1988 corvette, don't understand what it's doing?

[bohica2xo]

Compressor is capable of 400 psi discharge pressure. Can't see a problem with the compressor.

The sandy stuff in the oil is sealer.

[tourmax]

Compressor is capable of 400 psi discharge pressure. Can't see a problem with the compressor.

The sandy stuff in the oil is sealer.

Well, something is preventing the refrigerant from circulating. I’m starting to wonder if I have the front or rear reed plate backwards and its blocking return flow to the compressor.

Kinda grasping at straws now, can’t seem to find any other issues in the system....

[JohnHere]

Fan(s) working okay? I don't think you mentioned that previously. You did mention that the lines, hoses, and condenser appear to be open, although old hoses can deteriorate internally, not be obvious, and cause a blockage—something else to consider in a 32-year-old system.

I don't think it's the compressor, though, as mentioned earlier. You're getting plenty of pressure. For some reason, the refrigerant isn't making it around the loop and changing state where and when it should. If a blockage existed between the compressor outlet up to and including the evaporator, chances are the low-side pressure as measured at the accumulator would be very low or even pull into a vacuum. And you're not seeing that. On the other hand, 50 PSI on the low side translates to an evaporator temperature as warm as 60 degrees F., so I'm not surprised by the lack of any cabin cooling. Traditionally, this problem points to a condensing issue of some sort, a blockage, or an overcharge.

As suggested earlier, with the system running at a fast idle, try spraying the condenser with water once you have it back together with the welded-up original condenser and the new accumulator installed and see how it performs. If the pressures drop quickly into the normal range, you've identified a condensing issue. But if it still doesn't cool and pressures remain elevated, the refrigerant seems to be the only thing left to suspect, although I have no experience using hydrocarbon-based products like R-12a and don't know much about them.

[tourmax]

Its got a pusher and puller fan. Both work as per.

I just keep coming back to a blockage of some sort. Even when I pulled the low charge down to where it would start short cycling, the high side would still be in the 250-300 range and no cooling evident...

[Tim]

Maybe it is just me. I find it concerning that within 5 pages of posts. All sorts of things done and tried. Yet the concern of refrigerant has not been addressed. Most on this forum have seen others chase the rabbit down the hole with butane blended refrigerants.

This is interesting. I have popcorn so please continue on!

[tourmax]

Well, the condenser is toast.

Tig-ed the holes shut and pressurized the core.

Holes were good, but I found a few bubbles on a couple tubes (not next to the weld spots) where they joined the standpipe portion.

Pretty sure it wasn't from the weld. I used low heat and the tubes right next to the weld spots were good. The bubbles were very light, but that doesn't really matter. Gotta change it.

Strange thing is when I put it all back together and pulled vacuum, it held for a couple hours. But on pressure(shop air), teeny tiny little bubbles.

Oh well, there goes 680 bucks.......



At least the condenser won't be a subject of doubt any longer.

I think I'll cut it open just to see entire insides.....

[Tim]

Did this movie have no ending?

[tourmax]

Did this movie have no ending?

Waiting for parts.

On another note: I did order up a used condenser from an older C4 Vette. It's a tube/fin one, as opposed to the piccolo:



It's from an 85, so the fittings are wrong for my 88. 84/85 has the serpentine condenser, 86+ was piccolo. The tubes connections are in the right place, but instead of a block and o-rings like my 88, it uses line nuts.

I've tried a couple times to seal up the old piccolo one I have, with no real success. The cross tubes are connected to the stand pipes with some kind of solder/braze. But no matter what I try, I cannot get them to seal. There's just no way to get to the insides of the stand pipes and the aluminum/brazing that I can get to stick doesn't wick like solder does on copper, so there's no way to attack leaks around the back side of the tubes.

So since the my current one is knackered, I'm going to cut the inlet/outlet pipes off it. When the serpentine shows up, I'll TIG the Piccolo in/out lines to the serpentine condenser. Since the tubes will be out in the open, TIG-ing them will be a cake walk. I'll also be able to keep any heat from the TIG process away from any joints that are soldered/brazed from the factory. Once modified, I'll give it a try and see what I get.

I'm not overly worried about "loss of efficiency" going to the serpentine instead of the piccolo. The 88 was originally running r12 and the R12A is similar in properties (ie: cooling) as R12.

Plus, the serpentine one will be "flushable". That's a bonus when you're taking about something like a 1988 Corvette, where it seems that parts go obsolete almost daily.

Should be an interesting little experiment if nothing else and the new piccolo style one is still on the way if it doesn't work out....

[tourmax]

Waiting for parts.

Ahh, likely that new kind of waiting for parts.
Going 3 times to a shop that is supposed to be open and finding it always closed.
Having to resort to buy stuff online and pay shipment.
Having a dealer not respond to an inquiry whether a certain TXV on sale was a Chinese knockoff or a genuine Denso product.
Being refused sale of a Denso TXV due to the virus lockdown thing and having to remove one from an old s/h evaporator and hope it will work when it will be needed.
I've been through all of this and know how this feels.

Not really what I’m dealing with. I’m just waiting for shipping...

[tourmax]

So I've been digging around while waiting for parts. A couple issues have arisen.

1. Charge. My FSM ( real, not haynes or clymer) lists the charge for R12 (original fill for my 88) as 2.75 lbs. Labels on the car agree with the FSM. BUT.....while digging around in the TSB's for an 88 corvette, I came across a very short and brief service bulletin that CORRECTS the FSM. Seems GM spec'd the 88/89 Vettes at 2.25 Lbs, not 2.75 lbs as listed in the FSM and on the car labels. Somewhere along the way they had a printing error I guess, or someone at GM just plain effed up and incorrectly spec'd 2.75 lbs. So I would have been overcharged by at least .5 lbs if using R12, the equivalent of half a can of redtek (by their equivalency charts). Not sure if that was my whole problem, but it sure as heck wasn't helping it. No matter how you slice it, I was overcharged, by a fair amount. Seems to fall in line with most of the symptoms/problems I was having.

2. Cycling switch. Well, seems an r12 switch was set for around 25 psi and the R143A switches (later years) were set at around 20-22psi. Looking at the Redtek charts, it looks like it wants to be somewhere down around 20 psi. I've read several comments around the web that because of redteks temp glide, it's hard to say where the switch should be set and it's more of a "try it and see" deal to get a good setting.

As to which switch is already in my Vette, who knows? it could be either. I have no idea if anyone has ever changed it. Seems like a likely thing to have been changed as the car is 31 years old. No telling who has done what to it in it's past.

Luckily, The low cycling switch on my Vette actually has an adjustment screw. So once I get it up and running, at least I can adjust the CCOT so the evap doesn't freeze up and it will cycle properly for the r12a.

Of course, I've got to getting it working first (even if it's "crappily") before getting to the switch adjustment.....