Automotive Air Conditioning Information Forum

I am sure this information is in here somewhere but I did not find it. I am trying to resurrect an 89 Bronco for my granddaughter. This car only has 89000 on the clock because the previous owner blew the transmission and parked it in the desert. I have gone through the brake system, fuel system, overhauled the trans and now that it is back on the ground I am turning my attention to the A/C. Amazingly enough the system still has 40 lbs. of pressure and after jumping the compressor cutoff switch it actually slightly cools the low pressure line coming out of the evaporator housing. I really don't want to mess with a system that is that tight. I know for a fact that it sat in the desert and never moved for years. It has been a long time and as memory serves to do a 134 conversion requires a system flush/ oil change. Is there an r12 replacement available, if not would I need to replace the orifice and other stuff for the conversion?

Thanks for helping an old man with a failing memory.

1. you can get R12 on Facebook Marketplace
OR
2. back in the day, ppl simply removed the compressor, drained it, blew thru the lines using DRY compressed air OR nitrogen (available at welding supplies), and refilled with ester oil (POE), (making sure to fill the comp with the correct amount, so measure what you drain out), and be sure to measure what you get out of the hoses , evap, and condenser, and replace with correct amount of POE oil. Then charge with 134.
Please be aware that if you chose option 2, the condenser is not ideally suited for 134. So, you will get cold air, but it will be suboptimal to what it could be.
A proper 134 conversion would ask that you change the R12 condenser to a so-called PF or parallel flow 134 condenser

You could convert it to R-134a, but it sounds like your simplest option would be to keep it R-12, especially since the system doesn't seem to have a major leak anywhere. After years of sitting in the desert, whatever refrigerant DID leak out probably seeped from the front compressor seal, which I'm sure is shot by now.

If I owned this vehicle, I would replace the following: Compressor, brand new, not a rebuilt; orifice tube; accumulator; and every o-ring and seal that you can access (preferably all of them). I would also consider replacing any hoses based on inspection of same.

If you're going to keep it R-12, be sure to use the genuine article and not a so-called "R-12 replacement." As mentioned, real R-12 is still available from various sources, as is Mineral Oil, although R-12 is expensive nowadays. As such, ensure that the system is leak-free before evacuating and recharging it to factory specifications.

The specs that I have for this vehicle are as follows: 52 ounces net weight (3.25 pounds) of R-12, and 7.0 fluid ounces of Mineral Oil, or whatever the under-hood decal says (the decal takes precedence).

The 2 replies above two are certainly the experts and what they say is the right wat to do it.

- the following is a no-expert view reporting their real world experience -

I'm thinking if it still has 40psi of R12 (amazing actually) after all those years, how about just topping off with R12 to a solid sight glass and see how it does for how long? There is a acceptable spec for leaking over time and if its been sitting a long time it might even be within that spec, it would be worth a gamble in my naïve view.

It may just work for as long as she has the truck....and if it fails, then go as deep as you want on getting it up to date but why open a can of worms before it is necessary? The PF condensers are not expensive and they really make a difference.

FWIW, before I knew better, I quick converted (tightened the loose fitting and filled with 134a - didn't even vacuum it, believe it or not) a 87? R12 Jeep Cherokee and it ran cold for the 3 years I had it.

In my view, if the full repair will include replacing all the things that would be replaced if the system self-destructs (compressor, condenser, orifice), not much risk in giving it it a go as-is.

Let us know what approach you take and how it turns out.

andrew vanis wrote: ↑Wed Sep 06, 2023 12:04 pm I'm thinking if it still has 40psi of R12 (amazing actually) after all those years, how about just topping off with R12 to a solid sight glass and see how it does for how long? There is a acceptable spec for leaking over time and if its been sitting a long time it might even be within that spec, it would be worth a gamble in my naïve view.

To my knowledge, this system doesn't have a sight glass, so it must be charged by weight into a well-held vacuum. If it had an in-line sight glass or a sight glass integral with a receiver/dryer (this vehicle has an accumulator), yes, you could top it up using the sight glass.

After all those years in the desert heat (and cold), chances are the front compressor seal is shot. IMHO, it's just not worth taking a chance with scarce, expensive R-12, along with a questionable compressor.

"this system doesn't have a sight glass, so it must be charged by weight into a well-held vacuum"

^ wisdom speaks

..sitting down now

In 1989 on a Bronco it would depend on the system. Many had dealer installed A/C, and it could have many different compressors and systems.

Engine size and compressor type is a place to start. Also look at the hose connections. Hose clamps are a dead giveaway for an aftermarket system

Yes, R-12 is relatively expensive, even though it is plentiful as demand has been slow as older vehicles go off the roads.

Yes, R-12 is available to purchase.

I agree the easiest and maybe least expensive route is to stay R-12. My own 1988 Mazda truck is still R-12 (Arizona).