AC issues

[ScottD]

As part of my recent head gasket project, I also tried to fix the AC.

I did the following:

- new receiver/dryer
- new crush seals and o-rings
- new ac hoses
- r-134 fittings

I put a vacuum pump on the system for 20 minutes. Then I let it hold vacuum for 30min. It held 30in vacuum for 30 minutes so I thought I was good to go in terms of leaks.

I put 2 12 oz cans of r134 in plus a 4oz can of oil (2oz r134, 2oz oil). The ac was ice cold and I drove the car around for 1/2 hour with it on.

5 days later I go to drive it again and ac blows warm. Check the refrigerant level and it is low.

How could I pull 30in vac for 30min and have a leak? Any guesses where to look or common leak areas?

[glhs0426]

I have found my biggest enemy in an A/C system are the service ports. Pull a vacuum on the system and take one line off a service port. Let it set 30min. If there is no leak, install the loose hose back onto the service port and disconnect the other. I usually find the culprit to be one of the Schrader valves leaking.

[ScottD]

Are the Schrader valves pretty standard and available at any auto parts store?

[x.Gen]

did you put dye in when you recharged? grab some (or a cheap kit with light) with the valve cores/tool, save yourself a trip and some time chasing the leak (start with a good cleanup on all the hoses and at the ports, especially if the system was previously serviced or if you aren't sure).

[ScottD]

I didn't use dye when recharging since I thought it was leak free bc it pulled good vac

[glhs0426]

Are the Schrader valves pretty standard and available at any auto parts store?

Yes, the Schraders are pretty standard parts store items. I believe there are just two sizes for the A/C systems, and I don't remember what the R/T uses. Get a pair of each because the parts house will probably not have a listing for your car.

[BIGBRUDDA]

30 min is not an adequate test.It should hold vac overnight.The dye test will reveal leaks in visible areas only.You might try to get a "sniffer" or electronic leak detector. Aside from the joints the next likely leak point are the aluminum coils. Have you smelled "wet socks" inside the car.(leaky evaparator coil).

[135sohc]

30 min is not an adequate test.It should hold vac overnight.The dye test will reveal leaks in visible areas only.You might try to get a "sniffer" or electronic leak detector. Aside from the joints the next likely leak point are the aluminum coils. Have you smelled "wet socks" inside the car.(leaky evaparator coil).

+1 to everything. I take it one step further and after doing the initial vacuum down and holding for 24 hrs, charge with nitrogen and see if holds under posative pressure for another 24 hrs.

assuming theres not an internal leak I would almost put money on the receiver/dryer is leaking at one or both hose flanges. The slightest bit of rust and or all sealing surfaces not being perfectly flat is all it takes.

[x.Gen]

The dye test will reveal leaks in visible areas only.You might try to get a "sniffer" or electronic leak detector.(leaky evaparator coil).

agreed, but most of our systems are relatively accessible by sight. leaky evaporator will likely bleed dye out the drain. as expensive as the electronic detectors are, you could probably get a condenser and evaporator at a relative cost, if the leak isn't visible. unless you're friends with someone who'll allow access to one without charging for it. just guessing he's on a TM budget; $20, or $300...guess which way I went when I had to?

[glhs0426]

I'm glad you guys have 24hrs to check for a leak at each service port and then charging the system with nitrogen for another 24hrs. I'd go broke checking everything this way, and a customer would never hold still for this. 96hrs to check for a leak? Come on. If you see a 3inHG drop in 30min there is a leak.

[135sohc]

I'm glad you guys have 24hrs to check for a leak at each service port and then charging the system with nitrogen for another 24hrs. I'd go broke checking everything this way, and a customer would never hold still for this. 96hrs to check for a leak? Come on. If you see a 3inHG drop in 30min there is a leak.

I work on my OWN stuff and NEVER anyone else's crap for a very good reason.... So damn straight I take my time to do it right and throughly. Besides chryslers awesome a/c hose quality that has since been resolved I kinda take pride in that my a/c works and has worked year after year without having to recharge it every season.
Not to mention refrigerant is expensive (hint I dont use that garbage called 134a)

and how does 24+24 = 96hrs

[glhs0426]

I work on my OWN stuff and NEVER anyone else's crap for a very good reason.... So damn straight I take my time to do it right and throughly. Besides chryslers awesome a/c hose quality that has since been resolved I kinda take pride in that my a/c works and has worked year after year without having to recharge it every season.
Not to mention refrigerant is expensive (hint I dont use that garbage called 134a)

and how does 24+24 = 96hrs

I applaud your accomplishments in keeping the a/c going. Would you mind sharing with the rest of us the nitrogen charging setup?

24 one connector in vacuum + 24 the other connector in vacuum + 24 one connector in nitrogen pressure + 24 the other nitrogen connector in pressure = 96

[ScottD]

The FSM stated 30 minutes for the vac test which is why I did it that long. However, I could easily leave it hooked up overnight in my garage.

I think the Schrader valve could be a likely culprit.

I *may* have some extra crush seals, I could take the hoses off and go over all those connections again and make sure they are perfectly clean.

The condensor looks good from a visual inspection.

I hate to think the evaporator is the problem, I really don't want to pull the dash.

Thanks to all who have responded, this is good information. When my GLHS is back from body shop my last thing to do on it is get the AC working, good tips here.

[turbovanman²]

30 mins is more than adequate.

I would bet on the compressor shaft seal, I honestly don't see any evap cores leaking, its extremely rare.

There are 2 issues with 134a, its extremely small in size, molecule wise vs R12 and it doesn't leave a nice oily/green stain like R12 used to,

[135sohc]

I applaud your accomplishments in keeping the a/c going. Would you mind sharing with the rest of us the nitrogen charging setup?

24 one connector in vacuum + 24 the other connector in vacuum + 24 one connector in nitrogen pressure + 24 the other nitrogen connector in pressure = 96

small nitrogen tank from the welding supply shop, regulator to monitor/control it. usual a/c servicing manifold, cobble of connectors and a piece of high pressure hose (dont know where or what its from) setup just like your charging with refrigerant.

I rotate the compressor and do the entire system at once. 24 hours of vacuum and recheck, 24 hours of pressure and then do a final pull down.

[glhs0426]

small nitrogen tank from the welding supply shop, regulator to monitor/control it. usual a/c servicing manifold, cobble of connectors and a piece of high pressure hose (dont know where or what its from) setup just like your charging with refrigerant.

I rotate the compressor and do the entire system at once. 24 hours of vacuum and recheck, 24 hours of pressure and then do a final pull down.

So, if it the system has a leak how is it found?

[BIGBRUDDA]

Long term vac or press testing is not that difficult. You can literally do it in your sleep.
Vac it (30 in for 1hr) or charge it up( 150psi). Cap it off, test it again 24 hrs later. You're looking for appreciable press loss, and any vac loss(allow 2-3 in loss for reconnection).
FSM and auto service standards have been developed to accomadate garage service schedules.
It also suggests charging from an"official MOPAR 3 can gang manifold".

[135sohc]

So, if it the system has a leak how is it found?

Sniffer tester borrowed or I also have a micron counter similair to this one http://www.tequipment.net/Robinair14...?Source=Google otherwise look, hear and feel for a leak. unless its leaking internally the oily slime is hard to miss.

[glhs0426]

Sniffer tester borrowed or I also have a micron counter similair to this one http://www.tequipment.net/Robinair14...?Source=Google otherwise look, hear and feel for a leak. unless its leaking internally the oily slime is hard to miss.

How is charging a system with nitrogen beneficial? If a system is charged with nitrogen and a leak is noticed by a charge level drop in the nitrogen, how is the nitrogen leak detected? (my real senario). I have built an a/c system for my truck. It has not been charged yet. If I charge it with nitrogen and the charge leaks down over the 24hr period, how do I find the leak? There will be no oily slime because there is no oil in the system yet. BTW the vacuum will leak 3inHG in 30min, so, it has a leak.

[135sohc]

How is charging a system with nitrogen beneficial? If a system is charged with nitrogen and a leak is noticed by a charge level drop in the nitrogen, how is the nitrogen leak detected? (my real senario). I have built an a/c system for my truck. It has not been charged yet. If I charge it with nitrogen and the charge leaks down over the 24hr period, how do I find the leak? There will be no oily slime because there is no oil in the system yet. BTW the vacuum will leak 3inHG in 30min, so, it has a leak.

A system can react differently under posative vs negative pressure. many years ago after the annual receiver/drier & compressor seal overhaul we did the initial pull down and held it overnight, checked the next day and all was good.

Started charging and just starting on the 2nd can, Poof!!! Both sides of the receiver/drier connection blew the crush gaskets out like they were nothing. just going from negative to posative was all it took to pop the system. $20 of refrigerant gone, oil everywhere. If that had been nitrogen for the intial pressurising it would have been pennies worth of gas blowing out and nothing more. I dont know how to leak test for nitrogen (I'm sure theres a detector one could buy) but it does give you another tool to simulate closer to real working conditions to know if the system is sealed up or not before adding oil and refrigerant just to find it all oozing out. A 30lb nitrogen refill was $12 last time I got one, little soup can sized thing of 134a was $15 and its probably gone up even more since then.