2G 2G AC Not Working - Advise Help

[1greyawdtsi]

I recently relocated from Seattle WA to Charleston SC. Unlike Seattle
I know there is heat/humidity in the South. So I recently started to diagnose why the AC is not working.

Backstory: last December I swapped in a low mileage 4g63t (50k-ish) from a 97 Spyder GS-T into my ‘95 TSi. During the swap I disconnected the AC compressor and believe I left the entire AC system intact, unopened & swapped in engine, reinstalled existing ‘95 compressor.

Currently the AC switch illuminates - so I rented a loaner AC manifold gauge set. Initially the psi readings were pretty low. So far I have added a 12.3oz can of R134a with UV dye. I could hear the compressor kick on while adding refrigerant. I also looked with a UV light and can’t find any leaks. However after adding refrigerant the car still blows what feels like the outside air temps with zero cooling.

Now with the gauges correctly attached, open & the car running, AC and fan on high, idling - I’m getting a the low side reading that would fluctuate or cycle between 50/55-60ish psi and the high side staying steady at about 90-ish psi (see pic). It seems like the compressor kicks on and off fairly rapidly.

I’m reading a ton of threads but wondered if anyone has had any experience with a similar scenario & what the most logical & cost effective steps - I should take next? Thanks for reading and any suggestions.

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[1990TSIAWDTALON]

You need to vacuum down the system in order for it to take a full recharge of refrigerant. Low side numbers are 30-40ish and high side numbers I like to see 250+ if the system is working correctly.

I only do my own stuff so those are just the numbers I look for when I am trying to get an old system back up and working. A good flush of the system is not a bad idea either if you want it to be reliable.

I use this cheapass pneumatic vacuum pump to suck down the system. It is noisy because it uses compressed air but it does work good enough for a home enthusiast.

You would put a vacuum on the system, let it sit for 15-30 mins and make sure it isn't leaking down before you get to the refrigerant install. That pump would hook right to your gauges to do the suction. I suction both the low and high side and take a picture of the gauges then look again after letting it sit to see if they have moved down at all, indicating a leak somewhere.

 

[1greyawdtsi]

@90TSIAWDTALON That seems like the next logical & cost effective step.
However does it make any sense to change out the Receiver Dryer and then vacuum the system and recharge or just wait on that - in case I need to actually open up the system?
Also any thoughts on the low side reading & fluctuating at 50-60psi?
Last I also just remembered wondering why the driver side radiator/AC fan wasn’t necessarily running constantly while I ran the AC.
Anyway thanks again!

 

[steve]

I can't remember if I bought the cheaper 2.5 or 3 CFM Vacuum Pump from HF and it's pretty noisy too but not as loud at the air compressor your needs.
It and a gauge set was a lot less than one trip to a professional.

2.5 CFM Vacuum Pump

Amazing deals on this 2.5Cfm Vacuum Pump at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

Now that I'm thinking about it I likely got the more expensive one and used a coupon.

3 CFM Two Stage Vacuum Pump

Amazing deals on this 3Cfm 2-Stage Vacuum Pump at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

As I understand it you always replace the dryer if the system has been open or think it's been leaking. As was discussed in another thread purging with nitrogen isn't a bad idea but that's even more tools.

On a 1G I thought the AC condenser far runs as soon as you push in the AC switch but it's been far too long since I've drive my car to remember.

 

[DogWhistle]

Just redid the AC system on our '99 Spyder. The system had been left sealed, but had a leak and wouldn't stay charged. Replaced the compressor, drier, condenser and all the seals. Turns out one of the hoses had a pinhole leak, so both hoses were replaced too.

Pulled the evaporator coil out from inside and was ready to replace the accumulator valve, but RA listed the wrong model, so that was left in place and the evaporator reinstalled after cleaning.

The DSM AC systems only blow really cold when they are at maximum charge, following a good vacuuming of the system. Minimum 30 psi on the low side for a minimum and 50-60 psi at the max.

As to why you are getting fluctuation, you may have air in your system which will compress differently than the gas, and it is expanding and contracting as it makes its way through the system.

 

[1greyawdtsi]

The DSM AC systems only blow really cold when they are at maximum charge, following a good vacuuming of the system. Minimum 30 psi on the low side for a minimum and 50-60 psi at the max.

As to why you are getting fluctuation, you may have air in your system which will compress differently than the gas, and it is expanding and contracting as it makes its way through the system .

Thanks I appreciate your experience and insights: I will get it discharged, put a vacuum on it, recharge it and see if that works.

 

[1990TSIAWDTALON]

Here is FourSeasons recommended refrigerant capacity:

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