Converting AC system from R12 to R134a

neworleans · Post by **neworleans** » 20 Jun 2013, 10:37

Hello friends,

I have a question about converting the old R12 system to R134 system for my 91 Volvo 740.
I've posted this question in the 740's section but didn't get any answers so I am posting here, maybe some of you guys have an idea and this section seems like more active than the other section.

After doing some research, I found out that I need to put some adapters and evacuate the system before charging the Freon. I've got the adapters from Walmart yesterday but not sure how I am going to install it.

If you look at the picture, I think I need to insert the adapter at "2", is this right? is this where you charge the freon? in other words, is this the low side pressure port?

What is number "1" for?

Any input is appreciated...

Post by **jpr0204** » 20 Jun 2013, 10:52

neworleans,

The adapter kit you purchased at Wally World SHOULD have 2 different size fittings in it. The smaller of the two would be the low side adapter and should have a blue cap on it while the larger of the two is the high side adapter and should have red cap on it, though I've seen kits with both caps being black. If this is the case, the smaller of the two is the low side adapter.

Yes, # 2 appears to be smaller than #1 and would be considered the "low side" which is where the system should be charged. NEVER EVER try and charge the system through the "high side" Luckily, with the difference in the size of the adapters and the size of the freon fitting off the can it will only fit the low side.

The cylindrical cansister where the low and high side fittings are is the call an air conditioning accumulator or reciever/drier. that swich on the side is the a/c compressor clutch cycling switch.

If the A/C hasn't worked in a while or... even if it has, it's a good idea to get a small machine capable of putting the a/c system in a recovery (which where it takes all of the old R-12 refrigerant out of the system) and vacuum (to make sure it holds and there are no leaks.) after putting the new adapters on.

Then, go ahead and charge up the system with the new R134A refrigerent. Look around for a label underhood that tells you how many ounces of freon to put it. You don't want to put too much in as it may result in too high a pressure and a constant cycling of the A/C compressor.

The #1 fitting is for when you hook up an a/c machince to it to recharge or evacuate the system and/or for when you put a set of A/C guages on the system to get a reading of the pressure in the system.

- Joe

Post by **Ozark Lee** » 20 Jun 2013, 12:19

You really need to change the receiver / dryer and flush the old mineral oil out of the system with an AC flushing solution. Mineral oil is not compatible with R-134A systems. Ester oil is what I normally used for R-134A conversions on other makes and it is compatible with both R-12 and R-134A systems. PAG oil will work as well but it is for R-134A systems only.

I never had to mess with the AC on my 740s and, as such, I don't know what they used from the factory. They may have been shipped with Ester oil which would greatly simplify the conversion but you need to find out.

...Lee

neworleans · Post by **neworleans** » 20 Jun 2013, 12:58

Thanks for the replies.
I had my 850's ac checked last week at the volvo shop, he hooked the ac machine to the low side pressure port, recovered it first and then charged it. I am not sure if they have a different machine just for these old model cars but I don't think so, the machine is pretty big with a big freon tank, i wouldn't keep another machine in this size to hang around in the shop just for the old model cars

. Therefore I bought this set to convert it. I am going to bring it to the same shop and wanted to be prepared.

The adapters in the pictures came with the kit, I don't know which ones to install at the moment. Since they use only low side pressure side when charging, do I need to install the adapter for number 1?

Post by **jimmy57** » 20 Jun 2013, 13:10

The volvo changeover kit was cheap but I'm not sure if they still offer it.
Their kit had an accumulator, the adapters, an orifice (2.3 mm instead of the R12 3mm), and a bottle of Ester oil that mixes wioth the mineral oil and stops the potential for mineral oil gelling.
I have seen kits in parts stores that also had the ester oil.

Post by **rmmagow** » 02 Jul 2014, 12:32

Spend some time here: www.ackits.com. Years ago I used this site to help me convert an 89 Mazda to R134a. Wasn't too bad a job but I bought a vacuum pump, charging harness, new receiver dryer and other extra odds and ends. Site looks a lot different but I still think they can help.