A/C system fix where to begin?

[Jae 'Bird]

This is going to be a little bit in the future as I am still waiting on my second multi-function switch to arrive, the first one was defective smh. Anyway, I want to get my A/C working or at the very least figure out what's wrong, it hasn't had functioning A/C in over a decade. Here's what I know, there is a leak as the system is empty and has been for a long time, the compressor is not seized as it freely spins and there is no burnt clutch smell although this does not mean the compressor is still good just not obviously bad.
My question is where should I start? Should I put a small can of R-12 with the dye to see if 1. the compressor will come on and 2. see where the leak is so that I can figure out if its an expensive fix or not? Any advice is appreciated

 

[theterminator93]

I don't have specific details on the process, but I think converting to R134a would be my starting point. R12 hasn't been manufactured in something like 30 years and if you can find it, it will be expensive. I imagine you'll need to flush the system to clear out all the old mineral oil and replace both the accumulator and orifice tube. Then a fresh charge of R134a and just under a cup of new PAG oil.

You should just plan on breaking each seal and replacing all the O-rings. If you can find it, use Nylog blue to lubricate the replacement O-rings instead of PAG oil.

When you button everything up, pull a strong vacuum to check for leaks and draw out moisture - make sure it holds. You can add a UV reactive dye to the oil when you charge it; you can also use a UV light before you begin to see if there are any residual signs of a previous leak in any of the heat exchanges as well.

 

[White Lincoln]

If cost if not an issue, you could buy all the parts and just replace the whole unit. It is not that hard to do. Then take it to a garage and have them fill it. I ended up spending about $300 to replace all the parts on mine and have it filled by a shop. For years I had a really crappy A/C system. I now enjoy what I would call correct and working A/C.

 

[Jae 'Bird]

If cost if not an issue, you could buy all the parts and just replace the whole unit. It is not that hard to do. Then take it to a garage and have them fill it. I ended up spending about $300 to replace all the parts on mine and have it filled by a shop. For years I had a really crappy A/C system. I now enjoy what I would call correct and working A/C.

That's quite reasonable, 2 questions about that. Did the dash have to come out to replace anything? and then when you replaced the system, did it get refilled with r-134a? Are any new ac components I buy going to be r 134a by default?

 

[Kidd-7]

Not sure on your set up, but my parents have a 79 trans AM and had it covered to r134a from R12, apparently the only difference is the orifices.

 

[dDUBb]

Not sure on your set up, but my parents have a 79 trans AM and had it covered to r134a from R12, apparently the only difference is the orifices.

You can use R134 in an R12 system .. but they have different style condensors. It will work, just not as efficiently.

 

[KevinVarnes]

The compressors are the same '89-'97. Honestly (and I am assuming it is all original), all of the parts in the system are 35 years old at this point. I'd probably leave the evaporator core in and just flush that. No point in pulling the dash to replace it when it is probably perfectly fine. I'd definitely replace all of the hoses, o-rings, orifice tube, and probably the condenser (assuming a '94-'97 condenser is a drop in replacement). Up to you if you want to do the compressor and then refill with R134. You can still get R12 around here and it isn't that expensive, but you do have to search for it. You can walk into any parts store (not that I'd recommend buying it there) and get cans of R134.

 

[Jae 'Bird]

The compressors are the same '89-'97. Honestly (and I am assuming it is all original), all of the parts in the system are 35 years old at this point. I'd probably leave the evaporator core in and just flush that. No point in pulling the dash to replace it when it is probably perfectly fine. I'd definitely replace all of the hoses, o-rings, orifice tube, and probably the condenser (assuming a '94-'97 condenser is a drop in replacement). Up to you if you want to do the compressor and then refill with R134. You can still get R12 around here and it isn't that expensive, but you do have to search for it. You can walk into any parts store (not that I'd recommend buying it there) and get cans of R134.

This might sound like a dumb question but how would I flush out the evaporator core?

 

[theterminator93]

Get an A/C flush gun kit off Amazon and a gallon of lacquer thinner from a home improvement store. Hook it up to an air compressor and fill it with the thinner and squirt it into one side of the evaporator core and collect the discharge. Try and clean out the old oil from the compressor discharge line and compressor as best as you can. R134a doesn't mix with the mineral oil used in R12 systems and will simply collect at the bottom of the accumulator and not circulate through the system; it needs to be flushed so that the R134a compatible PAG oil can do its job properly. Fortunately you aren't looking to flush out metal shavings, so you can be less aggressive with your flushing than if you had a seized compressor.

Moisture is the enemy of refrigeration systems; it turns acidic when mixed with refrigerant and eats away at the system from the inside out. Pulling a vacuum before recharging lowers the vapor pressure and moisture literally boils away and is drawn out with the remaining air during evacuation. Any residual moisture in the system after charging is absorbed by a desiccant inside the accumulator. Whenever the system has been opened for service for any length of time the desiccant absorbs enough moisture from the atmosphere to become ineffective, so the accumulator needs to be replaced.

R134a and R12 have different operating pressures. To ensure the compressor can build up the higher pressures required by R134a, a different orifice tube needs to be used.

Get a condenser and the associated refrigerant lines and orifice tube for a 94-96 3.8 T-bird. The lines changed for 97 and are no longer available. Pre-94 still used R12. Add 6 oz of PAG-46 oil; add a little to the compressor to pre-lubricate it after flushing it but the bulk can go into the accumulator.

 

[White Lincoln]

That's quite reasonable, 2 questions about that. Did the dash have to come out to replace anything? and then when you replaced the system, did it get refilled with r-134a? Are any new ac components I buy going to be r 134a by default?

Nothing in the dash is touched, unless it is already an issue. New equipment runs on R134 and that is what the shop will most likely replace it with. Shop on RockAuto to see what prices you would get. Don't forget the discount code too. Someone usually posts it here.

I noticed that I bought all my parts in 2023 and I think they have not gone up that much. I did have some trouble with RockAuto not sending the right part, one was the compressor, it was larger than the OEM one and after them sending the same size twice, I made due. Also the line from the compressor to the compressor was not the right one and the shop that was going put in the freon said to use the original since it was not dirty. The just replaced the filter.

The worse I see you getting into is the fittings on the coolant lines being stuck or rusted and hard to remove. Other than that, it is all upper engine parts from the firewall out. Replace all the engine part parts if you can from the firewall forward.