j_martin

From Rad frame label on my '93..... 40 oz. R12. I'm guessing about 16 oz Duracool. Look it up in the chart on their site.

ofelas

Thanks; Ive read reports of 44oz & 32oz after Googling, but if you have a label stating 40oz from Chrysler that seems definitive.

So -

40oz R12
32oz R134a (80% of R12)
14oz Duracool 12a (35% of R12)

I got the info here - DuracoolŽ Quick Start Guide

The only thing I couldn't find was whether the Duracool uses the existing R12 fittings or whether I need the R-134a adaptors, and whether its existing oil carried is in addition to sort replaces mineral/ester oil.

j_martin

Duracool uses shrader valve flare fittings, same as R12. Pressure characteristics are very near R12.

ofelas

How do you find dura cool/propane-butane vs R12 for cooling ?

maybe368

Here is a thread that might help. I converted to 134A and it is all in this thread...Mark

ofelas

Hey Mark - "requested thread not found"

maybe368

That's weird, it works for me. It is a thread in the sticky in the body section called renew the ac system or something close to that...Mark



Try this:

https://www.dieseltruckresource.com/...system-313221/

j_martin

I find it works as good as or even slightly better than R12. I mix my own. 1 8oz can of IsoPro mountain stove fuel, and 14 oz of Coleman propane stove fuel. Coleman has proven to be the driest, which is critical. On a system like this, (40 oz) I'd evacuate it, then dump in the Isopro, then top it off with propane. There'll be an ounce or 2 left when it's perfect, but that's close enough on the blend.

On bigger jobs I pre-mix into a used 30 lb R12 can that's been re-valved with brass. If you ever weld on one of those, be sure the wind is at your back. I use outside breathing air also. One wiff of phosgene will wreck havoc on your lungs.

The trick is to find a way to tap the IsoPro. I have an old R12 top type can tapper that fits if you grind on the clamp a little. It's a one shot as it destroys the shrader valve in the can. I've found tap valves that the model boiler guys use that will work as well.

ofelas

Alrighty. I did the following -

New gaskets & o-rings everywhere.

5oz oil in the compressor, 2oz in condenser, 1oz in evaporator & 1oz in drier.

Nitrogen in the system at 300psi and it held for almost 2 hours - no drop in pressure at all.

Ran 26psi vacuum on the system and it held for 2 hours.

Sucked in 40oz of R12 with the compressor cycling at 1300rpm + Max AC + blower fan on high.

Compressor OFF: 50psi low side and 220psi high side
Compressor ON: 25psi low side and climbs in a few minutes to 450psi high side.
Faceplate vent temperatures - 46-50 F

Raising the rpm to 1200-1300 turns the compressor OFF and high side drops almost instantly to 200-250psi

Why am I getting such high side readings, and is it normal for the compressor to be ON constantly until it de-clutches at 1200rpm?

maybe368

Optimum charging condition of the vehicle is hot dry day, 2000 rpm, recirc off, windows open. The pressures don't mean that much in a vacuum of information. What is the temperature of the air coming out of the register most centrally located? A 30 or 40 degree drop from ambient air temp (measured a few inches in front of the condenser) is great. The temp of the air is the MOST important reading to tell optimum charge...Mark

ofelas

Understood about the air temp.

What I am concerned about is the 450psi high side pressures at idle as the compressor clutch doesn't disengage until 1200rpm.
This morning, after idling in traffic for several minutes, I heard a giant pig squeal from under the truck which I assume is the high pressure relief valve venting (FSM says it may do this at 450-550psi)

maybe368

I believe that if the "max ac" button is pushed, the compressor will always run. If not, it is turned on and off by temperature not rpm. 450 is way too high and you probably blew out the high pressure valve. It does not open and close, it blows, at least that is what mine did. If that happened you have lost the entire charge. Is your ac evap box possibly full of debris? I believe that this can cause high, high side pressure. The are a couple of how to's on this in the sticky...Mark

maybe368

Also, did you replace the filter dryer and expansion valve and flush out the evaporator and condenser? If not you may have way too much oil in the system...Mark

ofelas

HVAC box is 100% clean & debris free - I made sure of that when installing the HVAC box in my non AC truck last weekend. There is also no air in the system, and the condenser & discharge side is free of air/blockages.

My AC still blows very cold after the high pressure valve venting, and putting gauges on it still shows a full charge of refrigerant.

FSM claims after venting, its a tiny tiny amount that will not affect the charge.

ofelas

New drier, new expansion valve, new Mopar low pressure switch.

Condenser, compressor, lines & evaporator drained, flushed & air hosed.

Also - I miscalculated - the oil bottle is 8oz and I have about 1oz left, so I must have dumped in 7oz total. I could have sworn it said 10z, but I likely mis-converted ML to oz.