How much 134 refrigerant can it hold?

[d9103365]

I have a 77 Cordoba. My system has been converted to 134. I'm not sure how much refrigerant to put in it. I've put in 2 1/2 pounds so far. It needs to run a little colder at idle but I'm scared to add more because the pressure on the high side is getting high.

 

[q-ship]

I have a 77 Cordoba. My system has been converted to 134. I'm not sure how much refrigerant to put in it. I've put in 2 1/2 pounds so far. It needs to run a little colder at idle but I'm scared to add more because the pressure on the high side is getting high.

I have no idea what the proper amount of 134 would be in a converted 77 Cordoba, but it sounds like you have gone beyond the usable amount.

An otherwise stock R-12 system will never be very cool at idle with 134. The stock condenser and fan just can't do it. You will need to upgrade the condenser to a parallel flow unit, and maybe add an electric fan to keep the same idle/low speed cooling temps as R-12.

Also keep in mind that there is a fine line between the right amount of 134 for max cooling, and to much, which starts to decrease cooling very quickly.

The best way is to run the engine at about 2,500 RPM and take vent temperatures as you add refrigerant. Let it stabilize for a minute or so and add some more (just an ounce or so) till the vent temps drop a bit. At that point remove (or vent) whatever amount was added last and that is the max capacity for the system.

 

[zrxkawboy]

+1, you probably need to remove some at this point and start over.

 

[d9103365]

original 77 shop manual says it should hold 2 5/8 lbs of refrigerant....but that's R12...not sure if it would be the same for 134.

 

[5wndwcpe]

I believe the norm is to charge R134a at 80% of what the original (R12) was to be.

 

[sr-71]

There are a few ways you can do it. 1- install a site glass in front of the expansion valve and fill the system slowly untill you see clear liquid running thru the glass. Some dryers come with them. 2- slowly add freon, you will see the expansion valve freez up that means your getting close. add freon slowly untill the line coming out of the expansion valve defrosts......thats it dont add any more its full. 3 - find a freon charge unit ...its a glass tube with marks for lbs and so on...look up the cap. put the messured amount of freon in the tube and run it till it takes it all. and by the way 134a is colder than r-12. some free advice throw the v - compressor in the trash can and install a sanden unit unless your an original only nut...in that case HAVE FUN

I have a 30 lb can of r-12 it has about 10 lbs or more in it, and some 12oz cans if anybody wants them. you may need it all if your monkeing around with an old v compressor. Ive seen guys that have good ones but i went thru 4 or 5 of them on a 72 newport custom..I even rebuilt a few with new berings and front seals ..they never lasted long. I could never get the front seals to hold pressure for more than a year..plus the thing is so heavy.

oh yeah make sure you have a good vacum pump (I always like to start the charging with a good vac for at least an hour )the vac boils off the moisture and the right oil charge..if you need more info just ask.

 

[Slantsixdan]

80% of the nominal R12 charge amount, by weight, is correct. Sight glasses do not work properly with R134a.

 

[rrTor-Red]

I believe the norm is to charge R134a at 80% of what the original (R12) was to be.

I agree. Thats what we do. So, if the OP put 2.5 lbs in. First I'd check at the vents with as thermometer. If needed , add just a bit more if need be. 2.5 to 2.8 should be enough. Also, check for freon leaks for the added insurance.