Vacuum AC system (1 Viewer)

[Austrol]

So I’ve just completed the arduous task of replacing all the seals in the AC system to 134a seals, replaced the drier and added PAG oil, I’m currently pulling the vacuum and the pressure side holds -30 psi where as the high side slowly makes its way back to 0 when I do my pressure test.

all the research I’ve done indicates two things. Either ;

a) “If gauges have not moved after and hour you are good”

b) low pressure (blueindicator is the only indicator you need monitor.

sooooooooooooooooo what am I looking for. Hopefully option (b)

 

[Spook50]

Did you make double sure that both the gauge and service fitting valves are open on the high pressure side? Not sure what fittings you have connected to your service fittings, but the ones I use have built in valves so I have to make sure the necessary ones are open for evacuation and servicing. Also if your gauges can be calibrated make sure when they're open to just atmosphere that they're sitting exactly at 0. I have a good Yellow Jacket set that can be user calibrated.

 

[Austrol]

I believe so, I also added the r12 to 134a adapters.
I have also checked all the connections and when I turn the high pressure fitting at the coupler off it holds negative pressure.- the gauge holds negative pressure.

The photo of the high pressure side was taken after the vacuum port was closed for the pressure test.

I take it that both sides need to hold negative pressure?

 

[Spook50]

I believe so, I also added the r12 to 134a adapters.
I have also checked all the connections and when I turn the high pressure fitting at the coupler off it holds negative pressure.- the gauge holds negative pressure.

The photo of the high pressure side was taken after the vacuum port was closed for the pressure test.

I take it that both sides need to hold negative pressure?

They should, yeah. I would let it pull vacuum for 45min to an hour with all valves open and see where the needle sits. Also you don't want to add R12 to a system that has PAG oil in it. Not compatible and could cause issues & leaks.

 

[Austrol]

They should, yeah. I would let it pull vacuum for 45min to an hour with all valves open and see where the needle sits. Also you don't want to add R12 to a system that has PAG oil in it. Not compatible and could cause issues & leaks.

Yep! I’m converting the system to 134a.

Ill do the vacuum as you have suggested

 

[Austrol]

Okay, so I was running the vacuum now for 40 minutes and same thing, high pressure side (red) the pressure falls back to 0 whilst the low stays at -30psi...

Am I a dum dum with something?

 

[Spook50]

Okay, so I was running the vacuum now for 40 minutes and same thing, high pressure side (red) the pressure falls back to 0 whilst the low stays at -30psi...

Am I a dum dum with something?

If you made sure all the rest of the valves are open while drawing a vacuum it sounds like you've got a significant leak on your high side. What's puzzling is that as long as nothing's overly cold, your expansion valve should still be open, allowing vacuum to slowly equalize between the low and high pressure sides when you shut off the vacuum and close the valves on the gauge set. Something definitely seems not right.

Turns out I misread your post before, and thought you added R12 to the system after putting the PAG oil in, where you said you added the R12 to R134a service adapters.

Just to make sure I'm on the same wavelength as you, when you say pressure test you mean the leak check where you're making sure it holds vacuum, right? Vacuum pump off and valves on the gauge set closed?

 

[Austrol]

yep you got it!

I just wentto check on it now. It’s been connected for12 hours now. Seems like there is a slow leak..

 

[Spook50]

Yep looks like that's the case. I'm willing to bet the leak is somewhere in your high circuit since that's what lost vacuum first.

 

[Austrol]

Yep looks like that's the case. I'm willing to bet the leak is somewhere in your high circuit since that's what lost vacuum first.

Would you mind quickly explaining what section that may be?

I added it die PAG oil, should I run the system without gas to look for a leak?

 

[Spook50]

Would you mind quickly explaining what section that may be?

I added it die PAG oil, should I run the system without gas to look for a leak?

Running without a freon charge won't tell you anything. You might actually damage the pump if you do actually. I'd have to double check my FSM, but I believe the pressure switch in the evaporator housing will only switch off the electrical circuit if the expansion valve is closed and raises the pressure in the high pressure feed to it, so without a positive charge in the system you could damage the compressor. If you have the right amount of oil in there and it's got dye in it (and if you have enough freon) you could go ahead and charge it, run it for a few days of normal use, then check with a UV light to see where the leak is. At that point since you'll have to open the system to change whatever O-ring is leaking (rule of thumb: always lubricate a new O-ring with the fluid it'll be sealing before installing it. Helps immensely with preventing leaks. Learned that in my aircraft maintenance days), you'll need to replace the dryer again (especially do it if you didn't replace it already. Another rule of thumb is to replace the dryer with new every time you open the system. Luckily they're cheap but make sur eyou get a legit Denso dryer) and add 1/4 the total amount of oil needed for the system. I say 1/4 the amount because I think the amount of PAG oil needed is different from the amount of mineral oil. The amount of mineral oil is 8oz. total, so for any of the four major components of the system replaced, I would add 2oz. of oil.

 

[Austrol]

Running without a freon charge won't tell you anything. You might actually damage the pump if you do actually. I'd have to double check my FSM, but I believe the pressure switch in the evaporator housing will only switch off the electrical circuit if the expansion valve is closed and raises the pressure in the high pressure feed to it, so without a positive charge in the system you could damage the compressor. If you have the right amount of oil in there and it's got dye in it (and if you have enough freon) you could go ahead and charge it, run it for a few days of normal use, then check with a UV light to see where the leak is. At that point since you'll have to open the system to change whatever O-ring is leaking (rule of thumb: always lubricate a new O-ring with the fluid it'll be sealing before installing it. Helps immensely with preventing leaks. Learned that in my aircraft maintenance days), you'll need to replace the dryer again (especially do it if you didn't replace it already. Another rule of thumb is to replace the dryer with new every time you open the system. Luckily they're cheap but make sur eyou get a legit Denso dryer) and add 1/4 the total amount of oil needed for the system. I say 1/4 the amount because I think the amount of PAG oil needed is different from the amount of mineral oil. The amount of mineral oil is 8oz. total, so for any of the four major components of the system replaced, I would add 2oz. of oil.

Good tips, I just spent 100 on a Toyota drier... not too keen to replace that. I did not lube the darn washers .... I reallllly don’t want to get into my dash again. :/

 

[Spook50]

Good tips, I just spent 100 on a Toyota drier... not too keen to replace that. I did not lube the darn washers .... I reallllly don’t want to get into my dash again. :/

Denso is Toyota's OEM for A/C components. A new legit Denso dryer is $22 + shipping from Rockauto, so cheap insurance. P/N is 478-0101. From what I've been able to decipher in studying about A/C systems, once oil has been cycled through the system and gotten into the dryer, the desiccant can still absorb moisture from the gas flowing through it (still doing its job), but you're no longer able to vacuum the moisture out of the desiccant and it absorbs too much moisture once it's open to atmosphere.

Only issue I've had with looking up the Denso part and ordering from Rockauto is for some reason Rockauto, Amazon and even Denso themselves reference the wrong P/N for the expansion valve. I suspect you saw the thread I posted about that a few days ago. That was irritating.

 

[Michael Hanson]

Hi, Did you go back and check your fittings? Did you use green orings ? Always lube the o rings .Mike

 

[Austrol]

Hi, Did you go back and check your fittings? Did you use green orings ? Always lube the o rings .Mike

I did see that post... anyway life goes on, I’ll see if I can recycle the old drierfor the leak test.

Mike, I did use the green o rings from rock auto. I will spend today pulling it mostly apart ( I won’t do the dash as it’s a nightmare in my opinion) to lube.

I’ll keep you guys posted with my findings.
Thank you for all this great info

 

[Spook50]

I did see that post... anyway life goes on, I’ll see if I can recycle the old drierfor the leak test.

Mike, I did use the green o rings from rock auto. I will spend today pulling it mostly apart ( I won’t do the dash as it’s a nightmare in my opinion) to lube.

I’ll keep you guys posted with my findings.
Thank you for all this great info

If you haven't run the system and had any oil pump through the dryer yet, you're probably still okay to keep using it. I would advise you pull a vacuum on it for a good long time to make absolutely sure all the moisture is pulled out of the desiccant.

 

[Austrol]

Okay a positive update!

this morning I pulled apart the system (apart from the in das section) re cleaned all the fittings and wiped it down withPAG, used new new washers and coated them in oil too.

I also found an interesting discovery!! The retro fit kit for the 134a vacuum hose fittings that you screw on to the compressor. One of them had a fairly long housing, which would limit how much I could screw in the fitting.
This is what I think was the main culprite!!! So I bought a new one today and filled back the back end of it as much as possible whilst still retaining enough of the bolt to tighten it ... it gave me an extra 1-1.5 mm and I think it’s the difference I needed!

i ran the vacuum for 5 minutes to see if it would hold (as previously the high side would immediately drop) and it did for 15 minutes!

so now I’m letting the vacuum pump for about three hours and I’ll let it sit for that too!!

success I hope!

 

[Spook50]

Okay a positive update!

this morning I pulled apart the system (apart from the in das section) re cleaned all the fittings and wiped it down withPAG, used new new washers and coated them in oil too.

I also found an interesting discovery!! The retro fit kit for the 134a vacuum hose fittings that you screw on to the compressor. One of them had a fairly long housing, which would limit how much I could screw in the fitting.
This is what I think was the main culprite!!! So I bought a new one today and filled back the back end of it as much as possible whilst still retaining enough of the bolt to tighten it ... it gave me an extra 1-1.5 mm and I think it’s the difference I needed!

i ran the vacuum for 5 minutes to see if it would hold (as previously the high side would immediately drop) and it did for 15 minutes!

so now I’m letting the vacuum pump for about three hours and I’ll let it sit for that too!!

success I hope!

Something I completely forgot to mention earlier too, is did you make sure to remove the valve cores from the R12 fittings before putting the R134a fittings on?

 

[Austrol]

Something I completely forgot to mention earlier too, is did you make sure to remove the valve cores from the R12 fittings before putting the R134a fittings on?

no...

am I doomed again?

 

[Spook50]

no...

am I doomed again?

Doomed to start over with pulling vacuum lol. Not a big deal. Just gotta pop off the 134 fittings, unscrew the valve cores from the R12 fittings and pop the new ones back on. Not taking them out will keep you from pulling a vacuum on the actual system and will prevent you from getting any freon into it through the service fittings.

So as it turns out, you were pulling a vacuum only on the hoses from the gauge set