Automotive Air Conditioning Information Forum

Vehicle: 1988 Chevrolet 3/4 Crewcab (73-87 body style)
Engine: 2005 GM 6.0L V8
Compressor: Denso 10S17F
Orifice Tube: Ford Blue
Condenser: ACDelco Parallel Flow (156960)
Temperature: 93F w/ 60% humidity
High side: 325-350
Low side: 45-50
Center vent temp, at idle, max air, doors open: 60F
Center vent temp at 55mph, max air, doors closed: 52F


Hello all,

I just completed my A/C system on my engine swapped 1988 Chevrolet Crewcab, and I have to admit, I'm not entirely happy with its performance. The system is all new except for the evaporator, which was flushed. I used a Ford blue orifice tube, 8 oz of PAG46, and the shop that charged it said they only had to put 32 oz of R134a in the system. I vacuumed the system immediately after buttoning everything up, and the accumulator was the last thing installed. The A/C shop also vacuumed before they charged, per standard procedure. The accumulator and outlet fitting are sweating, and the suction line fitting at the compressor is cold/cool as well. Compressor discharge is hot, condenser outlet is warm. The evaporator inlet, at least where I can feel before I run out of visible tube, doesn't feel all that cold, just cool. At idle, pressures were about 45-50 low side, 350 high side. I am running 2 LT1 Camaro e-fans with proper fan shroud, and they come on with A/C pressure as they should (controlled by the PCM). Spraying water on the condenser dropped it to ~300-315, which is somewhat expected? At 1500+ RPM, the pressure would quickly rise enough to cut off the compressor via my HPCO (~455 psi, according to the spec). The cooling is OK, but seems like it should be better with a parallel flow and modern compressor. Once the sun went down, I took it for an extended highway drive, and the lowest temp I saw while moving was 51-52*. It actually got slightly cooler at idle - 49* or so. Temps were still in the 90F range.

Am I just expecting too much from the system, or is something wrong? Based on some troubleshooting guides I saw, high low side and high high side pressures could be caused by a non-sealing orifice tube. While filling the evaporator with some of the oil charge, some started to run out (evaporator line is level, shouldn't have tried to put oil in it, haha), so I used compressed air to blow the oil into the evaporator, and I accidentally "sealed" the blow gun against the tube. Did I blow my o-tube backwards into the liquid line, possibly?

Let me know if there is any other info I can provide.

Your high side pressures indicate a problem. Should not be tagging the HPCO at 93f

Either a condenser airflow problem, or way too much oil in the system.

The F body fans may be part of the problem. How much water did you hit the condenser with? If you soaked it good the high side should drop like a rock.

Is there a chance the shop added oil?

I wasn't charged for any additional oil on the invoice, but there is always the possibility they did so. As far watering down the condenser, I set the spray nozzle to mist and just let the fan pull that in. It dropped it relatively quickly, but only to ~300. Should I full on hose it down and see what happens?

Soak the condenser with water. See where the pressure goes.

It would not be the first time a shop added extra oil.

You used a GM part number for the condenser - is this a GM part or aftermarket?

.

The condenser is an ACDelco non-GM part.

Friday on my drive home from work (~15 minutes, 98F, full sun), it hit about 54F.

Did a bit more testing saturday morning, 84F out.

On initial startup, high side was 270, low side was 40.

Hosed down the condenser and it dropped to 225 or so, and 35 low side.

Went for an extended drive later in the day while it was about 100F, to visit a friend, and it would only pull down to 60F while going down highway at 70mph. On the drive home in the dark, it did eventually reach down to 48F or so, but with the fan turned down a bit to get that. Today, it seems to be cooling even worse; didn't have my thermometer with me to confirm, however.

Not sure what is going on, but getting a bit frustrated. I spent a decent amount of money to get the parallel flow, new compressor, hoses made up, etc. Did a bunch of research on how to get optimal cooling with a conversion. Winding up with these results is just disappointing. I feel like it can do much better. Maybe those 45* vent temps in Phoenix with traffic I keep hearing about, with R134a conversions, are a myth? LOL. Our humidity here in Texas has even been relatively low! I can only imagine how crappy this will be once we hit 90% humidity.

Measure the inlet tube and outlet tube of the evaporator. The outlet should be slightly colder. What I would do is reduce the refrigerant amount slightly. You may be slightly over charged. I would also be looking at your high side. Are all the air shields installed so the air flow gets across the condenser?

I personally do not like to convert from R 12 to R 134. Too many variables and having to "play" with the system.

When you cool the condenser, the pressures drop.

The parts you are missing:

1540107 Clutch
1580692 Fan
15164394 Lower Shroud
15088328 Upper Shroud

The F body fan was marginal in the F body. There is a reason the Suburban uses that monster 9 blade fan.

bohica2xo wrote:When you cool the condenser, the pressures drop.

The parts you are missing:

1540107 Clutch
1580692 Fan
15164394 Lower Shroud
15088328 Upper Shroud

The F body fan was marginal in the F body. There is a reason the Suburban uses that monster 9 blade fan.

My engine actually came out of a 2005 Sierra Denali with e-fans. I don't have room with the engine placement for a shroud and mechanical fan. Do you think the Denali e-fans would be adequate, assuming I can mount and seal them properly?

That being said, I would expect the cooling would be great on the highway with full on air flow at 70mph if everything was working correctly. I think my charge weight still needs some refinement, as well.

This is probably more along the lines of the fans that you want -

http://www.carparts.com/details/Chevrol ... oCmNjw_wcB

Looks like both of the fan/shroud assemblies are too wide for my radiator/core support. Bummer. I might look into a Mark VIII fan, I hear those move some massive air quantities.

I think I'm also going to have the system recovered and swap to a white orifice tube. I'm hoping the larger orifice will help bring down the high side pressures a bit.