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Discussion Starter #1
My V8 has been in the garage for a few things recently. New oil lines, fuel hoses, annual fluid changes etc....
Anyhoo, it just had the AC recharged today (leak on the AC manifold line) and I have an issue with air not coming through the vents cold.
The AC lines are all holding pressure and the system is full of freon. The ac compressor kicks in as it should, but there is regular uncooled air coming through the vents (the face vents)
One of the jobs I had done, was replacing the clevis pin on the clutch pedal, I think that maybe a vacuum line has been accidentally disconnected somewhere.
Where do the vacuum lines run to and from that might be causing this issue?
Maybe it's not vacuum lines at all??
Any advice on where to look would be most helpful!!!!
Thanks in advance.
Adam
 

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My car sneezes
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My V8 has been in the garage for a few things recently. New oil lines, fuel hoses, annual fluid changes etc....
Anyhoo, it just had the AC recharged today (leak on the AC manifold line) and I have an issue with air not coming through the vents cold.
The AC lines are all holding pressure and the system is full of freon. The ac compressor kicks in as it should, but there is regular uncooled air coming through the vents (the face vents)
One of the jobs I had done, was replacing the clevis pin on the clutch pedal, I think that maybe a vacuum line has been accidentally disconnected somewhere.
Where do the vacuum lines run to and from that might be causing this issue?
Maybe it's not vacuum lines at all??
Any advice on where to look would be most helpful!!!!
Thanks in advance.
Adam
How much refrigerant did they add?
Was the AC system flushed?
Did they add oil? If so, how much?
What are your pressures?
What settings are your HVAC controls set to?

There's no reason to be anywhere rear the vacuum lines when replacing clutch pin. Regardless see diagram for vacuum lines. If you assume the Lotus position, and look up above the gas pedal along the tunnel, you'll see a hard vacuum line with some elbows as it inters the area above the center tunnel ... that's where the fun starts
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My first thought is to check if the compressor is actually running. If you are just low on refrigerant it will stop and start. If you are very low it won't run at all. My guess is you don't have enough refrigerant and/or you have air in the system. I would go back to the shop and have them check it out with gauges. I would also check the heater valve. If it is stuck open you would get a lot of heat negating the cooling effect of the A/C.
David Teitelbaum
 

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Discussion Starter #4
Gmendoza, the ac shop put in 1.2kg of refrigerant. 6oz of oil I believe. Ac system flushed, yes.
Prior to the car going into the shop, the ac was losing refrigerant, but otherwise working fine. The leak was located and fixed.
Where is the heater valve located David?
Thanks again.
Adam
 

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My car sneezes
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Gmendoza, the ac shop put in 1.2kg of refrigerant. 6oz of oil I believe. Ac system flushed, yes.
Prior to the car going into the shop, the ac was losing refrigerant, but otherwise working fine. The leak was located and fixed.
Where is the heater valve located David?
Thanks again.
Adam
Pop the bonnet, see the blank area between the front fuse panel and the black box for the HVAC intake? Right behind that, up in the dash, bolted to the top of the pedal box is the heater control valve.
 

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I would also check the heater valve. If it is stuck open you would get a lot of heat negating the cooling effect of the A/C.
In the 4 cyl cars, the air from the face-level vents does NOT go through the heater matrix. So that wouldn't apply.
 

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Gmendoza, the ac shop put in 1.2kg of refrigerant. 6oz of oil I believe. Ac system flushed, yes.
Prior to the car going into the shop, the ac was losing refrigerant, but otherwise working fine. The leak was located and fixed.
Where is the heater valve located David?
Thanks again.
Adam
1.2kg of freon seems like a lot but maybe it's ok for a fully evacuated system, not sure if the service manual specifies the system capacity.

Just as a data point my 2003 V8 ac had been working great last summer (2019) but this summer it wasn't cooling much at all. Checked pressures and sure enough they were low. Compressor was engaging, high pressure line felt warm, low pressure line around ambient. Added 1ea 12oz can of R134a and it's back to fully functional - pressures good, high pressure line hot, low pressure line cold, 20+ deg temp drop from input to output air. Actually cool enough that I have to dial it back after running a while. 🤧

Helped a friend with his 2001 V8, his compressor wasn't kicking in at all. Added 1ea 12oz can of freon, now all is good.

Again just a reference here but my point is that checking the pressure and topping off the freon is an easy do, service port is readily accessible, once you crawl under the car that is 😁. And for a slow leak that costs me a $5 can of freon annually it's not worth chasing an elusive and non-obvious leak point.

Also I read somewhere that, unlike the old refrigerant systems, with R134a the service port plastic protective cap actually has a sealing function, beyond the primary seal at the port shrader valve, due to the smaller R134a molecule size. Anyway just make sure the caps are in place and tight.
 

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According to the manual in the Tech Data section under capacities, ONE (1) kg of R-134. The caps are only to keep dirt out. If they leak you change the valve cores. Some of the kits they sell contain R-134 and some sealer so it could seal small leaks and prevent the gas from leaking out anymore.
David Teitelbaum
 

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According to the manual in the Tech Data section under capacities, ONE (1) kg of R-134. The caps are only to keep dirt out. If they leak you change the valve cores. Some of the kits they sell contain R-134 and some sealer so it could seal small leaks and prevent the gas from leaking out anymore.
David Teitelbaum
That's what I always thought about the caps, protective only, but according to the attached article (see para 3) the R134a type does have a sealing function. I'll keep mine tight just in case. My valve cores were changed last year. I did snug them a bit during the recent charge process.

I briefly considered using a leak-stop freon product, but prefer not to introduce anything foreign to the system unless absolutely necessary.
 

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Discussion Starter #10
Heater valve appears to be working normally. All vacuum lines are good and connected, no apparent leaks.
Flaps inside the vents open and close as they should.
System holding a charge and full.
Dryer has not been replaced.
Hmmmm...
 

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My car sneezes
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Heater valve appears to be working normally. All vacuum lines are good and connected, no apparent leaks.
Flaps inside the vents open and close as they should.
System holding a charge and full.
Dryer has not been replaced.
Hmmmm...
What are your system pressures?
What are your controls set to?
 

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Heater valve appears to be working normally. All vacuum lines are good and connected, no apparent leaks.
Flaps inside the vents open and close as they should.
System holding a charge and full.
Dryer has not been replaced.
Hmmmm...
As a quick check of system functionality you can feel the ac lines under the car. Be careful, the high pressure line (smaller one) should be very (actually very, very, very) hot, low pressure line cool or cold.

This shows gauge connected to the low pressure port.

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Discussion Starter #13
Don’t know system pressure, I’ll check later.
What should they be at?
All controls are set correctly.
 

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Pressures may vary depending on ambient temp. Above photo (low pressure side) was taken with system operating, blowing cold air, ambient around 80deg F. Probably around 45psi is a comfortable starting point, again depending on your ambient temps.

Here is a chart, don't know how accurate it is but it looks reasonable:

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A good shop will replace the dryer and valve cores, check the oil in the system, evacuate and pressurize with Nitrogen and check for leaks. After fixing any leaks, evacuate again and fill with refrigerant and then perform a system test. Doing a through job takes a lot of time. Since time is money most shops take short cuts to get the job done faster. The caps are only thin plastic and can't hold back the high pressures inside the system. On the older systems that had -12 with the 1/4 " flare fittings you could use metal caps that can hold back pressure. The newer style service fittings used on -134 all use the plastic covers. They do keep the port clean but that's all they are meant to do.
David Teitelbaum
 

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Discussion Starter #16
Thanks all.
System has just had all new o rings and is as tight as a gnat's chuff!
New dryer and expansion valve on the way, hopefully that should help matters.
 

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Typically the expansion valve is not replaced unless it is bad or the system is contaminated. If they do replace it make sure they replace the cork insulation around it.
David Teitelbaum
 

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A good shop will replace the dryer and valve cores, check the oil in the system, evacuate and pressurize with Nitrogen and check for leaks. After fixing any leaks, evacuate again and fill with refrigerant and then perform a system test. Doing a through job takes a lot of time. Since time is money most shops take short cuts to get the job done faster. The caps are only thin plastic and can't hold back the high pressures inside the system. On the older systems that had -12 with the 1/4 " flare fittings you could use metal caps that can hold back pressure. The newer style service fittings used on -134 all use the plastic covers. They do keep the port clean but that's all they are meant to do.
David Teitelbaum
I think the Nissan guy's point was that the R134a port cap is the "seal of last resort." The schrader valve holds the bulk of the pressure but the cap holds back anything that happens to "seep" past the valve core, maybe like a slow tire leak. Of course if there was no valve core you would lose all the freon when the charge hose was disconnected.

I really don't know if his theory about R134a molecules being smaller holds up (small enough to get past a schrader valve that has a rubber seat but then stopped by a plastic cap seating on a metal tube??), but I guess stranger things happen. Possibly some of those small molecules find their way past the valve core threads.

Wikipedia is rarely authoritative but it does offer some food for thought on the schrader valve:

"Metal, and some hard plastic valve caps have a rubber-washer seal (or a synthetic-rubber-washer seal) inside to help make a hermetic seal. A cap equipped with such a secondary sealing means helps prevent air
[freon] from escaping from a slightly leaking valve core; substantial valve core leaks, however, may still find their way around the rubber washer. In addition, the rubber washer prevents the cap from loosening and falling off due to vibrations and hence being lost, by acting as a cushion between the cap and the valve stem and in this way damping the vibrations, though most caps are a softer plastic, making the need for a separate seal unnecessary."
 

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According to Shrader-Pacific, A/C Valve Application and Installation Manual:

"A5 Caps

All ports include thread features to attach a closure cap. Security of this cap is essential to the leak integrity of the port. Accordingly these caps include a rubber seal around the port mouth. SAE J639 requires that caps be used for charge ports, and suggest that these caps be tethered to prevent loss."

Their document is at this link:


I would trust the manufacturer. The information is on page 8 of their manual.
 

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Thanks all.
System has just had all new o rings and is as tight as a gnat's chuff!
New dryer and expansion valve on the way, hopefully that should help matters.
Sounds like you are blindly throwing parts at it. No disrespect but is the person doing the work know AC systems?

Dryers don't go bad unless the system was open to atmosphere for an extended period of time. Expansion valves usually don't fail unless contaminated. A pressure reading can tell you where, if there is a problem. When the system was flushed, was there any debris or metallic particles and in what direction was it flushed? What you find here can also give you an overall idea on the condition of the system. Was the system evacuated for an extended period of time to make sure all the flush solution evaporated? Most of the above were rhetorical questions but things to think about.

As for caps, they also have a seal. While not intended to be a primary seal, they do provide a backup seal for more than just dust. FYI, I've seen Esprits with worn cap seals allowing the cap to screw in deeper than normal pressing on the Shrader valve creating a leak. Moral of the story, caps & Shrader valves are BOTH maintenance items.

Long story short, seems like lack of knowledge is making this job more complicated than it should have been.
 
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