "expansion valve" but don't show a picture.

I'm not familiar with that. Anybody have a picture of where this expansion valve is located, and/or what it looks like?

Thanks in advance -

K

[Katrina/10]

That's just a generic statement, you don't have an expansion valve. You do have an orifice tube in the inlet pipe of your evaporator.

[LEEVON]

Most compressor suppliers including new and re-manufactured will only warranty them provided you replace these components. You will need the orifice tube, drier, and compressor. Those parts in a "kit" are common. Those with a flush and evac/charge are what you'll need. If you are switching to R134a there are different orifice tubes, I believe a Ford one which performs better.

[Sodell]

Keith, you are so knowledgeable about these trucks I wonder if you are pulling our leg....The system on these trucks use an orifice tube to regulate the flow.....you could put one of these on it for the heater valve though.....
[IMG][/IMG]

[Keith Seymore]

Thanks, guys.

I had it all apart and converted to R134A earlier in the summer and was cruising along happily until yesterday.

I'll flush everything out and try again. This is mostly practice for when I redo the a/c on my '63 Grand Prix.

Originally Posted by Sodell

Keith, you are so knowledgeable about these trucks I wonder if you are pulling our leg....The system on these trucks use an orifice tube to regulate the flow.....you could put one of these on it for the heater valve though.....

LOL - I'm not very knowledgable about air conditioning and power windows and emissions equipment, because that was all stuff we either didn't order or stripped off in the effort for more speed.

I like your proposal, though and will see if I can get that to fit on the GP...



K

[hatzie]

The expansion valve systems were used in the '70s. I'm not sure when GM changed over to the Orifice Valve system.

Any rig with the R4 compressor should have an orifice valve. The orifice valve has a filter that'll get crudded up by a compressor explosion. You'll want to flush out the whole system to get rid of all the pieces of dead compressor and replace the valve and the dryer.

[hatzie]

Be careful of your replacement compressors. The mid 90's T400 chassis used a Harrison R4 compressor that was intended for R134 before switching over to the Sanden.
The R12 and R134 manifolds and seals are different to mate with differing suction and pressure port profiles.
The R134a compressor has a 1/8" step in on the high side port.
The R12 compressor design ports are even.

Some folks will tell you to use different seals on the R134 compressor. That'll work till you get a hot day... then you dump your charge and spray hot AC oil all over the engine bay. Not remotely worth it.
Just be sure you have the right part to mate with your existing hose manifold or swap out the hose manifold to the later matching R134 fittings.

[Keith Seymore]

Originally Posted by hatzie

Be careful of your replacement compressors. The mid 90's T400 chassis used a Harrison R4 compressor that was intended for R134 before switching over to the Sanden.
The R12 and R134 manifolds and seals are different to mate with differing suction and pressure port profiles.
The R134a compressor has a 1/8" step in on the high side port.
The R12 compressor design ports are even.

Some folks will tell you to use different seals on the R134 compressor. That'll work till you get a hot day... then you dump your charge and spray hot AC oil all over the engine bay. Not remotely worth it.
Just be sure you have the right part to mate with your existing hose manifold or swap out the hose manifold to the later matching R134 fittings.

Thank you; I'll keep an eye on it as I am changing the compressor.

K

[Irish1941]

Keith, just throwing this out there but maybe look seriously at going to a Sanden 508 compressor instead of another GM R4.
A much better unit overall and just about falls in place. Whisper quiet clutch and much less drag on engine.
Your '87 still on V-belts?
Driver's side V-belt makes it a bit tougher hose & bracket wise but 508 body can be had in a few different mounting bolts configurations which can ease the install.
I've made brackets in the past but these guys have ready made ones:
http://www.alangrovecomponents.com/S..._Long_Pump.htm

And there is GM style rear manifold available for the compressor so vac/discharge hoses line up correctly.
If you were to go to serp belt, install is a snap.
I know there is a few threads on here about swapping on a Sanden.
If you're interested, I can dig out my notes & part numbers on the few I have done in the past.
And they fit in the GP nicely too. Doing one for a friend's '62 GP next month.
Like I said, just a thought if you're going through the trouble...

[BamaDave]

I'm interested in doing this in my 86. What parts are needed?

[gmachinz]

For these trucks, grab a serpentine conversion off a vortec 350 truck circa 1996-97 and be done with it-very good compressor. And, when using R134, be sure to use the R134 low and high pressure switches too.

[texasag91]

I just got my A/C replaced on the new truck (1990 GMC V3500) I just bought. To have the complete A/C warrantied you have to have a new compressor, orfice and drier. I think the warranty for mine was 2 years through NAPA service center.

About wether you have to use a different set up or conversion to use R12 vs R134. I think all that has changed over time. Years ago they said if you were going to convert from R12 to R134 you had to change out all the o rings because the R134 was a higher pressure system. Also, you supposed to swap out the vegetable oil in the old system to the new synthetic oil.

But according to my research and experience you don't have to do all that. I have 1991 GMC Jimmy that 3 years ago I had the engine and transmission rebuilt. They put the A/C back together but did not charge (ran out of money after the rebuild). So about 6 months later I decided to charge the system myself. Before I bought the recharge (R134) cans at Oriellys Auto I went to the the website of the company that made the R134. Can't remember the company name. According to them you don't have to change the o rings or the oil. I think the system has completely empty of R12 though. So I followed what they said. Added a little sythetic oil to the system and charged with R134. No conversion. My A/C runs ice cold with no problems for over 2 years. Just my thought on this conversation.

[texasag91]

Just something to add. I had the A/C replaced at a NAPA service center. After about a week the A/C belt constantly squealed when running it. I thought it would go away after it broke in but it didn't. So I went talked to a mechanic about it. He checked the system and everything was alright. He said that in the past he has not had much luck with NAPA belts. Everytime someone would come in with a sqeeky belt it was a NAPA belt. He said swap to a GATES belt. Went home a changed all my belts to GATES. Everything is all quite now. Still like NAPA as a company but not their belts.

[gmachinz]

I'm an HVAC guy among everything I do and here is the proper way to charge your AC system-and since its all going together fresh, there is no reason to NOT replace the little components-does rubber last forever and NOT deteriorate or shrink over time? NO. So, here's what to do:

1.) Use a chemical flush to pour about 8oz. in your evap core and lines-blow out with compressed air until empty.

2.) Install new orifice tube (variable not needed)

3.) Lubricate orings lightly with PAG 100 or 150 oil and install on all lines.

4.) Pour 4oz. of PAG 150 oil in your new receiver drier and another 4oz. in the inlet of your new compressor and slowly turn the clutch by hand with open end up to lubricate the internals really well.

5.) Install all fittings and components/low pressure switch.

6.) Using a good 2 or 3 CFM vacuum pump and R134 gauge set, pull the system into a vacuum until you read 28-30" of vacuum and hold it there for at least a half hour-turn off pump and wait 10 minutes....if from the time you turn the pump off until 10 minutes later there is no drop in vaccum, IMO its safe to assume there is no system leak and you're ready to charge the system.

7.) Begin charging with your R134 cans and start engine and set AC to max and monitor low/high pressure readings to verify proper pressures-refer to GM AC procedures and realize your numbers will be a little higher overall. Typically, low pressure should be a steady 35 and high around 80-90 on a full charge. Things that can affect the values are ambient temperatures and if there is a system blockage, the gauges may read a good vacuum but a really high side pressure (150 or higher) indicates a system block somewhere....and that requires dis-assembly for inspection. For example, a clogged orifice tube (common) will give you a quick vacuum pull down initially but may not take much or any refrigerant. This is the problem with parts store do-it-yourself charge cans with hoses....you really need a set of gauges to do an AC system properly.

The above list is what I follow when I do a typical AC overhaul.

[texasag91]

Hey thanks for reply gmachinz. I knew part of what you said but not all of it.

Two weeks ago I let a professional rebuild my A/C on my new 1990 GMC V3500 because I just don't have the equipment and tools to do it myself. As for my 1991 GMC Jimmy I charged it myself. When I picked up my Jimmy from the mechanic after the engine rebuild he said he didn't know if my A/C compressor was any good. So I tried charging it myself. Thought it was worth a try since everything was put back together correctly. If the recharge didn't work then I would just get a new A/C on the next vehicle upgrade.

[Jake Wade]

80-90 on the high side? that sounds a bit low.

I have always heard ambient temp doubled + 50 for high side with R134

[Sodell]

Originally Posted by gmachinz

I'm an HVAC guy among everything I do and here is the proper way to charge your AC system-and since its all going together fresh, there is no reason to NOT replace the little components-does rubber last forever and NOT deteriorate or shrink over time? NO. So, here's what to do:

1.) Use a chemical flush to pour about 8oz. in your evap core and lines-blow out with compressed air until empty.

2.) Install new orifice tube (variable not needed)

3.) Lubricate orings lightly with PAG 100 or 150 oil and install on all lines.

4.) Pour 4oz. of PAG 150 oil in your new receiver drier and another 4oz. in the inlet of your new compressor and slowly turn the clutch by hand with open end up to lubricate the internals really well.

5.) Install all fittings and components/low pressure switch.

6.) Using a good 2 or 3 CFM vacuum pump and R134 gauge set, pull the system into a vacuum until you read 28-30" of vacuum and hold it there for at least a half hour-turn off pump and wait 10 minutes....if from the time you turn the pump off until 10 minutes later there is no drop in vaccum, IMO its safe to assume there is no system leak and you're ready to charge the system.

7.) Begin charging with your R134 cans and start engine and set AC to max and monitor low/high pressure readings to verify proper pressures-refer to GM AC procedures and realize your numbers will be a little higher overall. Typically, low pressure should be a steady 35 and high around 80-90 on a full charge. Things that can affect the values are ambient temperatures and if there is a system blockage, the gauges may read a good vacuum but a really high side pressure (150 or higher) indicates a system block somewhere....and that requires dis-assembly for inspection. For example, a clogged orifice tube (common) will give you a quick vacuum pull down initially but may not take much or any refrigerant. This is the problem with parts store do-it-yourself charge cans with hoses....you really need a set of gauges to do an AC system properly.

The above list is what I follow when I do a typical AC overhaul.

That's how I did mine a few months ago. I had to rent the vacuum and gauges for $300.. I hope it last a while...I plan to keep the truck

[Keith Seymore]

Wow! Excellent input, guys. I appreciate the responses and detail; thank you for the writeup, gmachinz.

Originally Posted by Irish1941

Keith, just throwing this out there but maybe look seriously at going to a Sanden 508 compressor instead of another GM R4.
...
And they fit in the GP nicely too. Doing one for a friend's '62 GP next month.
Like I said, just a thought if you're going through the trouble...

My '87 is a "poly V" accessory drive with a single V belt for the AC. I think for the pickup I'm going to just slam another R4 on there but am considering the
Sanden for the GP, especially since it was a long compressor originally.

Originally Posted by gmachinz

I'm an HVAC guy among everything I do and here is the proper way to charge your AC system-and since its all going together fresh, there is no reason to NOT replace the little components-does rubber last forever and NOT deteriorate or shrink over time? NO. So, here's what to do:...

Again - thank you for the excellent write up. There is a lot of generic information out there but it's nice to have something so personalized.

As I mentioned, I had played around with this earlier in the spring, so I did the above (cleaned the orifice tube, changed the O rings, recharged with 134) but I didn't get a good vacuum, so I think my charge/pressures were a bit off. Performance was satisfactory but not "great".

I'm actually looking forward to taking another shot at this (and now I have a reason).

K

[gmachinz]

Yeah, you do need a few tools to do a complete AC overhaul but I figure if Im doing any of it, better to just do it all-but then again I do all of my own work so labor isn't an issue, just the parts cost....ya know? I just have a thing for keeping a nice interior and I'll be damned if I'm gonna sweat my butt off in an interior I just restored....lol

[gmachinz]

It can depend a lot of the quality of the AC compressor-I would say NEW assemblies run in the 90-110 range while most remanufactured units are in the 80-90 range....based on my experience. And, there is slightly less refrigerant used by volume in a converted system vs. r12 so as a whole, the numbers can be off a little.

[Just call me Sean]

I only vacuum and charge, usually with good results unless there is a bad part. For only $2 it is a good idea to change the orifice tube, especially if you have to change something else major. You don't get full warranty on auto store parts unless you change the orifice tube and dryer, and it is also a good idea to change the dryer since it removes moisture from the system and moisture doesn't help if you want it as cold as possible.

[MountainGoat1966]

I have all the tools and equipment, and a stash of 134-A but can't afford the parts to get the system going.
Sucks to be poor.
I do appreciate the proceedures you outlined just in case I ever do get the A/C working again.

[gmachinz]

No problem-I have been told by several "AC repair shops" that the retrofit kits don't work-and that may be true IF you skip steps duebto either cost or lack of AC experience. I just don't like doing things twice so if I'm going to replace any single part other than a section of line or an orifice tube, I'm just going to replace it all.

Also keep in mind while their is some validity to R134A in a retrofitted system not cooling as well as R12 in a converted R12 system, its a matter of slightly higher pressures moving through the condensor faster. So, in most cases if its a noticeable problem in your truck, a better shroud/fan or better yet a HO electric fan will usually solve this dilemma. Remember the faster freon or coolant is allowed to move through a radiator or condensor, you need to make up for that somewhere-imo I prefer an electric fan. Or a custom/newer style or larger diameter tube condensor/radiator will also slow the fluid velocity down a bit for better heat transfer.

[hatzie]

The kiss of death to retrofits is not purging the system of the old oil and crud and not replacing the consumables (Dryer and Orifice Valve).
Not adjusting the LPCO switch and not properly adding a HPCO switch to the high side are next in line. These will save your compressor when the system charge isn't perfect.

[Keith Seymore]

Ok - back in business. We'll see how it goes over these next few days.

Originally Posted by hatzie

Not adjusting the LPCO switch and not properly adding a HPCO switch to the high side are next in line. These will save your compressor when the system charge isn't perfect.

Can we have some discussion about how this is done?

K