svs

iTrader: (1)

My Haynes manual indicates I should charge the A/C system until it reaches 45 degrees at the vent. Well, last year that blew a hole in my condenser. What is the correct pressure for the system? Are R12 and R134a set to different pressures? How many pounds of R12 does a completely empty system need?

The system has been open for a year. I'm installing a new dryer and replacing the condenser this weekend (plus a few o-rings). Do I need to do anything other than evacuate the system and fill?

If I try R134a because it is less expensive, can I just evacuate and refill with R12 if the cooling isn't satisfactory? Would anything else need changed?

NZConvertible

Download the S5 FSM's HVAC chapter. It has all the info you need on system charging.

http://www.teamfc3s.org/main/factory...ual/1989_1991/

Do a search for "R134". Lots of threads discussing the swap.

Johny zoom

iTrader: (5)

Replace the TXV if it has been open for a year

J-Rat

iTrader: (2)

DId you invert the can? If so you would have caused the damage to your compressor.

And I would avoid 134a at all costs.

jackhild59

iTrader: (7)

You really need to flush that system. The system has been open for a long time, allowing water vapor into the system. If anyone has ever converted that car to 134a and put in either POE oil or God forbid PAG oil, you will never be able to dry the system out. Those two lubricants don't just absorb moisture, they chemically react with it. The lubricity is gone and your compressor will grind itself into what is known as 'The Black Death' syndrome. This is when the compressor grind its seals and internal parts into a fine black greasy residue that coates the interior of the system. This is a real disaster and you want to avoid this at all costs.

So you cannot just add some new oil: it will become contaminated by the old oil and break down too.

Another reason to flush: Most of the time when a car is 'converted' it is because the system had a leak. Someone buys what is known as a 'Death Kit' at Walmart or autozone and adds the refrigerant and some more oil. The refrigerant leaks out, they repeat the process, again adding more oil. Your car could have lots of oil in it that does not belong. This contributes to high head pressures, poor cooling and 'Black Death'

You must take each and every part off the system and flush it with a flushing agent. Lots of experienced shops use mineral spirits and a compressor to blow it through. Count on using several gallons. Flush it through and reuse it several times through each part. Finish each part with a virgin flush. I personally use Brake Cleaner, the no residue kind.

One thing: you never flush a compressor with any flushing agent. You add the new oil into the intake and rotate the compressor by hand untill the oil comes out the exhaust. Do this 5-10 times until you are sure the only oil in the compressor is your new fresh oil.

The bad news: Your condensor cannot be flushed effectiively. Your expansion valve cannot be flushed. You will need new parts.

You are going to need all new orings, because after you take them apart, even if they were previously leak free, the old rings are unlikely to reseal.

OTOH, if you are sure the system has never seen a retro kit you can merely replace the dryer and flush the compressor.

Add in the correct amount of oil, from the FSM. This is never the amount that is included in the 'Death Kit' package. I recommend using POE/Ester oil if you are converting to 134A. Use mineral oil labeled specifically for R12 if you are using R12 or Freeze12. Add half the oil into the dryer, add the other half into the compressor or remove the valve core in the low side and carefully add it by applying vacuum to the highside fitting.

Then pull your deep vacuum and check that the system hold the vacuum. I do this overnight. If it doesn't you must find your leak. If it holds, then recharge with the correct amount of R12, stated in the FSM. Use Freeze12's charge guide to determine the correct charge. I always recharge by weight into a vacuum.

If you are using 134A there is no correct charge. You can use rule's of thumb such as 75-85% of the R12 charge, or the highside pressure should be 2.5 X the outside temperature in *F, but let me restate: There is no correct charge. You have just ventured into the realm of experimentation.

As with all things on a car and especially our 7's, it is better to think it through and fix it right, fix it once. This stuff just isn't as simple as deciding which refrigerant you want to use today.

svs

iTrader: (1)

J-Rat, We were using a 30# cylinder and might have gotten a little greedy.

jackhild59, Thanks. Looks like I’m going to have some extra work to do tonight.

Johny zoom, What is a TXV?

NZConvertible

Thermostatic expansion valve. See FSM page U-44. It's referred to just as an expansion valve.