A/C Question

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Oct 11, 2018 | 08:02 AM

#16

Ozzie H.

Laughing Gas

Joined: Nov 2013

Posts: 1,207

Likes: 60

From: S.E. Louisiana;so far USA

Quote:

Originally Posted by Pale340

What about the expansion valve? Could that be the issue? The blower motor works at all levels, low to high, the heater works, the vent blows ambient, and when I put it to A/C it gets colder but no less than 74 degrees. The system is still holding pressure. The 3.5 pounds is actually 3.5 12oz cans of R134. So roughly 42oz.

It could be, but if it was working properly before, it's probably still working correctly. When the bulb is warm the valve should open; when it's frozen, it should close. If I'm remembering correctly, the PAG oils don't mix with the old R12 mineral oils; hence a complete system flush is in order when making the change. Any mineral oil trace will be a problem. The R134a cooling potential is lower than the old R12 systems, but it should do better than a 10 degree difference if all is right. Be sure that the heater is not putting any heat into the mix. There is a pressure/temperature relationship on the refrigerant gas. If you know the pressure (low side) in the evaporator it should give you a good idea of its temperature.

Oct 13, 2018 | 08:11 AM

#17

CharlieXLT

Tuned

Joined: Sep 2017

Posts: 403

Likes: 19

From: Warren, Texas

A week ago, I swapped out my original compressor for a new Sanden in my 77 Supercab. Dryer and condenser change. Rest of system was flushed. Put in 28 ounces of 134a and it works great. Temp at the vents gets down to 35 to 38 degrees. If you put in 42 ounces, I'd say you went too far.