Vintage Air System not too cool????!!!!

[5.7 hemi]

I have a Vintage Air GenIV unit in my early b body. Sanden 508 compressor, condensor is 24x18 and all other stuff needed for it is new. Granted, I got this about 3-4 yrs. ago, needed to have during the mock up stage, I got it vacuumed and charged about 4 wks. ago. I have a done my own vacuum on it with my snap on vacuum pump, and I let it run for a couple hours, disconnect the pump and watched the gauges for a few days and it was holding steady at 30hgs. So off the the a/c shop I go. They put a vacuum on it for 30 minutes, check to make sure it's holding, then fill it with r134a, (1lb 8oz) and it's blowing out the vents at 40 degrees. Low side at idle is 20-30 and high side is 200-250. The fans kick on at 250, and it comes down to 200, and repeats. The compressor is running doing it's job and all is well. The ambient temp that morning was 80 ish. So I take the car for a spin today, ambient temp is 107 and my thermamentor is reading over 70 out of the vent. I come home, switch to the wifes maggy, and its putting out about 60 ish from the vent, wtf is going on?? I check the VA instructions, and they call for low side pressure of 6-12 and the high side 160-250. So I'm good on the high side, but I'm high on the low side. Should I have them take out some r134a or add or what? VA says that the temp out of the vents should be 36-40 degrees.

Now VA had me check the heater control valve, blend door compressor, etc., and all work as they should. My dual spal fans pull 2700 cfm and cool the motor just fine. So I thought I would ask if anyone has a solution before I call VA in the morning. Thanks for the help guy/gals.

 

[70dart340]

Sounds like the TXV valve isn't set right or some kind of restriction on the low side, like a plugged filter.

 

[RedFish]

Lowering the temperature of the refridgerant while in liquid form is the science of a/c.
The fan should run contiuously when the a/c is on. That way the fan doesn't need a temp sensor on the refridgerant it simply ignores coolant temperature when neccessary.

 

[tasvalowna]

are you sure all the ducts are fitted on and sealed up ok?
so it was cooling ok at the shop with a 80 ambient and is no good at a 107 ambient?
You need to see if its sweating back when the ambient is high and fit your guages and see what the pressures are doing with the high ambient.The condensor fan switch will be fine so dont worry about that one as long as its still cycling ok.
You might find the condensor is under sized for the high ambient . So if its running over 350 psi on the discharge when the ambient is up and the fan is running then thats probably is whats going on .
So long as the suction pressure is around 20 psi , there wont be a blockage . If youre suction pressure is too high , its a possibility that the hot water valve isnt closing off all the way , to check that just crimp a hose off in the engine bay and see what it does . if its heating the evaporator , that will bring the suction pressure up.Most factory ac run at around 20 psi , i dont think it needs to be as low as 6 and on some machines that can be too low and you can run into oil pumping issues . Its not a great idea to run the fan all the time when the ac is on as you can have too low a head pressure which can cause other issues.If they charged about 800 grams into the system , it should be fine .Taking gas out will lower the suction pressure but depending on the size of your receiver drier , i imagine the gas charge isnt too far away . There could be an issue with how the condensor is mounted too , is it in front or behind the radiator ,and is there a gap around the engine fan / post a pic , that would help.
cheers Ben

 

[GaryS]

I had a malfunctioning heater valve with my Gen IV with electronic controls. I switched to a manual valve and now it will freeze me out at 100F...and I have a convertible.

The Vintage Air tech also said the line pressures are fussy for proper operation and to avoid annoying harmonics. He gave me different numbers from the original instructions, but I can't recall what they were.

 

[prrc]

This... You need to install a trinary switch so the fan comes on with the compressor.

Lowering the temperature of the refridgerant while in liquid form is the science of a/c.
The fan should run contiuously when the a/c is on. That way the fan doesn't need a temp sensor on the refridgerant it simply ignores coolant temperature when neccessary.

 

[5.7 hemi]

Tasvalowna, the ducts are seales to the unit with no leaks from them. The condensor damn near fills the entire core opening, so I'm sure it's big enough. I have disconnected the heater hoses to eliminate the heater core and the same problem exists. The condensor is mounted in front of the radiator so thats not a problem. I'll gets pics posted asap.

GaryS, this is the 3rd heater control valve and I even sent in the controler with harness, the main harness and the ecu back to VA, they tested all of them and they were good.

Prrc, I have a trinary switch installed and the fans turn on when the a/c is on, they cycle on and off to the high side pressure (200 off and 250 on) and if no a/c is selected, they come on when the water temp hits 195 (180 t-stat).

 

[5.7 hemi]

last pic

 

[RustyRatRod]

I think it needs more refrigerant. That high side pressure is low for 134a. You normally see over 300 PSI. 250 is R12 territory.

 

[66plyValiant]

I think it needs more refrigerant. That high side pressure is low for 134a. You normally see over 300 PSI. 250 is R12 territory.

x2 did the shop charge it to R12 spec's? most shops will charge an old system to 80% charge of what came in the R12 system; problem is yours is not an old system and also not meant for R12 so its possibly undercharged

 

[5.7 hemi]

I cant be 100% positive, but I was standing right there while they worked on it and they said it was charged with 1.8 lbs, so an assumption of mine is that it's full. Does 1.8 lbs. mean 1lb 8ozs? That could be what's wrong, not having the math right for the amount of r134a.

 

[GaryS]

I found the troubleshooting info their tech gave me.

High-side pressures s/b 160-250, and low-side 6-12.

 

[5.7 hemi]

Thanks GaryS, I did find that in the instructions. I also called my dad and he said that 1.8lbs. is NOT 1lb 8oz. and that 1.8lbs is 1lb 8 tenths of a pound so the total amount of r134a should be just under 29oz.

I screwed up when I told the ac shop to charge it to 1lb 8oz, so I'm undercharged as StrokerScamp had said, now I'm off to the store to get a 12oz can put some in.....with any luck this will fix my problem.

 

[5.7 hemi]

That didn't work, so I have an appt. next weds. and VA will be on the phone as we try to figure this **** out.

 

[Revhendo]

I'm not a fan of trinary switches. I prefer a binary switch and then use a relay for fan request when the a/c is on. This keeps the fans on at all times when the a/c is on to keep the condenser cooler regardless of compressor cycle. Speeking of which, does the compressor constantly cycle? And for the silly question, have you tried reprogramming the control module again?

 

[67Dart273]

I do NOT understand why they are insisting on running the evap at such low temp/ pressure. Makes no sense to me, and seems like it would be inefficient as hell.

 

[5.7 hemi]

Rev, the compressor will cycle but its infrequent. The fans come on and off as the high side pressure goes up and down and when the coolant temp reaches 195 they come on whether or not the ac is on. I dont know how to reprogram the module.

67dart273, I'm just following the VA instructions cause I don't know **** when it comes to ac.

 

[Revhendo]

Should be in the instruction sheet towards the back. This unit is totally controled by a computer module if I remember correctly. There should be a grey wire that you ground, turn the key on, work the levers through their motions and then unground the wire.

 

[5.7 hemi]

They (VA) hasn't mentioned to do that and I did find something about resetting the ecu.

 

[5.7 hemi]

They (VA) hasn't mentioned to do that and I did find something about resetting the ecu.

 

[funwithfuel]

If you run your fans continuous, your low side should show 15-20psi if you've got a sight glass on your drier it should show steady liquid flow, no bubbles. Your high side you wanna see 200- 225 . I would find an old timer that can charge systems for performance vs volume. I'm sure the mfg wants a specific volume but it depends how long your service hoses are and other variables like if the tech purged noncondenseables from storage or not. I always charge with the fans running across the condenser and charge w liquid. Good luck. The last thing , with the system running look for ice-ups along the high side lines indicating a possible obstruction also shoot temps across your evaporator coil again looking for ice-ups or sudden rise in temp again indicating obstructions. All across the face of the evaporater coil should be cold w no hot spots.return line back to comp should be cold as well . Does that system use an orifice tube or expansion valve. Valves sometimes fail not common.

 

[GaryS]

FWIW, the Vintage Air tech said that if the low side pressure is too high, it can cause annoying harmonics at maximum cooling settings, and that was one of the issues I had.

 

[toolmanmike]

Look for a difference in temp between the inlet and outlet of the dryer. There should be no difference in temp. I would replace the dryer. It is 3 years old and even though it may have had plastic caps on the fittings to seal it, the desiccant inside is contaminated. The vacuum pump won't revive a bad dryer. Just a thought. tmm

 

[5.7 hemi]

I have an appt. tomorrow at the a/c shop and VA is gonna be on the phone so we should be able to figure out whats going on. So I'm keeping my fingers crossed!

 

[65-440]

I agree, 6-12psi low side is too low. 20 sbould be right on. Stupid question, is the fresh air door closed or is the blower motor pulling in that hot 107 degree air which is making the a/c system seem to be under cooling ? If it is pulling in outside air than I would say a 30 degree difference is good !